The Effects of Hydroperiod on Macroinvertebrate Assemblages Of

The effects of hydroperiod on macroinvertebrate assemblages of temporary and permanent floodplain wetlands and how this relates to taphonomy and the palaeoecological record

Dale Richard Campbell, BEnvSc&Mgt(Hons)

School of Environmental Sciences Charles Sturt University

December 2020

A thesis submitted according to the requirements for the Degree of Doctor of Philosophy at Charles Sturt University, Thurgoona, New South Wales

Example of a temporary wetland (top) and permanent wetland (middle) on the Ovens River floodplain. Photo of Ovens River, Victoria, Australia (bottom).

Certificate of Authorship

I hereby declare that this submission is my own work and to the best of my knowledge and belief, understand that it contains no material previously published or written by another person, nor material which to a substantial extent has been accepted for the award of any other degree or diploma at Charles Sturt University or any other educational institution, except where due acknowledgement is made in the thesis. Any contribution made to the research by colleagues with whom I have worked with at Charles Sturt University or elsewhere during my candidature is fully acknowledged. I agree that this thesis be accessible for the purpose of study and research in accordance with normal conditions established by the

Executive Director, Library Services, Charles Sturt University or nominee, for the care, loan and reproduction of the thesis, subject to confidentiality provisions as approved by the

University.

Name: Dale Campbell

Signature: D. Campbell

Date: 18.12.2020

Acknowledgements

To my supervisors: A/Prof. Paul Humphries (Charles Sturt University), Dr Nicole McCasker

(Charles Sturt University) and A/Prof. Michael Reid (University of New England) thank you for your supervision and assistance.

I would like to thank Dr Wayne Robinson and Mr Simon McDonald for statistical advice. Dr

Daryl Nielsen for his statistical advice and insight into wetlands and their fauna. Advice was greatly appreciated. Also, Mrs Deanna Duffy for creating the maps of the Ovens River floodplain used in this study.

Finally, I would like to thank my family and friends for your support and help, I could not have done this without you.

This study was conducted in accordance with the National Parks Act 1975 and the Flora and

Fauna Guarantee Act 1988, permit number 10008752.

This research was supported by the Australian Government Research Training Program

(RTP) Scholarship.

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Abstract

Live macroinvertebrate sampling provides a snapshot in time of wetland assemblages present, whereas subfossils in sediments integrate patterns over seasons, years, and even longer periods. Subfossils found in wetland sediments, although potentially rich in biological and ecological information, are, however, unevenly distributed, and incomplete, due to decomposition, post-mortem transport, burial, compaction, and other chemical, biological, or physical activities. Researchers have only recently begun to consider how preservation biases may influence some of the apparent patterns within the palaeoecological record. The aim of this study was to determine how the live macroinvertebrate assemblages in temporary and permanent floodplain wetlands translate to the death assemblages, and by inference, how well the live assemblage is represented in the death assemblage found in sediment traps and surface sediments. Macroinvertebrates were sampled via live sampling, sediment traps

(macroinvertebrate remains) and from the top 20 mm of wetland surface sediments

(subfossils). Sampling was undertaken in 12 permanent and 12 temporary wetlands on the

Ovens River floodplain, Victoria, Australia. Results show macroinvertebrate assemblages of temporary and permanent wetlands are significantly different, and that the macroinvertebrate assemblages collected vary depending on the sampling method undertaken, predominately due to the loss of soft-bodied genera, and the gain of macroinvertebrates, e.g. Terrestrial genera. A large proportion of the live macroinvertebrate assemblage (particularly Diptera and

Coleoptera) translated into the sediment traps (remains assemblage), which then translated into the wetland surface sediments as subfossils, strengthening their use in future palaeoecological studies. Many macroinvertebrates demonstrate potential to be indicators of hydroperiod, as some only occur in a specific wetland type. Therefore, it is possible to determine hydroperiods of waterbodies using the presence/absence of certain macroinvertebrate genera. Further, this thesis suggests that macroinvertebrate subfossils

iv could be used to reconstruct historical waterbody hydroperiod over time in future palaeoecological studies.

Table of Contents Certificate of Authorship ...... ii Acknowledgements...... iii Abstract ...... iv Chapter 1: General Introduction ...... 1 1.1 Floodplains and wetlands ...... 1 1.2 Hydroperiod ...... 3 1.3 Macroinvertebrates ...... 7 1.4 Palaeoecology (remains and subfossil macroinvertebrates) ...... 13 1.5 Taphonomy ...... 14 1.6 Thesis aims ...... 15 1.7 Thesis structure ...... 16 Chapter 2: Effects of hydroperiod on the macroinvertebrate assemblages of temporary and permanent floodplain wetlands ...... 18 2.1 Introduction ...... 18 2.2 Methods ...... 23 2.2.1 Study area ...... 23 2.2.2 Field methods...... 29 2.2.3 Laboratory methods...... 34 2.2.4 Statistical methods ...... 35 2.2.4.1 Effect of hydroperiod on the temporal patterns of physical-chemical properties of the water in floodplain wetlands ...... 36 2.2.4.2 Effect of hydroperiod on temporal patterns of total abundance, richness, individual Genera abundances and assemblage composition of live macroinvertebrates in floodplain wetlands ...... 36 2.2.4.3 Relationship between physical-chemical properties and assemblages ...... 38 2.2.4.4 Identifying macroinvertebrate indicators of hydroperiod ...... 38 2.3 Results ...... 39 2.3.1 Effect of hydroperiod on the temporal patterns of physical-chemical properties of the water in floodplain wetlands ...... 39 2.3.2 Effect of hydroperiod on temporal patterns of total abundance, richness, individual Genera responses and assemblage composition of live macroinvertebrates in floodplain wetlands ...... 43 2.3.3 Relationships between the physical-chemical properties and macroinvertebrate assemblages ...... 56 2.3.4 Identifying macroinvertebrate indicators of hydroperiod ...... 57 2.4 Discussion ...... 61

2.4.1 Effect of hydroperiod on the temporal patterns of physical-chemical properties of the water in floodplain wetlands ...... 62 2.4.2 Effect of hydroperiod on macroinvertebrates in floodplain wetlands ...... 63 2.4.3 Relationships between the physical and chemical properties of the water and the macroinvertebrates recovered ...... 66 2.4.4 Key macroinvertebrate indicator Genera for hydroperiod ...... 67 2.5 Conclusion ...... 72 Chapter 3: Effect of hydroperiod on the accumulation of macroinvertebrate remains, organic and inorganic matter in floodplain wetlands ...... 74 3.1 Introduction ...... 74 3.2 Methods ...... 77 3.2.1 Study area ...... 77 3.2.2 Field methods...... 78 3.2.3 Laboratory methods...... 79 3.2.4 Statistical methods ...... 81 3.2.4.1 Effect of hydroperiod on sedimentation rates of organic and inorganic matter ...... 81 3.2.4.2 Effect of hydroperiod on the abundance, taxonomic richness and assemblage composition of macroinvertebrates in sediment traps ...... 82 3.2.4.3 Identify indicator Genera of wetland hydroperiod ...... 83 3.2.4.4 Comparison of sediment trap assemblages to live macroinvertebrate assemblages .. 83 3.3 Results ...... 84 3.3.1 Effect of hydroperiod on accumulation rates of organic and inorganic matter ...... 84 3.3.2 Effect of hydroperiod on the sediment trap macroinvertebrate remains abundance, taxonomic richness and assemblage composition...... 86 3.3.3 Indicator Genera of wetland hydroperiod ...... 93 3.3.4 Comparison of live and sediment trap macroinvertebrate assemblages ...... 98 3.4 Discussion ...... 106 3.4.1 Determine the effect of hydroperiod on sedimentation rates of organic and inorganic matter in floodplain wetlands...... 106 3.4.2 Determine the effect of hydroperiod on the abundance, taxonomic richness and assemblage composition of macroinvertebrates that accumulate in the sedimentation process of floodplain wetlands ...... 107 3.4.3 Identify indicator taxa of wetland hydroperiod type (temporary/permanent) ...... 110 3.4.4 Comparison of sediment trap assemblages to live macroinvertebrate assemblages collected in Chapter 2 ...... 111 3.5 Conclusion ...... 116 Chapter 4: Effect of hydroperiod on the accumulation and persistence of macroinvertebrate subfossils in the surface sediments of floodplain wetlands ...... 118

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4.1 Introduction ...... 118 4.2 Methods ...... 120 4.2.1 Field methods...... 120 4.2.2 Laboratory procedures...... 125 4.2.3 Statistical methods ...... 127 4.2.3.1 Effect of hydroperiod on the abundance, taxonomic richness and assemblage composition of surface sediment subfossils ...... 127 4.2.3.2 Identification of indicator Genera of wetland hydroperiod ...... 128 4.2.3.3 Comparison of live, trap and surface sediment macroinvertebrate assemblages ..... 128 4.3 Results ...... 129 4.3.1 Effect of hydroperiod on the abundance, taxonomic richness and assemblage composition of surface sediment subfossils ...... 129 4.3.2 Identification of indicator Genera of wetland hydroperiod ...... 139 4.3.3 Comparison of live, trap and surface sediment macroinvertebrate assemblages ...... 144 4.4 Discussion ...... 155 4.4.1 Effect of hydroperiod on the abundance, taxonomic richness and assemblage composition of surface sediment subfossils ...... 155 4.4.2 Identification of indicator Genera of wetland hydroperiod ...... 159 4.4.3 Comparison of live, trap and surface sediment macroinvertebrate assemblages ...... 160 4.5 Conclusion ...... 165 Chapter 5: General Discussion ...... 166 5.1. Effect of hydroperiod on macroinvertebrates ...... 166 5.2. Macroinvertebrate assemblage change and translation ...... 166 5.3. Effect of hydroperiod and taphonomy on macroinvertebrates ...... 167 5.4. Macroinvertebrates as biological indicators of hydroperiod ...... 168 5.5. Reconstruction of hydroperiod and past environments using macroinvertebrates ...... 170 5.6. Recommendations for the future ...... 170 5.7. Final Conclusions ...... 175 Chapter 6: References ...... 176

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Chapter 1: General Introduction

1.1 Floodplains and wetlands

Floodplains and wetlands are beneficial to the environment and society; they are highly productive and provide habitat for aquatic and terrestrial flora and fauna (Calhoun et al.,

2017; Kingsford, 2000), including birds, reptiles, amphibians, mammals, fish, and particularly invertebrates (Bunn & Arthington, 2002; Denny, 1994; Williams, 2006).

Wetlands improve water quality by slowing the flow of water, collecting and retaining sediment, nutrients and pollutants in the process of sedimentation. These sites are often the points of groundwater recharge and aid in flood prevention and minimisation. Floodplains and wetlands provide many natural resources (food, timber, water), are highly productive areas for farming and agriculture, and provide many recreational opportunities (Gennet et al.,

2013; Tockner et al., 2008).

A floodplain is the land adjacent to a river which is slightly higher in elevation and becomes inundated and flooded during periods of high-water volumes in the river system (flooding).

Floodplain and wetland ecosystems are subject to high levels of natural variability (likely to change often) at different scales, with flooding (wet) and drying (dry) phases being the most extreme (Shilpakar, Thoms, & Reid, 2020). Floodplain ecosystems possess an inherent capacity to manage the transition between wet and dry phases, as well as variation in the frequency, magnitude and duration of the phases over longer timescales (Bino, Wassens,

Kingsford, Thomas, & Spencer, 2018; Colloff & Baldwin, 2010; Shilpakar et al., 2020).

Wetlands, found on floodplains, are defined as areas of permanent, periodic or intermittent inundation that hold still or very slow-moving water, leading to the development of hydric soils, and are characterised by biota adapted to flooding (Boulton et al., 2014; Williams,

2006). The Ramsar Convention on Wetlands defines them as “areas of marsh, fen, peatland

1 or water, whether natural or artificial, permanent or temporary, with water that is static or flowing, fresh, brackish or salt, including areas of marine water the depth of which at low tide does not exceed six metres” (www.ramsar.org). Wetlands are commonly described as being either temporary or permanent, depending on their predictability (reliability of wetland flooding event) and duration of filling. Generally, permanent waterbodies are very rare naturally in the environment (Williams, 2006) and this is particularly true for Australia.

Permanent waterbodies are predictably filled, experience variation in water levels, typically depending on environmental conditions. In these systems, the annual inflow of water via precipitation and run-off exceeds the minimum annual loss in 90% of years. However, during extreme drought, these permanent waterbodies may dry out; for example, under severe El

Niño conditions (Burkett & Kusler, 2000; Erwin, 2009; Nielsen & Brock, 2009; Williams,

2006). Most aquatic ecosystems can be considered temporary, with varying hydroperiods and degrees of drying (Boulton et al., 2014; Williams, 2006).

Floodplains and wetlands can change due to natural and anthropogenic processes over time

(Erwin, 2009; Gell, Perga, & Finlayson, 2018; Tockner & Stanford, 2002). They are recognised as being amongst the most threatened ecosystems in the world (Tockner et al.,

2008) mainly because of water resource development, land clearing, agricultural development, and climate change. The latter is expected to alter annual water yields, flow seasonality and the frequency and intensity of extreme droughts and flooding events in the future (Colloff et al., 2016; Finlayson, Davis, Gell, Kingsford, & Parton, 2013; Pittock &

Finlayson, 2011; Teng, Chiew, Vaze, Marvanek, & Kirono, 2012). It is estimated that approximately 50% of the world’s wetlands have been severely damaged or destroyed in the last century (Verhoeven & Setter, 2010; Xu et al., 2019), highlighting the need to protect and preserve these ecosystems. To adequately protect floodplain wetlands, it is essential that we understand not just the present-day state, but the patterns and processes of change of such

2 environments (Damuth, DiMichele, Potts, Sues, & Wing, 1992; Ralph et al., 2011; Smol,

Birks, & Last, 2001).

Contemporary studies are useful for describing and quantifying current dynamics of floodplain wetlands and their components, but do not identify their trajectory over time or how they developed (Delcourt & Delcourt, 1991; Foster, Schoonmaker, & Pickett, 1990).

Long-term studies are usually costly (Lindenmayer et al., 2012), and therefore are rarely undertaken. However, palaeoecological studies can aid in determining how floodplain wetlands and their components have changed and developed over time (Gell et al., 2018;

Schoonmaker & Foster, 1991; Smol et al., 2001). Understanding these changes, and the conditions involved, can aid in predicting the path of these environments into the future, and, ultimately, allow more insight into how to manage, protect and preserve these environments.

1.2 Hydroperiod

The length of time freestanding water is present in a wetland, regardless of its source, is referred to as the hydroperiod (Waterkeyn, Grillas, Vanschoenwinkel, & Brendonck, 2008;

Williams, 2006). The hydroperiod is, therefore, the pattern of flooding and drying within a wetland. Wetland hydroperiod is the result of the balance between inflows and outflows of water, local climate, wetland storage capacity, and the subsurface soil, geology, and groundwater conditions (Bauder, 2005; Mitsch & Gosselink, 2000; Montgomery, Hopkinson,

Brisco, Patterson, & Rood, 2018; Murray-Hudson, Wolski, Murray-Hudson, Brown, &

Kashe, 2014).

Hydroperiod dominates the establishment and maintenance of specific habitat types and associated fauna and flora (Babbitt, Baber, & Tarr, 2003; Brendonck, Pinceel, & Ortells,

2017; Calhoun et al., 2017; Correa-Araneda, Urrutia, Soto-Mora, Figueroa, & Hauenstein,

2012; Daniel, Gleason, Cottenie, & Rooney, 2019; Gleason & Rooney, 2018; Pires, Stenert,

& Maltchik, 2019). Indeed, it is recognised as one of the most important influences on waterbodies, affecting many ecological functions (Williams, 2006). Hydroperiod has been shown to affect vertebrate and invertebrate species richness, community composition and assemblage structure (Spencer, Blaustein, Schwartz, & Cohen, 1999; Wiggins, Mackay, &

Smith, 1980), invertebrate abundance, biomass, and production (Leeper & Taylor, 1998), the size, diversity, and abundance of predators present (Schneider & Frost, 1996), and vegetation communities (Correa-Araneda et al., 2012; Foti, del Jesus, Rinaldo, & Rodriguez-Iturbe,

2012; Miller & Zedler, 2003).

Hydroperiod also affects the physical and chemical characteristics of wetlands, through its influence on depth, size and substrate type (Williams, 2006). Temporary wetlands experience more unpredictable and variable conditions than permanent ones; with shorter and less predictable hydroperiods, and greater daily, seasonal and inter-annual variability in the physico-chemical conditions. For example, water temperature in temporary wetlands is known to vary by > 200 C (Boulton et al., 2014; Silver, Vamosi, & Bayley, 2012; Williams,

2006). Salinity in temporary wetlands can reach very high levels due to drying and concentration of salts in receding waters (Nielsen & Brock, 2009; Nielsen, Brock, Rees, &

Baldwin, 2003).

Wetland flora and fauna are generally considered to be well adapted to variable wetting and drying cycles (Schwartz & Jenkins, 2000). However, species differ in their response to drying and their ability to recover following re-wetting. The flora and fauna associated with temporary wetlands are largely generalists, for example Diptera, capable of making use of resources when available (Williams, 2006). Other non-specialised species, such as Odonata and Ephemeroptera, often recolonise temporary systems when conditions become favourable.

However, there are some highly specialised species, such as Podocopida (ostracods) and

Spinicaudata (clam shrimp), that have adapted to survive under temporary conditions only

(Silver et al., 2012; Williams, 1996, 2006; Zacharias & Zamparas, 2010). Many species found in temporary wetlands have morphological, life-history or dispersal mechanisms that allow them to survive the cyclical drying of the ponds, typically on an annual basis (Schwartz

& Jenkins, 2000; Williams, 1997, 2006). These taxa are often poor competitors in permanent waters; e.g. Podocopida, Spinicaudata, Notostraca (tadpole shrimp), and Anostraca (fairy shrimp) (Wellborn, Skelly, & Werner, 1996; Williams, 2006). Permanent wetlands, on the other hand, also support generalist species that lack adaptions to survive and recover from wetland drying; these species are usually larger and slower growing, such as large fish.

Consequently, assemblages in temporary and permanent waters often differ (Williams, 2006).

When temporary wetlands dry, they change into terrestrial systems and are utilised by terrestrial flora and fauna before reverting to aquatic systems when the water returns. The wetting, drying and re-wetting experienced in temporary systems contribute to nutrient release and transformation processes, changing nutrient availability. This process leads to highly productive periods of growth and colonisation in wetlands, known as boom and bust cycles, when the water returns (Jenkins, Boulton, & Ryder, 2005; Kingsford, Curtin, &

Porter, 1999; Williams, 2006).

Australia is the driest inhabited continent (Khan, 2008; Lough & Hobday, 2011). Knowledge about Australia’s past climate is limited, and how the climate has changed over time is not well known, particularly for the last 2000 years. This is due to the absence of suitable natural archives and/or the cost and technical difficulty associated with collecting and analysing the samples (Evans, Tolwinski-Ward, Thompson, & Anchukaitis, 2013). Reconstructions of past climate variability for Australia is important, as the region contains several major atmospheric and oceanic circulation features with hemispheric or near-global influences; for example, the El Niño–Southern Oscillation (ENSO) (Allen, Hope, Lam, Brown, & Wasson,

2020; Chiew, Piechota, Dracup, & McMahon, 1998; Freund, Henley, Karoly, Allen, &

Baker, 2017;Gergis, Neukom, Gallant, & Karoly, 2016). Generally, information about past climates, from a few hundred to a few thousand years ago, can be accessed via environmental records using tree rings, corals, ice from glaciers and sediment cores (Bradley, 1999; Fisher,

2002; Last & Smol, 2006; Smol et al., 2001; Zinke et al., 2017). In Australia, there are no documented records prior to European settlement. While Australian Aboriginals have a vast traditional ecological knowledge of Australian environments, there is limited recorded knowledge on past climates, temperatures and rainfall events. There is also limited natural records (e.g. trees old enough for tree ring analysis), and there has been no glacial activity since the last Ice Age (Barrows, Stone, Fifield, & Cresswell, 2001, 2002) to infer past climates. As a result, detailed information about the climate of the last 1000 - 2000 years is limited, compared to the Northern Hemisphere (Gergis et al., 2016). However, what palaeoclimate records there are, indicate that rainfall over most of Australia has been variable over many thousands of years (Pittock, 2003; Pittock et al., 2003).

Given that aquatic assemblages are largely structured by hydroperiod, long-term records that associate fluctuations in water availability are valuable, as they demonstrate that contemporary aquatic assemblages can contribute to reconstructions of climatic history, and provide predictions of biotic response to projected hydrological changes. Hydroperiod data, however, is scarce. Tracking changes in wetland water levels is costly, requires specialised monitoring equipment, travel, repeated visits, and involves extensive time to acquire, as hydroperiods of waterbodies can last days, weeks, months and even years (Ryan, Palen,

Adams, & Rochefort, 2014). Monitoring is also difficult, as sites are often in remote places and hard to study, due to the natural variability and inconsistency in the flooding and drying cycles. Therefore, physical monitoring is rarely implemented for more than a few years, with the observed dynamics limited to the particular climatic range of the years of study (Kissel,

Halabisky, Scherer, Ryan, & Hansen, 2020; Lee et al., 2015). Without long-term hydroperiod

6 data, it is difficult to adequately monitor changes in the hydrologic regime of wetlands, to understand general patterns across different wetland types, and to distinguish the difference between natural and abnormal changes to wetland hydrology. However, the palaeoecological record can be used to provide insight into past environments and has the potential to be used to reconstruct long-term hydroperiods of waterbodies.

1.3 Macroinvertebrates

Hydroperiod has a significant effect on macroinvertebrates and is recognised as an important driver of wetland macroinvertebrate assemblage structure (Batzer, Pusateri, & Vetter, 2000;

Collinson et al., 1995; Schneider & Frost, 1996; Silver et al., 2012; Waterkeyn et al., 2008;

Wellborn et al., 1996), taxonomic richness (Spencer et al., 1999; Wiggins et al., 1980), abundance, and reproductive success (Leeper & Taylor, 1998). Examples of macroinvertebrates include: arthropods (insects, mites, scuds and crayfish); molluscs (snails, limpets, mussels and clams); annelids (segmented worms); nematodes (roundworms); and platyhelminths (flatworms). Macroinvertebrates can be aquatic or terrestrial and are some of the most diverse and abundant organisms on the planet (Gullan & Cranston, 2014); found in all environments, and are known to respond to changes in environmental conditions (Bonada,

Prat, Resh, & Statzner, 2006; Cairns & Pratt, 1993; Gullan & Cranston, 2014).

In the past, the study of macroinvertebrates from temporary waterbodies has been overlooked, and generally, comparisons of temporary and permanent wetlands are rare.

Limited studies comparing macroinvertebrate assemblages of temporary and permanent wetlands have been undertaken in America, Europe, Australia and South Africa (Bazzanti &

Bella, 2004; Hillman & Quinn, 2002; Quinn, Hillman, & Cook, 2000; Waterkeyn et al.,

2008). Generally, greater diversity and abundance of macroinvertebrates are found in permanent systems (Brooks, 2000; Collinson et al., 1995; Della Bella, Bazzanti, & Chiarotti,

2005; Neckles, Murkin, & Cooper, 1990; Silver et al., 2012), and these are thought to be positively correlated with the length of the hydroperiod (Boix, Sala, & Moreno-Amich,

2001;Gleason & Rooney, 2018). The longer the hydroperiod, the greater time for colonisation and potential for multiple generations of short-lived organisms to occur.

Aquatic macroinvertebrates are commonly used as biological indicators of waterbody conditions as they spend most, or all of their lives in, and around water, and respond to natural and anthropogenic change within the environment (Cairns & Pratt, 1993; Metcalfe,

1989; Pinel-Alloul, Méthot, Lapierre, & Willsie, 1996; Sharma & Rawat, 2009). The potential to distinguish hydroperiod using macroinvertebrates has not been fully explored and utilised to date. Previously, Hillman & Quinn (2002) compared permanent and temporary wetlands following experimental flooding in a forested floodplain on the Murray River. They found consistent differences between the biota of temporary and permanent wetlands, including chironomids. During the study, numerous live chironomids were found in temporary and permanent wetlands, and they suggested that there was potential to characterise wetland types based on the chironomid assemblages present. This was confirmed by a subsequent study of subfossil chironomid head capsules collected from wetland surface sediments (Campbell, Humphries, McCasker, & Nielsen, 2018). The assemblages of temporary and permanent wetlands are known to differ; some genera are common to both temporary and permanent wetlands, whereas others are only found in temporary or permanent wetlands (Campbell et al., 2018; Williams, 2006). Therefore, there is potential to use the live macroinvertebrates, their remains and subfossils which accumulate in waterbody sediments, and the palaeoecological record, to reconstruct wetland hydroperiods over time.

Due to their high preservation potential, macroinvertebrate subfossils have been used extensively in palaeoecological studies as indicators of past conditions (Smol et al., 2001;

Walker, 1987, 2001). Macroinvertebrates are often thought of as fragile, and unlikely to

8 preserve. However, the chitinous portions of the macroinvertebrate exoskeleton can be extremely strong and resistant to decay, and preserve in high numbers in excellent condition, given suitable preservation conditions (Frey, 1964; Grimaldi & Engel, 2005; Labandeira &

Sepkoski, 1993; Rasnitsyn & Quicke, 2007; Smol et al., 2001).

The accumulation of macroinvertebrate subfossils is influenced by many processes and factors, including the organism itself, and the presence/absence of preservable body parts, depositional conditions, waterbody morphometry, transport, mixing, resuspension and the different types of taphonomic losses (Behrensmeyer, Kidwell, & Gastaldo, 2000; Kidwell &

Flessa, 1995; Rasnitsyn & Quicke, 2007). In recent times, the incompleteness of the subfossil record has been recognised, however, the nature of this incompleteness – i.e. what is present, what is missing, and why – is not adequately understood (Behrensmeyer, Kidwell, &

Gastaldo, 2009; Kidwell & Behrensmeyer, 1988; Rasnitsyn & Quicke, 2007; Smith, Cook, &

Nufio, 2006). Understanding subfossil macroinvertebrate biases is critical for determining the limitations on the use of subfossil macroinvertebrate data, and for distinguishing between true patterns and artefacts in the palaeoecological record (Smith et al., 2006).

Macroinvertebrate orders frequently used in palaeoecological studies include Diptera (Table

1.1), Coleoptera (Table 1.2) and Trichoptera (Table 1.3). These orders are commonly found in sediments, preserve well, have been widely studied (live and subfossils), and contain genera which utilise different environments and conditions. For example, Diptera

(predominately Chironomidae) are the most widely used macroinvertebrates in palaeoecological studies; have been used as proxies for a broad range of environmental variables including climate change, the anoxic state of waterbodies and the presence/absence of fish populations (Table 1.1). Chironomids possess features that make them highly desirable in palaeoecological studies, are highly abundant and diverse with an estimated

15,000+ species worldwide (Armitage, Pinder, & Cranston, 2012). The Chironomidae family

9 as a whole has an extremely wide tolerance range; there are species in virtually every lotic and lentic environment, from the Arctic to the tropics, however, there are also species which can only survive under certain environmental conditions. Chironomids also possess a highly chitinised head capsule, known to preserve and persist in the palaeoecological record. These features make them useful indicators of past environments and conditions (Armitage et al.,

2012; Smol et al., 2001). Coleoptera (Table 1.2) and Trichoptera (Table 1.3) have also been used successfully in palaeoecological studies, as they possess similar features desirable in palaeoecological studies; i.e. abundance, diversity, tolerance range, and chitinous exoskeletons. To date, they have not been utilised as much as Diptera, however, they have been used in studies of environmental reconstruction.

Table 1.1 Environmental parameters reconstructed (and sources) based on Diptera subfossil remains extracted from aquatic sediment profiles.

What was reconstructed Source material Climate change Brooks, 2006; Dimitriadis & Cranston, 2001; Larocque-Tobler, Grosjean, Heiri, Trachsel, & Kamenik, 2010; Walker, Smol, Engstrom, & Birks, 1991 Environmental change Lotter, Birks, Hofmann, & Marchetto, 1997 Temperature Chang, Shulmeister, & Woodward, 2015; Eggermont et al., 2010; Heiri, Birks, Brooks, Velle, & Willassen, 2003; Heiri et al., 2007; Rees, Cwynar, & Cranston, 2008; Walker & Cwynar, 2006 Dissolved oxygen Luoto & Salonen, 2010; Quinlan & Smol, 2001a; Verbruggen, Heiri, Meriläinen, & Lotter, 2011 pH/acidification Brodin & Gransberg, 1993; Charles et al., 1990; Henrikson, Olofsson, & Oscarson, 1982; Kubovčík & Bitušík, 2006 Salinity Verschuren, Tibby, Sabbe, & Roberts, 2000; I. Walker, Wilson, & Smol, 1995 Depth Barley et al., 2006; Chen et al., 2014; Engels, Cwynar, Rees, & Shuman, 2012; Luoto, 2009; Verschuren et al., 2000 Eutrophication Langdon, Ruiz, Brodersen, & Foster, 2006; Prat & Daroca, 1983 Total phosphorus Brooks, Bennion, & Birks, 2001; Zhang et al., 2006 Chlorophyll a Brodersen & Lindegaard, 1999; Langdon et al., 2006; Woodward & Shulmeister, 2006 Anoxia Heiri & Lotter, 2003 Hydrology Gandouin, Franquet, & Van Vliet-Lanoë, 2005; Gandouin, Maasri, Van Vliet-Lanoe, & Franquet, 2006; Gandouin et al., 2007 Hydroperiod Campbell et al., 2018 Reservoir impoundment Hall, Leavitt, Dixit, Quinlan, & Smol, 1999; Prat & Daroca, 1983 Palaeoflow Howard et al., 2010 Methane availability Van Hardenbroek et al., 2010; Wooller et al., 2012 Vegetation Brodersen, Odgaard, Vestergaard, & Anderson, 2001; Langdon, Ruiz, Wynne, Sayer, & Davidson, 2010 Presence/absence of fish Langdon et al., 2010; Sweetman & Smol, 2006; Uutala, 1990 population Trophic status of a Brodersen & Lindegaard, 1999; Brooks et al., 2001; lake/waterbody Verbruggen et al., 2011 Substrate Verschuren et al., 2000

Table 1.2. Environmental parameters reconstructed (and sources) based on Coleoptera subfossil remains extracted from aquatic sediment profiles.

What was reconstructed Source material Temperature Atkinson, Briffa, & Coope, 1987; Marra, Shulmeister, & Smith, 2006; Ponel et al., 2003 Climate Coope, 2010; Lemdahl, 2000 Climate change Lemdahl, 1991; Marra, Smith, Shulmeister, & Leschen, 2004; Porch & Elias, 2000 Flow Howard, Wood, Greenwood, & Rendell, 2008 Vegetation changes Ponel et al., 2003 Environmental conditions Koivula, 2011; Lemdahl, 2000 Environmental change Ponel et al., 2007 Riverbed hydraulic Osborne, 1988 conditions River discharge Smith & Howard, 2004 Floodplain connectivity Davis, Brown, & Dinnin, 2007 Floodplain disturbance Davis et al., 2007 events Riverine landscape Davis et al., 2007 evolution Water depth/movement Boswijk & Whitehouse, 2002

Table 1.3. Environmental parameters reconstructed (and sources) based on Trichoptera subfossil remains extracted from aquatic sediment profiles.

What was reconstructed Source material Flow Drysdale, Carthew, & Taylor, 2003; Elias, 2001; Greenwood, Wood, & Monk, 2006; Howard, Wood, Greenwood, & Rendell, 2009; Pawłowski et al., 2015 Palaeolimnology Solem & Birks, 2000 Climate change Ponel et al., 2007; Solem & Birks, 2000; Williams & Eyles, 1995 Environmental conditions Greenwood, Agnew, & Wood, 2003; Seddon et al., 2019 Environmental change Ponel et al., 2007; Wilson, 1988 Salinity Rumes, Eggermont, & Verschuren, 2005 Macroclimate Williams, Westgate, Williams, Morgan, & Morgan, 1981

1.4 Palaeoecology (remains and subfossil macroinvertebrates)

Palaeoecology is the study of past environments. It is mainly concerned with reconstructing past biota, populations, communities, landscapes, environments, and ecosystems from available geological and biological evidence (Birks & Birks, 2006; Smol et al., 2001). A range of biological proxies, including pollen, plant macrofossils, macroinvertebrates

(predominately Diptera, Coleoptera, Trichoptera), molluscs, microinvertebrates (ostracods,

Cladocera), diatoms, chrysophycean cysts, and testate amoebae have been used in freshwater environments, whereas dinoflagellate cysts, diatoms, pollen, foraminifera, coccolithophores, and radiolarians preserved in marine sediment records have been used (Birks & Birks, 2006;

Smol et al., 2001).

Many palaeoecological studies have focused on the composition of lake sediments, as these are relatively stable environments (Gandouin et al., 2005; Gandouin et al., 2006). There has been a perception that sedimentary records from fluvial systems are unreliable, due to the dynamics of their hydrology, and the evidence that floodplain lakes are typically relatively short-lived. However, these wetlands can be sustained over a long period and can yield useful palaeoecological information (Amoros & Van Urk, 1989; Cooper & McHenry, 1989;

Erskine, McFadden, & Bishop, 1992; Gell et al., 2005; Michelutti, Hay, Marsh, Lesack, &

Smol, 2001; Schönfelder, Gelbrecht, Schönfelder, & Steinberg, 2002). Recently, there have been increased efforts to apply palaeoecological approaches to fluvial systems (Amoros &

Van Urk, 1989; Gell et al., 2005; Michelutti et al., 2001; Schönfelder et al., 2002). However, comparisons of temporary and permanent waterbodies in palaeoecological studies are rare, even though the former are the most abundant aquatic ecosystem worldwide (Williams,

2006).

The subfossil record in wetland sediments, although potentially rich in biological and ecological information, is inherently uneven and incomplete (Behrensmeyer, Kidwell, &

Gastaldo, 2009; Kidwell & Behrensmeyer, 1988). Decomposition, post-mortem transport, burial, compaction, and other chemical, biological, or physical activity act as filters between the ‘live assemblage’ and the ‘death assemblage’ or subfossil record. Recognition of taphonomic processes that have taken place will lead to a better understanding of palaeoenvironments, organisms, and improved reconstructions.

1.5 Taphonomy

Taphonomy of macroinvertebrates is poorly understood, even though macroinvertebrates are widely used in palaeoecological studies, as outlined above. Taphonomy is the study of what happens to an organism after its death, and its discovery as a fossil (Behrensmeyer &

Kidwell, 1985; Behrensmeyer et al., 2009), and includes decomposition, post-mortem transport, burial, compaction, and other chemical, biological, or physical activity which affects the remains. The ability to recognise taphonomic processes that have taken place can lead to a better understanding of past environments, and the organisms which occurred.

Taphonomic studies are needed to allow for accurate reconstruction of past assemblages, and to interpret past environmental conditions. Previously, it was thought that most macroinvertebrates preserved and that the live macroinvertebrate assemblage was represented as a remain/subfossil/death assemblage collected in sediments (Frey, 1964). However, as has been described above, some macroinvertebrates preserve well, and accumulate in the palaeoecological record, whereas others do not. Understanding how the live macroinvertebrate assemblage translates to its death assemblage in sediment cores in palaeoecology studies is poorly understood, and has received limited attention (Seddon et al.,

2019).

Taphonomic processes within wetlands influence the macroinvertebrate remains which accumulate and preserve, and currently little is known about these processes in aquatic

14 environments, including wetlands (Frey, 1964; Rumes et al., 2005; Smith et al., 2006; Van

Hardenbroek, Heiri, Wilhelm, & Lotter, 2011). Environmental conditions are known to affect the preservation and decay of remains. However, how abiotic or biotic environmental factors influence macroinvertebrate remains is not well known. Some factors may be beneficial or detrimental to the decomposition of remains, and therefore potentially bias the subfossil record. The effect of hydroperiod on taphonomy is not understood, and is currently a knowledge gap in palaeoecology. As previously described, temporary wetlands experience greater physical and chemical changes in the short and long term than permanent wetlands during both their aquatic and terrestrial phase. Differences in the environmental conditions found in temporary and permanent wetlands could potentially influence taphonomic processes acting on macroinvertebrate remains in both the standing water, surface sediment and the sediment profile, potentially leading to preservational bias. Therefore, understanding the effect of hydroperiod on taphonomic processes is required. Resolution of the issue is complicated by the degree of variability associated with climatic conditions, and the timeframe over which the factors influence decay; i.e. microbial or chemical decomposition need to be considered. Laboratory-based experiments have a role in identifying and quantifying some of the taphonomic processes, but their applicability to the field will be hampered by the number of factors operating, and combinations experienced, which cannot be replicated. To understand the potential effect of hydroperiod on taphonomy, hydroperiod based taphonomic studies are needed.

1.6 Thesis aims

The overarching aim of this thesis was to investigate the effects of wetland hydroperiod on live macroinvertebrates and how this translates to the macroinvertebrate palaeoecological record.

The specific aims of this thesis were to examine:

The effect of hydroperiod on live macroinvertebrates in temporary and permanent wetlands on the Ovens River floodplain (Chapter 2);

The effect of hydroperiod on macroinvertebrate remains in temporary and permanent wetlands (Chapter 3); and

The effect of hydroperiod on surface sediment subfossil macroinvertebrates (Chapter 4).

1.7 Thesis structure

This thesis explores the effect of hydroperiod on macroinvertebrate assemblages as they translate from live macroinvertebrates, to remains collected in sediment traps, and then into subfossil assemblages found in surface sediments in temporary and permanent wetlands.

Chapter 1: Establishes the context of this thesis, highlighting the effect of hydroperiod on flora and fauna in temporary and permanent wetlands, including macroinvertebrates, and how the hydroperiod influences taphonomy and the palaeoecological record.

Chapter 2: Describes the study area on the Ovens River floodplain in Victoria and the effect wetland hydroperiod has on the physical and chemical conditions of temporary and permanent wetlands, and the live macroinvertebrate assemblages present.

Chapter 3: Outlines the effect of hydroperiod on the accumulation of organic and inorganic material, and macroinvertebrate remains in temporary and permanent wetlands collected in sediment traps. A comparison of the sediment trap macroinvertebrate assemblages to the live macroinvertebrate assemblages collected in Chapter 2 is included.

Chapter 4: Describes the effect of wetland hydroperiod on surface sediment macroinvertebrate subfossils in temporary and permanent wetlands. It includes a comparison of macroinvertebrate assemblages collected during live sampling (Chapter 2), the remains assemblage found in the sediment traps (Chapter 3), and those collected from wetland surface sediments to ascertain how well the macroinvertebrates translate from the live, to remains and subfossil assemblages.

Chapter 5: Draws together and discusses the results and conclusions from previous chapters and the effect of wetland hydroperiod on macroinvertebrates, taphonomy and the palaeoecological record in temporary and permanent wetlands. Recommendations on the use of macroinvertebrates, remains and subfossils in future palaeoecological studies on floodplain wetlands are suggested.

Chapter 2: Effects of hydroperiod on the macroinvertebrate assemblages of temporary and permanent floodplain wetlands

2.1 Introduction

Floodplain wetlands – permanent, periodic or intermittent waterbodies – are dynamic features of the riverscape, recognised as areas of high productivity and biodiversity, and capable of supporting a wide array of flora and fauna, including mammals, birds, reptiles, amphibians, fish and invertebrates (Bunn & Arthington, 2002; Chessman & Hardwick, 2014; Denny,

1994; Norman, 2003; Williams, 2006). Physical, chemical and biological conditions in floodplain wetlands vary spatially and temporally and play a major role in structuring the assemblages and life histories of resident or transitory organisms they support (Bjørnstad &

Grenfell, 2001; Coquillard, Muzy, & Diener, 2012; Menu, Roebuck, & Viala, 2000).

Floodplain wetlands retain still or very slow-moving water, have hydric soils, and support fauna and flora adapted to flooding and drying cycles (Boulton et al., 2014; Williams, 2006).

They can be further classified as permanent or temporary, depending on the predictability of inundation and its duration (Nuttle, 1997). In unmodified riverscapes, most floodplain wetlands are temporary in nature and undergo recurrent flooding and drying phases, and can be characterised by a gradient of permanency, ranging from very temporary to permanent

(Schwartz & Jenkins, 2000).

The length of time freestanding water is present in a wetland, regardless of its source, is referred to as the hydroperiod (Waterkeyn et al., 2008; Williams, 2006). The hydroperiod is defined by the pattern of flooding and drying within a wetland and dominates the establishment and maintenance of specific habitat types, and their species composition

(Babbitt et al., 2003; Brendonck et al., 2017; Correa-Araneda et al., 2012; Daniel et al., 2019;

Gleason & Rooney, 2018; Pires et al., 2019). Wetland hydroperiod is the result of the balance between inflows and outflows of water, local climate, wetland storage capacity, and the

18 subsurface soil, geology, and groundwater conditions (Bauder, 2005; Mitsch & Gosselink,

2000; Montgomery et al., 2018; Murray-Hudson et al., 2014).

The physical, hydrological, and chemical characteristics of temporary wetlands differ from permanent wetlands because of differences in depth, size and substrate type (Williams, 2006).

Temporary wetlands have more unpredictable and variable conditions than permanent ones; with shorter and less predictable hydroperiods, and greater daily, seasonal and inter-annual variability in physical-chemical conditions (Silver et al., 2012; Williams, 2006). How these characteristics influence the fauna and flora in temporary and permanent floodplains is poorly understood.

Many organisms that utilise floodplain environments have life histories and reproductive patterns adapted to seasonal and irregular flooding and drying cycles (Robinson, Tockner, &

Ward, 2002; Tonkin, Bogan, Bonada, Rios‐Touma, & Lytle, 2017; Williams, 2006). The frequency and extent of inundation of floodplain wetlands globally has been heavily modified, due to anthropogenic activities, such as river regulation and floodplain alteration and, as a result, biological diversity and productivity have declined or are under threat (Bunn

& Arthington, 2002; Tockner, Pusch, Borchardt, & Lorang, 2010). Thus, understanding how organisms respond and cope with natural flooding and drying cycles is important for protecting biodiversity.

Hydroperiod is an important driver of wetland macroinvertebrate assemblage structure

(Batzer et al., 2000; Collinson et al., 1995; Schneider & Frost, 1996; Silver et al., 2012;

Waterkeyn et al., 2008; Wellborn et al., 1996), taxonomic richness (Spencer et al., 1999;

Wiggins et al., 1980), abundance and reproductive success (Leeper & Taylor, 1998).

Globally, however, few studies have compared the macroinvertebrate assemblages of temporary and permanent wetlands. Those that have occurred have taken place in North

America, Europe, Australia, and South Africa (Bazzanti & Bella, 2004; Hillman & Quinn,

2002; Quinn et al., 2000; Waterkeyn et al., 2008). Generally, a greater diversity and abundance of macroinvertebrates are found in permanent systems (Brooks, 2000; Collinson et al., 1995; Della Bella et al., 2005; Neckles et al., 1990; Silver et al., 2012), and this is thought to be positively correlated with the length of the hydroperiod. Detailed understanding of the effect hydroperiod has on temporary and permanent wetlands, and its impact on macroinvertebrate abundance, richness, and the assemblages present, is currently lacking.

Patterns in the abundance and assemblage structure of macroinvertebrates in floodplain habitats are also thought to be closely linked to the changes in spatial habitat heterogeneity that accompanies a flooding and drying phase (Marshall, Sheldon, Thoms, & Choy, 2006).

During periods of flooding and consequent hydrological connectivity, conditions may be relatively uniform, with low environmental heterogeneity within floodplain waterbodies

(Ward & Tockner, 2001). However, during the drying phase, floodplain waterbodies fragment and disconnect and show a greater diversity of water temperatures, turbidity, nutrient content, and substrata (Amoros & Bornette, 2002). Therefore, increasing our understanding of how hydroperiod influences the physical-chemical conditions in wetlands and how they respond over time, influencing the macroinvertebrates that inhabit them, should be a priority.

Biota of wetlands are generally considered to be well adapted to highly variable wetting and drying cycles (Williams, 2006). However, taxa differ in their response to drying and their ability to recover following re-wetting. Biota associated with temporary wetlands are largely generalists, capable of utilising resources when available (Williams, 2006). Other non- specialised taxa, which recolonise temporary systems when conditions become favourable, disperse from more permanent sites. Some specialised genera have adapted to survive only under temporary conditions, whereas others can only survive in wetlands with permanent

20 water (Williams, 1997). Consequently, assemblages in temporary waterbodies typically differ from those of permanent waters (Collinson et al., 1995; Hill et al., 2017; Williams, 2006).

How macroinvertebrate assemblages differ between temporary and permanent waterbodies of the same floodplain has received little attention (Boulton & Lloyd, 1991; Chessman &

Hardwick, 2014; Hillman & Quinn, 2002; McInerney, Stoffels, Shackleton, & Davey, 2017;

Quinn et al., 2000). Previous studies looking at within-floodplain differences tend to suffer from low-level replication and coarse levels of macroinvertebrate identification and, as such, equivocal differences were potentially obtained. In order to compare and determine differences in macroinvertebrate assemblages, higher levels of replication are needed.

Additionally, using genus/species resolution for identification would provide greater knowledge of how hydroperiod affects different taxa utilising temporary and permanent wetlands.

Limited attempts to identify invertebrate genera that could be indicators of hydroperiod in floodplain wetlands have been undertaken (Campbell et al., 2018; Hillman & Quinn, 2002;

Quinn et al., 2000; Seminara, Vagaggini, & Stoch, 2015, 2016). Macroinvertebrates are widely used as biological indicators in aquatic ecosystems and can be used to determine the health, environmental conditions, and changes to waterbodies (Carew, Pettigrove, Metzeling,

& Hoffmann, 2013; Hershey, Lamberti, Chaloner, & Northington, 2010; Lawrence et al.,

2010; López-López & Sedeño-Díaz, 2015; Norris & Morris, 1995). There is the potential to use macroinvertebrates as biological indicators of hydroperiod, given, as mentioned above, some organisms prefer temporary environments whereas others prefer permanent ones

(Campbell et al., 2018; Lillie, 2003; Williams, 2006). Understanding which macroinvertebrates utilise temporary and permanent systems would allow the development of biological proxies to reconstruct changes in hydroperiod and water availability over time due

21 to natural and anthropogenic activity. However, opportunities for such work have decreased as river systems become more regulated due to anthropogenic intervention.

Most rivers around the world, including Australia, are highly regulated systems (Haines,

Finlayson, & McMahon, 1988; Nilsson, Reidy, Dynesius, & Revenga, 2005; Walker, 1985).

River regulation in many cases has changed the hydroperiod of floodplain wetlands; some temporary wetlands have become permanent and some permanent wetlands have become temporary (Frazier & Page, 2006; Klimas, 1988). Regulation can alter the seasonality of river flows, their frequency, duration, magnitude, timing, predictability and variability and is recognised as threatening the natural ecological condition of riverine systems (Frazier &

Page, 2006; Kingsford, 2000). Understanding the natural effect of river flooding on floodplain function, and how this influences the physical and chemical properties of the wetlands, and the organisms which inhabit them, is important as most rivers are now regulated and changed from their natural state. The Ovens River in Victoria is one of the few remaining mostly unregulated systems in Australia, and is the last such system in southeastern Australia within the Murray-Darling Basin (Cottingham et al., 2001; Skipworth &

Tate, 2016; Vietz, 2007). The Ovens River floodplain was therefore chosen as the study area to investigate and characterise the properties of temporary and permanent wetlands.

The aims of this chapter are to:

1) Determine the effect of hydroperiod on the temporal patterns of physical-chemical properties of the water in floodplain wetlands.

2) Determine if the temporal patterns of total abundance, richness, individual genera abundance, and assemblage composition of macroinvertebrates differ between temporary and permanent floodplain wetlands.

3) Determine relationships between the physical and chemical properties of the water and the assemblage composition of macroinvertebrates in temporary and permanent wetlands.

4) Identify macroinvertebrate genera that can be used as indicators of temporary and permanent wetlands to distinguish wetland hydroperiod.

2.2 Methods

2.2.1 Study area

The Ovens River, situated in south-eastern Australia, is largely unregulated and is considered close to its natural hydrologic state due to limited regulation and water extraction (Marren &

Woods, 2011; Marren et al., 2011; Schumm, Erskine, & Tilleard, 1996; Vietz, Stewardson, &

Finlayson, 2006). The Ovens Catchment covers an area of 7,813 km2 and contributes 6 - 14% of the total flow of the Murray River – Australia’s longest river (Adhikary, Muttil, & Yilmaz,

2017). The Ovens River (191 km long) is the main river in the Ovens Catchment and originates on the northern side of the Victorian Alps, and flows in a north-westerly direction.

The catchment is characterised by multiple narrow V-shaped mountain valleys in the upper catchment and broad flat alluvial floodplains in the lower catchment. In the upper catchment, the river is 5 - 10 m wide and 1 - 2 m deep, containing small rapids with a steep channel gradient of around 6.5 m.km-1. Down river of Porepunkah, the valley broadens and transitions into open alluvial floodplains. The river in the lower catchment has a low gradient of less than 1m.km-1 and comprises a network of meandering and anastomosing channels. In its lower reaches, the Ovens River can be 40 - 50 m wide and up to 10 m deep.

The Ovens River is perennial, and receives water from its three main tributaries – Buckland,

Buffalo and King Rivers (Figure 2.1). The monthly discharge at the Peechelba gauging station (close to the study area) varies between 200 and 30,200 ML.day-1, with high flow occurring in the Australian winter months (June to September) (Victorian Water Resource

Data Warehouse, 2011). The River in the upper and middle regions is unregulated, but the flow downstream is partially regulated due to the storages on the Buffalo and King tributaries. Nevertheless, the Ovens River is still considered close to its natural hydrologic state. The Ovens River typically experiences annual flooding during the winter-spring period, due to a combination of heavy rainfall and snow melt in the upper catchment area, and periods of low flows and drying during summer (Schumm et al., 1996).

Figure 2.1. (Top) Ovens River floodplain study area location. (Left) Map of the Ovens River and it main tributaries. (Right) Extent of the floodplain in the lower catchment. Red square indicates lower Ovens River and floodplain.

The climate of the Ovens River Catchment is influenced by its topography and location. The average rainfall is higher in the alpine regions than on the alluvial plains (1127 and 636 mm, respectively), with most rainfall occurring in the winter months (Bureau of Meteorology,

2011). Potential evaporation in the catchment increases northwards and ranges from 0 - 40

24 and 125 - 200 mm.month-1 in winter and summer, respectively (Bureau of Meteorology,

2013). The riverine plains and alluvial flats are primarily cleared for agriculture, while the hills and alpine areas are covered by native eucalyptus and plantation forests.

The climate of the area is classified as warm and temperate (Peel, Finlayson, & McMahon,

2007). At Peechelba, the closest long-term recording station to the study site in north-eastern

Victoria, the average annual temperature and rainfall is 15.1°C and 582 mm, respectively.

The mean winter diurnal temperature ranges from 2.8 - 13.8°C, and in summer from 13.2 -

30.7°C (Bureau of Meteorology, 2013).

The study area on the lower Ovens River floodplain, near Peechelba (Figure 2.1), supports an open, mixed-age river red gum (Eucalyptus camaldulensis) forest, with scattered patches of black wattle (Acacia mearnsii) and an understorey of various native and introduced grasses, sedges and herbs (Parkinson, Mac Nally, & Quinn, 2002). Wetlands are filled by overbank and anastomosing channel flows in most years, and support a diverse array of aquatic and semi aquatic vegetation. Historically, forest on the floodplain was selectively logged and used for grazing (King, Humphries, & Lake, 2003; Mac Nally, Cunningham, Baker, Horner, &

Thomson, 2011; Thoms, Ogden, & Reid, 1999). Gold mining and dredging has occurred in parts of the catchment (Davies et al., 2018; Davies et al., 2019).

Hydrology

Discharge from the Ovens River at Peechelba is variable throughout the year (Figure 2.2).

From January to May, discharges are generally low (<2500 ML.day-1), then increase prior to peaking in September to October (>20,000 ML.day-1) and then rapidly decline. Low flows are associated with summer, and high flows are associated with winter and spring. The Ovens

River typically experiences annual flooding during winter-spring, due to a combination of

25 heavy rainfall and snow melt in the upper catchment area, and periods of low flows and drying during summer.

25000

1 -

20000 ML.day 15000

10000

5000 Meanmonthly flow

0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Time of year (Months)

Figure 2.2. Mean monthly discharge for the Ovens River at Peechelba from 1994 to 2019. Data sourced from data.water.vic.gov.au

Daily discharge ranged from zero to over 100,000 ML.day-1at Peechelba (Figure 2.3) and the river breaks its banks when flows exceed 15,000 ML.day-1. The Ovens River generally has a low-flow period from January to June, increasing from July to October, and then rapidly declining. During the 2017/18 study period, flows in the Ovens River were abnormally low due to a major drought occurring in Australia.

Figure 2.3. Ovens River Discharge (ML.day-1) at Peechelba gauging station for the period 1/1/2016 - 31/12/2018; orange line indicates the study period. Calculated from data derived from https://riverdata.mdba.gov.au/peechelba

The lower Ovens River floodplain area contains over 1,800 temporary and permanent wetlands, with variable hydroperiods ranging from a few days to months (North East

Catchment Management Authority, 2020). It has been suggested that wetlands that contain permanent water may have a connectivity with, and are maintained by, groundwater (Hillman

& Quinn, 2002; Quinn et al., 2000). However, little is known about the groundwater of the

Ovens River floodplain, or if there is an actual wetland connection for temporary and permanent wetlands (Cottingham et al., 2001). Groundwater levels have been monitored since 1988 in regards to depth below the natural surface (m) and elevation, and indicate that the water table height has been fairly consistent, although there has been a slow decline since

1997 (Figure 2.4).

Figure 2.4. Groundwater depth and elevation on the lower Ovens River floodplain from 1988 to 2019. Blue dots represent maximum annual recovery levels, red line is 3 year rolling average. Source https://www.g-mwater.com.au/water-resources/groundwater/management/lowerovensgma

Changing groundwater poses a serious threat to floodplain ecosystems (Cunningham,

Thomson, Mac Nally, Read, & Baker, 2011). At the time of sampling, most of Australia, including the study area, was experiencing the effects of severe drought and below-average rainfall, which would influence groundwater levels. Groundwater is likely to be encountered

9 - 13 m below the surface of the floodplain (Figure 2.4). Permanent wetlands on the floodplain were often deeper than temporary wetlands, and occurred at lower elevations. If there is an interaction between the permanent wetlands, and the groundwater below, this may give rise to their increased permanence.

To explore a potential groundwater connection, wetland elevation was measured on the lower

Ovens River floodplain area, and indicated that temporary wetlands varied in elevation from

133 - 149 m, compared to 133 - 144 m for permanent wetlands. Temporary wetlands had a median elevation of 140.5 m whereas permanent wetlands had a median elevation of 137 m.

When compared, there was a significant difference in wetland type elevation on the floodplain (W = 23.5, df 23, P<0.01). This suggests that there is the potential for groundwater

28 sources to help maintain some wetlands on the floodplain. Wetlands with groundwater access are known to have increased diversity and fluctuation patterns of water depth, duration, surface area and physical chemical properties (Custodio, 2000). Groundwater-dependent ecosystems require the input of groundwater to maintain their current composition and functioning (Murray, Hose, Eamus, & Licari, 2006; Murray, Zeppel, Hose, & Eamus, 2003).

However, as noted previously, wetland hydroperiod is the result of the balance between inflows and outflows of water, local climate, wetland storage capacity, and the subsurface soil, geology, and groundwater conditions. Other factors, or a combination of factors, may potentially explain why some wetlands dry while others retain permanent water on the floodplain.

2.2.2 Field methods

Twelve temporary and 12 permanent wetlands on the lower Ovens River floodplain were sampled to compare the effect of hydroperiod on their physical-chemical properties and the macroinvertebrate assemblages present (Figure 2.5). Hydroperiods of temporary and permanent wetlands on the lower Ovens River floodplain have been regularly monitored since 2014 by Dale Campbell in regard to flooding and drying patterns. Additionally, wetlands in the study area have also been observed by Dr Paul Humphries who has visited the area for the past 25 years. Wetlands selected were known to undergo complete drying, or maintain permanent water. Sampling was undertaken monthly from October 2017 to July

2018; only 10 sampling events occurred, as flooding of the river and floodplain area prevented access.

Figure 2.5. Location of 12 temporary and 12 permanent wetlands where live macroinvertebrates were collected (temporary sites red, permanent sites blue).

To select the wetlands to be sampled for this study, all wetlands within the study area of approximately 24 km2, that had road access, were consecutively numbered. Using a random number generator, the first 12 temporary and 12 permanent wetlands were chosen and selected if safe and suitable for sampling. If a wetland was not suitable, the next wetland on the randomised list was selected.

Flooding on the lower Ovens River floodplain commenced in September 2017. Monthly sampling for macroinvertebrates and recording of wetland water physical-chemical conditions began in October 2017 (spring) and continued for 10 months until July 2018

(winter), when flooding recommenced (Table 2.1). Sampling of permanent wetlands covered all four seasons (n = 10 sampling events), whereas the temporary wetlands were predominately dry by mid-autumn 2018, with sampling restricted to spring, summer and early autumn (Figure 2.6).

Physical attributes of each of the 24 wetlands were measured and categorised. Wetland location and elevation was recorded using a GPS. Wetland size was classified as small, medium and large (small ≤ 10 m2, medium > 10 m2 ≤ 50 m2, large > 50 m2), and wetland depth was categorised as shallow, medium and deep (shallow ≤ 0.5 m, medium > 0.5 m ≤ 1.5 m, deep > 1.5 m) (Table 2.1). Hydroperiod (duration of water) of wetlands was also recorded

(Figure 2.6). Sampling of the temporary wetlands ended when they were completely dry, whereas all the 12 permanent wetlands were sampled for the full 10 months.

At each sampling event, five replicate spot measurements of the physical and chemical conditions within each wetland were taken. Water temperature (ºC), dissolved oxygen

(mg.L-1), pH, turbidity (NTU) and conductivity (mS.cm-1) were recorded at half the depth of the water column using a calibrated Horiba U-50 Series multi-parameter water quality meter.

All water parameter measurements were recorded between 10:00 and 14:00 hrs to minimise temporal confounding. On each sampling occasion, from each wetland, 250 mL of surface water was collected for Chlorophyll a determination; samples were filtered, frozen and kept in the dark until laboratory processing.

Wetland macroinvertebrate assemblages were sampled at each sampling event using a 250

μm sweep net drawn through open water (30 s), around vegetation (30 s) and around woody

31 debris (45 - 60 s), to produce a single integrated sample for each wetland, following the protocol of Hillman & Quinn (2002) and Quinn et al. (2000). Samples were washed into storage jars and preserved in 70% ethanol, for later sorting and identification. On each sampling occasion, the site within a wetland was chosen by taking a randomly generated number of paces away from a fixed point on the edge of each wetland. The direction of travel was determined by the toss of a coin. This was to minimise potential bias in sampling due to variations in depth, vegetation growth and the distribution of fallen structures (tree branches and logs). Additionally, on each sampling event, sites were sampled randomly to prevent time-of-day bias.

Table 2.1. Sampling regime and characteristics of each of the 12 temporary and 12 permanent wetlands sampled.

No. of Elevation Site# sampling Size## Depth### (masl) Wetland type events Temporary T1 6 Large Shallow 143 T2 5 Small Medium 133 T3 3 Large Shallow 138 T4 6 Large Deep 139 T5 6 Medium Deep 142 T6 6 Medium Medium 138 T7 5 Small Shallow 145 T8 6 Medium Shallow 145 T9 1 Medium Shallow 141 T10 10 Large Medium 149 T11 3 Medium Medium 140 T12 5 Medium Deep 139

Permanent P1 10 Large Medium 133 P2 10 Large Deep 138 P3 10 Large Medium 137 P4 10 Medium Medium 133 P5 10 Large Medium 138 P6 10 Large Medium 144 P7 10 Medium Shallow 137 P8 10 Small Shallow 136 P9 10 Medium Deep 133 P10 10 Large Shallow 134 P11 10 Medium Deep 137 P12 10 Medium Deep 139

# T = temporary and P = permanent wetland site ## Size: small ≤ 10 m2, medium > 10 m2 ≤ 50 m2, large > 50 m2 ### Depth: shallow ≤ 0.5 m, medium > 0.5 m ≤ 1.5 m, deep > 1.5 m

Figure 2.6. Number of sampling visits, sampling month and seasons. Red shading indicates the temporary wetlands which had variable hydroperiod lengths (1 - 9 months), arranged from shortest to longest; blue shading indicates the permanent wetlands sampled (10 months).

2.2.3 Laboratory methods

Macroinvertebrates were extracted from individual samples in Bogarov trays and identified under a stereo microscope (35 - 60x magnification) to genus level except for Collembolans

(Family level) and the Aquatic Lepidopteran larvae, Nematoda and Nematomorpha (Phyla level). Organisms were identified using standard taxonomic keys, guides and textbooks:

Diptera (Cranston, 1996, 2000; Madden, 2009; Webb, Doggett, & Russell, 2016), Coleoptera

(Hangay & Zborowski, 2010; Lawrence & Slipinski, 2013; Watts, 2002), Mollusca (Smith,

1979), Mites (Colloff & Halliday, 1998; Harvey, 1998), Odonata (Theischinger & Hawking,

2003, 2006; Watson, 1991), Ephemeroptera (Dean & Suter, 1996), Hymenoptera (Andersen,

1991; Shattuck, 2000), Orthoptera (Rentz, 2003, 2010), Blattodea (Rentz, 2014), Araneae

(Whyte & Anderson, 2017), macroinvertebrate textbooks (CSIRO, 1991; Gooderham &

Tsyrlin, 2002; Hawking & Smith, 1997). In addition, the online freshwater macroinvertebrate guide produced by the Centre for Freshwater Ecosystems, La Trobe University, Australia was used. Both aquatic and terrestrial macroinvertebrates were identified. As some orders/genera have both aquatic and terrestrial forms, these were kept separate. Terrestrial macroinvertebrate orders/genera are denoted by a T (e.g. Coleoptera T).

Chlorophyll a processing required its extraction from planktonic cells, which involved filtering the water, then extracting the filtrate with methanol. Once the extracts were obtained, chlorophyll a was measured using a multi-wavelength spectrophotometric/spectrum at 666 nm and 750 nm. Individual samples were read twice, before and after the addition of HCl, using the methods described by Ritchie (2006).

2.2.4 Statistical methods

Wetlands were sampled monthly; temporary wetlands had variable hydroperiods compared to permanent. Temporary wetlands were sampled until dry. Once dry, they were excluded from the analyses. Macroinvertebrates were analysed at order and genus level using abundance and presence/absence data. The macroinvertebrates were then presented at order level, as initial summaries, and major differences in temporary and permanent wetlands identified (genus level differences were grouped together to show order differences). Due to macroinvertebrate genera richness, it was not possible to compare every genus collected. For the majority of the assemblage analysis, genus level was undertaken in this study. This provides high-level insights into the differences in macroinvertebrate assemblages found in temporary and permanent wetlands.

2.2.4.1 Effect of hydroperiod on the temporal patterns of physical-chemical properties of the water in floodplain wetlands

Boxplots comparing wetland physical-chemical properties for temporary and permanent wetlands over time were constructed for temperature, pH, dissolved oxygen, turbidity, conductivity and chlorophyll a. To determine the effect of wetland type (temporary, permanent) and time on the physical-chemical properties of wetland water, non-metric multidimensional scaling (NMDS) ordinations were undertaken. Physical-chemical data was normalised, adjusting variables measured on different scales to a notionally common scale.

To show the effect of time on wetland physical-chemical properties, a time-based SIMPER analysis was undertaken comparing sampling times: 1 (October) and 5 (February), 5 and 10

(February - July), and 1 and 10 (October - July) to determine which physical-chemical properties changed and which caused dissimilarity over the sampling period. This design was undertaken as it allowed contrasts to compare starting, mid-point and ending conditions during the study period.

2.2.4.2 Effect of hydroperiod on temporal patterns of total abundance, richness, individual Genera abundances and assemblage composition of live macroinvertebrates in floodplain wetlands

Boxplots comparing abundance (number of individuals), order richness (number of orders present) and genus richness (number of genera present) in temporary and permanent wetlands were constructed. Additionally, time-based boxplots showing changes in order abundance, over the 10 sampling events, were constructed.

General linear models (using a Poisson distribution) were used to determine the effect of wetland type, sampling time and the wetland type × sampling time interaction on macroinvertebrate total abundances, order richness, genera richness and compared via

ANOVA analysis of deviance. The 10 most abundant macroinvertebrate orders were tested the same way to determine the effect of wetland type, sampling time and the wetland type ×

36 time interaction. Poisson distribution was used as data collected had an excess of zero counts due to the presence of rare or uncommon genera (Sileshi, 2008).

Non-metric multidimensional scaling (NMDS) was conducted on abundance and presence/absence of assemblage data at the genus level to compare the effect of wetland type on macroinvertebrate assemblage composition. Ordinations were undertaken for: 1) All wetlands and sample times; 2) Wetlands were pooled to represent the full wetland macroinvertebrate assemblage over the full sampling period; and 3) the orders Diptera and

Coleoptera were analysed separately as they were abundant, diverse and contained genera showing an association with wetland type. All abundance data were transformed using base log10(x+1) to reduce the influence of the highest abundances and increase the influence of the lowest abundances (Clarke & Warwick, 1994). The Bray–Curtis dissimilarity measure was used to construct dissimilarity matrices between samples and used as the basis for the ordinations (Clarke, 1993). To compare the assemblages based on the shared presence or absence of genera in each sample, the Jaccard similarity coefficient was used (Legendre &

Gallagher, 2001; Real & Vargas, 1996).

NMDS ordination was undertaken to explore the effects of time on macroinvertebrate assemblages using abundance and presence/absence data. To show the effect of time more clearly, temporary and permanent wetland assemblages were plotted separately.

Permutational multivariate analysis of variance (PERMANOVA), a non-parametric multivariate statistical test, was used to compare groups of objects and test the null hypothesis that the centroids and dispersion of the groups, as defined by the measure of space, are equivalent for all groups (Clarke & Gorley, 2015). In this study, PERMANOVA was used to test the effect of wetland type, sampling time, and the wetland type × sampling time interaction on macroinvertebrate assemblages at genus level, using both abundance and

37 presence/absence data. Monte Carlo simulations were used to model the probability of different outcomes, with 10,000 simulations run. Using both abundance and p/a data helps ensure patterns and differences found are not an artefact of sampling differences between the two wetland types (temporary and permanent).

2.2.4.3 Relationship between physical-chemical properties and assemblages

To test the effect of wetland physical-chemical properties on macroinvertebrate assemblages at genus level, BioENV was undertaken. BioENV was used to perform permutation tests on environmental variables (temperature, pH, DO, NTU, conductivity and chlorophyll a), to determine which of the measured variables produced the highest correlation with the biological data (macroinvertebrate abundance and presence/absence data sets).

2.2.4.4 Identifying macroinvertebrate indicators of hydroperiod

SIMPER analysis was used to determine the contribution of each macroinvertebrate genus to the overall compositional differences between the wetland types (Clarke, 1993). SIMPER was performed on log10(x+1) transformed abundance and presence/absence data sets. All genera, (aquatic and terrestrial) and orders which contributed to compositional dissimilarity were reported.

All univariate analyses were conducted using R (Version 3.6.3), and all multivariate analyses were conducted in PRIMER 7 and PERMANOVA (Clarke & Gorley, 2006; Clarke &

Warwick, 1994). All permutation tests were based on 10,000 randomisations.

In this thesis, live remains and subfossil macroinvertebrates were identified to genus level, where possible, as it was the lowest level for all three sampling methods, particularly for remains and subfossils as they are usually only parts and not intact individuals. As the biodiversity of sampling was multi-species, there is an implicit assumption that aggregates of such multi-species genera represent the same pattern as the sum of individual species. I

38 acknowledge that all species within a genus may not act the same and there may be differences among species which are not shown at genus level.

2.3 Results

2.3.1 Effect of hydroperiod on the temporal patterns of physical-chemical properties of the water in floodplain wetlands

Water temperature followed a consistent trend for both temporary and permanent wetlands over the course of the study period (Figure 2.7a). Temperature was low post-flooding in

October 2017, around 15°C for both wetland types, then increased steadily and was >20°C over the next 5 months (November - March). By April 2018, water temperatures began to decline steadily in both wetland types from >20°C to <16°C. Water temperature continued to decline, with temperatures of <6°C recorded in permanent wetlands in July 2018. Over the sampling period, temperatures in the wetlands varied from <6 to >25°C.

Wetland pH showed no trend and was variable over the entire sampling period, fluctuating between 5.2 and 7.5 for temporary and permanent wetlands, respectively (Figure 2.7b).

Dissolved oxygen levels followed a consistent pattern for temporary and permanent wetlands, with levels at their highest immediately post-flooding (>4 mg.L-1) for both temporary and permanent wetlands (Figure 2.7c). Over the sampling period, oxygen levels declined to <3 mg.L-1 during summer (December - March) in both the temporary and permanent wetlands and then slowly increased, reaching post-flooding levels on the last sampling occasion (>4 mg.L-1) (July 2018).

Turbidity was variable for both wetland types, ranging from <10 to >1000 NTU, but was generally <125 NTU for both wetland types (Figure 2.7d). Turbidity increased over the sampling period in both the temporary and permanent wetlands. Temporary wetlands generally had a higher median turbidity than permanent wetlands, 53.75 NTU compared to

37.3 NTU, respectively. For permanent wetlands, turbidity only started to increase after April

2018, by which time most of the temporary wetlands were already dry.

Wetland conductivity varied from <0.1 to >0.3 S cm-1, but was generally in the range 0.1 to

0.2 S cm-1 for both temporary and permanent wetlands (Figure 2.7e). Conductivity showed the same trend for temporary and permanent wetlands, and generally increased over the sampling period. Conductivity was low post-flooding in temporary and permanent wetlands in October 2017 (<0.1 S cm-1), and started to increase from January 2018 (>0.1 S cm-1).

Chlorophyll a levels generally showed the same trend for temporary and permanent wetlands, increasing over the sampling period (Figure 2.7f). Levels varied from <10 µg L-1 to >400 µg

L-1 due to algal blooms, but were generally <100 µg L-1 over the entire sampling period.

Figure 2.7. Boxplots for wetland physical-chemical properties for temporary and permanent wetlands over time: a) Temperature; b) pH; c) Dissolved oxygen; d) Turbidity; e) Conductivity; and f) Chlorophyll a. Blue denotes permanent wetlands, red denotes temporary wetlands. Note variable y-axis.

To determine the effect of wetland type and time on the physical-chemical properties of wetland water, two separate NMDS ordinations were undertaken. The ordinations showed no separation based on wetland type (temporary and permanent) (Figure 2.8a). However, time had a significant effect on wetland physical-chemical properties (Figure 2.8b). Time-based ordination showed groupings of physical-chemical properties of wetland sites based on sampling events 1 to 10.

Figure 2.8. Non-metric multidimensional scaling ordination of normalised wetland physical- chemical data comparing: a) Wetland type (left); and b) Sampling time (right). Blue denotes permanent wetlands, red denotes temporary wetlands.

To show the effect of time on wetland physical-chemical conditions, a time-based SIMPER analysis was undertaken comparing sampling time events 1 and 5, 5 and 10, and 1 and 10

(Table 2.2). When conditions at sampling times 1 and 5 were compared, dissolved oxygen explained a high proportion of the dissimilarity (29.53%), followed by conductivity

(27.64%), and temperature (13.79%). Chlorophyll a, NTU and pH each contributed less than

12% of the dissimilarity. When the physical-chemical conditions of sampling time events 5 and 10 were compared, temperature explained 30.05% of the dissimilarity, followed by chlorophyll a, 26.10%, and dissolved oxygen, 18.33%. Conductivity, NTU and pH each again contributed less than 12% of the dissimilarity. Comparing sampling time events 1 and 10 indicated that chlorophyll a explained 46.38% of the dissimilarity followed by temperature,

17.76%, dissolved oxygen, 14.40%, NTU, 13.78%, pH, 5.69% and conductivity, 2%.

SIMPER comparisons of sampling times showed that all physical-chemical conditions measured in wetlands changed over time, explaining the movement seen in the sampling time-based ordination (Figure 2.8b).

Table 2.2. Results of SIMPER analysis showing the effect of sampling times on wetland physical-chemical variables by comparing sampling events 1 & 5, 5 & 10, and 1 & 10.

Time events Variable Contribution % Cumulative contribution % 1 & 5 DO 29.53 29.53 Conductivity 27.64 57.17 Temperature 13.79 70.96 Chlorophyll a 11.62 82.58 NTU 11.16 93.74 pH 6.26 100.00

5 & 10 Temperature 30.05 30.05 Chlorophyll a 26.10 56.15 DO 18.33 74.48 Conductivity 11.31 85.79 NTU 10.10 95.90 pH 4.10 100.00

1 & 10 Chlorophyll a 46.38 46.38 Temperature 17.76 64.14 DO 14.40 78.54 NTU 13.78 92.32 pH 5.69 98.00 Conductivity 2.00 100.00

2.3.2 Effect of hydroperiod on temporal patterns of total abundance, richness, individual Genera responses and assemblage composition of live macroinvertebrates in floodplain wetlands

A total of 28,398 macroinvertebrates were collected in 181 samples (61 temporary and 120 permanent wetland samples), with 13,946 collected from temporary wetlands and 14,452 from permanent wetlands. Temporary wetland samples ranged in macroinvertebrate abundance from 35 - 618 individuals, with a median of 200, whereas the permanent wetlands ranged from 29 - 352 individuals, with a median of 105.5, nearly half that of the temporary wetlands (Figure 2.9a).

Individuals from 31 orders were collected during wetland macroinvertebrate sampling, of which 20 were aquatic and 11 terrestrial. A total of 30 orders were collected in temporary wetlands, whereas only 25 were collected from permanent wetlands. Twenty-four orders were common to both temporary and permanent wetlands and 7 showed a preference for a particular wetland type. Podocopida, Spinicaudata, Isopoda, Scolopendromorpha, Nematoda and Nematomorpha were only collected in temporary wetlands and Unionida was only found in permanent wetlands. Order richness in temporary wetlands ranged from 3 - 19 with a median of 11, whereas permanent wetlands ranged from 1 - 15 with a median of 7 (Figure

2.9b).

A total of 167 genera were collected, with 148 from temporary wetlands and 129 from permanent wetlands. Of the total genera, 110 were common to both temporary and permanent wetlands. The number of genera in temporary wetlands ranged from 10 - 61 per sample, with a median of 30, whereas permanent wetlands ranged from 6 – 51, with a median of 16

(Figure 2.9c).

Figure 2.9. Boxplots comparing: a) Macroinvertebrate Order total abundance; b) Order richness; and c) Genera richness in temporary and permanent wetlands on the Ovens River floodplain. Blue denotes permanent wetlands, red denotes temporary wetlands. Note variable y-axis scale.

Individuals from the orders Diptera, Hemiptera, Decapoda and Coleoptera were the most frequently collected and accounted for 20,483 (72.1%) of the total, with 9,203 collected from temporary and 11,280 from permanent wetlands. Diptera were the most abundant macroinvertebrates in both temporary and permanent wetlands, with a total of 10,455 collected (4,179 from temporary and 6,276 from permanent wetlands). The abundance of each macroinvertebrate order was variable, with larger median abundances of most orders occurring in temporary wetlands. Diptera, Hemiptera, Decapoda, Coleoptera, Hygrophila and

Odonata were collected in high abundances in both temporary and permanent wetlands

(Figure 2.10). Diptera was the most abundant macroinvertebrate order collected; temporary wetland samples contained a median of 57, whereas permanent wetlands had a median of

43.5. Diptera abundances ranged from 3 - 329 and from 0 - 193 in temporary and permanent wetlands, respectively. The orders Podocopida, Anomopoda, Collembola T, Hymenoptera T

44 and Spinicaudata were collected in greater abundances in temporary wetlands, and were infrequent or absent in permanent wetlands (Figure 2.10). Trichoptera and Unionida occurred in greater abundances in permanent wetlands, whereas Orthoptera T, Lepidoptera and

Turbellaria were collected in low abundances (<5) in both wetland types.

Figure 2.10. Boxplots comparing macroinvertebrate Order abundances in temporary and permanent wetlands on the Ovens River floodplain: a) Diptera; b) Hemiptera; c) Decapoda; d) Coleoptera; e) Hygrophila; f) Odonata; g) Podocopida; h) Trichoptera; i) Ephemeroptera; j) Acariformes; k) Anomopoda; l) Collembola T; m) Araneae; n) Hymenoptera T; o) Spinicaudata; p) Orthoptera T; q) Unionida; r) Lepidoptera; and s) Turbellaria. Orders ranked from highest to lowest abundance. Blue denotes permanent wetlands, red denotes temporary wetlands. Note variable y-axis scale. T denotes Terrestrial Orders.

Macroinvertebrate total abundance over the 10 month sampling period was variable for both temporary and permanent wetlands (Figure 2.11a). Temporary and permanent wetlands showed a consistent trend whereby abundances were highest during the 4 months post- flooding and then steadily declined. When water was present, temporary wetlands supported higher macroinvertebrate abundances than the permanent wetlands. Wetland type, sampling time and their interaction all had a significant effect on the total abundance of macroinvertebrates (P<0.001) (Table 2.3).

Macroinvertebrate order richness showed a similar trend to genera richness over time (Figure

2.11b) and was also variable, ranging from 3 - 19 orders in temporary wetlands and 1 - 15 orders in permanent wetlands. Order richness increased for the first 2 months post- flooding, and then declined for both temporary and permanent wetlands from December 2017. Order richness was generally higher in the temporary wetlands and was significantly affected by both wetland type and time (P<0.001), however, no significant interaction between wetland type and time was detected (P>0.05) (Table 2.3).

Macroinvertebrate genera richness varied greatly over the 10 month sampling period.

Temporary and permanent wetlands followed a consistent trend (Figure 2.11c), genera richness increased for the 3 months post-flooding, peaking in December 2017. During

December, temporary wetlands had a median of 44 genera compared to 37.5 in permanent.

Genera richness in temporary wetlands ranged from 25 - 61, whereas in permanent wetlands it varied from 17 - 51. Macroinvertebrate genera richness declined after sampling in January

2018 and continued through to the end of sampling in July 2018. By July 2018, all the temporary wetlands were dry and the permanent wetlands contained a median of 13.5

Genera. When water was present, temporary wetlands always had a higher genera richness than the permanent wetlands. For genera richness, the effect of wetland type and time were both significant (P<0.001), but no significant interaction between wetland type and time was detected (P>0.05) (Table 2.3).

Figure 2.11. Boxplots comparing Macroinvertebrates: a) Total abundance; b) Order richness and; c) Genus richness over time for temporary and permanent wetlands on the Ovens River floodplain during the 10 month study period (October 2017 to July 2018). Blue denotes permanent wetlands, red denotes temporary wetlands. Note variable y-axis scale.

Table 2.3. Results for GLM testing the effect of wetland type (temporary and permanent) and sampling event for Total abundance, Order richness and Genera richness.

Variable Df Deviance P Total abundance Wetland type 1 2037.32 < 2.2e-16 *** Sampling time 9 990.03 < 2.2e-16 *** Wetland type × Sampling time 8 77.06 < 2.2e-16 ***

Order richness Wetland type 1 6.73 < 2e-16 *** Sampling time 9 158.02 < 2e-16 *** Wetland type × Sampling time 8 1.92 0.1741

Genera richness Wetland type 1 74.61 0.009501 ** Sampling time 9 294.5 < 2.2e-16 *** Wetland type × Sampling time 8 1.85 0.165503

Abundances of all macroinvertebrate orders in temporary and permanent wetlands varied greatly over the 10 month sampling period (Figure 2.12). Diptera was the most abundant and consistently collected order in both temporary and permanent wetlands, followed by

Hemiptera, Decapoda, Coleoptera, Hygrophila, Odonata, Trichoptera, Ephemeroptera,

Acariformes, Araneae, and Hymenoptera T. Generally, abundance increased post-flooding in the spring/summer period (October to March) and then rapidly declined, and was generally higher in the temporary wetlands. The orders Podocopida, Anomopoda, Collembola T, and

Spinicaudata were collected predominately in temporary wetlands from October 2017 to

January 2018, and were generally highest in October before steadily declining. The orders

Orthoptera T, Lepidoptera and Turbellaria were collected in low abundances in temporary and permanent wetlands in late spring and summer (October to February). Unionida were only collected from permanent wetlands.

Figure 2.12. Boxplots comparing macroinvertebrate Order abundances over time (10 month sampling period) in temporary and permanent wetlands on the Ovens River floodplain: a) Diptera; b) Hemiptera; c) Decapoda; d) Coleoptera; e) Hygrophila; f) Odonata; g) Podocopida; h) Trichoptera; i) Ephemeroptera; j) Acariformes; k) Anomopoda; l) Collembola T; m) Araneae; n) Hymenoptera T; o) Spinicaudata; p) Orthoptera T; q) Unionida; r) Lepidoptera; and s) Turbellaria. Orders ranked from highest to lowest abundance. Blue denotes permanent wetlands, red denotes temporary wetlands. Note variable y-axis scale. T denotes Terrestrial Orders.

Wetland type had a highly significant effect for 9 of the 10 most abundant orders, (P<0.001,

Table 2.3) and no effect on Ephemeroptera (P>0.05, Table 2.4). For the 10 most abundant orders, sampling time had a highly significant effect on their occurrence (P<0.001, Table

2.4). The interaction of wetland type and sampling time had a highly significant effect on 7 of the top 10 most abundant orders, except Hemiptera, Coleoptera and Podocopida (P>0.05,

Table 2.4).

Table 2.4. Analysis of deviance results from GLM comparing the top 10 most abundant macroinvertebrate Orders in temporary and permanent wetlands on the Ovens River floodplain in 2017/2018.

Order Variable Df Deviance P Diptera Wetland type 1 578.97 < 2.2e-16 ***

Sampling time 9 422.87 < 2.2e-16 *** Wetland type × Sampling time 8 109.04 < 2.2e-16 ***

Hemiptera Wetland type 1 756.26 < 2.2e-16 ***

Sampling time 9 314.32 < 2.2e-16 *** Wetland type × Sampling time 8 2.37 0.1234

Decapoda Wetland type 1 37.55 8.905e-10 ***

Sampling time 9 4.57 0.03224 * Wetland type × Sampling time 8 17.67 2.631e-05 ***

Coleoptera Wetland type 1 398.68 <2e-16 ***

Sampling time 9 1174.2 <2e-16 *** Wetland type × Sampling time 8 0.89 0.3446

Hygrophila Wetland type 1 245.96 < 2.2e-16 ***

Sampling time 9 928.15 < 2.2e-16 *** Wetland type × Sampling time 8 16.18 5.761e-05 ***

Odonata Wetland type 1 138.36 < 2.2e-16 ***

Sampling time 9 443.71 < 2.2e-16 *** Wetland type × Sampling time 8 14.16 0.0001682 ***

Podocopida Wetland type 1 1466.3 < 2e-16 ***

Sampling time 9 2063.6 < 2e-16 *** Wetland type × Sampling time 8 0 0.9982

Trichoptera Wetland type 1 271.04 < 2.2e-16 ***

Sampling time 9 221.42 < 2.2e-16 *** Wetland type × Sampling time 8 85.18 < 2.2e-16 ***

Ephemeroptera Wetland type 1 0.02 0.8851

Sampling time 9 413.82 < 2.2e-16 *** Wetland type × Sampling time 8 52.24 4.913e-13 ***

Acariformes Wetland type 1 14.99 0.0001082 ***

Sampling time 9 49.14 2.381e-12 *** Wetland type × Sampling time 8 11.29 0.0007791 ***

NMDS ordinations were used to explore the effects of wetland type on the composition of macroinvertebrate assemblages using abundance and presence/absence data (Figure 2.13).

Ordinations on all samples showed a clear separation of temporary and permanent wetlands’ assemblages for both abundance and presence/absence data (Figure 2.13a and 2.13b).

When samples were pooled for macroinvertebrate abundance and presence/absence, NMDS plots showed a clear separation and grouping by wetland type (Figure 2.13c and 2.13d). The macroinvertebrate orders Diptera and Coleoptera, tested individually, also separated out on wetland type for both data sets (Figure 2.13e-h).

Figure 2.13. NMDS ordinations comparing temporary (red) and permanent (blue) wetland macroinvertebrate assemblages at different levels of classification for abundance and presence/absence data (P/A) showing separation by wetland type: a) All sites and sampling events abundance; b) All sites and sampling events P/A; c) Sampling events combined abundance; d) Sampling events combined P/A; e) Diptera only abundance; f) Diptera only P/A; g) Coleoptera only abundance; and h) Coleoptera only P/A.

The effect of time was investigated via NMDS ordinations for both abundance and presence/absence data. To visualise the trends in assemblage composition over time, temporary and permanent wetlands were plotted separately (Figure 2.14). Overall, a time effect on macroinvertebrate assemblages was observed. Temporary wetland assemblages showed macroinvertebrate abundance and presence/absence data grouping by sampling event

(Figure 2.14a, b). Permanent wetland macroinvertebrate assemblages showed a similar pattern, with grouping of similar sampling times and a general movement from left to right over the sampling period for both abundance and presence/absence data (Figure 2.14c, d).

Figure 2.14. Macroinvertebrate assemblages over time (10 months) for temporary and permanent wetlands: a) Abundance data temporary only; b) P/A temporary only; c) Abundance data permanent only; and d) P/A permanent sites only.

PERMANOVA was undertaken on the abundance and presence/absence data sets to further explore the effects of wetland type, sampling event, and interaction on the macroinvertebrates sampled. Analysis showed highly significant wetland type, sampling event and interaction effects for both the abundance and presence/absence data sets (P<0.0001, and Monte Carlo values of 0.0001, Table 2.5). For both data sets, wetland type accounted for most of the variation, followed by sampling event and their interaction.

Table 2.5. Results for PERMANOVA (perm) and Monte Carlo (MC) analysis comparing wetland type, sampling event, and wetland type × sampling event interaction for abundance and presence/absence data.

Abundance data Source Df MS Pseudo-F P(perm) P(MC) Wetland type 1 18928.00 10.09 0.0001 0.0001 Sampling time 9 10654.00 5.68 0.0001 0.0001 Wetland type × sampling time 8 3262.90 1.74 0.0001 0.0001 Residual 162 1875.80 Total 180

Presence/Absence data Wetland type 1 19526.00 7.46 0.0001 0.0001 Sampling time 9 10145.00 3.88 0.0001 0.0001 Wetland type × sampling time 8 4109.10 1.57 0.0001 0.0001 Residual 162 2616.80 Total 180

2.3.3 Relationships between the physical-chemical properties and macroinvertebrate assemblages

To test the effects of the wetland physical-chemical properties measured on the macroinvertebrate assemblages present on the abundance and presence/absence data sets,

BioENV analysis was undertaken. Analysis indicated that temperature, conductivity and DO were significant, whereas pH, turbidity and chlorophyll a had no effect on either the abundance or presence/absence (P/A) data sets (Table 2.6).

Table 2.6. BioENV analysis of wetland physical-chemical properties on macroinvertebrate abundance and P/A data sets.

Abundance BioENV log10(x+1) P/A Environment variables Rho P value% Rho P value% Temperature 0.145 0.1 0.135 0.1 Ph -0.035 88.2 -0.025 79.2 DO 0.074 0.7 0.07 0.3 NTU 0.01 41.5 0.015 33.7 Conductivity 0.086 0.7 0.083 0.6 Chlorophyll a -0.033 82.5 -0.009 58.2

Water temperature was the best single predictor variable measured and the main physical- chemical driver of macroinvertebrate abundance and presence/absence assemblages present.

This was followed by the temperature and conductivity interaction and the effect of the temperature/DO/conductivity interaction (Table 2.7).

Table 2.7. Best environmental variable correlations for wetlands on the Ovens River floodplain.

Best result for each number of variables log10(x+1) P/A No.Vars Corr. Selections Rho P value% Rho P value% 1 Temperature 0.145 0.1 0.135 0.1 2 Temperature, Conductivity 0.166 0.1 0.157 0.1 3 Temperature, DO, Conductivity 0.179 0.1 0.169 0.1

2.3.4 Identifying macroinvertebrate indicators of hydroperiod

SIMPER analysis was undertaken to calculate the contribution of each macroinvertebrate genus (%) to the dissimilarity between temporary and permanent wetlands (Table 2.8).

Diptera accounted for 33.37 and 30.65% of the dissimilarity for log10(x+1) abundance and

P/A data, respectively, and was the most diverse order, with 37 Genera. Coleoptera accounted for 13.57 and 14.36% of the dissimilarity for abundance and P/A data, respectively, and included 31 Genera. Hemiptera accounted for 12.84 and 10.61% of the dissimilarity for abundance and P/A data, respectively, with 17 Genera. Hygrophila, with 9 Genera, accounted for 8.73 and 10.3% of the dissimilarity for abundance and P/A data, respectively. Diptera,

Coleoptera, Hemiptera and Hygrophila combined accounted for 68.51 and 65.92% of the dissimilarity between temporary and permanent wetland assemblages for abundance and presence/absence data, respectively. These four orders contained 29 indicator genera, half of all the indicator genera identified, which showed a preference for a wetland type. Some 9

Diptera showed a wetland preference, 5 temporary and 4 permanent, while 14 Aquatic

Coleoptera showed a preference for temporary wetlands. Of the Hygrophila, 4 showed a wetland type preference, 3 temporary and 1 permanent. Hemiptera had 2 indicator genera which were only collected in permanent wetlands. The prevalence of indicator genera in these

4 orders explains the large dissimilarity between temporary and permanent wetlands on the

Ovens River floodplain.

Table 2.8. SIMPER analysis at Genus level for abundance and presence/absence data comparing assemblage dissimilarity in temporary and permanent wetlands on the Ovens River floodplain.

Abundance data Presence/Absence data Contribution No. Contribution Order (%) Genera Order (%) Diptera 33.37 37 Diptera 30.65 Coleoptera 13.57 31 Coleoptera 14.36 Hemiptera 12.84 17 Hemiptera 10.61 Hygrophila 8.73 9 Hygrophila 10.30 Decapoda 5.90 4 Acariformes 7.19 Odonata 5.23 8 Odonata 4.98 Acariformes 4.42 13 Decapoda 4.34 Ephemeroptera 2.95 3 Trichoptera 2.89 Trichoptera 2.88 6 Ephemeroptera 2.46 Hymenoptera T 1.52 7 Hymenoptera T 2.38 Podocopida 1.50 1 Araneae 1.94 Collembola T 1.38 4 Collembola T 1.07 Araneae 1.28 3 Anomopoda 0.89 Anomopoda 1.10 1 Orthoptera T 0.75 Spinicaudata 0.74 1 Podocopida 0.72 Orthoptera T 0.40 3 Coleoptera T 0.70 Coleoptera T 0.38 3 Spinicaudata 0.65 Turbellaria 0.30 1 Nemertea 0.52 Nemertea 0.27 1 Turbellaria 0.48 Unionida 0.27 1 Unionida 0.37 Lepidoptera 0.23 2 Lepidoptera 0.34 Haplotaxida T 0.19 1 Haplotaxida T 0.33 Julida T 0.13 1 Julida T 0.21 Dermaptera T 0.07 1 Diptera T 0.16 Diptera T 0.07 2 Dermaptera T 0.14 Amphipoda T 0.06 1 Nematoda 0.13 Arhynchobdellida 0.06 1 Nematomorpha 0.13 Nematoda 0.06 1 Amphipoda T 0.10 Nematomorpha 0.06 1 Arhynchobdellida 0.10 Scolopendromorpha T 0.03 1 Scolopendromorpha T 0.08 Isopoda T 0.02 1 Isopoda T 0.04 T Terrestrial Orders/Genera

The 38 genera associated with temporary wetlands came from 14 orders, while the 19 genera associated with permanent wetlands came from 10 orders (Table 2.9). Most macroinvertebrate orders collected contained an indicator genera for hydroperiod, with the orders Coleoptera and Diptera containing the most, followed closely by Acariformes.

Table 2.9. The number of indicator Genera in different Orders for temporary and permanent wetlands on the Ovens River floodplain.

No. of indicator Genera Order Temporary Permanent Diptera 5 4 Coleoptera 14 - Odonata 1 1 Hygrophila 3 1 Decapoda 1 - Podocopida 1 - Spinicaudata 1 - Acariformes 3 4 Collembola T 3 - Hymenoptera T 2 - Isopoda T 1 - Scolopendromorpha T 1 - Nematoda 1 - Nematomorpha 1 - Hemiptera - 2 Trichoptera - 3 Unionida - 1 Lepidoptera - 1 Orthoptera T - 1 Diptera T - 1 T Terrestrial Orders/Genera

At the genus level, 57 indicator genera were identified and, of these, 38 were only collected in temporary wetlands and 19 were only collected in permanent wetlands (Table 2.10). Some potential indicator genera were collected frequently, whereas others were not, suggesting factors other than hydroperiod alone were influencing the occurrence of macroinvertebrates in wetlands on the floodplain.

Table 2.10. Frequency of occurrence of live macroinvertebrate indicator Genera found in temporary and permanent wetlands on the Ovens River floodplain out of a maximum of 12.

Wetland type Order Indicator Genus Temporary Permanent Diptera Cladopelma 10 - Cryptochironomus 10 - Microchironomus 11 - Microtendipes 11 - Anopheles 7 - Paracladopelma - 10 Ablabesmyia - 7 Procladius - 9 Monopelopia - 6 Coleoptera Antiporus 10 - Bidessini 6 - Chostonectes 5 - Erestes 10 - Hyphydrus 4 - Lancetes 8 - Megaporus 7 - Necterosoma 8 - Sternopriscus 2 - Enochrus 5 - Helochares 7 - Limnoxenus 3 - Spercheus 5 - Hydraena 1 - Hemiptera Diplonychus - 7 Merragata - 5 Trichoptera Oecetis - 3 Anisocertropus - 9 Triaenodes - 6 Odonata Xanthagrion 4 - Rhadinosticta - 6 Lepidoptera Lepidoptera - 2 Hygrophila Isidorella 10 - Physastra 11 - Segnitila 11 - Glyptophysa - 10 Unionida Velesunio - 7 Decapoda Macrobrachium 3 - Podocopida Ostracoda 11 - Spinicaudata Limnadopsis 9 - Acariformes Acercella 10 -

Wetland type Order Indicator Genus Temporary Permanent Hydrachna 7 - Neumania 8 - Limnochares - 8 Sigthoria - 5 Unionicola - 3 Halotydeus - 2 Collembola T Entomobryidae 3 - Sminthuridae 2 - Hypogastruridae 4 - Hymenoptera T Rhytidoponera 2 - Abispa 2 - Orthoptera T Torbia - 1 Diptera T Muscidae - 2 Isopoda T Porcellio 1 - Scolopendromorpha T Cormocephalus 2 - Nematoda Nematoda 3 - Nematomorpha Nematomorpha 4 - T Terrestrial Orders/Genera

2.4 Discussion

All physical-chemical properties measured in temporary and permanent wetlands were variable over the sampling period and there was no significant difference between wetland types. The addition of water, and rising water temperatures in late spring/early summer, had a significant effect on the macroinvertebrate assemblages present. On average, the abundance of macroinvertebrates in temporary wetlands tended to be twice that of the permanent wetlands, while the genus richness associated with both was similar. However, the assemblages associated with temporary and permanent wetlands were significantly different.

Many macroinvertebrates found on the Ovens River floodplain demonstrated association for wetlands with a specific hydroperiod. Of the 57 indicator genera identified, 38 genera were only collected in temporary wetlands and 19 only occurred in permanent wetlands. This suggests that it is possible to distinguish wetland type based on the presence of indicator

61 genera found in the live macroinvertebrate assemblages. The main findings will be discussed below.

2.4.1 Effect of hydroperiod on the temporal patterns of physical-chemical properties of the water in floodplain wetlands

Overall, physical and chemical conditions of temperature, pH, dissolved oxygen, turbidity, and conductivity and chlorophyll a levels were similar for both temporary and permanent wetlands. Temporary wetlands showed greater variability in conditions over time, while permanent wetlands showed less variability and were generally more constant, which is consistent with other studies (Anusa, Ndagurwa, & Magadza, 2012; Detenbeck, Taylor,

Lima, & Hagley, 1996; Whigham & Jordan, 2003; Williams, 2006). Most physical and chemical properties of wetlands can be influenced by their hydroperiod (Van den Broeck,

Waterkeyn, Rhazi, Grillas, & Brendonck, 2015). The greater variability seen in the temporary wetlands is influenced by their size, depth and surrounding environment, factors known to influence the residence time of the water which in turn affects the water temperature, conductivity, and dissolved oxygen content of individual wetlands (Boven, Stoks, Forró, &

Brendonck, 2008; Williams, 2006).

The physical and chemical parameters recorded in the wetlands represent snapshots in time; these variables are in a constant state of flux and more intensive measurements would probably show greater differences and variability between temporary and permanent wetlands.

2.4.2 Effect of hydroperiod on macroinvertebrates in floodplain wetlands

Macroinvertebrate abundances were significantly higher in temporary wetlands than permanent, and several mechanisms may be contributing to this pattern. Temporary wetlands are known to undergo boom and bust cycles due to the release of dissolved nitrogen and phosphorous from sediments, and dissolved carbon from floodplain litter following flooding

(Baldwin & Mitchell, 2000). The drying and wetting phases in temporary wetlands often prevents the establishment of large aquatic predators, such as fish, which can prey heavily on macroinvertebrates, influencing their abundance (Corti, Kohler, & Sparks, 1996; Dorn,

2008). Higher productivity and lower predation pressure may explain why the temporary systems support a higher abundance of macroinvertebrates than permanent systems (Conner

& Day, 1982; Mitsch, Taylor, & Benson, 1991). It has also been shown that productivity is highest in wetlands with pulsing hydroperiods (Mitsch et al., 1991).

Macroinvertebrate abundances changed over time and were highest in the post-flooding

(spring/summer) period before declining through the autumn/winter period. These changes are associated with air and water temperatures influencing wetland properties and the biological requirements of the macroinvertebrates. Higher abundances of macroinvertebrates associated with temporary wetlands may also be a side effect of hydroperiod; with receding water levels concentrating the macroinvertebrates present, resulting in higher abundances.

Macroinvertebrate taxonomic richness was also significantly different, with greater genus and order richness associated with temporary than permanent wetlands. Previous studies typically indicate a positive relationship between hydrological permanency and aquatic invertebrate richness in Europe (Collinson et al., 1995; Della Bella et al., 2005; Rundle, Foggo, Choiseul,

& Bilton, 2002; Waterkeyn et al., 2008), North America (Brooks, 2000; Tarr, Baber, &

Babbitt, 2005; Whiles & Goldowitz, 2005), South America (Stenert & Maltchik, 2007), Asia

(Wu, Guan, Lu, & Batzer, 2019), and Africa (Nhiwatiwa, Brendonck, & Dalu, 2017). With

63 longer hydroperiods, a greater chance of macroinvertebrate colonisation occurs (Florencio,

Serrano, Gómez-Rodríguez, Millán, & Díaz-Paniagua, 2009; Schneider & Frost, 1996;

Waterkeyn et al., 2008). However, in Australia most floodplain wetlands are temporary in nature due to the aridity and variability of the climate (Jenkins et al., 2005). As a result, the macroinvertebrate fauna may have adapted to life in temporary systems, which could potentially explain why temporary systems are more Genera-rich.

Assemblages of macroinvertebrates associated with temporary and permanent wetlands were significantly different on the Ovens River floodplain. It has been shown that the duration, frequency and predictability of the aquatic phase highly influences macroinvertebrate assemblages in temporary systems and influences what can survive, reproduce and persist

(Williams, 1997).

The hydroperiod determines how long aquatic life stages of macroinvertebrates have to mature, or how essential active dispersal or a desiccation‐tolerant life stage is for their survival in temporary systems (Bischof et al., 2013; Strachan, Chester, & Robson, 2016;

Williams, 1997). To be successful in temporary systems, macroinvertebrates must have a life history that allows them to survive periodic drying. Hydroperiod is recognised as a major influence on macroinvertebrate trait selection (Wellborn et al., 1996). Different genera have adapted to varying degrees of wetland permanence according to their capacity to resist desiccation during one or more stages of their lifecycles, and their ability to disperse and colonise after re-wetting events (Williams, 2006; Wissinger, 1999). Genera associated with temporary systems often have short lifecycles, desiccation resistant eggs, a diapause phase and active dispersal capabilities, while those found in permanent waters are often larger, slower to develop and often lack the ability to survive and recover after drying. The findings of this study support those of other studies which have found species assemblages in

64 temporary waterbodies differ from those of permanent waters (Sanderson, Eyre, & Rushton,

2005; Williams, 1997, 2006).

Assemblage composition in temporary wetlands typically undergoes changes during inundation (Vanschoenwinkel et al., 2010). Depending on the location and hydroperiod of the wetland, two to three successional phases can usually be distinguished in community development (Boix, Sala, Quintana, & Moreno-Amich, 2004; Lake, Bayly, & Morton, 1989).

In general, communities are dominated initially by resident species recruited from the dormant propagule bank (temporal dispersal), then followed by a period dominated by flying colonists (Jocque, Riddoch, & Brendonck, 2007). This supports the results for Podocopida,

Anomopoda and Spinicaudata that occurred in high numbers immediately post-flooding in temporary wetlands due to dormant propagule/egg banks. As time progressed, flight-based colonisers such as Diptera, Ephemeroptera, and Odonata increased in both temporary and permanent wetlands.

The differences observed in the biological assemblages of macroinvertebrates due to hydroperiod can be seen in other organisms. Previous work has shown that fish (Baber,

Childers, Babbitt, & Anderson, 2002; Chick, Ruetz, & Trexler, 2004; Escalera & Zambrano,

2010; Pazin, Magnusson, Zuanon, & Mendonca, 2006), amphibians/reptiles (Babbitt, 2005;

Babbitt et al., 2003; Cogger, 2014; Snodgrass, Komoroski, Bryan, & Burger, 2000), microinvertebrates (Brock, Nielsen, Shiel, Green, & Langley, 2003; Brucet et al., 2005;

Havel, Eisenbacher, & Black, 2000; Shiel, Green, & Nielsen, 1998), and plants (Foti et al.,

2012; Miller & Zedler, 2003; Vivian-Smith, 1997) can be associated with a specific wetland type. The utilisation and preference of different aquatic habitats by organisms highlights the importance of hydroperiod heterogeneity in the environment for maintaining biodiversity.

2.4.3 Relationships between the physical and chemical properties of the water and the macroinvertebrates recovered

Of the physical and chemical parameters measured (temperature, pH, dissolved oxygen, turbidity, conductivity and chlorophyll a), temperature was the only one in isolation that had a significant effect on macroinvertebrate assemblages for both the abundance and presence/absence data sets. Water temperatures followed seasonal patterns and reflected ambient conditions. In spring/summer, when water temperatures were high, macroinvertebrate abundances and richness were also high, before declining through autumn and particularly in winter. Macroinvertebrates are known to respond to specific changes in water conditions and, as a result, are often used as biological indicators of water quality and conditions (Sharma & Rawat, 2009).

Temperature plays an important part in the lifecycle of macroinvertebrates, and body temperature is linked to changes in ambient temperature (Gullan & Cranston, 2014;

Mellanby, 1939). Temperature change can harm or benefit macroinvertebrates; abundances and diversity can decline in winter and increase in summer. Higher temperatures can accelerate lifecycle rates through faster development, maturation and reproduction, resulting in a quicker turnover of generations and higher abundances. For instance, chironomids are generally the most abundant and diverse macroinvertebrate found in aquatic systems; temperature is known to affect larval and pupal development, the time required for eggs to hatch, and the hatching success rate (Armitage et al., 2012; Eggermont & Heiri, 2012). The abundance and diversity of some chironomid subfamilies has been linked to temperature, both along elevation (Bigler, Heiri, Krskova, Lotter, & Sturm, 2006) and latitudinal gradients

(Larocque, Pienitz, & Rolland, 2006). Diamesinae, Podonominae and some Orthocladiinae commonly occur in cold water environments (Armitage et al., 2012; Oliver, 1971; Pinder,

1986, 1995), whereas Chironominae and Tanypodinae are normally found in higher

66 abundances and diversity at intermediate-warm temperatures (Armitage et al., 2012;

Eggermont & Heiri, 2012). In this study, only Chironominae, Tanypodinae and some

Othocladiinae were collected, indicating the occurrence of warm and cold water in wetlands on the Ovens River floodplain, influencing chironomid subfamilies present.

2.4.4 Key macroinvertebrate indicator Genera for hydroperiod

While some macroinvertebrates were common to both temporary and permanent wetlands, others were restricted to a single wetland type. This indicates that there is potential to determine and characterise waterbody hydroperiod based on the presence of macroinvertebrate indicator genera identified. Nearly every macroinvertebrate order collected contained potential indicator genera for wetland hydroperiod.

The macroinvertebrate assemblages of most aquatic systems are dominated by Diptera from the family Chironomidae, in terms of abundance and taxonomic richness, with an estimated

15,000+ species worldwide (Armitage et al., 2012). Their juvenile stages are mostly restricted to freshwater environments; this makes them one of the most diverse and abundant wetland faunal groups. The chironomid family, as a whole, has an extremely wide tolerance range; with species in virtually every lotic and lentic environment from the Arctic to the tropics (Armitage et al., 2012). It is therefore not surprising that some chironomid genera demonstrate a habitat preference based on hydroperiod. A total of 8 chironomid genera showed associations with a specific wetland type, with Cladopelma, Cryptochironomus,

Microchironomus, and Microtendipes only collected in temporary wetlands, and

Paracladopelma, Ablabesmyia, Procladius, and Monopelopia only collected in permanent wetlands. The chironomid genera associated with temporary wetlands are known to prefer shallow, warm, vegetated waters, whereas genera associated with permanent waters prefer colder, deeper waters (Campbell et al., 2018). A similar pattern was shown previously for subfossil chironomid head capsules in sediment of temporary and permanent wetlands on the

Ovens River floodplain (Campbell et al., 2018). Others have also collected chironomids that have evolved to utilise habitats with varying hydroperiods (Bazzanti, Seminara, & Baldoni,

1997; Benigno & Sommer, 2008; Frouz, Matena, & A., 2003).

The Coleoptera, also a highly diverse macroinvertebrate group, accounted for a large proportion of the indicator genera collected. Some 14 genera were exclusively associated with temporary systems, while no indicator genera were identified for permanent wetlands.

Aquatic coleopterans clearly demonstrate a habitat preference, based on wetland hydrology.

The greater abundance and richness of aquatic Coleoptera in temporary systems, compared to permanent systems, has also been reported elsewhere (Fairchild, Cruz, Faulds, Short, &

Matta, 2003; Fairchild, Faulds, & Matta, 2000; Robson & Clay, 2005). Coleopterans are prominent early colonisers following inundation (Hillman & Quinn, 2002; Vinnersten,

Lundström, Petersson, & Landin, 2009). The temporary wetlands on the Ovens River floodplain support a diverse and abundant Coleopteran fauna, which peaked post-flooding.

This finding is supported by Vinnersten et al. (2009), who found differences in genera are clearly associated with hydroperiod.

Hygrophila (snails) contained genera which exhibited habitat preference, based on wetland hydroperiod in the present study. Isidorella, Physastra and Segnitila were only collected in temporary systems, whereas Glyptophysa was only collected in permanent systems. Of particular interest is Isidorella, a genus of air-breathing freshwater snails able to aestivate in the sediment/mud when conditions become unfavourable and re-emerge when conditions improve (Stevens, 2002). Snails are collected in nearly all types of wetlands, and assemblages are influenced by hydrologic conditions (Wu, Guan, Ma, et al., 2019). The air-breathing pulmonate genera are known to tolerate hypoxia and temporary or seasonal drying (e.g.

Isidorella that was only collected in temporary wetlands in this study), whereas non- pulmonates, which use gills to breathe, require oxygenated water to survive and rarely

68 tolerate drying (Pennak, 1989), were absent. In wetlands, some snails have restricted distributions, whereas others can be widespread (Boix & Batzer, 2016). Snails generally have poor dispersal capabilities, which may enhance their ability to serve as bioindicators (Wu,

Guan, Lu, & Batzer, 2017). This also suggests that the presence or absence of snails could be a potential indicator of wetland hydroperiod.

Podocopida and Spinicaudata (ostracods and clam shrimp) were only collected in temporary wetlands in this study. Podocopida and Spinicaudata are recognised as temporary wetland specialists and indicators of temporary systems; they produce drought-resistant eggs which require drying and wetting to stimulate hatching, and are prone to predation. Temporary systems often cannot support higher-level large predators, such as fish, due to the wetting and drying cycle. Ostracods are commonly collected in most inland waters, including temporary systems (Vandekerkhove, Namiotko, Hallmann, & Martens, 2012). They are early colonisers of temporary waterbodies (Nielsen, Hillman, Smith, & Shiel, 2002) and have adapted to survive in temporary waterbodies (Aguilar-Alberola & Mesquita-Joanes, 2011). Clam shrimp are known from temporary ponds or streams, and occasionally lakes, on all continents

(Martin & Belk, 1988; Martin, Felgenhauer, & Abele, 1986; Weeks, Marcus, & Alvarez,

1997; Weeks, Zofkova, & Knott, 2006). It is believed their preference for temporary waters is an evolutionary response to avoid fish predation. Hence, there is the potential to determine wetland hydroperiod using the presence of Podocopida and Spinicaudata which prefer temporary waters.

In this study, the order Collembola T demonstrated habitat occupation based on hydroperiod and Entomobryidae, Sminthuridae and Hypogastruridae were only collected in temporary wetlands. Collembolans were rarely collected in permanent wetlands; they are essentially terrestrial occurring in soil and organic matter, but many are associated with water.

Collembolans have a highly water-repellent body cuticle that causes them to float, aggregate

69 and disperse when wet (Chang, 1966; Deharveng, D’Haese, & Bedos, 2007; Hale, 1964;

Hopkin, 1997; Schuppenhauer & Lehmitz, 2017; Schuppenhauer, Lehmitz, & Xylander,

2019). Collembolans are prone to predation, and this may potentially explain why they show a preference for temporary wetlands. Their occurrence could be used as a potential indicator of wetland hydroperiod.

The freshwater mussel, Velesunio, was only collected in permanent wetlands on the Ovens

River floodplain, and would probably die or be scavenged in temporary systems. Velesunio are an indicator of permanent waters in floodplain systems; however, there is evidence they can survive in temporary wetlands and intermittent streams, tolerate hypoxic conditions, elevated temperatures and drought, and are capable of anaerobic metabolism when removed from water for up to 1 year (Sheldon & Walker, 1989; Walker, 1981; Walker, Byrne, Hickey,

& Roper, 2001). Therefore, there is some doubt as to their reliability as an indicator genera of wetland type. Hyriids are widespread in Australian inland waters, except in ephemeral and saline waters (Walker et al., 2001). Additional research on their habitat specificity could lead to more confidence in their reliability as a potential indicator of hydroperiod.

On the Ovens River floodplain, three Trichoptera genera (Oecetis, Anisocertropus, and

Triaenodes) were only collected in permanent wetlands, suggesting they could potentially be used to determine hydroperiod, and demonstrate a hydroperiod-based habitat preference.

Previous studies have shown that Trichoptera demonstrate a preference for aquatic habitats with a longer hydroperiod (Jannot, Wissinger, & Lucas, 2008; Porst, Naughton, Gill,

Johnston, & Irvine, 2012). However, some genera have adapted and are known to survive in temporary systems (Wissinger, Eldermire, & Whissel, 2004). Hydroperiod directly influences the development time available (Jannot et al., 2008), and is also known to influence trichopteran diversity (Maltchik, Stenert, Spies, & Siegloch, 2009). Of particular interest in this study was the relatively abundant Oecetis, which build cases out of sand and silt, and are

70 known to preserve well in the sediment record. Based on positive identification of these cases, Oecetis may have potential for use in reconstructing wetland hydroperiod over time.

Macroinvertebrates exhibit a wide variety of adaptations to cope with wetlands of different hydroperiod (Williams, 1996, 1997, 2006). Generally, macroinvertebrates of temporary systems are often smaller, undergo rapid growth and development, are rapid colonisers and have good dispersal capabilities (e.g. Podocopida, Spinicaudata, and Coleoptera). The most important adaptation organisms need to survive in temporary systems is a dormancy phase

(diapause) that enables them to pause their development and cope with varying environmental conditions (e.g. Podocopida, Spinicaudata have egg banks, whereas aestivation potential has been seen in some Hygrophila, Diptera and Coleoptera) (Williams,

2006). Permanent wetlands, on the other hand, support generalist species that lack adaptations to survive and recover from wetland drying; these species are usually larger and slower growing such as bivalves, consequently, assemblages in temporary and permanent waters often differ (Williams, 2006).

Some macroinvertebrates have the potential to be used as biological indicators to determine hydroperiod. In the present study, each of the indicator genera was not always collected in every wetland of one particular type. For example, Cryptochironomus was collected in 10 of

12 temporary wetlands whereas Oecetis was only collected in 3 of 12 permanent wetlands sampled suggesting other variables, besides hydroperiod, influences their presence or absence. Further testing and validation via the use of different sampling methods, sampling frequencies, locations/habitats, and along hydroperiod gradients would assist in the authentication of macroinvertebrates as biological indicators for hydroperiod. Also, better understanding of habitat requirements and life history of macroinvertebrates associated with wetlands would be beneficial.

2.5 Conclusion

The results of this study have shown it is possible to distinguish the hydroperiod of a wetland based on the live macroinvertebrate assemblages present. Many genera are universal and occur in both wetlands; however, there are sufficient that occur and survive only in temporary or permanent wetlands and consequently their presence can be used as a reliable indicator of wetland hydroperiod. Hydrology and hydroperiods of aquatic systems are susceptible to change due to natural and anthropogenic activity. Macroinvertebrate remains, including those of indicator genera identified, accumulate and preserve in aquatic systems as subfossils.

Therefore, it should be possible to determine changes in wetland hydroperiod over time using macroinvertebrates preserved in the palaeoecological record.

Sustainability of wetland ecosystems depends on their biological integrity and anthropogenic activity. With increasing demands for water, regulation of river systems will increase and the natural cycles within wetlands will change. Already, approximately 50% of the world’s wetlands have been destroyed or damaged in the last century (Fraser & Keddy, 2005; Mitsch

& Gosselink, 2000). The impact of river regulation on river flows (Arthington & Pusey,

2003; Maheshwari, Walker, & McMahon, 1995), wetting and drying cycles (Kingsford,

2000; Reid & Brooks, 2000) and the potential impact of climate change (Erwin, 2009; Mitsch et al., 2013; Nielsen & Brock, 2009; Winter, 2000) cannot be fully predicted. However, such changes will generate new hydrological conditions on floodplains affecting the functionality of wetlands and the structure of the macroinvertebrate communities they support. This study highlights the importance and value of temporary and permanent wetlands for macroinvertebrates and the need to protect all wetland types, to preserve and support biodiversity for the future.

This chapter highlighted significant differences in the macroinvertebrate assemblages of temporary and permanent wetlands, and that it is possible to distinguish wetland type based

72 on assemblages and indicator genera present. Many genera show promise to be indicators of wetland hydroperiod (temporary and permanent). Macroinvertebrate exoskeletons are known to accumulate and preserve in aquatic systems, with the potential to determine wetland hydroperiod. Chapter 3 continues to examine the effect hydroperiod has on macroinvertebrate remains in temporary and permanent wetlands and determines how well the live assemblages translate to the remains assemblages collected in sediment traps, and if macroinvertebrate remains can be used to distinguish wetland hydroperiod of temporary and permanent waterbodies.

Chapter 3: Effect of hydroperiod on the accumulation of macroinvertebrate remains, organic and inorganic matter in floodplain wetlands

3.1 Introduction

Wetland sedimentation is the process of organic and inorganic particulate matter gravimetrically accumulating as substrate within a system. Sediment sources include those from flood waters, run-off, aerial (allochthonous inputs) and those from the wetlands themselves (autochthonous inputs) (Nahlik & Mitsch, 2008). Wetlands reduce water velocity and flow, and thereby promote sedimentation (Brueske & Barrett, 1994) and generally intercept and retain more suspended material than they export. Wetlands are mostly located between terrestrial and riverine environments, making them receptive to run-off and sediment deposition sourced from both (Nahlik & Mitsch, 2008; Tockner & Stanford, 2002).

There are relatively few studies on sedimentation and accumulation rates in wetlands, due to the difficulties involved in measuring sediment deposition quantitatively (Dillon, Evans, &

Molot, 1990), and limited work comparing sedimentation in temporary and permanent wetlands on floodplains. Previous studies have measured wetland sedimentation via the use of horizon markers (Harter & Mitsch, 2003; Knaus & Van Gent, 1989), sediment traps and bottles (Fennessy, Brueske, & Mitsch, 1994; Gardner, 1980; Mitsch et al., 2014; Nahlik &

Mitsch, 2008), isotope testing (Appleby, 2002; Eghbal, Ghazban, & Sharifi, 2013;

Szmytkiewicz & Zalewska, 2014), sedimentation plates (Braskerud, 2001) and dendrogeomorphic techniques (Hupp & Morris, 1990). Deposition of sediment from the water column is dependent on many factors, including the hydrologic residence time, wind and wave action, sediment particle size and texture, flocculation of suspended particles, vegetation, and characteristics of the inflow water (Boto & Patrick, 1979; Braskerud, 2001;

Fennessy et al., 1994; Settlemyre & Gardner, 1977).

During sedimentation, the remains of terrestrial and aquatic flora and fauna also settle out and can accumulate (Frey, 1964; Smol, Birks, & Last, 2001). Remains from the live assemblage found in the surface layer of sedimentary records are known as death assemblages (Kidwell,

2013) and are subject to physical reworking, bioturbation, scavenging, disintegration, and other post-mortem processes (Kidwell, 2013). These remains generally reflect the live assemblage, and once held in the sediment layer are referred to as subfossils. Invertebrates are often thought of as fragile and soft-bodied organisms; however, those with chitinous exoskeletons are resistant to breakdown and can be preserved in high numbers, and in excellent condition, given the right preservation environment (Grimaldi & Engel, 2005;

Labandeira & Sepkoski, 1993; Rasnitsyn & Quicke, 2007; Smol et al., 2001). Due to their high preservation potential, macroinvertebrate subfossils have been used extensively in palaeoecological studies as indicators of past conditions (Smol et al., 2001; Walker, 1987,

2001), and for the reconstruction of a wide variety of past environmental variables including: climate change (Brooks, 2006; Dimitriadis & Cranston, 2001; Larocque-Tobler et al., 2010;

Lemdahl, 1991; Marra et al., 2004; Porch & Elias, 2000; Walker et al., 1991), temperature

(Chang et al., 2015; Eggermont et al., 2010; Heiri et al., 2003; Heiri et al., 2007; Rees et al.,

2008; Walker & Cwynar, 2006), lake trophic status (Brodersen & Lindegaard, 1999; Brooks et al., 2001; Verbruggen et al., 2011), water depth (Barley et al., 2006; Chen et al., 2014;

Engels et al., 2012; Luoto, 2009; Verschuren et al., 2000), oxygen availability (Luoto &

Salonen, 2010; Quinlan & Smol, 2001a; Verbruggen et al., 2011), pH (Brodin & Gransberg,

1993; Charles et al., 1990; Henrikson et al., 1982; Kubovčík & Bitušík, 2006), hydrology

(Gandouin et al., 2005; Gandouin et al., 2006; Gandouin et al., 2007), flow (Drysdale et al.,

2003; Elias, 2001; Greenwood et al., 2006; Howard et al., 2008, 2009; Howard et al., 2010;

Pawłowski et al., 2015), vegetation (Brodersen et al., 2001; Langdon et al., 2010), and salinity (Rumes et al., 2005; Verschuren et al., 2000; Walker et al., 1995).

The incomplete state of the subfossil record has been appreciated for some time (Smol et al.,

2001), but what is present, what is missing, and why is not adequately understood, even though this affects most biological interpretations attempted using the subfossil record (Alin

& Cohen, 2004; Flessa & Brown, 1983; Kidwell & Behrensmeyer, 1988). Environmental and taphonomic processes can affect and bias the accumulation of remains in aquatic environments, and it is currently unknown if hydroperiod can influence these processes.

Understanding the accumulation process of remains is vital if macroinvertebrate subfossils found in palaeoecological studies are to be used to their full potential. In Chapter 2 the abundance, taxonomic richness, compositional and assemblage differences in the live macroinvertebrates occurring in temporary and permanent wetlands on the Ovens River floodplain were described. These differences were predominantly due to the effect of wetland hydroperiod. Chapter 3 will determine how the differences in the live macroinvertebrate assemblages in temporary and permanent wetlands translate to the remains assemblages collected in sediment traps and ascertain if, and how, hydroperiod influences this process.

The aims of this chapter are to:

1) Determine the effect of hydroperiod on sedimentation rates of organic and inorganic matter in floodplain wetlands.

2) Determine the effect of hydroperiod on the abundance, taxonomic richness and assemblage composition of macroinvertebrates that accumulate in the sedimentation process of floodplain wetlands.

3) Identify indicator Genera of wetland hydroperiod.

4) Compare the sediment trap assemblages to the live macroinvertebrate assemblages collected in Chapter 2.

3.2 Methods

3.2.1 Study area

A total of 24 wetlands on the lower Ovens River floodplain were sampled (12 temporary and

12 permanent) to compare the effect of hydroperiod on the accumulation of macroinvertebrate remains, and organic and inorganic sediments (Figure 3.1). Sampling was undertaken in the same wetlands used to assess the live macroinvertebrates (Chapter 2).

Figure 3.1. Location of 12 temporary and 12 permanent wetlands where sediment traps were placed on the Ovens River floodplain, South Eastern Australia (temporary sites red, permanent sites blue).

3.2.2 Field methods

Sediment traps were placed in each of the 24 study wetlands from June 2017 - June 2018 to measure macroinvertebrate remains and organic and inorganic matter accumulation over a 12 month period. Sediment traps were placed at the deepest point in each wetland (Brodersen &

Lindegaard, 1999; Heiri, 2004; Real, Rieradevall, & Prat, 2000; Schmäh, 1993) as studies have shown that such samples of macroinvertebrate subfossils provide an integrated sample of the whole waterbody assemblage (Heiri, 2004). The deepest point has the longest time under water, maximising the potential for sediment and macroinvertebrate remains to accumulate, particularly in temporary wetlands. The deepest point was located visually in temporary wetlands and established by measuring depth in the permanent wetlands, prior to trap establishment. Due to the different nature of hydroperiods in the temporary and permanent wetlands, sediment traps were removed from temporary wetlands once the surface waters had dried, and after one year of field exposure in the permanent wetlands. Sediment trap collections reflect the full inundation time of the wetlands; it was considered inadvisable to collect samples more frequently due to the risk of sediment disturbance when accessing the traps.

Sediment trap design

Traps used to sample sediment deposition and accumulation of macroinvertebrate remains were constructed based on a modified design of Fennessy et al. (1994). Traps were made from 250 mm lengths of 150 mm diameter PVC pipe, closed at one end with an end-cap

(Figure 3.2). Traps were sunk vertically into each wetland with the opening approximately 5 cm above the substratum, and designed to collect new or resuspended sediments settling from the water column, as opposed to older sediments rolling or sliding across the soil surface via bed-material transport (Gardner, 1980). To minimise trapping sediment disturbed during placement, traps were pre-filled with water and capped. Trap covers were removed after 1 h

78 to minimise the volume of disturbed sediment settling in the tubes. In permanent wetlands, individual traps were attached by a line to the bank to aid in their location and retrieval.

Figure 3.2. Traps used to collect sediments and macroinvertebrate remains in temporary and permanent wetlands: a) trap design; b) deployed trap; and c) example of the dried contents collected within a trap.

3.2.3 Laboratory methods

Laboratory procedures

At the conclusion of the study, or when the water level of the wetland fell below the trap opening, the traps were recapped, removed, and transported to a greenhouse for drying.

Temporary caps were replaced with a fine mesh to allow drying and exclude additional arthropods from contaminating the samples. Once air-dry, the traps were placed in a drying oven at 50°C for 24 h to remove any remaining moisture, prior to determining the weight of particulate matter. Material from each trap was weighed and a 10% subsample taken for organic and inorganic matter content determination. This involved weighing crucibles and subsamples, which were then placed in a 105°C drying oven for 12 h, then allowed to cool to

<30°C before samples were removed and reweighed. The samples were then placed in a furnace for 4 h at 550°C to burn off the organic matter, allowed to cool, and weighed to determine the organic matter lost.

The remaining material from each sediment trap was processed for macroinvertebrate remains. Samples were wet-sieved into different sized fractions (10, 5, 2, 1 mm and 106 µm) which were then examined under a stereo microscope (35–60x) for invertebrate remains. Due to the large quantities of fine sediment material retained on the 106 µm sieve, these samples were subjected to kerosene flotation to assist in the extraction of small remains such as chironomid head capsules, using the method described by Rolland & Larocque (2007). Each sample was washed into a 500 mL Erlenmeyer flask, brought to a volume of 300 mL with

80% ethanol, and then 100 mL of kerosene was added and the flask capped and gently inverted 5 times to minimise the formation of an emulsion. The presence of an emulsion increases the time of separation, or prevents the separation, of the two solutions. Flasks were left undisturbed until the kerosene and ethanol layers completely separated. For each flask, material at the kerosene/alcohol interface was transferred into a beaker using a large syringe, filtered to condense the sample, and then flushed into a labelled storage container with 80% ethanol. As some macroinvertebrate remains are composed of materials other than just chitin, the material matrixes remaining after flotation were examined under the microscope and any remains extracted for identification.

After filtering, the extracted material was transferred to a Bogarov counting tray and examined under a stereo microscope (35–100x). Remains were removed using fine dissecting forceps or a paint brush, examined under a dissecting light microscope (100x) and identified to genus level, where possible. Organisms were identified using standard taxonomic keys, guides and textbooks: Diptera (Cranston, 1996, 2000; Madden, 2009; Webb et al., 2016);

Coleoptera (Hangay & Zborowski, 2010; Lawrence & Slipinski, 2013; Watts, 2002);

Mollusca (Smith, 1979); Acarina (Harvey, 1998); Odonata (Theischinger & Hawking, 2003,

2006; Watson, 1991); Hymenoptera (Andersen, 1991; Shattuck, 2000); Orthoptera (Rentz,

2003, 2010); Blattodea (Rentz, 2014); Araneae (Whyte & Anderson, 2017); and

80 macroinvertebrate textbooks (CSIRO, 1991; Gooderham & Tsyrlin, 2002). In addition, the online freshwater macroinvertebrate guide produced by the Centre for Freshwater

Ecosystems at La Trobe University, Australia was also used. Both aquatic and terrestrial macroinvertebrate remains recovered from the samples were identified. As some orders/genera have both aquatic and terrestrial forms, these were kept separate. Terrestrial macroinvertebrate orders/genera are denoted by a T (e.g. Coleoptera T). Each identifiable macroinvertebrate remain/part was counted as a different individual (Quinlan & Smol,

2001b).

3.2.4 Statistical methods

3.2.4.1 Effect of hydroperiod on sedimentation rates of organic and inorganic matter

The effect of hydroperiod (temporary vs permanent) on total sediment weight, organic and inorganic matter content in temporary and permanent wetlands was compared using boxplots and the Wilcoxon rank sum test (Zar, 1999). To calculate the accumulation rates (volume of new material in kg), the total weight of the organic and inorganic content within each sediment trap was divided by the trap surface area and scaled up to 1 m2.

Soil type was determined using the soil texture/ribbon test, and the material that accumulated in sediment traps was determined to be a silty clay loam; with a soil density of 1.5 g.cm-3

(McDonald, Isbell, Speight, Walker, & Hopkins, 1998).

The vertical rate (height of new material) of sediment deposition was calculated using the equation by Demissie, Fitzpatrick, & Cahill (1992), where:

W H = D × A

H = Sedimentation rate in centimetres (cm) W = Weight of sediment deposited D = Density of the deposited sediment A = Area of sediment deposition

3.2.4.2 Effect of hydroperiod on the abundance, taxonomic richness and assemblage composition of macroinvertebrates in sediment traps

The total abundances of macroinvertebrates, their genera richness and order richness in sediment traps in temporary and permanent wetlands were compared using the Wilcoxon rank sum test (Zar, 1999). The Wilcoxon rank sum test, a nonparametric version of the t-test for independent samples, converts the actual numbers to ranks and was used because the data was not normally distributed. Significance was set at P 0.05. Boxplots comparing Total and order abundances, order richness, and genus richness in temporary and permanent wetlands were made to better visualise the differences in the data and were compared using the

Wilcoxon rank sum test.

To test for the effect of wetland type (permanent vs temporary) on macroinvertebrate assemblage composition accumulated in the sediment traps, Non-metric multidimensional scaling (NMDS) was conducted on the genus level abundance and presence/absence of macroinvertebrate assemblage data sets. Abundance data was transformed using log10(x+1) to reduce the influence of the highest abundances and increase the influence of the lowest abundances (Clarke & Warwick, 1994). The Bray–Curtis dissimilarity measure was used to construct dissimilarity matrices between samples and used as the basis for the ordinations

(Clarke, 1993). To compare the assemblages, based on the shared presence or absence of genera in each sample, the Jaccard similarity coefficient was used (Legendre & Gallagher,

2001; Real & Vargas, 1996).

PERMANOVA was again used to test the effect of wetland type on the macroinvertebrate remains collected in the sediment traps, and Monte Carlo analysis used to model the probability of different outcomes.

3.2.4.3 Identify indicator Genera of wetland hydroperiod

SIMPER (similarity percentage analysis) was used to calculate the contribution of each macroinvertebrate genus/order (as a %). The dissimilarity between temporary and permanent wetlands was calculated on log10(x+1) abundance data and presence/absence data sets. All genera and orders contributing to compositional dissimilarity were reported. SIMPER analysis was also used to identify indicator genera responsible for driving differences in the wetland assemblages and to determine the contribution of each taxon to the overall compositional differences between the wetland types (Clarke & Warwick, 1994).

3.2.4.4 Comparison of sediment trap assemblages to live macroinvertebrate assemblages

The assemblages of macroinvertebrate remains in the sediment traps were compared to the known live assemblages to determine how well the live assemblage (Chapter 2) transfers to the trap remains assemblage. NMDS ordinations comparing wetland type and sampling method were undertaken using the presence/absence data. Ordinations were performed at the

All genera level of classification, and additional ordinations were performed for the Diptera and Coleoptera assemblages separately, as they were abundant, diverse, and well preserved.

PERMANOVA was also used to test the effect of wetland type, sampling method and their interaction on the assemblages of macroinvertebrate remains, while Monte Carlo analysis was used to model the probability of different outcomes.

All univariate analyses were conducted using the freeware, R (Version 3.6.3), and all multivariate analyses were conducted in PRIMER 7 and PERMANOVA (Clarke & Gorley,

2006; Clarke & Warwick, 1994). All permutation tests were based on 10,000 randomisations.

3.3 Results

3.3.1 Effect of hydroperiod on accumulation rates of organic and inorganic matter

The total weights of material which collected in the sediment traps varied; temporary wetlands ranged from 14.87 - 242.78 g with a median of 95.9 g, whereas permanent wetlands varied from 22.27 - 643.91 g with a median of 73.0 g (Figure 3.3a). There was no significant difference in the total sediment weight that accumulated in the temporary and permanent wetlands on the Ovens River floodplain (W = 75, df 23, P>0.05).

Organic matter content of temporary wetlands varied from 10.4 - 60.0% with a median of

25.6%, whereas permanent wetlands varied from 12.8 - 38.2% with a median of 24.9%.

There was no significant difference in the organic matter content of material that accumulated in the sediment traps of temporary and permanent wetlands (W = 58, df 23, P>0.05).

Inorganic matter content in temporary wetlands varied from 40.0 - 89.6% with a median of

74.4%, whereas permanent wetlands varied from 61.8 - 87.2% with of median of 75.1%

(Figure 3.3c). Again, there was no significant difference in the amount of inorganic matter that accumulated in the sediment traps of temporary and permanent wetlands (W = 86, df 23,

P>0.05).

In the process of sedimentation, macroinvertebrate remains accumulated, and in temporary wetlands varied from 0.36 - 1.62 cm-2 with a median of 0.57 cm-2, whereas permanent wetlands’ accumulation rates varied from 0.52 - 2.05 cm-2 with of median of 1.34 cm-2

(Figure 3.3d). When compared, there was a significant difference in macroinvertebrate remains abundance in temporary and permanent wetlands (W = 117, df 23, P<0.01). It is estimated that the temporary wetlands accumulated from 3,565 - 16,184 remains with a median of 5,700, whereas the permanent wetlands accumulated from 5,206 - 20,542 remains with a median of 13,440 remains per m2.

Vertical accumulation rates varied: in temporary wetlands, rates varied from 0.5 - 9.2 mm.year-1 with a median of 3.6 mm.year-1, whereas permanent wetlands varied from 0.8 -

25.1 mm.year-1 with a median of 2.8 mm.year-1 (Figure 3.3e). When compared, there was no significant difference between wetland types (W = 75, df 23, P>0.05).

Figure 3.3. Boxplots comparing: a) Total weight; b) Organic content %; c) Inorganic content %; d) Remains accumulation rate cm-2; and e) Vertical accumulation rate (mm.year-1) in temporary and permanent wetlands. Blue denotes permanent wetlands, red denotes temporary wetlands. Note variable y-axis.

Estimates of the total sediment and its organic and inorganic matter content in temporary and permanent wetlands varied. For total material accumulated, it is estimated that temporary wetlands accumulated between 0.84 - 13.74 kg m-2year-1 with a median of 5.43 kg m-2year-1 whereas permanent wetlands accumulated between 1.26 - 37.70 kg m-2year-1 with a median of

4.13 kg m-2year-1. Organic matter accumulation in sediment traps also varied between wetland type: temporary wetlands accumulated between 0.33 - 2.95 kg m-2year-1 with a median of 1.11 kg m-2year-1 whereas permanent wetlands accumulated between 0.34 - 5.69 kg m-2year-1 with a median of 0.86 kg m-2year-1. Inorganic matter accumulation also varied with wetland type, and was estimated at between 0.52 - 12.31 kg m-2year-1 with a median of

3.99 kg m-2year-1 for temporary wetlands, and between 0.92 - 32.01 kg m-2year-1 with a median of 0.86 kg m-2year-1 for permanent wetlands.

3.3.2 Effect of hydroperiod on the sediment trap macroinvertebrate remains abundance, taxonomic richness and assemblage composition.

A total of 4,012 identifiable macroinvertebrate remains, representing 132 genera, were collected in the sediment traps. Of these, 1,447 (36%) were collected in temporary and 2,565

(64%) were collected in permanent wetlands. Macroinvertebrate remains commonly collected belonged to the orders Diptera, Coleoptera, Hymenoptera T, Acarina and Hygrophila. Diptera were the most frequently collected remain in both temporary and permanent wetlands, representing >60% of the total macroinvertebrate remains collected in this study. Of the 132 genera identified from the remains, 100 were collected in temporary, whereas 77 were collected in permanent wetlands. Fifty-five genera were collected only from temporary wetlands, whereas 32 genera were collected only from permanent wetlands.

The total abundance of macroinvertebrate remains collected in sediment traps ranged from 92

- 363 with a median of 237.5 subfossils in permanent wetlands, compared to 63 - 286 with a median of 100.5 in temporary systems (Figure 3.4a). When compared, there was a significant difference in macroinvertebrate remains abundance in temporary and permanent wetlands (W

= 117, df 23, P<0.01).

Order richness in temporary wetlands ranged from 5 - 12 with a median of 9, whereas permanent wetlands ranged from 5 - 9 with a median of 7 (Figure 3.4b), and when compared, were not significantly different (W = 45.5, df 23, P>0.05).

The macroinvertebrate genera richness in temporary wetlands ranged from 24 - 44 with a median of 29, whereas permanent wetlands ranged from 19 - 36 with a median of 27 (Figure

3.4c), and were not significantly different (W = 30.5, df 23, P>0.05).

Figure 3.4. Boxplots comparing: a) Remains total abundance; b) Order richness; and c) Genus richness in temporary and permanent wetlands on the Ovens River floodplain. Blue denotes permanent wetlands, red denotes temporary wetlands. Note variable y-axis scale.

Macroinvertebrates from 18 orders contributed to the remains composition collected in temporary wetlands, compared to 13 orders in permanent wetlands (Table 3.1). Diptera remains, the dominant remains type collected, comprised 38.63% of the temporary composition, compared to 76.26% in permanent wetlands. Coleoptera comprised 19.70% of the temporary wetland remains composition, compared to 5.98% in permanent wetlands.

Acarina remains were similar in both wetland types and comprised 12.44% and 8.61% of the trap remains collected in temporary and permanent wetlands, respectively. Hymenoptera T remains comprised 17.14% of the trap remains collected in temporary wetlands, compared to

0.47% in permanent wetlands. For temporary wetlands, the five most abundant orders

87 collected were Diptera, Coleoptera, Hymenoptera T, Acariformes and Hygrophila and accounted for 92.4% of the composition of the trap remains, compared to permanent wetlands, where Diptera, Acariformes, Coleoptera, Hygrophila and Hemiptera accounted for

97.5% of the composition of the trap remains.

Table 3.1. Breakdown by Order of total abundances and composition (%) of macroinvertebrate remains extracted from sediment traps in temporary and permanent wetlands.

Temporary Permanent Order Total Composition % Order Total Composition % Diptera 559 38.63 Diptera 1956 76.26 Coleoptera 285 19.7 Acariformes 222 8.65 Hymenoptera T 248 17.14 Coleoptera 151 5.89 Acariformes 180 12.44 Hygrophila 131 5.11 Hygrophila 65 4.49 Hemiptera 41 1.6 Coleoptera T 36 2.49 Trichoptera 31 1.21 Hemiptera 24 1.66 Odonata 12 0.47 Podocopida 11 0.76 Hymenoptera T 12 0.47 Blattodea T 11 0.76 Unionida 3 0.12 Odonata 6 0.41 Orthoptera T 2 0.08 Orthoptera T 5 0.35 Diptera T 2 0.08 Dermaptera T 5 0.35 Decapoda 1 0.04 Anomopoda 4 0.28 Coleoptera T 1 0.04 Diptera T 3 0.21 Podocopida 0 0 Hemiptera T 2 0.14 Spinicaudata 0 0 Spinicaudata 1 0.07 Anomopoda 0 0 Araneae 1 0.07 Araneae 0 0 Isopoda T 1 0.07 Hemiptera T 0 0 Trichoptera 0 0 Blattodea T 0 0 Unionida 0 0 Isopoda T 0 0 Decapoda 0 0 Dermaptera T 0 0 T Terrestrial Orders/Genera

At the order level, there was no significant difference in the abundance of the 14 orders collected in temporary and permanent wetlands: Odonata, Hygrophila, Unionida, Decapoda,

T T Podocopida, Spinicaudata, Anomopoda, Acariformes, Araneae, Orthoptera , Hemiptera ,

T T T Diptera , Isopoda and Dermaptera (P>0.05) (Figure 3.5, Table 3.2). However, there were

88 significant differences for 7 orders. The orders Diptera and Trichoptera were collected in significantly greater abundances in permanent wetlands compared to temporary wetlands, whereas Coleoptera, Hemiptera, Hymenoptera T, Coleoptera T and Blattodea T were collected in significantly greater abundances in temporary wetlands (all P<0.001, except Hemiptera,

P<0.05).

Figure 3.5. Macroinvertebrate Order level boxplots comparing temporary and permanent wetland trap remains abundances on the Ovens River floodplain: a) Diptera; b) Coleoptera; c) Acariformes; d) Hymenoptera T; e) Hygrophila; f) Hemiptera; g) Coleoptera T ; h) T T T Trichoptera; i) Odonata; j) Podocopida; k) Blattodea ; l) Orthoptera ; m) Diptera ; n) T T Dermaptera ; o) Anomopoda; p) Unionida; q) Hemiptera ; r) Decapoda; s) Spinicaudata; t) T Araneae; and u) Isopoda . Blue denotes permanent wetlands, red denotes temporary wetlands. Note variable y-axis scale. T refers to Terrestrial Orders/Genera.

Table 3.2. Results of Wilcoxon t test comparing total macroinvertebrate remains Order abundances for temporary and permanent wetlands on the Ovens River floodplain, df=23.

Order W P value Significance Diptera 131 0.00073 *** Coleoptera 25.5 0.007831 *** Hemiptera 109 0.02589 * Odonata 87 0.3452 NS Trichoptera 120 0.001046 *** Hygrophila (both) 62.5 0.6022 NS Unionida 90 0.07802 NS Decapoda 78 0.3593 NS Podocopida 60 0.1662 NS Spinicaudata 66 0.3593 NS Anomopoda 54 0.07861 NS Acariformes (both) 86 0.4352 NS Araneae (both) 66 0.3593 NS Hymenoptera T 0 3.10E-05 *** Coleoptera T 14 0.000286 *** Orthoptera T 55.5 0.1924 NS Hemiptera T 60 0.1658 NS Blattodea T 36 0.006947 *** Diptera T 66 0.652 NS Isopoda T 66 0.3593 NS Dermaptera T 48 0.0363 NS T Terrestrial Orders/Genera Asterisks show level of significance: NS, not significant; *P<0.05; **P<0.01; ***P<0.001.

Non-metric multidimensional scaling (NMDS) of macroinvertebrate remains abundance and presence/absence data sets for the sediment traps showed separation based on wetland type

(Figure 3.6a & b). Of interest is the temporary wetland T10 (red triangle, far left in Figure

3.6a & b) that showed a close affinity to the permanent wetlands based on both data sets. T10 had the longest hydroperiod of the temporary wetlands examined, with water present for 10 months (Chapter 2).

The orders Diptera and Coleoptera were abundant, diverse, preserved well and were explored individually. Diptera composition again separated based on wetland type, with separation

91 seen on the x-axis for abundance (Figure 3.6c) and presence/absence (Figure 3.6d).

Coleoptera showed a similar separation for the abundance (Figure 3.6e) and presence/absence data (Figure 3.6f).

Figure 3.6. NMDS ordinations of abundance log10(x+1) and Presence/Absence (P/A) data: a) All Genera abundance log10(x+1); b) All Genera P/A; c) Diptera abundance log10(x+1); d) Diptera P/A; e) Coleoptera abundance log10(x+1); and f) Coleoptera P/A. Note: Temporary wetland T10 is the red triangle in Figure 3.6a & b which showed closer affinity to permanent wetlands. Blue denotes permanent wetlands, red denotes temporary wetlands.

PERMANOVA analysis confirmed that wetland type had a highly significant effect on the macroinvertebrate assemblages found at the All genera, Diptera only and Coleoptera only levels (P<0.0001, and Monte Carlo values of 0.0001, Table 3.3).

Table 3.3. Results from PERMANOVA (perm) and Monte Carlo (MC) analysis comparing the effect of wetland type at the All Genera, Diptera only and Coleoptera only assemblages for both the abundance and presence/absence data sets.

Genera Data Source Df MS Pseudo-F P(perm) P(MC) All Genera log10(x+1) Wetland type 1 10230.00 10.40 0.0001 0.0001 Residual 22 984.15 Total 23 P/A Wetland type 1 10763.00 5.20 0.0001 0.0001 Residual 22 2071.50 Total 23

Diptera only log10(x+1) Wetland type 1 9230.40 12.93 0.0001 0.0001 Residual 22 713.91 Total 23 P/A Wetland type 1 9008.40 5.20 0.0001 0.0001 Residual 22 1301.90 Total 23

Coleoptera only log10(x+1) Wetland type 1 8407.40 5.81 0.0001 0.0001 Residual 22 1447.10 Total 23 P/A Wetland type 1 10868.00 4.01 0.0001 0.0002 Residual 22 2712.30 Total 23

3.3.3 Indicator Genera of wetland hydroperiod

SIMPER analysis undertaken on the abundance and presence/absence data sets calculated the percentage contribution of each order to the dissimilarity between temporary and permanent wetlands (Table 3.4). For both data sets, Diptera was the main driver of the assemblage dissimilarity between temporary and permanent wetlands accounting for 43.77 and 34.89% of the abundance and presence/absence data, respectively. Coleoptera accounted for a further

18.66% in the abundance data and 22.56% for presence/absence, and Hymenoptera T accounted for 10.88 and 8.75% of the dissimilarity between wetland types, respectively.

Combined, these 3 orders (Diptera, Coleoptera and Hymenoptera T) accounted for 73.31 and

66.02% of the dissimilarity between the assemblages of temporary and permanent wetlands.

Table 3.4. Dissimilarity (%) between temporary and permanent wetlands due to individual Orders based on SIMPER analysis of log10(x+1) abundance and the presence/absence data sets and the number of Genera identified within each Order.

Log10(x+1) data P/A data Contribution No. of Contribution Order Order % Genera % Diptera 43.77 36 Diptera 34.89 Coleoptera 18.66 29 Coleoptera 22.56 Hymenoptera T 10.88 9 Hymenoptera T 8.57 Hygrophila 6.15 9 Hemiptera 7.22 Hemiptera 5.29 12 Coleoptera T 6.88 Coleoptera T 4.36 13 Hygrophila 6.72 Trichoptera 1.97 1 Odonata 2.33 Acariformes 1.95 2 Trichoptera 1.93 Odonata 1.63 3 Blattodea T 1.88 Blattodea T 1.23 4 Orthoptera T 1.23 Orthoptera T 0.74 2 Diptera T 1.08 Diptera T 0.6 2 Dermaptera T 0.86 Dermaptera T 0.53 1 Unionida 0.76 Podocopida 0.52 1 Anomopoda T 0.73 Anomopoda 0.47 1 Hemiptera T 0.5 Unionida 0.42 1 Acariformes 0.47 Hemiptera T 0.27 1 Podocopida 0.46 Isopoda T 0.15 1 Isopoda T 0.27 Araneae 0.13 1 Araneae 0.24 Decapoda 0.12 1 Decapoda 0.24 Spinicaudata 0.12 1 Spinicaudata 0.21 T Terrestrial Orders/Genera

Some 86 genera showed a unique habitat preference based on wetland type and, of these, 55 only occurred in temporary wetlands compared to 31 in permanent wetlands (Tables 3.5 and

3.6). Unique genera of temporary wetlands were derived from 16 orders with aquatic and terrestrial origins compared to 8 orders, all with aquatic origins, in permanent wetlands.

Table 3.5. Number of indicator Genera identified within each Order from remains collected from temporary and permanent wetlands on the Ovens River floodplain.

Wetland Orders Temporary Permanent Diptera 6 13 Coleoptera 13 6 Hemiptera 1 7 Hygrophila 4 1 Podocopida 1 - Spinicaudata 1 - Anomopoda 1 - Acariformes 1 - Araneae 1 - Odonata - 1 Trichoptera - 1 Unionida - 1 Decapoda - 1 Hymenoptera T 6 - Coleoptera T 12 - Hemiptera T 1 - Blattodea T 4 - Diptera T 1 - Isopoda T 1 - Dermaptera T 1 - T Terrestrial Orders/Genera

Table 3.6. Macroinvertebrate indicator Genera in each Order associated with temporary and permanent wetlands on the Ovens River floodplain, based on the remains recovered.

Wetland type Order Temporary Permanent Diptera Cladopelma - Cryptochironomus - Microchironomus - Microtendipes - Culex - Odontomyia - - Paracladopelma - Ablabesmyia - Coelopynia - Larsia - Paramerina - Procladius - Corynoneura - Paraborniella - Monopelopia - Riethia - Bezzia - Anopheles - Tipulidae Coleoptera Antiporus - Bidessini - Chostonectes - Erestes - Hyderodes - Hyphydrus - Lancetes - Megaporus - Necterosoma - Sternopriscus - Paracymus - Spercheus - Sclerocyphon - - Notomicrus - Hydraena - Chrysomelidae - Aulonogyrus - Onychonhydrus - Dytiscidae Hemiptera Agraptocorixa - - Microvelia - Naucoris

Wetland type Order Temporary Permanent - Plea - Sigara - Tenagogerris - Hydrometra - Diplonychus Hygrophila Gyraulus - Isidorella - Physastra - Segnitila - - Glyptophysa Podocopida Ostracoda - Spinicaudata Limnadopsis - Anomopoda Daphiniidae - Acariformes Piona - Araneae Lycosidae - Odonata - Hemianax Trichoptera - Oecetis Unionida - Velesunio Decapoda - Cherax Hymenoptera T Iridomyrmex - Myrmecia - Polyrhachis - Rhytidoponera - Sceliphron - Abispa - Coleoptera T Anoplognathus - Phyllotocus - Phoracantha - Coptocercus - Phoracantha - Paropsis - Megacephala - Scydmaenidae - Staphylinidae - Hetroceridae - Elateridae - Lamprima - Hemiptera T Psaltoda - Blattodea T Panesthia - Laxata - Ellipsidion - Coptotermes - Diptera T Cydistomyia - Isopoda T Porcellio -

Wetland type Order Temporary Permanent Dermaptera T Labidura - T Terrestrial Orders/Genera

3.3.4 Comparison of live and sediment trap macroinvertebrate assemblages

During the live macroinvertebrate sampling, a total of 167 genera were collected, with 148 collected in temporary compared to 129 in permanent wetlands. Of these, 38 genera were unique to temporary and 19 to permanent wetlands. In the sediment traps, 132 genera were collected with 100 derived from temporary and 77 from permanent wetlands and, of these, 55 and 31 genera were unique to temporary and permanent wetlands, respectively.

Overall, macroinvertebrates translated well from the live assemblage to the remains assemblage collected in the sediment traps. Macroinvertebrates that possess hard body parts, particularly from the orders Diptera, Coleoptera and Hygrophila, translated well from the live to the remains assemblages (Table 3.7). For example, for Diptera in temporary wetlands, 33 genera were collected during the live sampling and 23 were collected in the sediment trap sampling, and 23 genera were common to both sampling methods. In comparison, in permanent wetlands, 32 genera were collected during the live sampling and 30 were taken during the trap sampling and, of these, 28 were common to both sampling methods. The taxa

Nemertea, Nematoda, Nematomorpha, Turbellaria, Arhynchobdellida, Collembola T and

Lepidoptera, which lack hard body parts, were only collected by live sampling, and were not detected in sediment trap assemblages. Aquatic genera were most commonly collected by live sampling, with few terrestrial genera collected. In the sediment traps, aquatic genera again dominated, however, the richness of terrestrial genera, such as Coleoptera T,

Hymenoptera T and Blattodea T was higher compared to live macroinvertebrate sampling, particularly in temporary wetlands. For example, only 2 Coleoptera T genera were collected during the live sampling whereas 13 were collected in the sediment traps.

Table 3.7. Number of Genera collected during live and sediment trap sampling of macroinvertebrates in temporary and permanent wetlands on the Ovens River floodplain and the number of Genera common to both sampling methods.

Wetland type Temporary Permanent Sampling method Live Trap Shared Live Trap Shared Order Genera Genera Genera Genera Genera Genera Diptera 33 23 23 32 30 28 Coleoptera 31 23 20 17 16 11 Hemiptera 15 5 5 17 11 11 Ephemeroptera 3 0 0 3 0 0 Odonata 7 2 2 7 3 3 Trichoptera 3 0 0 6 1 1 Hygrophila 8 8 8 6 5 5 Unionida 0 0 0 1 1 1 Decapoda 4 0 0 3 1 1 Podocopida 1 1 1 0 0 0 Spinicaudata 1 1 1 0 0 0 Anomopoda 1 1 1 1 0 0 Acariformes 9 2 2 10 1 1 Lepidoptera 1 0 0 2 0 0 Araneae 3 1 1 3 0 0 Nemertea 1 0 0 1 0 0 Nematoda 1 0 0 0 0 0 Nematomorpha 1 0 0 0 0 0 Turbellaria 1 0 0 1 0 0 Arhynchobdellida 1 0 0 1 0 0 Collembola T 4 0 0 1 0 0 Hymenoptera T 7 9 6 5 3 3 Coleoptera T 3 13 2 3 1 1 Orthoptera T 2 2 2 3 2 2 Hemiptera T 0 1 0 0 0 0 Mantodea T 0 0 0 0 0 0 Blattodea T 0 4 0 0 0 0 Diptera T 1 2 0 2 1 1 Isopoda T 1 1 1 0 0 0 Amphipoda T 1 0 0 1 0 0 Scolopendromorpha T 1 0 0 0 0 0 Scutigeromorpha T 0 0 0 0 0 0 Julida T 1 0 0 1 0 0 Dermaptera T 1 1 1 1 0 0 Haplotaxida T 1 0 0 1 0 0 T Terrestrial Orders/Genera

For the temporary wetlands, 22 indicator genera were common to both sampling methods and an additional 16, collected in the live sampling, were absent or not indicator genera based on the sediment trap sampling (Table 3.8). An additional 30 indicator genera identified in the sediment traps were either not collected or not indicator genera of hydroperiod, based on the live sampling.

For permanent wetlands, 8 indicator genera were collected during both live and sediment trap sampling (Table 3.8). An additional 11 genera, identified as indicator genera during live sampling, were not collected or not indicator genera of hydroperiod, based on sediment trap sampling. Some 23 new indicator genera identified from sediment trap sampling were not collected, or not indicator Genera of hydroperiod, based on the live sampling.

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Table 3.8. Occurrence of indicator Genera (I) based on live and sediment trap sampling of macroinvertebrates in temporary and permanent wetlands. L = Live and T = Sediment trap sampling while B indicates the presence of indicator Genera common to both sampling methods (live and trap). Occurrence = the total number of wetlands of each type where the Genera were collected.

Sampling Indicator Sampling Indicator method occurrence method occurrence Temporary Indicator Genera L T I Permanent Indicator Genera L T I Diptera Culex 1 T Diptera Ablabesmyia 7 6 B

Cladopelma 10 6 B Anopheles 1 T

Cryptochironomus 10 7 B Bezzia 1 T

Microchironomus 11 7 B Coelopynia 2 T

Microtendipes 11 8 B Corynoneura 1 T Odontomyia 2 T Larsia 7 T Coleoptera Antiporus 10 2 B Monopelopia 6 3 B Bidessini 6 2 B Paraborniella 2 T Chostonectes 5 2 B Paracladopelma 10 11 B Enochrus 5 1 B Paramerina 3 T Erestes 10 5 B Procladius 9 2 B Helochares 7 L Riethia 1 T Hyderodes 1 T Tipulidae 1 T Hydraena 1 L Coleoptera Aulonogyrus 3 T

Hyphydrus 4 2 B Dytiscidae 3 T

Lancetes 8 7 B Chrysomelidae 3 T

Limnoxenus 3 L Hydraena 4 T

Megaporus 7 3 B Notomicrus 1 T

Necterosoma 8 2 B Onychonhydrus 2 T Paracymus 1 T Hemiptera Diplonychus 7 1 B Spercheus 5 2 B Hydrometra 2 T Sternopriscus 2 9 B Merragata 5 L Sclerocyphon 1 T Microvelia 2 T Odonata Xanthagrion 4 L Naucoris 1 T Hemiptera Agraptocorixa 2 T Plea 1 T Hygrophila Gyraulus 3 T Sigara 5 T Isidorella 10 1 B Tenagogerris 1 T Physastra 11 1 B Odonata Hemianax 2 T Segnitila 11 2 B Rhadinosticta 6 L Decapoda Macrobrachium 3 L Trichoptera Anisocertropus 9 L

Podocopida Ostracoda 11 2 B Oecetis 3 8 B

Spinicaudata Limnadopsis 9 1 B Triaenodes 6 L Anomopoda Daphiniidae 3 T Hygrophila Glyptophysa 10 1 B Acariformes Acercella 10 L Unionida Velesunio 7 3 B

Hydrachna 7 L Decapoda Cherax 1 T

Neumania 8 L Acariformes Halotydeus 2 L

Piona 2 T Limnochares 8 L

Araneae Lycosidae 1 T Sigthoria 5 L T Collembola Entomobryidae 3 L Unionicola 3 L

Hypogastruridae 4 L Lepidoptera Lepidoptera 4 L T Sminthuridae 2 L Orthoptera Torbia 1 L T T Hymenoptera Abispa 2 2 B Diptera Muscidae 2 L Iridomyrmex 6 T Myrmecia 1 T Polyrhachis 2 T Rhytidoponera 2 2 B

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Sampling Indicator Sampling Indicator method occurrence method occurrence Temporary Indicator Genera L T I Permanent Indicator Genera L T I Sceliphron 2 T T Coleoptera Anoplognathus 5 T Coptocercus 2 T Elateridae 2 T Hetroceridae 3 T Lamprima 1 T Megacephala 2 T Paropsis 1 T Phoracantha 1 T Phyllotocus 1 T Scydmaenidae 1 T Staphylinidae 3 T T Hemiptera Psaltoda 2 T T Blattodea Coptotermes 5 T Ellipsidion 1 T

Laxata 1 T

Panesthia 1 T T Isopoda Porcellio 2 1 B T Scolopendromorpha Cormocephalus 2 L Nematoda Nematode 3 L Nematomorpha Nematomorpha 4 L T Dermaptera Labidura 4 T T Diptera Cydistomyia 1 T T Terrestrial Orders/Genera

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The macroinvertebrate assemblages collected during the live and sediment trap sampling were compared via NMDS ordinations using the presence/absence data sets only (Figure 3.7).

At the All genera level, macroinvertebrate assemblages showed clear separation based on wetland type on the y-axis, while on the x-axis separation based on the sampling method was apparent (Figure 3.7a). Ordination indicates that it is possible to distinguish wetland type using live and sediment trap remains of macroinvertebrates and that the assemblage collected during live sampling differs to that associated with the sediment trap remains sampling.

Diptera only and Coleoptera only ordinations both showed separation based on wetland type, although the separation was not as clear for the All genera data (Figure 3.7b & c). Wetland type separated out on the x-axis for Diptera only whereas Coleoptera only separated on the y- axis. For both the Diptera and Coleoptera only assemblages, the live macroinvertebrate assemblages showed more similarity, whereas the remains assemblages collected in the sediment traps were more variable. A comparison of sampling methods (live vs trap) for

Diptera only and Coleoptera only both showed separation based on method, with some mixing, indicating that there was some similarity between the assemblages collected using the different sampling methods.

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Figure 3.7. NMDS ordinations comparing wetland type, temporary (red) and permanent (blue), and sampling method (live solid/trap outline) macroinvertebrate assemblages for Presence/Absence data: a) All Genera; b) Diptera only; and c) Coleoptera only.

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The effects of wetland type (temporary vs permanent) and sampling method (live vs trap) on macroinvertebrate assemblages collected were investigated further via PERMANOVA and

Monte Carlo analysis. Analyses indicated the wetland type, sampling method, and their interaction all had a significant effect on the macroinvertebrate assemblages collected (Table

3.9). For All genera, the sampling method explained most of the variation in the macroinvertebrate assemblages, followed by wetland type. For Diptera and Coleoptera only, wetland type accounted for most of the variation followed by the sampling method. For All genera and for Diptera and Coleoptera only, the wetland type × sampling method interaction was significant and contributed to the assemblage differences. However, its effect was weaker than the individual effects of wetland type and sampling method, implying it is not the main driver of the assemblage differences seen.

Table 3.9. PERMANOVA (perm) and Monte Carlo (MC) analysis comparing the effect of wetland type (temporary and permanent) on the Ovens River floodplain and sampling method (live, sediment trap) and wetland type × sampling method interaction on the presence/absence of macroinvertebrate assemblages.

Genera Source df SS MS Pseudo-F P(perm) P(MC) All Genera Wetland type 1 16766.0 16766.0 10.36 0.0001 0.0001 Sampling method 1 26686.0 26686.0 16.49 0.0001 0.0001 Wetland type × Sampling method 1 6407.3 6407.3 3.96 0.0001 0.0001 Residual 43 69579.0 1618.1 Total 46 119360.0

Diptera only Wetland type 1 18610.0 18610.0 21.68 0.0001 0.0001 Sampling method 1 6842.6 6842.6 7.97 0.0001 0.0001 Wetland type × Sampling method 1 2948.3 2948.3 3.43 0.0008 0.0021 Residual 43 36917.0 858.5 Total 46 65251.0

Coleoptera only Wetland type 1 21254.0 21254.0 9.19 0.0001 0.0001 Sampling method 1 13786.0 13786.0 5.96 0.0001 0.0001 Wetland type × Sampling method 1 6190.8 6190.8 2.68 0.0013 0.0023 Residual 43 99410.0 2311.9 Total 46 140450.0

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3.4 Discussion

3.4.1 Determine the effect of hydroperiod on sedimentation rates of organic and inorganic matter in floodplain wetlands.

In the present study, the volume of material accumulating in temporary and permanent wetlands was not significantly different. Both wetland types are major sinks for organic and inorganic material on the Ovens River floodplain, confirming the findings of previous studies

(Craft & Casey, 2000; Gell et al., 2009; Noe & Hupp, 2009). The vertical accumulation rate of sediment in the current study was estimated at 3.60 and 2.80 mm per year in temporary and permanent wetlands, respectively, indicating that both wetland types are infilling with sediment at a similar rate. Previous studies into sediment accumulation in Australian wetlands have shown that the wetlands are always gaining new material (Finlayson et al.,

2013) and that, historically, sedimentation rates were low (Gell et al., 2009), approximately

0.1 - 1 mm.year-1 (Gell et al., 2006). The sedimentation rates recorded in the present study were nearly 3 - 4 times higher than the maximum pre-European historical rate. Sedimentation rates have seen an increase of up to 10 - 30 mm.year-1 due to the effects of catchment disturbance and soil erosion associated with non-indigenous agricultural practices over the last 200 years (Gell et al., 2006; Gell & Reid, 2014).

A sediment budget of the Ovens River catchment revealed that 78 kt year-1 of suspended material is exported, and that 13% is deposited on the floodplain (De Rose et al., 2005). This may account for the high accumulation rates recorded in the sediment traps. Sedimentation is recognised as a major cause of wetland degradation (Luo, Smith, Allen, & Haukos, 1997;

Zedler & Kercher, 2005), and threatens the ability of wetlands to store and hold water (Luo et al., 1997) potentially altering wetland hydrology, volume, and hydroperiod length (Flower et al., 2009; Gleason & Euliss, 1998).

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Deposition of material from the water column is dependent on a combination of factors, including the physical characteristics of the waterbody and its surrounding environment, particle properties (e.g. size, weight, texture) and the effect of time (Boto & Patrick, 1979;

Braskerud, 2001; Fennessy et al., 1994; Settlemyre & Gardner, 1977). In the process of sedimentation in the present study, temporary and permanent wetlands collected significantly different rates of macroinvertebrate remains. Temporary wetlands collected a median of 0.57 subfossils per cm2, compared to 1.34 remains per cm2 in permanent wetlands. Currently, little is known about the drivers affecting the accumulation of macroinvertebrate remains and this is recognised as a major knowledge gap in palaeoecology, requiring future work (Smol et al.,

2001). Factors, such as live macroinvertebrate abundances, the number of generations possible due to hydroperiod, taphonomic processes and preservation conditions would all influence the accumulation of remains in wetlands.

3.4.2 Determine the effect of hydroperiod on the abundance, taxonomic richness and assemblage composition of macroinvertebrates that accumulate in the sedimentation process of floodplain wetlands

There were significantly more macroinvertebrate remains in the traps of permanent wetlands compared to temporary wetlands on the Ovens River floodplain in the present study.

Hydroperiod is known to influence the number of macroinvertebrate generations per year

(Armitage et al., 2012; Tokeshi, 1995): temporary systems are limited by water availability, while permanent systems can potentially support more generations, resulting in greater abundances of remains accumulating. Variable preservation conditions in temporary and permanent wetlands may potentially explain the differences in the abundance of remains found. The wetting and drying phase in temporary wetlands is known to increase decomposition of organic matter (Neckles & Neill, 1994; Reddy & Patrick, 1975; Swift,

Heal, & Anderson, 1979), and that decomposition is limited in permanent waterlogged conditions (Van Bodegom, Broekman, Van Dijk, Bakker, & Aerts, 2005). Further, the

107 sediment and the sediment-water interface of permanent waterbodies are known to become anoxic (Boulton et al., 2014), potentially aiding in the preservation and accumulation of remains. The abundance of macroinvertebrate remains collected in wetlands is a balance between the inputs seen in Chapter 2 and the taphonomic processes and conditions influencing their decomposition and preservation. Factors, including the relative abundance of live macroinvertebrates, the presence of hard or soft body parts, and potential differences in preservation conditions would influence the abundance of remains in temporary and permanent wetlands.

Overall, there was no significant difference in macroinvertebrate remains richness at order and genus level in sediment traps in temporary and permanent wetlands. Both temporary and permanent wetlands were rich in macroinvertebrates; the diversity reflects the different underlying features of temporary and permanent systems’ hydroperiods. Generally, for live macroinvertebrates, higher richness and diversity are associated with permanent systems and are thought to be positively correlated with the length of the hydroperiod allowing for a greater chance of colonisation (Florencio et al., 2009; Schneider & Frost, 1996; Waterkeyn et al., 2008). However, temporary wetlands are also known to have high macroinvertebrate richness, as many genera have adapted to conditions only found within them (Williams, 1997,

2006). In Australia, most floodplain wetlands are temporary in nature due to the aridity and variability of the climate (Jenkins et al., 2005). Selected macroinvertebrate fauna of floodplain wetlands have adapted to life in different conditions (temporary and permanent) and this potentially explains why both systems are rich in remains.

The five most abundant orders collected in temporary wetland sediment traps were Diptera,

Coleoptera, Hymenoptera T, Acariformes and Hygrophila, whereas in permanent wetlands,

Diptera, Acariformes, Coleoptera, Hygrophila and Hemiptera dominated. A common feature of these orders is that individuals all have hard body parts, or protective shells, likely to

108 preserve and accumulate. In both temporary and permanent wetlands, Diptera remains were the most common subfossil collected, and represented 38.63 and 76.26% of the composition, respectively. Diptera was also the most abundant order collected during the live sampling

(Chapter 2). Aquatic Diptera are known to be highly abundant and diverse (Armitage et al.,

2012), with a high preservation potential; many genera within the order (e.g. chironomids) have larvae with chitinised head capsules which are known to preserve and accumulate (Heiri et al., 2003). Compositional differences between wetland types may be related to hydroperiod limiting the number of generations possible. For example, within the order Diptera, the chironomids have short lifecycles, high turnover rates and fecundity and can produce multiple generations per year, depending on conditions (Armitage et al., 2012; Tokeshi,

1995).

In the present study, Coleoptera represented 19.70 and 5.98% of the subfossils collected in temporary and permanent wetlands, respectively, and they also have a high preservation potential due to chitinised and sclerotinised body parts (Erickson, 1988; Smith, 2000).

Coleopterans were collected in higher abundances and richness in temporary than permanent wetlands during the live sampling (Chapter 2) and this may account for the compositional differences seen in the sediment traps during this study.

The terrestrial order Hymenoptera T represented 17.14 and 0.47% of the macroinvertebrate remains collected from temporary and permanent wetlands, respectively, in the present study.

Hymenoptera T were not abundant in the live macroinvertebrate samples (Chapter 2).

Remains in this order were predominately from ants, which have chitinous head capsules

(Hölldobler & Wilson, 1990; Peeters, Molet, Lin, & Billen, 2017). The large compositional difference between temporary and permanent wetlands is most likely related to the effect of hydroperiod and the drying of the temporary wetlands. Ants are opportunistic, utilising and inhabiting floodplains and temporary wetlands during the dry terrestrial phase (Ballinger,

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Lake, & Mac Nally, 2007; Ballinger, Mac Nally, & Lake, 2005; Mertl, Ryder Wilkie, &

Traniello, 2009), and are then potentially trapped and killed when inundation occurs.

The assemblages of macroinvertebrate trap remains collected in temporary and permanent wetlands on the Ovens River floodplain were significantly different and reflect the assemblage differences seen during the live sampling (Chapter 2). The findings of the present study support those of others who have found the live assemblages in temporary waterbodies differ from those of permanent waters (Sanderson et al., 2005; Williams, 1997, 2006). This study also showed that the differences in the live macroinvertebrate assemblages of temporary and permanent wetlands translated to the remains death assemblages collected in sediment traps in the wetlands.

Sediment traps in temporary and permanent wetlands were shown to have different macroinvertebrate assemblages. In the present study, some macroinvertebrates (e.g.

Podocopida, Spinicaudata) were only found in temporary wetlands whereas others (e.g.

Trichoptera, Unionida) only occurred in permanent wetlands. Hydroperiod is known to influence which macroinvertebrates survive, reproduce and persist in different waterbodies

(Williams, 1997). Many macroinvertebrates have adapted to life in waterbodies with different hydroperiods (Williams, 2006). Typically, the genera associated and adapted to life in temporary systems often have short lifecycles, desiccation resistant eggs, a diapause phase and active dispersal capabilities, while those found in permanent waters are often larger, slower to develop and often lack the ability to survive and recover after drying (Williams,

2006).

3.4.3 Identify indicator taxa of wetland hydroperiod type (temporary/permanent)

In the present study, many macroinvertebrate genera were common to both temporary and permanent wetlands whereas others were restricted to a single wetland type. Sediment trap

110 sampling revealed that 86 genera demonstrated habitat preference based on wetland type: 55 genera only occurred in temporary wetlands whereas 31 genera were only associated with permanent wetlands. Unique genera of temporary wetlands were derived from 16 orders, compared to 8 orders in permanent wetlands. The indicator orders/genera of temporary wetlands (e.g. aquatic orders Diptera, Coleoptera, Hemiptera, Hygrophila, Podocopida,

Spinicaudata, Anomopoda, Acariformes, and Araneae, and terrestrial orders Hymenoptera T,

Coleoptera T, Hemiptera T, Blattodea T, Diptera T, Isopoda T and Dermaptera T) have aquatic and terrestrial origins whereas the indicators for permanent wetlands (e.g. Diptera,

Coleoptera, Hemiptera, Odonata, Trichoptera, Hygrophila, Unionida and Decapoda) were solely of aquatic origin. While temporary wetlands act as both aquatic and terrestrial environments, there is potential for macroinvertebrate remains from both systems being incorporated into the traps. As permanent wetlands always contain water, it is less likely that terrestrial macroinvertebrates utilise these environments. Additionally, flooding of temporary wetlands would also result in the displacement and potential death of many terrestrial macroinvertebrates which then settle out of the water column, and accumulate.

The identification of these indicator genera suggests that the hydroperiod influences the macroinvertebrates associated with temporary and permanent wetlands on the Ovens River floodplain and that there is potential to determine wetland hydroperiod based on the macroinvertebrates recovered in either live sampling or sediment trapping.

3.4.4 Comparison of sediment trap assemblages to live macroinvertebrate assemblages collected in Chapter 2

Sediment traps collected fewer genera than the live sampling in the present study as the soft- bodied organisms did not preserve. During live macroinvertebrate sampling, a total of 167 genera were collected, with 148 in temporary wetlands, and 129 in permanent wetlands. Of

111 these, 38 genera were unique to temporary wetlands whereas 19 were unique to permanent wetlands. In the sediment trap sampling, a total of 132 genera were collected, with 100 from temporary wetlands and 77 from permanent wetlands, of which 55 were unique to temporary and 31 unique to permanent wetlands, respectively. The orders Diptera, Coleoptera and

Hygrophila translated well from the live to the sediment trap sampling, however, Collembola

T, Lepidoptera, Ephemeroptera, Amphipoda, Nemertea, Nematode, Nematomorpha and

Turbellaria, collected during live sampling, failed to accumulate in the sediment traps.

Transition from live sampling to the death assemblage in the sediment traps is heavily dependent on the presence of hardened body parts (e.g. head capsules, wings, cases/shells), with good preservation potential.

In temporary wetlands, 148 genera were collected during live sampling, 100 genera were collected during trap sampling, of which 76 genera were common to both, whereas in permanent wetlands 129 were collected during live sampling, 76 genera were collected in trap sampling, of which 69 were common to both. Approximately 51.35 and 53.48% of the live macroinvertebrate assemblages translated to remains found in temporary and permanent wetlands, respectively. However, for orders with preservable body parts, the translation percentage was much higher. For example, Diptera in temporary wetlands, 33 and 23 genera were collected during live and trap sampling, respectively, of which 23 genera were common to both sampling methods. In comparison, in permanent wetlands, 32 and 30 genera were collected during the live and trap sampling respectively, of which 28 were common to both sampling methods. Approximately 69.69 and 87.5% of the Diptera genera translated from the live organisms to trap remains in temporary and permanent wetlands, respectively. A previous study by Van Hardenbroek et al. (2011) found similar translation rates of live chironomids to surface sediment subfossils. Coleoptera showed a similar trend, with 31 and

23 genera collected during live and trap sampling, respectively, for temporary wetlands, of

112 which 20 genera were common to both sampling methods. In comparison, in permanent wetlands, 17 and 16 genera were collected during the live and trap sampling, respectively, of which 11 were common to both sampling methods. Approximately 64.51 and 64.70% of

Coleoptera genera translated from live organisms to remains in temporary and permanent wetlands, respectively. Orders lacking preservable body parts did not translate well from live to sediment traps; e.g. Collembola T, 4 and 1 genera were collected in temporary and permanent wetlands, respectively, during live sampling, none of which translated to remains collected in the sediment traps. This illustrates the importance of preservable body parts and why some orders/genera preserve well, whereas others are lost (Frey, 1964; Rumes et al.,

2005; Smith et al., 2006; Smol et al., 2001; Van Hardenbroek et al., 2011).

Sediment traps generally collected fewer genera than live sampling, predominately due to the loss of soft-bodied genera. However, factors such as the trap design (trap size and trap placement) and macroinvertebrate lifecycles may also have an influence, as the traps used were biased to collect fall-out from the water column in the deepest point. Hence, benthic, sedentary, or edge-dwelling genera may be under-represented in the sediment traps. The placement of larger, or more traps, in different locations, may reduce bias. However, this would increase the costs involved. Trapping of remains is a cost-effective method of macroinvertebrate sampling, and despite the loss of soft-bodied genera, does not affect the potential to determine and distinguish wetland hydroperiod. Concentrating on orders with hard parts, such as Diptera and Coleoptera alone, also has the potential to be used to determine the hydroperiod of wetlands.

Both wetland type and sampling method had a significant effect on macroinvertebrate assemblages. At the All genera level, sampling method explained most of the variation in the assemblages, followed by wetland type, implying that the assemblages collected in the sediments traps differ from the live assemblages due to the loss of soft-bodied genera, or the

113 addition of new genera in sediment traps not present/collected during live sampling. The similarity in assemblages between the wetland types suggests that similar taphonomic processes occur in both temporary and permanent wetlands influencing the macroinvertebrate assemblages. For the Diptera and Coleoptera only assessments, wetland type explained most of the variation and suggests that hydroperiod influences the assemblages found regardless of the sampling method. The similarity between sampling methods demonstrates there is a good translation from the live to the sediment trap assemblage due to the presence of highly chitinous and sclerotised body parts.

Taphonomic processes within wetlands influence the macroinvertebrate remains which accumulate, and currently little is known about these processes in aquatic environments, including wetlands (Frey, 1964; Rumes et al., 2005; Smith et al., 2006; Van Hardenbroek et al., 2011). Insights from this study indicate that macroinvertebrate body structure strongly influences its occurrence as remains in sediment traps. Genera with hard body parts (e.g.

Diptera, Coleoptera) accumulated well in traps whereas soft-bodied genera lacking these parts (e.g. Collembola T), known to inhabit wetlands based on the live sampling, were absent from the sediment trap assemblages. Size and thickness of the remains also appears to influence their preservation potential; the most common remains were derived from small genera (e.g. Diptera, Hymenoptera T, Acarina) whereas remains from larger-bodied genera were uncommon (e.g. Odonata, Decapoda). Large remains may be prone to damage, movement, or are not resuspended and move centrally in wetlands, or lost due to taphonomic processes. Remains that are thin and easily damaged, or broken, may be under-represented, when compared with the living assemblage. For example, Hemiptera were abundant during live sampling (Chapter 2), however, they were not well represented in the trap remains assemblage.

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The relative abundance of an organism when alive also appears to influence its occurrence in traps. Chironomids were the most abundant live macroinvertebrate and the most abundant remains collected in the sediment traps. Organisms that are rare or uncommon when alive are less likely to be found even before the taphonomic processes begin (Van Hardenbroek et al.,

2011). The type of remains may also affect their accumulation and preservation, and bias interpretation. For example, macroinvertebrates undergoing numerous moults may be over- represented in the death assemblage. For Diptera, intact remains were rare, and were predominately head capsules derived from the death assemblage or instar moults.

Variations within genera can influence remains/subfossil accumulation and preservation

(Brooks, Langdon, & Heiri, 2007; Iovino, 1976; Walker, 1987). In this study, Diptera head capsules from Chironomidae preserved better than Orthocladiinae and Tanypodinae, which were prone to splitting. While not directly tested, basin morphology can also influence remains assemblages and taphonomy through controls on the physical processes which can lead to resuspension, transport, and re-deposition of remains (Eggermont, De Deyne, &

Verschuren, 2007; Heiri, 2004; Kurek & Cwynar, 2009; Larsen & MacDonald, 1993; Luoto,

2010, 2012; Van Hardenbroek et al., 2011; Walker, 1987). Previous work (Smith, 2012;

Smith et al., 2006) has suggested that variables such as insect size, morphology, and taxonomic group, and depositional factors, including environment type, bathymetry, and energy levels influence if, and how well, macroinvertebrates preserve.

Overall, in this study, there was a good translation from the live to the death assemblage. It is thought that most aquatic macroinvertebrate genera leave some morphologically identifiable remains in waterbody sediments (Frey, 1964). However, the death assemblage is heavily dependent on the macroinvertebrates present, the presence of hard/soft body parts and the taphonomic processes. How the live macroinvertebrate assemblage translates to its death assemblage is poorly understood and has received limited scientific study (Seddon et al.,

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2019). Previous studies have found a good translation from the live to the death assemblage remains of organisms with chitinous body parts (Rumes et al., 2005; Van Hardenbroek et al.,

2011).

Understanding the factors responsible for macroinvertebrate remains/subfossil preservation or loss, abundance, occurrence, and distribution is important to support the inferences made from palaeoecological and palaeolimnological studies (Sayer, Davidson, Jones, & Langdon,

2010). Detailed taphonomic studies on macroinvertebrates are needed to aid in the interpretation of palaeoecological records. Understanding the causes of potential bias is important for determining the limitations on the use of macroinvertebrate subfossil data, and for distinguishing between true and artificial patterns within the palaeoecological records.

3.5 Conclusion

The present study confirms that both temporary and permanent wetlands act as sediment sinks, collecting large volumes of organic and inorganic matter and macroinvertebrate remains. It also showed it is possible to distinguish the hydroperiod of a wetland based on the macroinvertebrate remains which accumulate in the sedimentation process. Many genera are not habitat-specific and occur in both wetland types; however, there are many that occur and survive only in temporary or permanent wetlands and their presence can be used as a indicator of wetland hydroperiod. Additionally, a large proportion of the live macroinvertebrate assemblage collected preserves and accumulates as remains in the sediment traps, and has the potential for incorporation into the surface sediment and the palaeoecological record of the wetlands. The differences in the assemblages of macroinvertebrate remains and identification of indicator genera suggests there is potential to determine wetland hydroperiod using either live or macroinvertebrate remains, and further

116 suggests, subfossils in sediments could possibly be used to reconstruct historical waterbody hydroperiods.

Chapter 4 explores the effects of hydroperiod on wetland macroinvertebrates by examining the top 20 mm of surface sediments in temporary and permanent wetlands. The impact of many years of accumulation of subfossils, the taphonomic decay process, multiple flooding/drying cycles, and variable environmental conditions on the macroinvertebrate assemblages present are assessed. The Chapter aims to continue with the exploration from live macroinvertebrate assemblages to remains assemblages (sediment traps), to surface sediment subfossils and their integration into the palaeoecological record of wetlands.

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Chapter 4: Effect of hydroperiod on the accumulation and persistence of macroinvertebrate subfossils in the surface sediments of floodplain wetlands

4.1 Introduction

Wetlands act as nature’s historian, archiving and recording the surrounding environment’s history within their sediments (Birks, Lotter, Juggins, & Smol, 2012; Smol et al., 2001). In the process of sedimentation, the remains of aquatic and terrestrial organisms accumulate in the surface sediments of waterbodies (Frey, 1964; Smol et al., 2001). These organic remains are a valuable source of information, providing evidence of the prevailing environmental conditions under which they were deposited, and are indicators of environmental processes and disturbances (Smol et al., 2001). Macroinvertebrates are often thought of as fragile and unlikely to preserve. However, the chitinous portions of the macroinvertebrate exoskeleton can be extremely strong and resistant to decay, and can preserve in high numbers and in excellent condition given suitable preservation conditions (Frey, 1964; Labandeira &

Sepkoski, 1993; Rasnitsyn & Quicke, 2007; Smol et al., 2001)

It is believed that the subfossil assemblages in surface sediments can provide a spatially- integrated and representative sample of the living assemblage that is better than live sampling of the water column, which only provides a snapshot in time (Birks et al., 2012). Surface sediments, usually the top 20 mm, represent years of accumulation, depending on sedimentation rates (Frey, 1964; Smol et al., 2001). Subfossils are the actual organic remains, or other evidence, such as nests of animals, that are not ancient enough to be considered true fossils but can neither be considered modern (Smol et al., 2001). The accumulation of macroinvertebrate subfossils is influenced by many processes and factors, including the organism itself, and the presence/absence of preservable body parts, depositional conditions, waterbody morphometry, transport, mixing, resuspension and the different types of

118 taphonomic losses (Behrensmeyer et al., 2000; Kidwell & Flessa, 1995; Rasnitsyn & Quicke,

2007).

As previously noted in Chapter 3, the incompleteness of the subfossil record has been appreciated for some time, but the nature of this incompleteness – i.e. what is present, what is missing, and why – is not adequately understood (Behrensmeyer et al., 2009; Kidwell &

Behrensmeyer, 1988; Rasnitsyn & Quicke, 2007; Smith et al., 2006). Understanding the biases in subfossil macroinvertebrate assemblages is critical for determining the limitations on the use of subfossil macroinvertebrate data, and for distinguishing between true patterns and artefacts in the palaeoecological record (Smith et al., 2006).

Palaeoecological studies have predominately focused on permanent waterbodies, such as lakes, which have relatively stable environments over interannual timeframes (Gandouin et al., 2005; Gandouin et al., 2006), however European and North American studies have detected drier phases within the last 12,000 years (Birks & Birks, 2006; Smol et al., 2001).

Historically, there has been a perception that sedimentary records from fluvial systems are unreliable, due to the dynamics of hydrology and the evidence that floodplain waterbodies are typically short-lived (Cooper & McHenry, 1989; Erskine et al., 1992; Rang & Schouten,

1989). However, floodplain wetlands can be sustained over a long period and have been shown to yield useful palaeoecological information (Amoros & Van Urk, 1989; Gell et al.,

2005; Michelutti et al., 2001; Schönfelder et al., 2002).

Comparisons of temporary and permanent wetlands in palaeoecological studies are rare, and therefore the effect hydroperiod has on the subfossil macroinvertebrates in the surface sediments of wetlands is largely unknown. In the previous two chapters, the effect of hydroperiod on the live macroinvertebrates and macroinvertebrate remains in sediment traps in temporary and permanent wetlands was examined, and significant differences in

119 abundance, richness, composition and the assemblages were identified. Importantly, consistent patterns in macroinvertebrate assemblage structure and indicator taxa were found that distinguished temporary from permanent wetlands in both live and sediment trap samples. The objective of the current chapter is to investigate if these patterns translate to the subfossil macroinvertebrates found in wetland surface sediments and, in particular, what influence hydroperiod has on this translation.

This chapter aims to:

1) Determine the effect of hydroperiod (temporary/permanent) on the abundance, taxonomic richness and assemblage composition of macroinvertebrates that accumulate in the surface sediments of temporary and permanent floodplain wetlands.

2) Identify indicator Genera of wetland hydroperiod based on subfossils found.

3) Compare macroinvertebrate assemblages collected during live sampling (Chapter 2), and the remains assemblage found in the sediment traps (Chapter 3) to those collected from wetland surface sediments to determine how the macroinvertebrate assemblage translates from the live, to remains and subfossil assemblages.

4.2 Methods

4.2.1 Field methods

A total of 24 wetlands on the lower Ovens River floodplain were sampled for surface sediment macroinvertebrate subfossils (12 temporary and 12 permanent) (Figure 4.1). Surface sediment sampling was undertaken in the same temporary and permanent wetlands used to assess the live macroinvertebrates in Chapter 2, and macroinvertebrate remains that accumulated in sediment traps in Chapter 3. Sampling was undertaken in June 2018, after sediment traps were removed from the permanent wetlands. At the time of sampling, all the

120 temporary wetlands were dry, whereas all the permanent wetlands contained water. Sediment sampling followed the same protocol used by Campbell et al. (2018) when they found significant differences in subfossil chironomid head capsules from temporary and permanent wetlands. This study continues that work by examining the full macroinvertebrate assemblage and comparing findings to the live and sediment trap remains assemblages.

Figure 4.1. Location of the 12 temporary and 12 permanent wetlands where surface sediments were collected on the Ovens River floodplain, South-Eastern Australia (temporary sites red, permanent sites blue).

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The top 20 mm of surface sediment in each wetland was sampled, as per similar studies

(Campbell et al., 2018; Gajewski, Bouchard, Wilson, Kurek, & Cwynar, 2005; Rees et al.,

2008); and the contents potentially represent 5 - 20 years of accumulation (Campbell et al.,

2018). Surface sediment samples were taken from the deepest point in each wetland, as studies indicate they provide an integrated sample of the whole waterbody assemblage

(Brodersen & Lindegaard, 1999; Campbell et al., 2018; Heiri, 2004; Real et al., 2000;

Schmäh, 1993). The deepest point was located visually in temporary systems, and by using a measuring rod in the permanent systems. A 2 m2 quadrat was established at the deepest point, and 10 cores (90 mm diameter × 20 mm deep) were taken randomly from within it.

Individual core samples had a volume of 119.71 cm3 (surface area 59.86 cm2, depth 2 cm), and a pooled volume of 1197.10 cm3. Disturbance to the surface sediment was kept to a minimum, and if snags, roots, or rocks were encountered, affecting the quality of the sample, the sample was discarded and resampled elsewhere within the quadrat. Surface sediment samples were collected using a 90 mm PVC pipe.

For temporary wetlands, the sampling device was pushed into the ground, and then a sharp knife was used to cut around the sampler. Excess soil was trimmed flush with the end of the device before the sediment was removed. The process was repeated 10 times for each wetland, and the 10 samples were then combined to create one large sample to represent each wetland site (Figures 4.2 and 4.3).

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Figure 4.2. Diagram and photo of coring device used to sample sediments from temporary wetlands.

Figure 4.3. Stages involved in the sampling of surface sediments of temporary wetlands: (a) Sampling device with hole in the upper surface to allow air to escape when pushed into the sediment; (b) Pushing the sampler into the dry sediment; (c) Cutting around the sampling device to facilitate sample removal; (d) Exposed sample with excess soil; (e) Excess soil removed with a knife level with the base of the sampling unit; (f) Example of intact sample removed from the sampling device; (g) Example of the 10 surface sediment cores used to make up a sample for each wetland.

For permanent wetlands, a different sampling technique was used. Sediments were collected using a 200 mm section of 90 mm PVC pipe with a purpose-made cap containing a one-way valve (Figures 4.4 and 4.5). The device was slowly pushed into the sediment to a depth of approximately 100 mm with the valve open, allowing the water to escape. The base of the valve was covered with fine mesh to prevent sediments/subfossils from being lost. The

123 sample was carefully lifted with a spade and the bottom covered with a modified end-cap to allow drainage. Upright, labelled wet cores were returned to the laboratory in their pipe sections and allowed to drain.

Figure 4.4. Diagram and photo of sampling device made to extract sediment cores from the permanent wetlands.

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Figure 4.5. Stages involved in the sampling of surface sediments of permanent wetlands: (a) Actual sampling device and push-stick used to remove samples from the tubes once collected; (b) Valve on top of the unit to allow water to escape as the unit was pushed into the wet sediment; (c) Wet sediment dried out in an oven to remove excess water; (d) Dried core after removal from the PVC sampler; (e) A sediment core showing the different strata present and the plastic base cap used to contain the wet sample in the tube at collection, and during transport; (f) Device used to hold the dry core to remove the top 20 mm of sediment; used to ensure a consistent sample depth; (g) Separation of the sample for extraction; and (h) Example of the 10 surface sediment cores used to make up a sample from each wetland.

4.2.2 Laboratory procedures

Since this study was comparing macroinvertebrate subfossils collected from wet and dry sediments, an unbiased method of sampling was required to obtain a standardised sediment core. The surface sediment in permanent wetlands was saturated with water and the top 20 mm of wet sediment had a different density to that of the dry, temporary wetlands. For uniformity, surface sediments from permanent wetlands were dried to approximately the same moisture content of the temporary cores by placing them (within the collection tube) in an oven at 40°C for approximately 5 h. Once dry, each core was sectioned and the top 20 mm removed for processing (Figure 4.5).

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The 10 pooled surface sediment samples for each wetland were placed in a bucket of warm water containing powdered sodium hexametaphosphate (water softener) and allowed to sit for

24 h, to help break up the soil particles. Sediment samples were then wet-sieved to remove particles greater than 106 µm, processed as in Chapter 3, and identified. Matter collected on the different sized sieves (10 mm, 5 mm, 2 mm, 1 mm, and 106 µm) was examined under a microscope, and the subfossils extracted.

Material collected on the 106 µm sieve consisted of a fine matrix of small remains, sediment, and organic material. These samples were processed further using the kerosene flotation method described by Rolland & Larocque (2007), and outlined in Chapter 3.

Macroinvertebrate subfossils were removed using fine dissecting forceps or a paint brush, examined under a dissecting light microscope (100x) and identified to genus level, where possible. Macroinvertebrates were identified using standard taxonomic keys and guides:

Diptera (Cranston, 1996, 2000; Madden, 2009; Webb et al., 2016); Coleoptera (Hangay &

Zborowski, 2010; Lawrence & Slipinski, 2013; Watts, 2002); Mollusca (Smith, 1979);

Acarina (Harvey, 1998; Harvey & Growns, 1998); Odonata (Theischinger & Hawking, 2003,

2006; Watson, 1991); Hymenoptera (Andersen, 1991; Shattuck, 2000); Orthoptera (Rentz,

2003, 2010); Blattodea (Rentz, 2014); Araneae (Whyte & Anderson, 2017); and macroinvertebrate guides (CSIRO, 1991; Gooderham & Tsyrlin, 2002). The online freshwater macroinvertebrate guide, produced by the Centre for Freshwater Ecosystems at La

Trobe University Australia, was also used. All aquatic and terrestrial macroinvertebrate subfossils recovered were identified. As some orders/genera have both aquatic and terrestrial forms, these were kept separate. Terrestrial macroinvertebrate orders/genera are denoted by a

T (e.g. Coleoptera T). Subfossils were also compared to reference material collected and identified during the live macroinvertebrate sampling (Chapter 2).

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4.2.3 Statistical methods

Statistical techniques used to analyse the data in this chapter are similar to those used and outlined in Chapters 2 and 3, and allows for the comparison of macroinvertebrate assemblages collected during the live, sediment trap and surface sediment sampling.

4.2.3.1 Effect of hydroperiod on the abundance, taxonomic richness and assemblage composition of surface sediment subfossils

The Wilcoxon rank sum test (Zar, 1999) was used to compare surface sediment macroinvertebrate subfossil total abundances, genera richness and order richness in temporary and permanent wetlands. Significance was set at P 0.05.

Boxplots comparing total abundance, order richness, and genus richness in temporary and permanent wetlands were made. Additionally, boxplots for all macroinvertebrate orders comparing temporary and permanent wetlands were produced to better visualise the data.

Non-metric multidimensional scaling (NMDS) was conducted on the abundance and presence/absence of macroinvertebrate assemblage data sets at genus level, to compare the effect of hydroperiod (permanent vs temporary). The orders Diptera and Coleoptera were again tested separately as they were abundant, diverse, and contained genera showing an association for certain wetland hydroperiods. All abundance data was transformed using log10(x+1) (Clarke & Warwick, 1994) and the Bray–Curtis dissimilarity measure was used to construct dissimilarity matrices between samples, and used as the basis for the ordinations

(Clarke, 1993). To compare the assemblages, based on the shared presence or absence of genera in each sample, the Jaccard similarity coefficient was used (Legendre & Gallagher,

2001; Real & Vargas, 1996).

PERMANOVA was then used to test the effect of wetland type on the full macroinvertebrate assemblages at genus level, as well as for the Diptera and Coleoptera only assemblages

127 collected in the surface sediments using log10(x+1) for the abundance and presence/absence data sets. Monte Carlo analysis was used to model the probability of different outcomes.

4.2.3.2 Identification of indicator Genera of wetland hydroperiod

SIMPER (similarity percentage analysis) was used to calculate the contribution of each macroinvertebrate genus/order (as a %), and the dissimilarity between temporary and permanent wetlands was calculated for the abundance and presence/absence data sets.

SIMPER analysis was also used to identify indicator genera responsible for driving differences in the wetland assemblages, and to determine the contribution of each taxon to the overall compositional differences between the wetland types (Clarke & Warwick, 1994). All genera and orders collected that contributed to compositional dissimilarity between the wetlands are reported.

4.2.3.3 Comparison of live, trap and surface sediment macroinvertebrate assemblages

To compare the macroinvertebrate assemblages collected during live, sediment trap and surface sediment sampling, NMDS ordinations comparing the wetland type and sampling method were undertaken on the P/A data only. Ordinations were performed for the full assemblage at genera level, and for the Diptera only and Coleoptera only assemblages which were tested separately. PERMANOVA was used to assess the effects of wetland type and sampling method, and their interaction, on the macroinvertebrate assemblages collected during the live, sediment trap and surface sediment sampling for the All genera assemblages, and for the Diptera only and Coleoptera only assemblages separately. Again, Monte Carlo analysis was used to model the probability of different outcomes.

All univariate analyses were conducted using R (Version 3.6.3), and all multivariate analyses were conducted in PRIMER 7 and PERMANOVA (Clarke & Gorley, 2006; Clarke &

Warwick, 1994). All permutation tests were based on 10,000 randomisations.

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4.3 Results

4.3.1 Effect of hydroperiod on the abundance, taxonomic richness and assemblage composition of surface sediment subfossils

A total of 8,061 identifiable macroinvertebrate subfossils, representing 165 genera, were collected from the wetland surface sediments. Of these, 2,994 subfossils (37.1%) were collected in temporary whereas 5,067 (62.9%) were collected in permanent wetlands.

Abundances of macroinvertebrate subfossils collected in temporary wetlands ranged from 87

- 398 individuals, with a median of 259, whereas those in permanent wetlands ranged from

249 - 681 individuals, with a median of 356 (Figure 4.6a). When compared, there was a significant difference in subfossil abundances in temporary and permanent wetlands (W =

120, df 23, P<0.001).

A total of 27 macroinvertebrate orders were collected in wetland surface sediments, 25 orders were collected in temporary, and 17 were collected in permanent wetlands (Figure 4.6b). For temporary wetlands, order richness ranged from 10 - 17 with a median of 15.5, whereas order richness in permanent wetlands ranged from 6 - 12 with a median of 10.5. When compared, there was a significant difference in order richness in temporary and permanent wetlands (W

= 9, df 23, P<0.001).

Of the 165 macroinvertebrate genera extracted from the surface sediments, 142 were collected in temporary wetlands and 102 were present in permanent wetlands (Figure 4.6c).

For temporary wetlands, the number of genera collected ranged from 36 - 70 with a median of 47.5, whereas for permanent wetlands the number of genera collected ranged from 29 - 42 with a median of 36.5. When compared, there was a significant difference in genera richness in temporary and permanent wetlands (W = 10, df 23, P<0.001).

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Figure 4.6. Boxplots comparing subfossils: a) Total abundance; b) Order richness; and c) Genus richness in temporary and permanent wetlands on the Ovens River floodplain. Blue denotes permanent wetlands, red denotes temporary wetlands. Note variable y-axis scale.

The five most abundant orders in temporary wetlands were Diptera, Coleoptera,

Hymenoptera, Acariformes and Hygrophila, representing 85.94% of all the subfossils collected, whereas in permanent wetlands, Diptera, Coleoptera, Acariformes, Trichoptera and

Hemiptera represented 96.59% of the subfossil composition (Table 4.1). Diptera were the most common subfossils collected in wetland surface sediments, representing 41.21% of the composition in temporary, compared to 78.55% in permanent wetlands. This was followed by

Coleoptera, comprising 20.57% of the subfossils in temporary, and 7.82% in permanent wetlands. Macroinvertebrate subfossils collected in temporary and permanent wetlands were generally from aquatic orders/genera. However, in temporary wetlands, approximately 20% of the subfossil composition was from terrestrial orders/genera, compared to approximately

1% in permanent wetlands.

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Table 4.1. Breakdown by Order of total abundances and composition (%) of subfossils extracted from surface sediments in temporary and permanent wetlands on the Ovens River floodplain. Terrestrial Orders/Genera denoted by T.

Temporary Wetlands Permanent Wetlands Order Total Composition (%) Order Total Composition (%) Diptera 1231 41.12 Diptera 3980 78.55 Coleoptera 616 20.57 Coleoptera 396 7.82 Hymenoptera T 354 11.82 Acariformes 299 5.90 Acariformes 222 7.41 Trichoptera 128 2.53 Hygrophila 150 5.01 Hemiptera 91 1.80 Coleoptera T 125 4.18 Hygrophila 68 1.34 Podocopida 80 2.67 Odonata 29 0.57 Hemiptera 34 1.14 Hymenoptera T 28 0.55 Orthoptera T 33 1.10 Decapoda 15 0.30 Haplotaxida T 33 1.10 Unionida 7 0.14 Blattodea T 28 0.94 Coleoptera T 6 0.12 Odonata 25 0.84 Blattodea T 5 0.10 Anomopoda 14 0.47 Diptera T 4 0.08 Hemiptera T 8 0.27 Araneae 3 0.06 Dermaptera T 8 0.27 Orthoptera T 3 0.06 Diptera T 7 0.23 Hemiptera T 3 0.06 Spinicaudata 5 0.17 Dermaptera T 2 0.04 Julida T 5 0.17 Podocopida 0 0.00 Decapoda 4 0.13 Spinicaudata 0 0.00 Isopoda 3 0.10 Anomopoda 0 0.00 Araneae 2 0.07 Mantodea T 0 0.00 Mantodea T 2 0.07 Isopoda 0 0.00 Scolopendromorpha T 2 0.07 Scolopendromorpha T 0 0.00 Arhynchobdellida 2 0.07 Scutigeromorpha T 0 0.00 Scutigeromorpha T 1 0.03 Julida T 0 0.00 Trichoptera 0 0.00 Arhynchobdellida 0 0.00 Unionida 0 0.00 Haplotaxida T 0 0.00

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The most abundant subfossil orders collected in wetland surface sediments were Diptera,

Coleoptera, Acariformes, Hymenoptera T, Hygrophila and Coleoptera T (Figure 4.7).

Diptera subfossils were highly abundant in temporary and permaent wetlands; in temporary wetlands abundances varied from 22 - 214 with a median of 101, whereas in permanent wetlands, abundances varied from 183 - 587 with a median of 275.5. The orders Trichoptera,

Hemiptera, Podocopida, Odonata, Orthoptera T, Blattodea T and Haplotaxida were found in medium to low abundances in temporary and permanent wetlands. The orders Decapoda,

Anomopoda, Hemiptera T, Diptera T, Dermaptera T, Unionida, Spinicaudata, Araneae, Julida

T, Isopoda T, Mantodea T, Scolopendromorpha T, Arhynchobdellida and Scutigeromorpha T rarely occurred as subfossils in both wetland types.

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Figure 4.7. Surface sediment subfossil Orders ranked from highest to lowest abundance comparing wetland type: a) Diptera; b) Coleoptera; c) Acariformes; d) Hymenoptera T; e) Hygrophila; f) Coleoptera T; g) Trichoptera; h) Hemiptera; i) Podocopida; j) Odonata; k) Orthoptera T; l) Blattodea T; m) Haplotaxida T; n) Decapoda; o) Anomopoda; p) Hemiptera T; q) Diptera T; r) Dermaptera T; s) Unionida; t) Spinicaudata; u) Araneae; v) Julida T; w) Isopoda T; x) Mantodea T; y) Scolopendromorpha T; z) Arhynchobdellida; and aa) ScutigeromorphaT. Blue denotes permanent wetlands, red denotes temporary wetlands. Note variable y-axis scale. T denotes Terrestrial Orders.

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For 12 orders, there was a significant difference between temporary and permanent wetlands’ subfossil abundances (df 23, P<0.05) (Table 4.2). The orders Hymenoptera T, Coleoptera T,

Podocopida, Orthoptera T, Blattodea T, Haplotaxida T, Anomopoda, Dermaptera and

Spinicaudata occurred in significantly greater abundances in temporary wetlands whereas the orders Diptera, Trichoptera, and Unionida occurred in significantly greater abundances in permanent wetlands. For 15 orders collected, Coleoptera, Acariformes, Hygrophila,

Hemiptera, Odonata, Decapoda, Hemiptera T, Diptera T, Araneae, Julida T, Isopoda T,

Mantodea T, Scolopendromorpha T, Arhynchobdellida, and Scutigeromorpha T , there was no significant difference between temporary and permanent wetlands (df 23, P>0.05).

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Table 4.2. Results of Wilcoxon t test comparing surface sediment total macroinvertebrate Order abundances for temporary and permanent wetlands on the Ovens River floodplain df=23. NS not significant; *P<0.05; **P<0.01; ***P<0.001.

Order W P value Significance Diptera 140.0 9.60E-05 *** Coleoptera 50.0 0.2135 NS Acariformes 99.5 0.1185 NS Hymenoptera T 1.0 4.25E-05 *** Hygrophila 60.5 0.5234 NS Coleoptera T 4.5 7.73E-05 *** Trichoptera 126.0 0.000383 *** Hemiptera 104.5 0.06189 NS Podocopida 30.0 0.002846 ** Odonata 86.0 0.4264 NS Orthoptera T 12.0 0.00031 *** Blattodea T 28.0 0.008486 ** Haplotaxida T 0.0 9.04E-06 *** Decapoda 96.0 0.1279 NS Anomopoda 30.0 0.002754 ** Hemiptera T 46.5 0.09558 NS Diptera T 59.5 0.4056 NS Dermaptera T 41.0 0.03796 * Unionida 108.8 0.006633 ** Spinicaudata 48.0 0.0363 * Araneae 82.5 0.373 NS Julida T 54.0 0.07861 NS Isopoda T 54.0 0.07802 NS Mantodea T 60.0 0.1658 NS Scolopendromorpha T 60.0 0.1658 NS Arhynchobdellida 60.0 0.1658 NS Scutigeromorpha T 66.0 0.3593 NS T Terrestrial Orders/Genera

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NMDS of macroinvertebrate subfossil abundance and presence/absence data sets comparing temporary and permanent wetlands both showed a separation based on wetland type on the x axis (Figure 4.8a & b). The orders Diptera and Coleoptera were abundant, diverse, and preserved well, so were explored individually. The Diptera only assemblage again separated out based on wetland type on the x axis for both abundance and presence/absence data

(Figure 4.8c & d). The Coleoptera only assemblage also showed separation based on wetland type on the x axis for both abundance and presence/absence data (Figure 4.8e & f).

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Figure 4.8. NMDS ordinations for abundance and Presence/Absence (P/A) data: a) All Genera abundance log10(x+1); b) All Genera P/A; c) Diptera log10(x+1); d) Diptera P/A; e) Coleoptera log10(x+1); and f) Coleoptera P/A. Blue denotes permanent wetlands, red denotes temporary wetlands.

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PERMANOVA analysis revealed a significant wetland type effect for both the abundance and presence/absence data sets for the All genera assemblage, and the Diptera only and

Coleoptera only assemblages (P<0.0001, and Monte Carlo values of 0.0001), Table 4.3.

Table 4.3 Results from PERMANOVA (perm) and Monte Carlo (MC) analysis comparing the effect of wetland type at the All Genera, Diptera only and Coleoptera only assemblages for both the abundance and Presence/Absence (P/A) data sets.

Genera Data Source Df MS Pseudo-F P(perm) P(MC)

All Genera log10(x+1) Wetland type 1 11260.0 10.3 0.0001 0.0001

Residual 22 1092.5

Total 23 P/A Wetland type 1 13327.0 5.8 0.0001 0.0001

Residual 22 2308.5 Total 23

Diptera only log10(x+1) Wetland type 1 7845.3 9.9 0.0001 0.0001

Residual 22 790.7

Total 23 P/A Wetland type 1 9679.0 5.8 0.0001 0.0001

Residual 22 1663.3 Total 23

Coleoptera only log10(x+1) Wetland type 1 11518.0 9.3 0.0001 0.0001

Residual 22 1243.0

Total 23 P/A Wetland type 1 14969.0 6.3 0.0001 0.0001

Residual 22 2380.2 Total 23

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4.3.2 Identification of indicator Genera of wetland hydroperiod

SIMPER analysis undertaken on the abundance and presence/absence data calculated the contribution of each macroinvertebrate genus (%) to the dissimilarity between temporary and permanent wetlands (Table 4.4). For both abundance and presence/absence data, Aquatic

Diptera was the main driver of the assemblage dissimilarity between temporary and permanent wetlands, contributing 37.69% and 26.61%, respectively. Aquatic Coleoptera accounted for 18.87% of the abundance data and 22.56% of the presence/absence data. For the abundance data, the top 5 orders, Diptera, Coleoptera, Hymenoptera T, Coleoptera T, and

Hygrophila accounted for 75.15% of the dissimilarity between the wetland types. The top 5 orders for the presence/absence data were Diptera, Coleoptera, Coleoptera T, Hygrophila and

Hymenoptera T, accounting for 70.02% of the dissimilarity between temporary and permanent wetlands. Aquatic genera accounted for 78.73% of the dissimilarity in the abundance data, and 71.26% in the presence/absence data.

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Table 4.4. Results of condensed Genera level (all macroinvertebrates) SIMPER analysis on Log10(x+1) data and P/A data comparing temporary and permanent wetlands. Count refers to the number of Genera identified in each Order.

Abundance data P/A data Order Contribution % Count Order Contribution % Diptera 37.69 40 Diptera 26.61 Coleoptera 18.87 30 Coleoptera 20.42 Hymenoptera T 6.45 11 Coleoptera T 10.16 Coleoptera T 6.37 19 Hygrophila 6.78 Hygrophila 5.77 9 Hymenoptera T 6.05 Hemiptera 4.59 10 Hemiptera 5.06 Acariformes 2.49 7 Odonata 3.42 Trichoptera 2.48 1 Orthoptera T 2.99 Odonata 2.42 5 Blattodea T 2.54 Orthoptera T 1.99 5 Acariformes 2.28 Blattodea T 1.77 4 Haplotaxida T 1.79 Haplotaxida T 1.70 1 Hemiptera T 1.44 Podocopida 1.44 1 Trichoptera 1.33 Decapoda 0.86 2 Diptera T 1.22 Anomopoda 0.80 1 Decapoda 1.03 Hemiptera T 0.75 3 Podocopida 1.03 Diptera T 0.74 4 Anomopoda 0.99 Dermaptera T 0.55 1 Dermaptera T 0.98 Unionida 0.54 1 Unionida 0.94 Julida T 0.36 1 Araneae 0.54 Spinicaudata 0.33 1 Spinicaudata 0.53 Araneae 0.32 2 Julida T 0.46 Isopoda T 0.22 1 Isopoda T 0.43 Scolopendromorpha T 0.16 1 Scolopendromorpha T 0.28 Arhynchobdellida 0.14 1 Arhynchobdellida 0.27 Mantodea T 0.14 2 Mantodea T 0.27 Scutigeromorpha T 0.07 1 Scutigeromorpha T 0.13 T Terrestrial Orders/Genera

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Of the 165 genera collected from the surface sediments, 79 were common to both temporary and permanent wetlands, and 86 showed an association for a wetland type. Of the latter, 63 were only collected in temporary wetlands whereas 23 genera were only associated with permanent wetlands (Table 4.5 and Table 4.6). Temporary wetlands contained more indicator genera, from a diverse range of orders, and included genera with aquatic and terrestrial associations, whereas permanent wetlands had fewer indicator genera, from fewer orders, and were all aquatic.

Table 4.5. Summary of the number of subfossil macroinvertebrate indicator Genera at Order level found in temporary and permanent wetlands on the Ovens River floodplain.

Wetland Order Temporary Permanent Diptera 5 7 Coleoptera 13 2 Hemiptera 1 4 Hygrophila 3 - Podocopida 1 - Spinicaudata 1 - Anomopoda 1 - Acariformes 1 5 Arhynchobdellida 1 - Trichoptera - 1 Unionida - 1 Decapoda - 1 Acariformes - 5 Araneae - 1 Hymenoptera T 6 - Coleoptera T 15 - Orthoptera T 4 - Hemiptera T 1 - MantodeaT 2 - Blattodea T 1 - Diptera T 2 - Isopoda T 1 - Scolopendromorpha T 1 - Scutigeromorpha T 1 - Julida T 1 - Haplotaxida T 1 - T Terrestrial Orders/Genera

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Table 4.6. Full list of subfossil macroinvertebrate indicator Genera found in surface sediments in temporary and permanent wetlands on the Ovens River floodplain. FO = Frequency of Occurrence, out of a maximum of 12 possible wetlands.

Temporary Wetlands Permanent Wetlands Order Genera FO Order Genera FO Diptera Cladopelma 7 Diptera Paracladopelma 10 Cryptochironomus 10 Ablabesmyia 7 Microchironomus 10 Coelopynia 1 Microtendipes 10 Paramerina 1 Culex 1 Pentaneura 4 Coleoptera Antiporus 7 Monopelopia 3 Bidessini 4 Riethia 1 Chostonectes 3 Coleoptera Notomicrus 3 Erestes 7 Aulonogyrus 4 Hyphydrus 4 Hemiptera Rheumatometra 1 Lancetes 9 Hydrometra 2 Megaporus 5 Diplonychus 6 Necterosoma 6 Merragata 3 Sternopriscus 7 Trichoptera Oecetis 9 Enochrus 1 Hygrophila Glyptophysa 5 Helochares 11 Unionida Velesunio 6 Paracymus 4 Decapoda Paratya 1 Spercheus 3 Acariformes Limnochares 2 Hemiptera Agraptocorixa 1 Sigthoria 1 Hygrophila Isidorella 7 Trombidium 3 Physastra 7 Unionicola 6 Segnitila 3 Halotydeus 2 Podocopida Ostracoda 7 Araneae Tetragnathidae 1 Spinicaudata Limnadopsis 4 Anomopoda Daphiniidae 7 Acariformes Hydrachna 1 Hymenoptera T Myrmecia 3 Polyrhachis 4 Rhytidoponera 3 Diamma 1 Sceliphron 3 Perga 2 Coleoptera T Anoplognathus 8 Eupoecila 2 Phyllotocus 3 Coptocercus 4 Paropsis 1 Pheropsophus 3 Megacephala 3

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Temporary Wetlands Permanent Wetlands Order Genera FO Order Genera FO Saprinis 1 Scydmaenidae 3 Staphylinidae 5 Sericesthis 3 Elateridae 3 Porrostoma 2 Calosoma 2 Lamprima 5 Orthoptera T Atractomorpha 2 Chortoicetes 4 Gryllotalpa 3 Teleogryllus 8 Hemiptera T Nabis 2 Mantodea T Orthodera 1 Tenodera 1 Blattodea T Panesthia 4 Diptera T Lucilia 2 Sarcophaga 1 Isopoda T Porcellio 3 Scolopendromorpha T Cormocephalus 2 Scutigeromorpha T Allothereua 1 Julida T Ommatoiulus 3 Arhynchobdellida Richardsonianus 2 Haplotaxida T Haplotaxida 12 T Terrestrial Orders/Genera

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4.3.3 Comparison of live, trap and surface sediment macroinvertebrate assemblages

Total genera richness was not consistent across the three sampling methods; it was highest for the live macroinvertebrate sampling, lowest in the sediments traps, and then increased again in the surface sediments (Table 4.7). The number of indicator genera identified across the three sampling methods also varied. For the temporary wetlands, the richness of indicator genera increased 38, 55 and 63 for the three sampling methods, respectively, whereas indicator genera in permanent wetlands increased from live to sediment trap and then declined in surface sediments (19, 31 and 23, respectively).

Table 4.7. Comparison of live, sediment trap and surface sediment Genera collected on the Ovens River floodplain. Total Genera collected, total Genera collected in wetland types, and total number of Genera unique to wetland types.

Sampling Total Genera method collected Temporary wetlands Permanent wetlands

All Genera Unique Genera All Genera Unique Genera Live 167 148 38 129 19 Trap 132 100 55 77 31 Surface 165 142 63 102 23

Based on the results from the three different sampling methods used (live, sediment trap, surface sediment), not all genera readily translated from the live state to subfossils in the surface sediment strata (Table 4.8). Genera within the orders such as Diptera, Coleoptera, and

Hygrophila readily translated from the live stage to the sediment traps, then into the surface sediment, in both temporary and permanent wetlands. However, taxa such as Collembola,

Lepidoptera, Ephemeroptera, Amphipoda, Nemertea, Nematoda, Nematomorpha and

Turbellaria, present during the live macroinvertebrate sampling, failed to accumulate in the sediment traps, or in the surface sediments of the wetlands. For some orders, the number of genera increased across the three different sampling methods: e.g. in temporary wetlands 3

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Coleoptera T genera were collected during the live sampling, whereas 13 were collected in the sediment traps, and 19 were found in the surface sediments. However, for other orders, the number of genera decreased across the three different sampling methods: e.g. in permanent wetlands, 6 Trichoptera genera were identified during live sampling whereas only

1 genera translated into the sediment traps, and the surface sediments.

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Table 4.8. Number of Macroinvertebrate Genera collected during live, sediment trap and surface sediment sampling in temporary and permanent wetlands on the Ovens River floodplain.

Temporary Wetlands Permanent Wetlands Order Live Trap Surface Live Trap Surface Diptera 33 23 33 32 30 35 Coleoptera 31 23 28 17 16 17 Hemiptera 15 5 6 17 11 9 Ephemeroptera 3 0 0 3 0 0 Odonata 7 2 5 7 3 5 Trichoptera 3 0 0 6 1 1 Hygrophila 8 8 8 6 5 6 Unionida 0 0 0 1 1 1 Decapoda 4 0 1 3 1 2 Podocopida 1 1 1 0 0 0 Spinicaudata 1 1 1 0 0 0 Anomopoda 1 1 1 1 0 0 Acariformes 9 2 2 10 1 6 Lepidoptera 1 0 0 2 0 0 Araneae 3 1 1 3 0 2 Collembola T 4 0 0 1 0 0 Hymenoptera T 7 9 11 5 3 5 Coleoptera T 3 13 19 3 1 4 Orthoptera 2 2 5 3 2 1 Hemiptera T 0 1 3 0 0 2 Mantodea T 0 0 2 0 0 0 Blattodea T 0 4 4 0 0 3 Diptera T 1 2 4 2 1 2 Isopoda T 1 1 1 0 0 0 Amphipoda T 1 0 0 1 0 0 Scolopendromorpha T 1 0 1 0 0 0 Scutigeromorpha T 0 0 1 0 0 0 Julida T 1 0 1 1 0 0 Dermaptera T 1 1 1 1 0 1 Nemertea 1 0 0 1 0 0 Nematoda 1 0 0 0 0 0 Nematomorpha 1 0 0 0 0 0 Turbellaria 1 0 0 1 0 0 Haplotaxida T 1 0 1 1 0 0 Arhynchobdellida 1 0 1 1 0 0 T Terrestrial Orders/Genera

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NMDS ordinations were undertaken on the presence/absence data sets to compare the effect of wetland type (temporary/permanent) and sampling method (live, sediment trap and surface sediment) on the macroinvertebrate assemblages present (Figure 4.9). For the All genera macroinvertebrate assemblage ordination, a complete separation based on wetland type occurred on the x axis, and separation based on the sampling method (live, sediment trap and surface sediment) was seen on the y axis (Figure 4.9a). Ordination indicated that the assemblages collected using the different sampling methods (live, trap and surface sediment) were different to each other and that there was a greater similarity between the live and surface sediment assemblages, compared to those collected in sediment traps for both temporary and permanent wetlands. Ordination suggests it is possible to distinguish wetland type using live and subfossil macroinvertebrates, and that the assemblages collected using the different sampling methods differ.

The Diptera only assemblage ordination comparing live, sediment trap and surface sediment sampling again showed separation based on wetland type on the x axis (Figure 4.9b).

However, the assemblages from the sampling methods showed some mixing, indicating there was some similarity in the Diptera assemblages collected across the three sampling methods.

A similar pattern was seen in the Coleoptera only assemblages (Figure 4.9c).

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Figure 4.9. NMDS ordinations comparing wetland type, temporary (red) and permanent (blue) and sampling method (live sample = solid triangle, sediment trap = outline triangle, surface sediment = square) for macroinvertebrate assemblages using presence/absence data: a) All Genera; b) Diptera only; and c) Coleoptera only.

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PERMANOVA and Monte Carlo analysis indicated that the macroinvertebrate assemblages

(All genera, Diptera and Coleoptera) differed significantly by wetland type, sampling method

and the interaction of the two (Table 4.9). In all cases, the variation contributed by the

interaction term was the least, and it was not the main driver of the assemblage differences

seen. Wetland type accounted for most of the variation seen in the Diptera and Coleoptera

assemblages.

Table 4.9. PERMANOVA (perm) and Monte Carlo (MC) analysis comparing the effect of wetland type (temporary and permanent) and sampling method (live, sediment trap, surface sediment) and wetland type × sampling method interaction on the presence/absence data for the macroinvertebrate assemblages found.

Genera Source Df SS MS Pseudo-F P(perm) P(MC) All Genera Wetland type 1 26893.0 26893.0 14.59 0.0001 0.0001 Sampling method 2 35222.0 17611.0 9.55 0.0001 0.0001 Wetland type × Sampling method 2 9640.0 4820.0 2.61 0.0001 0.0001 Residual 65 119850.0 1843.8 Total 70 191620.0

Diptera only Wetland type 1 28872.0 28872.0 28.20 0.0001 0.0001 Sampling method 2 9071.3 4535.6 4.43 0.0001 0.0001 Wetland type × Sampling method 2 3438.8 1719.4 1.68 0.0418 0.0502 Residual 65 66561.0 1024.0 Total 70 107930.0

Coleoptera Wetland type 1 34079.0 34079.0 14.67 0.0001 0.0001 only Sampling method 2 18316.0 9158.2 3.94 0.0001 0.0001 Wetland type × Sampling method 2 8478.3 4239.2 1.83 0.004 0.0078 Residual 65 150960.0 2322.5 Total 70 211750.0

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Analysis of the live, sediment trap and surface sediment sampling identified the genera associated with temporary and permanent wetlands on the floodplain (Table 4.10 and Table

4.11). Some orders/genera showed good indicator potential across all three sampling methods

(e.g. Diptera, Coleoptera, and Hygrophila), whereas others were only collected or demonstrated a wetland association based on one or two of the sampling methods used (e.g.

Collembola T, Hymenoptera T, and Trichoptera). Some indicator genera for temporary and permanent wetlands were collected frequently. For example, Microchironomus were collected from 11, 7 and 10 of the temporary wetlands during live, trap and surface sediment sampling, respectively. Other indicator genera were found infrequently and not necessarily in all wetlands of a particular type. For example, Macrobrachium, an indicator for temporary wetlands, was collected in only three of the temporary wetlands sampled and was absent as remains or subfossils in the sediment traps and surface sediments.

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Table 4.10. Occurrence of indicator Genera in temporary wetlands based on live, sediment trap and surface sediment sampling of macroinvertebrates. I = sampling method where the Genera was identified as an indicator. L = Live, T = Trap, S = Surface sediment.

Temporary Sampling method Orders Indicator Genera Live Trap Sediment Indicator Diptera Cladopelma 10 6 7 L, T, S Cryptochironomus 10 7 10 L, T, S Culex - 1 1 T Microchironomus 11 7 10 L, T, S Microtendipes 11 8 10 L, T, S Odontomyia - 2 - T Coleoptera Antiporus 10 2 7 L, T, S Bidessini 6 2 4 L, T, S Chostonectes 5 2 3 L, T, S Enochrus 5 1 1 L, T, S Erestes 10 5 7 L, T, S Helochares 7 - 11 L & S Hyderodes - 1 - T Hydraena 1 - - L Hyphydrus 4 2 4 L, T, S Lancetes 8 7 9 L, T, S Limnoxenus 3 - - L Megaporus 7 3 5 L, T, S Necterosoma 8 2 6 L, T, S Paracymus - 1 4 T & S Spercheus 5 2 3 L, T, S Sternopriscus 2 9 7 L, T, S Sclerocyphon - 1 - T Odonata Xanthagrion 4 - - L Hemiptera Agraptocorixa - 2 1 T & S Hygrophila Gyraulus - 3 - T Isidorella 10 1 7 L, T, S Physastra 11 1 7 L, T, S Segnitila 11 2 3 L, T, S Decapoda Macrobrachium 3 - - L Podocopida Ostracoda 11 2 7 L, T, S Spinicaudata Limnadopsis 9 1 4 L, T, S Anomopoda Daphiniidae - 3 7 T & S Nematoda Nematode 3 - - L Nematomorpha Nematomorpha 4 - - L Arhynchobdellida Richardsonianus - - 2 S Acariformes Acercella 10 - - L

Hydrachna 7 - 1 L & S

Neumania 8 - - L Piona - 2 - T Araneae Lycosidae - 1 - T

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Temporary Sampling method Orders Indicator Genera Live Trap Sediment Indicator Collembola T Entomobryidae 3 - - L

Hypogastruridae 4 - - L

Sminthuridae 2 - - L Hymenoptera T Abispa 2 2 - L & T

Diamma - - 1 S Iridomyrmex - 6 - T Myrmecia - 1 3 T & S Polyrhachis - 2 4 T & S Perga - - 2 S Rhytidoponera 2 2 3 L, T, S Sceliphron - 2 3 T & S Coleoptera T Anoplognathus - 5 8 T & S

Calosoma - - 2 S Coptocercus - 2 4 T & S Elateridae - 2 3 T & S Eupoecila - - 2 T & S Hetroceridae - 3 - T Lamprima - 1 5 T & S Megacephala - 2 3 T & S Paropsis - 1 1 T & S Pheropsophus - - 3 S Phoracantha - 1 - T Phyllotocus - 1 3 T & S Porrostoma - - 2 S Saprinis - - 1 S Scydmaenidae - 1 3 T & S Sericesthis - - 3 S Staphylinidae - 3 3 T & S Hemiptera T Psaltoda - 2 - T

Nabis - - 2 S Orthoptera T Atractomorpha - - 2 S

Chortoicetes - - 4 S Gryllotalpa - - 3 S Teleogryllus - - 8 S Mantodea T Orthodera - - 1 S Tenodera - - 1 S Blattodea T Coptotermes - 5 - T Ellipsidion - 1 - T

Laxata - 1 - T

Panesthia - 1 4 T & S Isopoda T Porcellio 2 1 3 L, T, S Scolopendromorpha T Cormocephalus 2 - 2 L & S Scutigeromorpha T Allothereua - - 1 S Julida T Ommatoiulus - - 3 S

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Temporary Sampling method Orders Indicator Genera Live Trap Sediment Indicator Dermaptera T Labidura - 4 - T Diptera T Cydistomyia - 1 - T Lucilia - - 2 S Sarcophaga - - 1 S Haplotaxida T Haplotaxida - - 12 S

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Table 4.11. Occurrence of indicator Genera in permanent wetlands based on live, sediment trap and surface sediment sampling of macroinvertebrates. I = sampling method where the Genera was identified as an indicator. L = Live, T = Trap, S = Surface sediment.

Permanent Sampling method Orders Indicator Genera Live Trap Sediment Indicator Diptera Ablabesmyia 7 6 7 L, T, S

Anopheles - 1 - T

Bezzia - 1 - T

Coelopynia - 2 1 T & S

Corynoneura - 1 - T Larsia - 7 - T Monopelopia 6 3 3 L, T, S Paraborniella - 2 - T Paracladopelma 10 11 10 L, T, S Paramerina - 3 1 T & S Pentaneura - - 4 S Procladius 9 2 - L & T Riethia - 1 1 T & S Tipulidae - 1 - T Coleoptera Aulonogyrus - 3 4 T & S

Beetle - 3 - T

Chrysomelidae - 3 - T

Hydraena - 4 - T

Notomicrus - 1 3 T & S

Onychonhydrus - 2 - T Hemiptera Diplonychus 7 1 6 L, T, S Hydrometra - 2 2 T & S Merragata 5 - 3 L & S Microvelia - 2 - T Naucoris - 1 - T Plea - 1 - T Sigara - 5 - T Tenagogerris - 1 - T Odonata Hemianax - 2 - T Rhadinosticta 6 - - L Trichoptera Anisocertropus 9 - - L

Oecetis 3 8 9 L, T, S

Triaenodes 6 - - L Hygrophila Glyptophysa 10 1 5 L, T, S Unionida Velesunio 7 3 6 L, T, S Decapoda Cherax - 1 - T

Paratya - - 1 S Acariformes Halotydeus 2 - 2 L & S

Limnochares 8 - 2 L & S

Sigthoria 5 - 1 L & S

Trombidium - - 3 S

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Permanent Sampling method Orders Indicator Genera Live Trap Sediment Indicator

Unionicola 3 - 6 L & S Lepidoptera Lepidoptera 4 - - L Orthoptera T Torbia 1 - - L Diptera T Muscidae 2 - - L Araneae Tetragnathidae - - 1 S T Terrestrial Orders/Genera

4.4 Discussion

4.4.1 Effect of hydroperiod on the abundance, taxonomic richness and assemblage composition of surface sediment subfossils

The current study showed that there were significantly greater subfossil abundances in permanent than temporary wetlands on the Ovens River floodplain. Comparisons of subfossil abundances in wetland systems with different hydroperiods are rare, however, chironomid subfossils have been found in higher abundances in the surface sediments of permanent than in temporary wetlands (Campbell et al., 2018). Potential reasons for greater macroinvertebrate subfossil abundances (see Chapter 3) include the length of the hydroperiods and the physical and chemical conditions within the wetlands. For short-lived organisms, such as macroinvertebrates, the length of the hydroperiod can influence the number of macroinvertebrate generations per year. Many macroinvertebrate orders, including

Diptera, can have multiple generations per year depending on hydroperiod duration

(Armitage et al., 2012; Tokeshi, 1995).

In permanent wetlands, the physical and chemical conditions are typically more constant than those experienced in the temporary wetlands, which change from aquatic to terrestrial (Silver et al., 2012; Williams, 2006). The sediment, and sediment-water interface of permanent waterbodies can become anoxic, providing favourable conditions for the preservation of invertebrate remains (Van Bodegom et al., 2005), whereas the wetting and drying phase and

155 higher oxygen levels found in temporary wetlands are known to increase decomposition of organic matter (Neckles & Neill, 1994; Reddy & Patrick, 1975; Swift et al., 1979).

Decomposition is known to be limited in permanently waterlogged conditions. There is also the potential for substantial loss of subfossils in temporary systems when surface sediments are exposed to wind, the effects of terrestrial decomposers, and scavengers (Hättenschwiler,

Tiunov, & Scheu, 2005; Singh & Gupta, 1977; Van Veen & Kuikman, 1990). In comparison, surface sediments of permanently inundated wetlands are covered by a water barrier that may protect the subfossils.

Subfossil macroinvertebrate order and genus richness were significantly greater in temporary than permanent wetland surface sediments in the current study. As previously discussed

(Chapter 3), permanent wetlands are thought to support more genera, as the duration of the hydroperiod allows for a greater chance of invertebrate colonisation (Florencio et al., 2009;

Schneider & Frost, 1996; Waterkeyn et al., 2008). However, temporary wetlands are also known to have high macroinvertebrate richness, as many genera have adapted to these conditions (Williams, 1997, 2006). These conclusions were based on live macroinvertebrate sampling and not subfossils, suggesting genera subfossil richness in surface sediments would be related to how well the different macroinvertebrate genera translate from the live to the death assemblages.

Additionally, since temporary wetlands act alternately as aquatic and terrestrial environments during the different phases of their flooding and drying cycle, there is potential for both aquatic and terrestrial macroinvertebrates to utilise the same space at different times (Adis &

Junk, 2002; Ballinger et al., 2007; Ballinger et al., 2005; Junk, 1997a, 2005). This may lead to the accumulation of subfossil-rich sediments comprised of a mixture of aquatic and terrestrial genera. This is a potential explanation as to why subfossil taxonomic richness was greater in the temporary wetlands in the current study.

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Further, since surface sediments represent years of macroinvertebrate accumulation, under different environmental conditions, increased richness would be expected. Surface sediments are known to reflect the live assemblage (Frey, 1964; Rumes et al., 2005; Van Hardenbroek et al., 2011). Previous work by Rumes et al. (2005), focusing on non-chironomid aquatic invertebrates, and excluding soft-bodied taxa, found that the recent death assemblages recovered from a single mid-lake surface sediment sample provided a more complete inventory of the local aquatic invertebrate communities, and the distribution of species among lakes, than exploratory live sampling of those taxa in a selection of littoral, benthic and pelagic habitats (Rumes et al., 2005).The majority of chironomid genera found during live sampling were recovered as remains/subfossils in surface sediments (Van Hardenbroek et al., 2011).

In temporary wetlands in the current study, Diptera, Coleoptera, Hymenoptera T, Acariformes and Hygrophila comprised 85.94% of the subfossils collected, whereas in permanent wetlands Diptera, Coleoptera, Acariformes, Trichoptera and Hemiptera remains comprised

96.59% of the subfossils. Overall, Diptera, Coleoptera, Hymenoptera T, Acariformes,

Trichoptera and Hygrophila dominated the surface sediment subfossil composition, and all have either chitinous and sclerotinised exoskeletons, or have shells or protective cases, which are likely to preserve and accumulate. Soft-bodied orders/genera often fail to accumulate and preserve in the surface sediments (Frey, 1964; Rumes et al., 2005; Van Hardenbroek et al.,

2011).

In the present study, Diptera represented 41.12 and 78.55% of the composition in temporary and permanent wetlands, respectively. Diptera are one of the most abundant and diverse macroinvertebrate orders found in aquatic ecosystems, have highly chitinous head capsules and are known to preserve and accumulate well (Armitage et al., 2012). During live macroinvertebrate sampling (Chapter 2), Diptera was the most abundant and diverse order

157 collected in temporary and permanent wetlands. The greater contribution of Diptera in permanent, relative to temporary wetlands, may be due to the length of the hydroperiod experienced, which influences the number of generations of chironomids possible per year

(Armitage et al., 2012; Tokeshi, 1995). During the live sampling (Chapter 2), multiple generations of chironomids were detected over the 10 month sampling period, based on the sizes of instars collected from the permanent wetlands.

Floodplains and wetlands that can oscillate between terrestrial and aquatic phases makes them alternately suitable for aquatic and terrestrial organisms (Adis & Junk, 2002; Junk,

1997a, 2005). The aquatic genera associated with temporary wetlands are known to survive flooding and drying (Williams, 1996, 1997, 2006), while the refilling of temporary wetlands can have a catastrophic effect on the terrestrial genera present (Adis & Junk, 2002; Ballinger et al., 2007; Ballinger et al., 2005; Talbot et al., 2018). Flooding causes the death of many terrestrial organisms, the remains of which then accumulate and preserve in sediment, thus explaining their occurrence in temporary wetlands and their general absence from permanent systems. Some terrestrial invertebrates can survive periodic flooding, however, they require special survival strategies and/or adaptions such as horizontal and vertical migration, and dispersal (Adis, 1997; Junk, 1997b). Generally, the surface sediment subfossil composition in the present study was dominated by aquatic taxa, particularly in permanent wetlands.

However, in temporary wetlands, more than 20% of the subfossil composition had terrestrial origins indicating terrestrial macroinvertebrates are utilising these environments when suitable. Due to the environmental conditions, most temporary wetlands on the Ovens River floodplain are terrestrial environments for a longer period than aquatic, and this potentially accounts for the increases in terrestrial fauna collected from temporary wetland surface sediments.

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The macroinvertebrate subfossil assemblages collected in temporary and permanent wetlands’ surface sediments were significantly different, and reflect the assemblage differences seen previously during live sampling (Chapter 2), and the sediment traps (Chapter

3). These findings support those of others who have found that the macroinvertebrate assemblages in temporary waterbodies differ from those of permanent waters (Campbell et al., 2018; Sanderson et al., 2005; Williams, 1997, 2006). Hydroperiod is recognised as an important driver of wetland macroinvertebrate assemblages (Batzer et al., 2000; Collinson et al., 1995; Schneider & Frost, 1996; Silver et al., 2012; Waterkeyn et al., 2008; Wellborn et al., 1996) and can influence which macroinvertebrates survive, reproduce and persist in different waterbodies (Williams, 1997). This influences the macroinvertebrates that can accumulate as subfossils in surface sediments. Typically, the genera associated and adapted to life in temporary systems often have short lifecycles, desiccation-resistant eggs, a diapause phase and/or active dispersal capabilities, while those found in permanent waters are often larger, slower to develop and often lack the ability to survive and recover after drying

(Williams, 2006).

Additionally, wetland surface sediments represent years, potentially decades, of accumulation and taphonomic losses under different environmental conditions (Staff & Powell, 1988), whereas the live and trap samples represent much shorter periods. The added factor of time allows for more and different remains/subfossils to accumulate, and influences the taphonomic decay/preservation process on remains, i.e. some remains might decay rapidly, some may take years, while others may not degrade.

4.4.2 Identification of indicator Genera of wetland hydroperiod

Of the 165 genera collected during wetland surface sediment sampling, 86 showed an association for a wetland type: 63 were only collected in temporary wetlands whereas 23 were only collected in permanent wetlands. Temporary wetlands contained more indicator

159 genera from a diverse range of orders, with aquatic and terrestrial origins, whereas permanent wetlands had fewer indicator genera from fewer orders, and were all aquatic. Unique genera of temporary wetlands were derived from 21 orders (9 aquatic and 12 terrestrial), whereas in permanent wetlands, indicator genera were derived from 9 orders and were all aquatic genera, indicating the significant effect hydroperiod has on the fauna present. Temporary and permanent wetlands support different aquatic macroinvertebrate assemblages (Batzer et al.,

2000; Campbell et al., 2018; Collinson et al., 1995; McInerney et al., 2017; Schneider &

Frost, 1996; Silver et al., 2012; Waterkeyn et al., 2008; Wellborn et al., 1996). Many macroinvertebrates can only be found under certain hydroperiods (Williams, 2006). Some genera are only found in temporary systems, whereas others can only be found in permanent systems (Williams, 1996, 1997, 2006). As previously shown in the live and sediment trap sampling (Chapters 2 and 3), many macroinvertebrates demonstrate a habitat association based on wetland hydroperiod. Some orders/genera only occur in temporary environments whereas others only occur in permanent, and this trend is also reflected in the wetland surface sediment subfossils found.

The presence of terrestrial taxa in the surface sediments of temporary wetlands demonstrates the effect of drying. Terrestrial macroinvertebrates utilise these spaces when dry (Ballinger et al., 2007; Ballinger et al., 2005; Williams, 2006), and their remains/subfossils are being incorporated into the surface sediments and palaeoecological record. This suggests there is potential to determine wetland hydroperiod based on the remains/macroinvertebrate subfossils found in the surface sediments of wetlands.

4.4.3 Comparison of live, trap and surface sediment macroinvertebrate assemblages

The comparison of the live macroinvertebrates, trap remains and surface sediment subfossil assemblages in the current study indicates that wetland type is the main driver of initial differences of live assemblages, and that trap and surface sediment assemblage changes

160 thereafter are primarily due to the loss of soft-bodied genera. This is true for both temporary and permanent wetlands. However, this loss is offset by gains of terrestrial genera, more common in temporary wetlands.

For both temporary and permanent wetlands, total genera richness was highest during live macroinvertebrate sampling, then declined based on the sediment traps, and then increased again in the wetland surface sediments. Of the 211 genera identified across live, trap and surface sediment sampling in temporary and permanent wetlands, 193 were collected in temporary wetlands of which 73 (37.82%) occurred across all 3 sampling methods. A further

49 genera (24.67%) were common to 2 sampling methods, while 71 (36.79%) were only associated with a single sampling method. In comparison, 150 genera were collected in permanent wetlands, of which 59 (39.33%) were collected across all 3 sampling methods, 37

(24.67%) were common to 2 sampling methods, while 54 genera (36.00%) were only collected in a single sampling method. The translation from the live, to remains and subfossils for the whole macroinvertebrate assemblage in both temporary and permanent wetlands was good; however, individual genera were lost or gained in the process.

For Diptera, 38 genera were identified across the 3 sampling methods of which 35 (92.10%) translated across from live, to trap and surface sediments, and 34 were identified in both temporary and permanent wetlands. In temporary wetlands, 23 genera (67.65%) were collected across all 3 sampling methods, 7 (20.59%) were common to 2 sampling methods, while 4 (11.76%) were only associated with a single type of sampling. In permanent wetlands, 28 genera (82.35%) were collected across all 3 sampling methods, 5 (14.71%) were common to 2 sampling methods, while 1 (2.94%) was only collected in a single sampling method. Similar translation rates of live chironomids to surface sediment subfossils have been shown elsewhere (Van Hardenbroek et al., 2011).

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Genera richness in sediment traps declined due to the loss of soft-bodied genera, which are then lost to the palaeoecological record. Factors such as the trap design, and macroinvertebrate lifecycles, may influence the conclusions as the traps were biased to collect fall-out from the water column, and benthic or sedentary organisms may be under represented in the sediment traps (Chapter 3). Genera richness associated with the surface sediments increased and probably reflects that the samples represent years of accumulation under different environmental conditions. Surface sediment sampling provides a more complete inventory of the local aquatic invertebrate communities than exploratory live sampling (Heiri, 2004; Rumes et al., 2005).

For the indicator genera associated with wetland type, richness increased (38, 55 and 63) for the three sampling methods (live, sediment traps and surface sediments, respectively) for the temporary wetlands. This increase was due to the presence of terrestrial macroinvertebrates in the temporary wetlands, few of which were encountered during live sampling. The terrestrial macroinvertebrate remains and subfossils collected in the sediment traps and from surface sediments confirms that temporary wetlands are utilised by terrestrial macroinvertebrates when dry (Adis & Junk, 2002; Ballinger et al., 2007; Ballinger et al., 2005; Junk, 1997a,

2005; Smith, 2000). In permanent wetlands, indicator genera richness increased from live to sediment trap sampling, and then declined in the surface sediments (19, 31 and 23, respectively). This may be explained by the fact that the sediment traps collected fresh macroinvertebrate remains that had not yet been lost and/or degraded due to the taphonomic processes that occur over time, and the presence of uncommon genera not collected during the live sampling. The decline in the number of indicator genera from trap to surface sediment sampling shows the potential effects of taphonomic losses, over time, on some orders and genera (Kidwell & Behrensmeyer, 1993; Staff & Powell, 1988). Greater losses of

162 genera would be expected in the surface sediments where the taphonomic processes have operated for a number of years, under a range of environmental conditions.

How well macroinvertebrate orders translated across the three different sampling methods used was variable. Orders such as Diptera, Coleoptera, and Hygrophila translated extremely well across live, sediment trap and surface sediment sampling in both temporary and permanent wetlands. However, taxa lacking preservable structures e.g. Collembola,

Lepidoptera, Ephemeroptera, Amphipoda, Nemertea, Nematode, Nematomorpha, and

Turbellaria were only collected during live sampling and did not accumulate in the sediment traps or the surface sediments (Frey, 1964). Note, the presence/absence of Lepidoptera can be determined via extraction of wing scales from sediments. The translation from the live to the death assemblages in sediment traps, and the surface sediments, is dependent on the presence of hard body parts such as head capsules, wings, and cases/shells (Frey, 1964; Smol et al.,

2001).

Taphonomic bias is known to be influenced by diverse biological and physical-chemical factors, which are, in turn, dependent upon the depositional environment (Smith, 2012; Smith et al., 2006). In the current study, the biases appeared to be similar in both temporary and permanent wetlands, even though wetland types experience different conditions, i.e. wet and dry phases compared to permanently wet. The factors controlling preservation quality include

‘insect input’ variables (e.g. insect size, morphology, and taxonomic group) and depositional factors (e.g. environment type, bathymetry, and energy levels (Smith, 2012; Smith et al.,

2006). Other than the fact that temporary wetlands have a dry phase, there is general similarity in the wetland physical and chemical conditions when they contained water (see

Chapter 2). Despite the differences in the two types of wetland, and the relative effects of the macroinvertebrates present, these are subordinate to the losses that occur because soft-bodied animals do not preserve. Differences in the translation of remains from the live to the

163 sediment traps and surface sediment remains are driven by the morphological dichotomy between soft and hard-bodied genera. Remains in the sediment traps are relatively new inputs, commencing the taphonomic process, and the losses and bias between wetland types influencing the subfossil assemblages found are likely to be incomplete. However, remains, particularly chitinous remains, are relatively resistant to biological, physical and chemical damage (Frey, 1964; Smol et al., 2001), whereas macroinvertebrates with shell remains i.e. gastropods and bivalves are known to be altered and degraded by physical and chemical properties such as pH over time (Cummins, 1994; Kidwell, Bosence, Allison, & Briggs,

1991; Walker & Goldstein, 1999).

The live and surface sediment macroinvertebrate assemblages show greater similarity to each other than the sediment trap remains, indicating that the live macroinvertebrate assemblage is well represented in the surface sediment subfossils and that the surface sediment reflects the live assemblage. Understanding the factors responsible for macroinvertebrate remains/subfossil preservation or loss, abundance, occurrence, and distribution is important to support the inferences made from palaeoecological and palaeolimnological studies (Sayer et al., 2010). Additional taphonomic studies on macroinvertebrates are needed to further understand and interpret the palaeoecological records (Smol et al., 2001).

Regardless of the sampling method used (live, sediment traps and surface sediment), genera were identified exhibiting associations with temporary and permanent wetlands. Wetland type can be distinguished based on the live, remains and subfossil macroinvertebrates present in the water and sediment. Some genera showed indicator potential across all three sampling methods whereas others were only collected or demonstrated wetland associations based on one or two of the sampling methods. Some indicator genera were collected frequently, while others occurred infrequently, suggesting variables other than hydroperiod alone affect the presence or absence of a macroinvertebrate in temporary and permanent wetlands.

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4.5 Conclusion

This study demonstrates that it is possible to distinguish the hydroperiod of a wetland based on the macroinvertebrate subfossils collected from wetland surface sediments. Many genera are not habitat-specific and occur in both wetland types; however, there are many that occur only in temporary or permanent wetlands and their presence can be used as a potential indicator of wetland hydroperiod. Additionally, a large proportion of the live macroinvertebrate assemblage translated into the sediment traps (remains assemblage), which then translated into the wetland surface sediments as subfossils, strengthening their use in future palaeoecological studies. The differences in the macroinvertebrate subfossil assemblages, and identification of indicator genera, suggests there is potential to determine wetland hydroperiod using either live, remains or subfossil macroinvertebrates, and that subfossils could be used to reconstruct historical waterbody hydroperiods over time in palaeoecological studies.

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Chapter 5: General Discussion

5.1. Effect of hydroperiod on macroinvertebrates

Understanding the factors responsible for the preservation or loss of macroinvertebrate subfossils, their abundance, occurrence, and distribution is important to support the inferences made from palaeoecological studies. This current study has demonstrated that hydroperiod has a significant effect on the composition of live macroinvertebrate assemblages in both temporary and permanent wetlands and that this difference translates to the remains collected in sediment traps and subfossil assemblages in surface sediments. For each of the three sampling methods used, it was possible to identify indicator genera based on their presence/absence and to distinguish wetland hydroperiod. Macroinvertebrate genera demonstrate habitat associations based on hydroperiod, with many only found in temporary or permanent wetlands.

5.2. Macroinvertebrate assemblage change and translation

As macroinvertebrates transfer from live, to trap remains and then surface sediment subfossil assemblages, soft-bodied taxa are lost in both temporary and permanent wetlands, and terrestrial genera are gained in the sediment of temporary wetlands. Hydroperiod is the main driver of the initial differences of live assemblages in temporary and permanent wetlands.

Translation of organisms is dependent on the presence of hard body parts, such as head capsules, wings and cases/shells, increasing their preservation potential (Frey, 1964; Smol et al., 2001). Temporary wetlands experience dry phases resulting in terrestrial macroinvertebrate inputs into the sediments.

In the present study, a total of 211 genera were identified across live, trap and surface sediment sampling methods in temporary and permanent wetlands. A total of 193 genera were collected in temporary wetlands, 73 genera (37.82%) were collected across all 3

166 sampling methods, 49 genera (24.67%) were common to 2 sampling methods, while 71 genera (36.79%) were only collected in a single type of sampling. In permanent wetlands, a total of 150 genera were collected, of which 59 genera (39.33%) were collected across all 3 sampling methods, 37 genera (24.67%) were common to 2 sampling methods, while 54 genera (36.00%) were only collected in a single type of sampling. There is a relatively good translation from live, to remains and subfossils for the entire macroinvertebrate assemblage in both temporary and permanent wetlands. However, genera can be lost or gained in this process. For orders/genera with hard body parts, such as Diptera and Coleoptera, a higher translation percentage occurred. For Diptera, 34 genera were identified in both temporary and permanent wetlands. In temporary wetlands, 23 genera (67.65%) were collected across all 3 sampling methods, 7 (20.59%) were common to 2 sampling methods, while 4 (11.76%) were only collected in a single type of sampling. In permanent wetlands, 28 genera (82.35%) were collected across all 3 sampling methods, 5 (14.71%) were common to 2 sampling methods, and 1 (2.94%) was only collected in a single type of sampling. A previous study (Van

Hardenbroek et al., 2011) found similar translation rates of live chironomids to surface sediment subfossils. The higher translation percentage demonstrates the importance of hard preservable body parts entering the subfossil assemblage, as it reflects the live assemblages.

This confirms previous studies that Diptera, particularly chironomids, have a useful role in palaeoecological studies (Armitage et al., 2012; Smol et al., 2001; Walker, 1987, 2001).

5.3. Effect of hydroperiod and taphonomy on macroinvertebrates

The taphonomic processes within wetlands have received limited scientific study (Seddon et al., 2019), but macroinvertebrates with chitinous body parts are known to withstand taphonomic processes, preserve and accumulate (Rumes et al., 2005; Van Hardenbroek et al.,

2011). The effects of hydroperiod on taphonomy are similarly not well understood.

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Environmental and depositional conditions experienced in temporary (wet and dry phases) and permanent (wet phase) wetlands vary, potentially influencing the physical, chemical, and biological taphonomic processes occurring in the short and long term, thus influencing the contents of the palaeoecological record. Results from the present study suggest that the decomposition of soft-bodied macroinvertebrates in both temporary and permanent wetlands is the dominant process whereby taxa are lost to surface sediments, with the differential effects of wetland hydroperiod being secondary. To better understand the potential effect of hydroperiod on taphonomy, additional studies are needed subjecting macroinvertebrate remains/subfossils to long-term field studies in wetlands experiencing different hydroperiods under different physical, chemical and biological conditions to ascertain their influence.

Detailed palaeoecological coring studies examining macroinvertebrate subfossils from sediment cores taken from temporary and permanent wetlands, assessing preservation differences e.g. preservation quality, would aid in understanding the potential long-term effects of hydroperiod on taphonomy.

5.4. Macroinvertebrates as biological indicators of hydroperiod

Aquatic macroinvertebrates are commonly used as biological indicators of waterbody conditions as they spend most, or all of their lifecycles in, and around water, and respond to natural and anthropogenic change within the environment (Cairns & Pratt, 1993; Metcalfe,

1989; Pinel-Alloul et al., 1996; Sharma & Rawat, 2009). Similarly, terrestrial macroinvertebrates are used as biological indicators of terrestrial environments (Gerlach,

Samways, & Pryke, 2013; Hodkinson & Jackson, 2005; McGeoch, 1998). This study has shown that both aquatic and terrestrial macroinvertebrates have the potential to be biological indicators for wetland hydroperiod. Based on each sampling method (live, sediment traps and surface sediment sampling), genera were identified by association with temporary and

168 permanent wetlands. For temporary wetlands 38, 55 and 63 genera were identified compared to 19, 31 and 23 genera in permanent wetlands, respectively. Potentially, the presence of any of the 57, 86, and 86 genera found during the live, trap and surface sediment sampling, respectively, could be used to indicate the hydroperiods (temporary or permanent) of wetlands.

Therefore, it is possible to determine hydroperiods of waterbodies using the presence/absence of certain macroinvertebrate genera found in live macroinvertebrate sampling as remains, or as surface sediment subfossils. By using subfossils within the palaeoecological record, it should be possible to determine wetland hydroperiods over time. Some genera showed indicator potential across all three sampling methods, whereas others were only collected or demonstrated wetland association based on one or two of the sampling methods undertaken.

Some indicator genera were collected frequently, while others occurred infrequently, indicating that there are more variables affecting the presence or absence of a macroinvertebrate genus in temporary and permanent wetlands than hydroperiod alone.

Indicator genera identified belong to orders or genera with preservable body parts, such as

Diptera, Coleoptera, Trichoptera, and Hygrophila, are likely to preserve and be incorporated into the palaeoecological record.

Not all potential biological indicators of hydroperiod identified in this study are of equal value, with some being better than others. Factors such as macroinvertebrate abundance (high or low), frequency of occurrence (common vs uncommon), and the presence/absence of preservable body parts will determine usefulness. Macroinvertebrates with high potential of being useful biological indicators belong to orders Diptera, Coleoptera, Trichoptera, and

Hygrophila. These groups were abundant, frequently found as live specimens and subfossils, and all possess preservable body parts. The value of these biological indicators in reconstructing past hydroperiods is also dependent on their incorporation and long-term

169 preservation and persistence in the palaeoecological record in temporary and permanent wetlands.

5.5. Reconstruction of hydroperiod and past environments using macroinvertebrates

To date, reconstruction of wetland hydroperiod has not been investigated by researchers.

However, the present study suggests that determining wetland hydroperiod using macroinvertebrate assemblages and the presence/absence of potential indicator genera in the palaeoecological record is eminently feasible. The hydroperiod of waterbodies varies over time, due to natural (e.g. climate), and anthropogenic factors. In many cases, the pre- disturbance pattern of wetting and drying of a wetland may be obscured over time. For example, wetlands that were previously periodically wet and dry, may have been artificially drained and terrestrial vegetation then become established. The analysis of sediment macroinvertebrates has the potential to shed light on the hydroperiod of such wetlands prior to draining.

In palaeoecological studies, how the live macroinvertebrate assemblage of waterbodies translates to the subfossil assemblage is poorly understood. However, the present study has shown that a large proportion of taxa with hard, preservable body parts translates well to the surface sediments. Soft-bodied genera fail to be incorporated into the subfossil record held in the surface sediments due to taphonomic processes occurring rapidly after death (i.e. within

12 months). However, from the present study, we now have a clear idea of what preserves, what is lost and why, and this knowledge will enhance all environmental reconstructions based on macroinvertebrates within the palaeoecological record.

5.6. Recommendations for the future

The following recommendations have been developed from undertaking the research for this thesis, which may aid and improve future studies:

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Macroinvertebrate sampling advantages and disadvantages

Based on the results from the present study, using three different sampling methods, all methods could be used to distinguish between temporary and permanent wetlands. For those embarking on a study of macroinvertebrates in such wetlands, live macroinvertebrate sampling is expensive, time-consuming and requires repeat sampling to gain a true representation of the assemblage, particularly for soft-bodied genera. Sediment trapping is cheaper, does not require repeated visits, and represents the macroinvertebrate assemblage over the entire deployment time. Sediment traps require less processing time than for live sampling. Surface sediment sampling is the cheapest trapping technique, is a one-off sampling event, involves less processing time when compared to live sampling, and provides a more comprehensive inventory of the local aquatic invertebrate assemblage than exploratory live sampling (Heiri, 2004; Rumes et al., 2005). Surface sediment samples represent years of accumulation and loss of macroinvertebrates under different environmental conditions and so integrate over time. Sediment traps and surface sediment sampling collects remains and subfossils of genera with tough preservable body parts, whereas soft-bodied genera are lost.

Further, since whole organisms generally do not preserve in sediment traps and surface sediment, greater familiarity of the genera is required to identify remains and subfossils. The advantages and disadvantages of each approach needs to be considered in light of the aims of the particular study, and the budget constraints. This thesis highlights the potential that palaeoecological studies can bring to ecological investigations.

Palaeoecological potential of temporary waterbodies

Temporary and permanent wetlands have value in future palaeoecological studies, as both accumulate and preserve macroinvertebrate remains. To date, most palaeoecological studies

171 have focused on permanent waterbodies, like lakes (Dimitriadis & Cranston, 2001; Gandouin et al., 2005; Gandouin et al., 2006). A potentially negative aspect of the dominance of studies of permanent systems is that they are often confined to small drainage basins, and experience few anthropogenic disturbances or physical constraints (Gandouin et al., 2005; Gandouin et al., 2006), and are naturally rare environments to begin with. One could potentially expect that these environments remain relatively constant − at least in comparison with floodplain wetlands, and wetlands of varying hydroperiods − and that the sediment records taken from these areas are possibly not a true representation of the wider landscape (Gandouin et al.,

2005; Gandouin et al., 2006). Floodplains and wetlands are known to yield useful palaeoecological information (Amoros & Van Urk, 1989; Gell et al., 2005; Michelutti et al.,

2001; Schönfelder et al., 2002). Further, since temporary wetlands are the most common aquatic environment, undertaking palaeoecological studies in these systems may potentially provide new insights into past environments and conditions, and could provide new research opportunities.

Combining taxonomic groups for greater palaeoecological insight

Studying the whole macroinvertebrate assemblage of wetlands can provide useful palaeoecological insight. However, in most cases, this is not a realistic or feasible option due to cost and technical difficulties. Macroinvertebrate palaeoecological studies should continue to focus on organisms that are known to preserve, have known ecological associations/requirements, and can be identified from remains. Such groups include Diptera,

Coleoptera, Trichoptera, Mollusca and Acarina. The use and development of these proxies, individually or in combinations, will continue to improve reconstruction potential.

Palaeoecological researchers and studies tend to focus on a particular group of organisms

(e.g. Diptera) whereas other macro- and microinvertebrates (e.g. ostracods, Cladocera) and other microorganisms (e.g. diatoms, chrysophycean cysts, testate amoebae), diatoms, pollen,

172 and plant macrofossils are ignored. If palaeoecologists investigating different taxonomic groups found within the palaeoecological record collaborated, combining knowledge bases, greater advances in palaeoecological reconstruction and insights into past environments and conditions could be achieved.

Value of terrestrial taxa in aquatic studies

Normally, terrestrial macroinvertebrate taxa are completely ignored in freshwater studies.

However, they can provide useful ecological information when remains and subfossils (e.g.

Coleoptera) are found in wetland sediments. Terrestrial macroinvertebrate taxa have their own ecological requirements, and their presence and relative abundance could provide information about the surrounding environment and conditions experienced.

Macroinvertebrate biology and ecology

More research into the biology and ecology of macroinvertebrates in floodplain wetlands is needed. Insight into the biology and ecology of taxa associated with wetlands, including lifecycles, habitat requirements, the ability to survive drying and flooding, and the effect of hydroperiod on fauna are needed. Further work investigating the macroinvertebrate fauna of temporary and permanent wetlands associated with different river and floodplain systems, flooding scenarios (frequency, timing, duration), as well as sampling of wetlands along hydroperiod gradients, would provide beneficial insights into the effect of hydroperiod on the fauna present. Studies into how macroinvertebrates colonise and utilise temporary systems are needed, as many temporary wetlands act as terrestrial systems for longer durations than aquatic systems. Additionally, how terrestrial macroinvertebrates are impacted by inundation at the conclusion of the terrestrial phase, and their incorporation into the palaeoecological record, needs further investigation.

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Macroinvertebrate taphonomy

Macroinvertebrate taphonomy is poorly understood due to the number of factors and possible interactions that can be involved. However, the factors responsible for macroinvertebrate remains/subfossil preservation or loss, abundance, occurrence, and distribution are important to know, so that the inferences made from palaeoecological and palaeolimnological studies are supported with evidence (Sayer et al., 2010). Understanding subfossil macroinvertebrate biases is crucial for determining the limitations on the use of subfossil macroinvertebrate data, and for distinguishing between true patterns and artefacts in the palaeoecological record

(Smith et al., 2006). From this thesis we now have a better understanding of what is present, what is missing, and why which was previously not adequately understood, even though this affects most biological interpretations attempted using the subfossil record (Alin & Cohen,

2004; Flessa & Brown, 1983; Kidwell & Behrensmeyer, 1988). Taphonomic studies looking at the full macroinvertebrate assemblage, or key orders commonly used in palaeoecological studies (e.g. Diptera, Coleoptera, and Trichoptera), would greatly strengthen results and confidence in reconstruction capabilities. Investigating the taphonomy of macroinvertebrates in different depositional environments, and under different physical/chemical conditions, would be useful.

Development of macroinvertebrate sampling and identification

Sampling, extraction and identification of live and subfossil macroinvertebrates is a time- consuming task, requiring skill. Therefore, simpler and more reliable methods of identification of macroinvertebrates could lead to increased knowledge, and possibly expand their use as indicator species for environmental monitoring and reconstruction. The use and application of new methods, for example DNA, environmental DNA, and artificial intelligence to identify macroinvertebrates could revolutionise macroinvertebrate studies in

174 the future (Bush et al., 2019; Carew, Pettigrove, Metzeling, & Hoffmann, 2013; Elbrecht,

Vamos, Meissner, Aroviita, & Leese, 2017; Joutsijoki et al., 2014; Mächler, Deiner,

Steinmann, & Altermatt, 2014).

5.7. Final Conclusions

This thesis has demonstrated that wetland hydroperiod has a significant effect on the macroinvertebrates in both temporary and permanent wetlands. It is possible to determine and distinguish wetland hydroperiod based on the assemblages and the presence/absence of indicator genera which showed habitat preference based on live sampling, trap remains and sediment subfossils. It has been shown that the macroinvertebrate assemblages change as they translate from the live to the subfossil assemblages in wetland sediments, predominately due to the loss or gain of genera. Further, this thesis also suggests that subfossils could be used to reconstruct historical waterbody hydroperiod over time in future palaeoecological studies.

Methodology used and developed within this study (trap sampling, surface sediment sampling) could be adapted to suit investigation of other palaeoecological proxies, including diatoms and plants. As other organisms are known to demonstrate habitat associations based on hydroperiod, multiple groups of organisms could be collected simultaneously, strengthening reconstruction potential with further evidence of current and past hydroperiod conditions.

Finally, this study highlights the importance of heterogeneity in floodplain and wetland environments to support and maintain macroinvertebrate biodiversity in temporary and permanent wetlands, and the need to protect, preserve, and study all types of aquatic environments.

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