Evidence for the physical effects of catchment sediment runoff preserved in estuarine sediments: Phase III (macrofaunal communities) June 2003 Technical Publication 222
Auckland Regional Council Technical Publication No. 222, June 2003 ISBN 1-877353-26-4, ISSN 1175 205X www.arc.govt.nz
on recycled paper
Evidence for the physical effects of catchment sediment runoff preserved in estuarine sediments: Phase III macrofaunal communities
C.J. Lundquist K. Vopel S.F. Thrush A. Swales
Prepared for Auckland Regional Council
NIWA Client Report: HAM2003-051
June 2003
NIWA Project: ARC03202
National Institute of Water & Atmospheric Research Ltd Gate 10, Silverdale Road, Hamilton P O Box 11115, Hamilton, New Zealand Phone +64-7-856 7026, Fax +64-7-856 0151 www.niwa.co.nz
Contents
Executive Summary iv
1. Introduction 1
1.1 Background 1
1.2 Study objectives 2
2. Methods 3
2.1 Sampling design 3
2.2 Sampling locations 3
2.3 Sampling design and sample processing 6
2.4 Macrofaunal analyses 7
2.5 Statistical analyses 7
2.6 Linking community analyses to environmental variables 8
3. Results 9
3.1 Description of communities found within each Auckland estuary 9
3.1.1 Mahurangi estuary (intertidal and subtidal cores) 9
3.1.2 Puhoi estuary (intertidal cores) 16
3.1.3 Okura estuary (intertidal cores) 17
3.1.4 Waitemata estuary (intertidal and subtidal cores) 19
3.1.5 Whitford embayment (subtidal cores) 22
3.1.6 Wairoa estuary (intertidal and subtidal cores) 23
3.1.7 Te Matuku estuary (Waiheke Island) (intertidal cores) 25
3.2 Comparison of communities within Auckland estuaries 27
3.2.1 Subtidal and intertidal comparisons 27
3.2.2 Across estuary comparisons 29
3.3 Predicting community composition with environmental data 33
4. Conceptual Model 37
5. Conclusions and Recommendations 39
6. Acknowledgements 43
7. References 45
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Executive Summary
Macrofaunal community structure is determined by a number of factors that can be influenced by sedimentation rates. Sedimentation in estuaries modifies estuarine morphology and sediment type, increases levels of suspended sediments, and changes the food resources available to macrofaunal communities. Sediment disturbances can be both chronic and catastrophic; however, the frequency of large events is likely to be particularly important in determining the abundance and structure of benthic communities.
Stratigraphic cores of estuarine sediments can be analysed to determine rates of sedimentation, changes in sediment grain size, and mass mortality events of bivalves preserved as layers of shells. These time series of sedimentation can be compared with present-day macrofaunal community data to allow us to interpret the long-term ecological effects of sedimentation history on macrofaunal communities.
This report is the third and final report of a three part series. In the first report, we reviewed what was known about the effects of catchment sediment runoff in estuaries and suggested procedures and methods to obtain estimates of sedimentation rates. In the second report, we presented analyses of sediment cores collected from Auckland estuaries (drowned valley estuaries: Mahurangi, Okura, Waitemata, Henderson, and Wairoa; tidal lagoons: Puhoi; and coastal embayments: Whitford, Te Matuku – Waiheke Island). In these analyses, pollen, caesium-137 (137Cs), lead-210 (210Pb), Zinc (Zn) and sediment particle size were used to determine sediment accumulation rates (SAR) for each of the estuaries.
In this third report, we present information on the communities of benthic macrofauna found in the areas from which the sediment cores were taken, as a regional ‘snap-shot’ of macrobenthic biodiversity in Auckland estuaries. Although muddy areas are generally thought of as being of low diversity, we found this was not necessarily the case. Instead, we found a range of community types in Auckland estuaries, varying among estuarine type as well as between subtidal and intertidal locations within individual estuaries. Two estuaries had notably low diversity, Puhoi Intertidal and Wairoa Intertidal estuaries, corresponding to the highest rates of sediment accumulation calculated in the Phase II study.
We present a conceptual model that can be used to predict likely changes in macrofaunal communities as Sediment Accumulation Rate (SAR) increases in estuaries, as may happen with increasing urbanisation. The model links community structure with aging of the estuary, incorporating predictable changes in macrofaunal community structure as estuaries progress from relatively open basins with large proportions of subtidal habitat to largely infilled areas of primarily intertidal habitat.
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Both the conceptual model and macrobenthic community data indicate that all three types of estuaries studied (tidal lagoons, drowned valley estuaries and coastal embayments) are comprised of diverse, variable communities at early stages of estuarine infilling (corresponding to low or natural rates of sediment accumulation). The three types of estuaries converge to a similar low diversity, stress-tolerant community as SAR increases and estuaries become infilled.
This research points to the need for further research on the long-term effects of sedimentation on different estuary types, as in this study, estuary types were not able to be examined at all stages of sedimentation. In addition, the study was limited to muddier sediments. As macrofaunal communities in sandier sediments are likely less tolerant of increased muddiness and higher levels of suspended sediment concentrations than are those in muddier sediments, studies of this type should be expanded to determine the effects of chronic and catastrophic levels of sediment deposition on these sandy communities. Finally, fundamental research is necessary to address the collection of physical data on sedimentation at scales relevant to the macrofaunal communities, in order to better analyse the effects of both net and gross sedimentation.
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1. Introduction
1.1 Background
The Auckland region is currently home to about a million people and a doubling of the population is anticipated to occur during the next 50 years. Urban development increases runoff of water and sediment during the earthworks phase, and contaminant loads increase as urban areas mature. Both of these factors can alter the composition and quantity of sediment deposited in estuaries (Williams, 1976; Douglas, 1985; Williamson, 1993; Morrissey et al. 2000; Swales et al. 2002). While some of this catchment sediment runoff is discharged directly to the sea, part of the sediment load is deposited in estuaries. Estuaries are particularly vulnerable to the effects of catchment land-use changes because of their close proximity to the sediment source and physical and biological processes that promote sedimentation. Auckland’s numerous and varied estuaries are highly valued features of the coastal environment, and are variously impacted by land runoff.
Evidence from prior studies (reviewed in Hume et al. 2002) has linked catchment development and sediment accumulation to ecological effects on estuarine macrofaunal communities. Long-term monitoring programmes have implicated increased quantities of fine sediments in the decline of populations of the horse mussel Atrina zelandica and changes in the structure of benthic faunal communities (Mahurangi estuary: Cummings et al. 2003. More direct and stronger evidence of the effects of mud deposition on benthic fauna is provided by biological processes studies that have directly examined the effects of sudden increases in the rate of sedimentation (Hewitt et al. 1998, Norkko et al. 1999, Nicholls et al. 2000, Lohrer et al. 2003) and increased levels of suspended sediments (Thrush et al. 1998, Ellis et al. 1999, Hewitt et al. 2001).
In this final phase of a three-part study, we identified robust indicators that can be used to quantify the physical effects of catchment sediment runoff on estuaries. In Phase I of our study, Hume et al. (2002) reviewed the relative merits of methods commonly used to reconstruct impacts of catchment development on estuaries based on analysis of sediment cores. In Phase II, we used these indicators to determine rates of sediment accumulation in seven estuaries (subtidal and intertidal environments) within the Auckland region (Swales et al. 2002).
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1.2 Study objectives
The objectives of the third phase of this study were to investigate the structural similarities of macrofaunal communities at ten locations with the Auckland region. These are the same sites that were analysed with sediment stratigraphic cores in Phase II. We present a regional ‘snap-shot’ of macrobenthic biodiversity within this cross-section of estuaries in the Auckland region, relating historical land-use patterns to current estuarine structure and macrofaunal communities.
Hume et al. (2002) argued that the effects of catchment sediment runoff on macrofaunal communities may not be captured in the stratigraphic record. Rather, stratigraphic records provide information about historical changes in net sedimentation rates, not necessarily preserving unequivocal evidence of direct mortality due to sedimentation events. However, correlations between sedimentation rates from the stratigraphic record and macrofaunal communities present at a location, combined with morphological information from an estuary should indicate some level of influence of catchment sediment runoff on long-term degradation of benthic communities.
The aim of this analysis is to link the physical effects of catchment sediment runoff with contemporary macrofaunal communities, and to develop a conceptual model of community change due to both natural processes (aging of estuaries) and accelerated sedimentation of terrestrial silts and clays derived from human activities in catchments. This model could then be used to predict the long-term effect catchment development on Auckland’s estuarine systems. We also investigate potential ecological indicators of the effect of SAR on macrofaunal community health in estuaries in the Auckland region.
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2. Methods
1.1 Sampling design
We use a “natural experiment” to investigate the effects of catchment runoff on the structure of estuarine macrofaunal communities. Community data from intertidal and subtidal flats are compared between different types of estuaries (tidal lagoon, drowned valley estuary, coastal embayment) and estuaries with different measured rates of sediment accumulation from the data collected in Phase II. Our hypothesis was that communities change naturally across each estuary, with variation in communities between subtidal and intertidal flats, as well as variation between estuary types. As a first step, we test for differences between macrofaunal communities of the intertidal and subtidal estuaries sampled. We then analyse these differences in community structure to determine if community patterns are related to estuary types, subtidal and intertidal differences in community composition, and physical effects of catchment runoff (as measured by SAR).
2.2 Sampling locations
In consultation with the Regional Council, several estuaries were selected that are representative of the common types of estuaries in the Auckland region: drowned- valleys, tidal-lagoons, and coastal embayments. Estuaries were also selected to give a range of different stages of catchment development, from mixed regenerating indigenous forest, to pasture land, to estuaries with partly urbanized catchments where land-use intensification (i.e., construction of life-style blocks) is likely to occur. We collected stratigraphic core samples and macrofaunal samples at three different locations in each estuary (Table, 1, Figure 1). Three of the seven estuaries were sampled at both intertidal and subtidal locations.
Drowned valley estuaries (Waitemata, Mahurangi, Okura, Wairoa) are the most common estuary type in the Auckland region. Importantly, the selected estuaries cover the entire range of infilling stages. The Waitemata Harbour is partially infilled, but remains largely subtidal. Infilling is most advanced in the tidal creeks of the upper Harbour. Infilling of the Mahurangi estuary is more advanced, with intertidal flats accounting for ~55% of its area (Swales et al. 1997). Subtidal areas dominate only in the lower reaches of the estuary. The Okura estuary has substantially infilled with sediment, with extensive intertidal flats flanking a narrow tidal channel. Mangroves
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are mainly restricted to the tidal flats fringing the upper estuary. The Wairoa estuary represents a mature drowned valley estuary, which has almost completely infilled with muddy sediments and has extensive intertidal mangrove mud flats.
Table 1: Estuaries selected for current study.
Date Estuary Type of estuary CER1 Code Sampled Mahurangi Drowned valley 5 Oct 01 MHI, MHS Puhoi Tidal lagoon 25 Oct 01 PUI Okura Drowned valley 16 Oct 01 OKI Waitemata Drowned valley 5 Jan 02 WTI, WTS
Whitford Coastal embayment 6 Oct 01 WHS Wairoa Drowned valley 124 Oct 01 WAI, WAS
Te Matuku (Waiheke Island) Coastal embayment 6 Oct 01 TMI
(1) CER = Catchment / Estuary (area) Ratio (2) Letter I & S refer to intertidal and subtidal locations respectively.
The Puhoi estuary is representative of the several tidal lagoons that fringe Auckland’s east coast, such as Orewa, Waiwera and Whangateau (Omaha). Tidal lagoons form where barrier systems, usually Holocene sandy spits, have built across bays or the mouth of a drowned river valley to enclose a marine water body. Tidal lagoons are typically highly infilled and have extensive areas of intertidal sand flats cut by narrow drainage channels. Typically about 70% of the surface area is intertidal (Hume and Herdendorf 1992). As a consequence, flows in the main body of the estuary are dominated by the tides, and tidal pumping facilitates exchange and flushing between the estuary and the sea.
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Figure 1: Auckland estuaries selected for the regional sedimentation study.
A coastal embayment is an extension of the sea into a recess or indentation in the coast. Whitford Bay is a compound estuary and can be described as a series of tidal creeks draining to a coastal embayment. Coastal embayments lie on the open coast, and are common on offshore islands (e.g., Te Matuku). Coastal embayments generally have little freshwater input and catchment sediment runoff has little effect in these estuaries. However, in situations where catchment sediment runoff is greater, such as Whitford where tidal creeks drain into the embayment, runoff will result in greater sedimentation in the embayment. The Te Matuka embayment has largely infilled with muddy sediments and receives runoff from a mixed pasture/native forest catchment.
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The estuaries can also be classified in to two groups based on catchment/estuary ratio: (1) estuarine systems with small Catchment/ Estuary Ratio (5–6) and (2) estuarine systems with large Catchment/ Estuary Ratio (16–124). Group one includes estuaries retaining large subtidal areas (Mahurangi, Waitemata, Whitford), although Te Matuku is an exception. Group two is represented by the largely intertidal Puhoi, Okura, and Wairoa estuaries (Table 1).
Table 2: Estuary and catchment characteristics (source: NIWA Estuary Environment Classification Database).
Estuary Area Intertidal Mangrove Tidal Prism1 Catchment Rainfall2 (km2) Area (%) Area (%) (106 m3) Area (km2) (mm yr-1)
Mahurangi 24.6 51 20 44.9 122.2 1620 Puhoi 1.7 71 27 2.7 43.0 1320 Okura 1.4 79 14 2.1 22.7 1320 Henderson 2.0 – – – 105.1 1390 Waitemata 79.9 36 12 216.1 427.3 1390 Whitford 11.1 82 11 18.5 61.0 1180 Wairoa 2.5 42 42 5.2 311.2 1360 Te Matuku 2.0 76 19 4.4 12.2 1360
Notes: (1) tidal prism estimated from the average surface area of estuary and spring tidal range. (2) rainfall is the areally weighted rainfall value obtained by overlaying the catchment boundary on the 30 year (1951- 1980) normal rainfall map surface.
2.3 Sampling design and sample processing
At ten sites (6 intertidal sites, 4 subtidal sites) we collected sediment cores from muddy substrates in low-wave energy environments, sites where undisturbed sedimentation records are most likely to be preserved, one sediment core (length = 30 cm) was taken at each of three adjacent locations from each site for complementary dating (210Pb, 137 Cs, pollen), analyses of heavy metals and particle size (Phase II of this study - for further details on sediment core collection and analysis, see Swales et al. 2002). For macrofaunal analysis, we collected 8 additional cores at random locations within a 10 m radius of each of the three sediment cores at each site. Mudflats at the intertidal sites were sampled at low tide, using a 13-cm-diameter corer for the macrofaunal cores. Subtidal flats at the subtidal sites (depths of < 10 m below chart datum) were sampled by SCUBA divers using a 10-cm-diameter core for macrofaunal cores. The location of each core sampling location was fixed to +/- 1 m using differential global position (DGPS) for subtidal sites and to +/- 5 m using hand- held GPS for intertidal cores (Appendix 1).
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2.4 Macrofaunal analyses
Core samples were sieved on a 500-µm mesh and the residues stained with Rose Bengal and preserved in 70% isopropyl alcohol in seawater. The macrofauna were then sorted, identified to the lowest possible/practical taxonomic level, counted and stored in 50% isopropyl alcohol. The number of individuals for subtidal cores was adjusted such that averages were based on the same volume as intertidal cores.
2.5 Statistical analyses
Univariate and multivariate statistical techniques were used to examine the relationship between the structure of the macrofaunal communities and the physical data (e.g., Sediment Accumulation Rates (SAR)) collected in Phase II from the sediment dating cores. The majority of the analytic techniques used are described in Clarke and Warwick (1994) and are included in the PRIMER package, a computer program developed at the Plymouth Marine Laboratory.
Univariate measures and graphical/distributional plots
We calculated Shannon-Wiener diversity using natural logarithms, species evenness as Pielou’s J’, and species richness as Margalef’s index from abundance data. Average k-dominance curves were calculated to demonstrate relative number of species dominating each site. Species were ranked in decreasing order of abundance and values were converted to percentage abundances relative to the total number of individuals in the sample.
Multivariate ordination
Non-parametric multivariate techniques were applied, as described in Clarke and Warwick (1994). Standardised abundance data were square-root transformed to reduce contributions to similarity by abundant taxa. Ranked matrices of similarities among samples were constructed using the Bray-Curtis similarity measure. Ordination was performed using non-metric multidimensional scaling. Significance tests for differences between groups were performed with the one-way ANOSIM permutation test. The contributions of taxa to similarities within groups and dissimilarities between groups of samples were analysed using the similarities percentages procedure (SIMPER).
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2.6 Linking community analyses to environmental variables
Our biotic data are matched by a suite of environmental variables measured at the same locations. These variables describe the physical properties of the substrate from which the samples were taken, e.g., mean and median particle diameter, mud content, zinc concentration, and SAR (see Swales et al. 2002 for detailed calculations of each of these parameters). We examined the extent to which this physical data is related to the observed biological pattern.
Community composition was analysed concurrently with environmental indices based on estuarine variables (Table 2), sedimentation rates and other variables that relate to the estimates of sedimentation rates calculated in Phase II (Swales et al. 2002). The SARs, expressed in mm yr-1, used in this section were derived from measurements of 137Cs for post-1953 A.D. as these rates were verified by other SAR calculations using other dating methods, and were most readily available for all core locations (Swales et al. 2002). We first used a Kruskal-Wallis test (non-parametric one-way ANOVA) to test for differences in SAR between sites. Post-hoc pairwise Bonferroni multiple comparison tests were calculated to determine differences between pairs of sites.
Canonical correspondence analysis (CCA) and partial canonical correspondence analysis (PCCA; ter Braak 1986) were used to assess the importance of SAR and other physical variables in influencing the macrobenthic community structure. In CCA, we performed two analyses: one with SAR as the sole environmental variable, and a second with SAR, mud content, Zinc content, mean grainsize, median grainsize, and catchment to estuary ratio. PCCA was used to discriminate the effect of SAR and estuary type from the effects of other physical co-variables. Co-variables used in the partial canonical correspondence analysis were: mud content, Zinc content, mean grainsize, median grainsize, maximum depth of Cs in the sediment cores, and catchment to estuary ratio. These analyses were performed using CANOCO (ter Braak and Smilauer 1998).
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3. Results
3.1 Description of communities found within each Auckland estuary
3.1.1 Mahurangi estuary (intertidal and subtidal cores)
The Mahurangi estuary is one of the largest drowned-valley systems on Auckland’s east coast (Fig. 2). The estuary has a high-tide surface area of 24.7 km2 and a tidal volume of ~44.9 million m3 (Table 2). At low tide, the main tidal channel is flanked by extensive intertidal flats composed of sands and muddy-sands, which are fringed by extensive mangrove stands (Swales et al. 1997). The estuary receives runoff from a 122-km2 catchment of which 65% drains to the head of the estuary at Warkworth. The estuary is an important recreational resource, widely used for boating and fishing and is also the site of a large-scale (~120 ha) pacific oyster industry established in the early 1970’s. Land-use in the catchment was primarily farming until 1975, at which time a Pinus radiata forest was planted in the upper reaches. There are two urban centres within the catchment, Warkworth and Snells Beach.
Locations sampled were both intertidal and subtidal flat environments in the Mahurangi estuary (Fig. 2). Intertidal locations were in the extensive intertidal flats on the eastern flank of the main tidal channel north of Grants Island and subtidal locations were on a flat ~0.5 km south of Grants Island between 4–5 m below chart datum. Both the intertidal and subtidal sediments were typically muddy fine-sands composed of fine silt (~20 µm modal diameter) and very fine sand (~100–150 µm modal diameter) (Swales et al. 2002). On the intertidal flat, mud content increased from ~5% (core MH-I1) to 20–40% (core MH-I3) with distance towards the head of the estuary. The subtidal sediments also contained quantities of coarse sand-sized shell fragments (Swales et al. 2002).
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Figure 2: Mahurangi estuary – location of intertidal and subtidal cores and major sub-environments.
A total of 22 taxa were found at the three intertidal Mahurangi sites (Appendix 2). The three sites were similar in average number of individuals and taxa per core (40.25 to 56.5 and 5.5 to 7 respectively, Table 3). The locations MHI-1 and MHI-2 were similar in community composition, and were dominated by polychaete species (Cossura sp., Aricidea sp. and Heteromastus filiformis, Table 5). The small deposit-feeding bivalve Nucula hartvigiana was the most abundant species at MHI-3, followed by Heteromastus filiformis and the polychaete Nicon aestuariensis (Table 5). The
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Shannon-Wiener diversity index was relatively low compared to other estuaries, ranging from 0.96 to 1.28, primarily due to the dominance of the fauna by few species (Figure 3).
More taxa were found in total at the three subtidal Mahurangi sites (Appendix 2), although average numbers of taxa per core (range 5.1 to 6.5) were similar to the intertidal Mahurangi sites. However, fewer individuals were present in each core compared to the intertidal Mahurangi cores, with an average number of individuals per core of between 13.9 and 21.3 individuals per core (Table 4). The three sites had similar community composition and were dominated by the bivalves Theora lubrica and Arthritica bifurca, species of the polychaete family Cirratulidae, and the polychaete species Labiosthenolepis laevis and Aricidea sp. (Table 6). Shannon- Wiener diversity indices were slightly larger than the indices calculated for the Mahurangi intertidal sites, ranging from 1.40 to 1.67, due to the more even distribution of individuals across taxa (Figure 4).
Table 3: Average, maximum and minimum number of individuals and taxa per core at intertidal estuarine locations.
Number of Individuals Number of taxa Estuary Site Average Max. Min. Average Max. Min. Mahurangi 1 49.5 69 33 5.5 7 4 2 56.5 78 27 7.0 10 4 3 40.3 81 16 6.3 9 3 Okura 1 24.5 37 13 9.9 13 6 2 23.8 30 9 8.3 10 5 3 28.5 54 20 7.4 9 5 Puhoi 1 12.9 38 2 2.8 4 2 2 11.1 20 2 2.9 5 1 3 38.4 79 11 2.8 4 2 Te Matuku (Waiheke) 1 19.75 31 9 8.3 12 5 2 39.3 51 31 9.8 12 7 3 22.3 31 15 9.0 12 7 Wairoa 1 8.6 18 2 3.5 5 2 2 7.6 12 3 1.8 3 1 3 8.3 14 4 3.3 5 2 Waitemata (Henderson) 1 78.5 131 49 10.8 15 9 2 49.8 79 32 11.4 15 7 3 108.6 182 61 9.1 12 7
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Table 4: Average, maximum and minimum number of individuals and taxa per core at subtidal estuarine locations. The number of individuals for subtidal cores was adjusted such that averages were based on the same volume as intertidal cores.
Estuary Site Number of Individuals Number of taxa Average Max. Min. Average Max. Min. Mahurangi 1 13.9 22.0 3.4 5.1 7 2 2 21.3 38.9 8.5 6.8 11 3 3 21.1 33.8 5.1 6.5 10 2 Wairoa 1 12.5 20.3 5.1 4.1 5 2 2 14.2 25.4 8.5 5.5 7 3 3 9.7 15.2 1.7 3.9 6 1 Waitemata (Te Atutu) 1 53.1 74.4 30.4 7.4 9 4 2 36.5 65.9 8.5 6.4 10 3 3 50.7 72.7 16.9 8.1 10 7 Whitford 1 11.2 30.4 3.4 3.6 7 2 2 7.6 11.8 3.4 3.6 6 1 3 10.4 13.5 5.1 3.9 5 2
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Table 5: The five dominant taxa collected at each intertidal site. When more than one taxa has the same rank, they are represented as (for example) ‘Theora / Aricidea’.
Location Sample Most abundant Ö Ö Ö Least abundant
Mahurangi 1 Cossura Heteromastus Aricidea Macrophthalmus Nicon 2 Cossura Heteromastus Aricidea Theora Oligochaeta 3 Nucula Heteromastus Nicon Phoxocephalidae Asychis
Okura 1 Heteromastus Aquilaspio Macrophthalmus Glycera Nereidae 2 Aquilaspio Scoloplos Heteromastus Macrophthalmus Helice / Glycera / Pectinaria 3 Heteromastus Paracorophium Helice Glycera Macrophthalmus
Puhoi 1 Oligochaeta spp. Paracorophium Helice Perinereis Nemerteana 2 Oligochaeta spp. Paracorophium Helice Nicon Perinereis / Scoloplos / Labiosthenolepis 3 Oligochaeta spp. Paracorophium Helice Austrovenus / Aotearia / Scoloplos
Te Matuku 1 Heteromastus Macrophthalmus Aquilaspio Paracorophium Austrovenus 2 Heteromastus Aquilaspio Macrophthalmus Oligochaeta Nemerteana 3 Heteromastus Aquilaspio / Scoloplos Austrovenus Macrophthalmus
Wairoa 1 Helice Paracalliope Oligochaeta Heteromastus Boccardia 2 Helice Paracalliope Oligochaeta Heteromastus None 3 Helice Oligochaeta Paracalliope Boccardia / Nemerteana
Waitemata 1 Aricidea Heteromastus Cossura Nereidae Austrovenus 2 Nucula Heteromastus Aricidea Cossura Nicon 3 Nucula Aricidea Austrovenus Heteromastus Torridoharpinia
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Table 6: The five dominant taxa collected at each subtidal site. When more than one taxa has the same rank, they are represented as (for example) ‘Theora / Aricidea.
Most Least Sample Abundant Ö Ö Ö Abundant Mahurangi 1 Theora Labiosthenolepis Cirratulidae Torridoharpinia Aricidea 2 Theora Labiosthenolepis Arthritica Cirratulidae Nucula / Pectinaria / Terebellides 3 Theora Arthritica Labiosthenolepis Aricidea Cirratulidae
Wairoa 1 Labiosthenolepis Arthritica Cirratulidae Aotearia Macrophthalmus 2 Paracalliope Labiosthenolepis Paronella Ophiuroidae Tanaidae 3 Aotearia Paronella Labiosthenolepis Tanaidae Phoxocephalidae
Waitemata 1 Nucula Paronella Phoxocephalidae Boccardia Cossura 2 Tanaidae Nucula Orbinidae Paronella Phoxocephalidae / Cossura 3 Cossura Nucula Paronella Theora Tanaidae
Whitford 1 Aotearia Aricidea Torridoharpinia Nucula Theora 2 Aotearia Macropthalmus Cossura Labiosthenolepis Aricidea 3 Aotearia Cossura Cirratulidae Aricidea Theora / Macrophthalmus / Maldanidae
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Shannon-Wiener Diversity 3.0 Evenness Richness 2.5
2.0
1.5
1.0
0.5
0.0 123 123 123 123 123 123 Mahurangi Okura Puhoi Waiheke Wairoa Waitemata
Figure 3: Average species diversity, evenness and richness for the three sampling locations at each intertidal site.
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Shannon-Wiener Diversity Evenness 2.5 Richness
2.0
1.5
1.0
0.5
0.0 123 123 123 123 Mahurangi Wairoa Waitemata Whitford
Figure 4: Average species diversity, evenness and richness for the three sampling locations at each subtidal site.
3.1.2 Puhoi estuary (intertidal cores)
The Puhoi estuary is one of several similar tidal-lagoon estuaries that fringe Auckland’s east coast north of the Whangaparoa Peninsula (Fig. 5). The estuary is sheltered from the sea by a large sand barrier at its mouth that has been constructed by wave action. The Puhoi estuary has a high-tide surface area of 1.7 km2 and a tidal prism of 2.7 x 106 m3 or ~6% of the tidal volume of the Mahurangi estuary (Table 2). The estuary is substantially infilled with sediment (i.e., ~70% intertidal). A quarter of the total estuary area has been colonised by mangrove. The main tidal channel is braided in the lower estuary with extensive intertidal sand flats, which become increasingly muddy with distance towards the head of the estuary. Because the estuary is largely intertidal (Table 2), there is almost complete exchange of estuarine water with each tidal cycle. The estuary receives runoff from a 43-km2 catchment. Present day catchment landcover is comprised of regenerating native forest (20%) and scrub (10%), production forestry (23%) and pasture (47%) (source: NZ Land Resource Inventory).
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Figure 5: Puhoi estuary – location of intertidal cores and major sub-environments.
Locations sampled were ~100-m apart on an intertidal mud flat in the upper reaches of Puhoi estuary adjacent to a channel meander (Fig. 5). The sediments were mixtures of fine silt (~20 µm modal diameter) and very fine sand (~100–150 µm modal diameter) similar to those of the Mahurangi estuary. The mud content of the cores varied between 5 and 20% (Swales et al. 2002).
The fauna found at the three intertidal Puhoi sites was composed of 11 different taxa (Appendix 2). Average number of taxa per core (2.8-2.9) was similar for all three sites, with relatively few species dominating the fauna (Table 3). The three sites were similar in species composition, dominated by oligochaetes, the amphipod Paracorophium excavatum, and the mud crab Helice crassa (Table 5). Average number of individuals per core were similar for two of the locations, PUI-1 and PUI-2 (12.9 and 11.1), while the sample PUI-3 contained approximately 3 times as many individuals (38.4). The Shannon-Wiener diversity index was lower at the Puhoi sites compared to the other intertidal sites, with a range of 0.55 to 0.74, due to both fewer taxa and because over 90% of the fauna was composed of only three species (Figure 3).
3.1.3 Okura estuary (intertidal cores)
The Okura estuary is a small, infilled drowned valley estuary, which opens to the sea in the southern lee of Whangaparoa Peninsula (Fig. 6). The estuary has a high-tide surface area of 1.4 km2 and a tidal prism of only ~5% of the Mahurangi estuary. A single main tidal channel is flanked on both sides by an intertidal flat, which
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submerges to an average depth of 1 m (Green and Oldman 1999). The estuary is funnel-shaped and its width, which is ~0.6 km at the mouth, rapidly diminishes towards the head of the estuary. In the middle estuary a shell spit, some 300-m long, extends across the intertidal flats from the northern shore. Seaward of the spit, intertidal sediments are sandy whereas above the spit the intertidal flats become increasingly muddy. The upper estuary is also fringed by extensive stands of mangrove. Because the estuary is largely intertidal, there is almost complete exchange of estuarine water with each tidal cycle. The estuary receives runoff from a 22.7-km2 catchment. Present day catchment landcover is dominated by native forest and scrub (43% area) and pasture (40% area) (Stroud et al. 1999). As urban development and rural intensification continues further landcover changes are anticipated. Construction of the Okura section of Albany–Puhoi highway occurred in 1998 and much of the Okura catchment is potentially available for rural intensification (Stroud et al. 1999).
Figure 6: Okura estuary – location of intertidal cores and major sub-environments.
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Locations sampled were on an intertidal flat in the upper reaches of the estuary and in close proximity to the pine plantation on its northern flank (Fig. 6). The locations were ~150-m apart and parallel to the main tidal channel. Intertidal sediments were typically muddy fine-sands composed of fine silt (~20 µm modal diameter) and very fine sand (~100–150 µm modal diameter) similar to the Mahurangi estuary. Below 5-cm depth the mud content of sediments were in the range 5–20 %. In core OK-I1, the mud content of sediments increased from 18 to 54% in the upper 5 cm of the sediment column, while cores OKI-1 and OKI-2 had similar mud contents of 5-20% throughout the core (Swales et al. 2002).
The fauna at the three Okura intertidal sites were relatively diverse compared to the Mahurangi and Puhoi intertidal sites. 27 different taxa comprise the fauna found at the site (Appendix 2). The average number of taxa per core was high (7.4 to 9.9), indicating a relatively diverse yet even fauna (Shannon-Wiener diversity values of 1.51 to 2.01) (Table 3, Figure 3). Heteromastus filiformis, the mud crab Macrophthalmus hirtipes, and the polychaete Glycera ovigera were among the five most dominant taxa at all sites (Table 5). Other dominant fauna included the spionid polychaete Aquilaspio aucklandica (MHS-1 and MHS-2), the polychaete Scoloplos leadamas (MHS-2), Paracorophium excavatum (MHS-3) and Helice crassa (Table 5).
3.1.4 Waitemata estuary (intertidal and subtidal cores)
The Waitemata Harbour is the largest estuary on Auckland’s east coast (Fig. 1). The estuary has a surface area of 80 km2 and a tidal prism (~216 million m3), which is five times larger than the next largest east coast estuary (Mahurangi). The Waitemata is a drowned valley (Fig. 7). The middle estuary between Te Atatu Peninsula and the Auckland Harbour Bridge is a shallow basin with water depths typically < 2 m below chart datum. The extensive subtidal flat east of Te Atatu Peninsula is dissected by channels which drain the upper harbour, Henderson and Whau Creeks. The Waitemata receives runoff from a 427-km2 catchment, which includes large areas of Auckland City, North Shore, Albany and West Auckland.
Henderson Creek is a tributary drowned-valley estuary of the Waitemata Harbour (Fig. 7). The estuary has a high-tide surface area of ~2.0 km2 and is sheltered from the harbour proper by the Te Atutu Peninsula. Henderson Creek has infilled with sediment and in its upper reaches, mangrove have entirely colonised the intertidal flat. At the mouth of the estuary is an extensive intertidal flat which has been colonised by mangroves. The estuary receives runoff from a 105.1-km2 catchment. Present day
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catchment landcover is comprised of regenerating native forest (49%) and scrub (5%), urban (21%) and pasture (25%) (source: NZ Land Resource Inventory).
Figure 7: Waitemata harbour - location of intertidal (Henderson) and subtidal (Te Atatu) and cores and major sub-environments.
Locations sampled were on a large intertidal mud bank at the mouth of Henderson Creek. Locations were ~100-m apart and parallel to the main tidal channel (Fig. 7). Sediments were mixtures of fine silt (~20 µm modal diameter) and very fine sand (~100–150 µm modal diameter). The sediment mud content varied between 5–12% (Swales et al. 2002).
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Subtidal locations sampled were ~1 km apart on the flat east of Te Atutu Peninsula bounded by the tidal channels draining the Henderson and Whau Creeks (Fig. 7). Here, sediments were typically muddy fine-sands composed of fine silt (~20 µm modal diameter) and very fine sand (~100–150 µm modal diameter). Mud content in the top 15-cm depth varied between 5-10% (Swales et al. 2002).
32 different taxa composed the fauna found at the three intertidal Waitemata (Henderson) sites (Appendix 2). The three sites had high average numbers of individuals (49.8 to 108.6) and average numbers of taxa per core (9.1 to 11.4) compared to other sites (Table 3). The sites did vary slightly in species composition and total abundance of dominant species (Table 5). Site WTI-1 had extremely high abundance of the polychaete Aricidea sp., with one 13 cm core containing 88 individuals of the species. Heteromastus filiformis and Cossura sp. were also dominant taxa at site WTI-1. The small deposit-feeding bivalve Nucula hartvigiana was the most abundant species at WTI-2 and WTI-3, roughly five times more abundant at site WTI-3. The bivalve Austrovenus stutchburyi was also present in high numbers at WTI-3. Heteromastus filiformis and Aricidea sp. were present in similar numbers (roughly 10 per core) at both WTI-2 and WTI-3. The Shannon-Wiener diversity index was somewhat high, ranging from 1.16 to 1.40, but not as high as that of the Okura intertidal fauna due to the dominance at Henderson by few species (Figure 3).
23 taxa in total were identified at the three Waitemata subtidal sites (Appendix 2). The average number of individuals and taxa per core (36.5 to 53.1 and 6.4 to 8.1 respectively) were the highest found at any of the subtidal locations sampled in this study (Table 4). These locations were similar to intertidal locations in species composition and general diversity and abundance of taxa. The bivalve Nucula hartvigiana was most abundant at site WTS-1, and second most abundant species at WTS-2 and WTS-3 (Table 6). The polychaetes Paraonella sp. and Cossura sp. were also present in large numbers at all three sites. Other taxa comprising the five most dominant taxa included Tanaidae sp., the amphipod Torridoharpinia hurleyi, the polychaetes Boccardia sp. and Levinsenia gracilis, and the bivalve Theora lubrica (Table 6). The Shannon-Wiener diversity index was relatively high compared to other subtidal sites, ranging from 1.51 to 1.78, due to the large number of individuals and even distribution of individuals among species (Figure 4).
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3.1.5 Whitford embayment (subtidal cores)
Whitford embayment (11.1 km2) is an infilled coastal embayment on the eastern periphery of the Auckland city (Fig. 8, Table 2). The estuary receives runoff from tributary tidal creeks, which have been colonised by dense stands of mangrove. Analysis of historical aerial photographs shows that the area of intertidal flat occupied by mangrove in the Mangemangeroa and Waikopua tidal creeks has increased by 50% in the last 50 years (Craggs et al. 2001). Furthermore, net sedimentation rates estimated from 137Cs and Zn profiles in sediment cores show accumulation of these muddy sediments increases towards the heads of these estuaries (Oldman and Swales, 1999; Craggs et al. 2001). Whitford embayment receives runoff from a 61- km2 catchment. Today ~40% of the Mangemangeroa catchment remains under bush/scrub landcover (Morrisey et al. 1999). This landcover pattern is typical of the entire Whit ford catchment.
Figure 8: Whitford embayment - location of subtidal cores and major sub-environments.
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Locations sampled were ~1.3 km apart on the subtidal flat east of Mellons Bay in water depths 5–6.5 m below chart datum (Fig. 8) within the zone of clay-rich mud accumulation identified by Gibbs et al. (2002). Subtidal sediments were typically muddy fine-sands composed of fine silt (~20 µm modal diameter) and very fine sand (~80–100 µm modal diameter) containing abundant shell valves of common estuarine bivalves. In the top ~10 cm of cores WH-S1 and WH-S2, the mud and very fine sand modes were present in roughly equal proportions, while below 10 cm depth the mud content of these sediments declined. In comparison, core WH-S3 showed an increase in mud content towards the sediment surface (Swales et al. 2002).
23 taxa in total were found at the three subtidal Whitford locations (Appendix 2). The three locations each had low average number of individuals and taxa per core (7.6 to 11.2 and 3.6 to 3.9 respectively, Table 4). The polychaete Aotearia sulcaticeps was the most dominant taxa at all three sites. Aricidea sp., Cossura sp., Cirratulidae, Macrophthalmus hirtipes and Torridoharpinia hurleyi also comprised the dominant fauna in at least one of the three locations, though rarely was more than one of each species found in each core (Table 6). The Shannon-Wiener diversity index was relatively low, ranging from 1.07 to 1.19, primarily due to the low number of individuals per core found at this site (Figure 4).
3.1.6 Wairoa estuary (intertidal and subtidal cores)
The Wairoa estuary is a mature (infilled) drowned-valley estuary fringing the southern shore of the Tamaki Strait (Fig. 9). The rapid “aging” of the estuary is unsurprising given the large catchment area (~311 km2) in comparison to the small estuary area (~3 km2). Mangroves have almost completely colonised the intertidal flats on either side of the meandering main tidal channel (Fig. 9, Table 2). The highly infilled state of the estuary suggests that a substantial quantity of the annual catchment sediment load is exported from the estuary to the open coast environment. Some of this sediment is likely to be deposited in the sheltered subtidal waters immediately beyond the mouth of the Wairoa estuary.
Locations sampled were on an intertidal mud flat in the lower estuary and a subtidal flat (~2.5–4.0 m below chart datum) beyond the mouth of the Wairoa estuary (Fig. 9). The intertidal locations were ~100-m apart and parallel to the main tidal channel. The mud flat was deeply incised by numerous meandering drainage channels covered by numerous crab burrows. The subtidal locations were located in a triangular arrangement ~1.8 km apart. The seabed at all locations was similar to Whitford Embayment, consisting of muddy fine sands and very fine sand containing shell
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valves of typical estuarine shellfish species. Subtidal sediments were also muddy fine- sands, however the sand modal size was somewhat larger (110–140 µm modal diameter). The subtidal sediments also contained quantities of coarse sand-sized shell fragments. Sediments in the intertidal cores were also generally muddier (mud content 40–60%) than the subtidal cores (mud content 5–40%; Swales et al. 2002).
Figure 9: Wairoa estuary - location of intertidal and subtidal cores and major sub-environments.
The number of taxa in total collected at the three intertidal Wairoa locations was most similar to the Puhoi intertidal estuary location, with only 14 different species collected from the three intertidal locations (Appendix 2). The three locations each had low average number of individuals and taxa per core (7.6 to 8.3 and 1.8 to 3.5 respectively; Table 3). Similar to Puhoi, the three sites were dominated by Helice crassa, Paracorophium excavatum and oligochaetes (Table 5). The number of crabs per core was 4-5 times higher than at the Puhoi sites. The Shannon-Wiener diversity index was low compared to other intertidal sites except for Puhoi, ranging from 0.45 to 0.98, primarily due to both the low number of individuals per core and the few species found at this site (Figure 3).
Substantially more taxa were found in the subtidal locations than the intertidal locations (Appendix 2). The average number of individuals per core was only slightly
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larger than the intertidal sites (9.7 to 14.2; Table 4); the average number of taxa was also slightly larger than the intertidal sites (6.4 to 8.1). Community composition was similar at the three subtidal locations, being dominated by polychaetes (Labiosthenolepis laevis, Aotearia sulcaticeps, and Paraonella sp.), although the bivalve Arthritica bifurca, the isopod Anthuridae sp., and Macrophthalmus hirtipes were found in different abundances at different locations (Table 6). The even distribution of individuals across species, combined with the relatively few individuals and species resulted in a somewhat variable Shannon-Wiener diversity index (though higher than that of the intertidal Wairoa sites), ranging from 1.17 to 1.58 (Figure 4).
3.1.7 Te Matuku estuary (Waiheke Island) (intertidal cores)
Te Matuku estuary is a small (Table 2) coastal embayment, which opens to the sea on the southern shore of Waiheke Island and 11 km north of the Wairoa estuary mouth (Fig. 10). The estuary is deeply indented into the surrounding terrain, which is up to 100 m above mean sea level. The estuary has largely infilled such that the main tidal channel is also intertidal. The upper estuary is also fringed by extensive stands of mangrove. Because the estuary is largely intertidal, there is almost complete exchange of estuarine water with each tidal cycle. The estuary receives runoff from a 12.2-km2 catchment. Present day catchment landcover is comprised of regenerating native forest (36%) and scrub (15%) and pasture (49%) (source: NZ Land Resource Inventory).
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Figure 10: Te Matuku estuary (Waiheke Island) - location of intertidal cores and major sub- environments.
Locations sampled were ~150 m apart on the mid-intertidal flat parallel to the main channel (Fig. 10). Sediments were typically muddy fine-sands composed of fine silt (~20 µm modal diameter) and very fine sand (~100–150 µm modal diameter. The mud content of sediments increased towards the estuary mouth from ~10–20% (TM- I1) to ~25–37% (TM-I3).
The intertidal Te Matuku (Waiheke Island) estuary had the largest total number of taxa found at any of the study estuaries: 35 total taxa found (Appendix 2). The average number of individuals per core was variable but generally higher than most of the subtidal sites, ranging from 19.75 to 39.3, while the average number of taxa was almost as high as that found at the Waitemata intertidal (Henderson) site (8.3 to 9.8; Table 3). Heteromastus filiformis was the most dominant species at all locations, and was 3-4 times more abundant at TMI-2 than TMI-1 and TMI-3. Other dominant taxa occurring at one of the three sampling locations included Aquilaspio aucklandica, Macrophthalmus hirtipes, Austrovenus stutchburyi, Paracorophium excavatum,
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oligochaetes, and nemerteans (Table 5). The Shannon-Wiener diversity index (ranging from 1.17 to 1.58) was high due to both a relatively even distribution of individuals across species and the relatively large abundance of individuals and species, (Figure 3).
3.2 Comparison of communities within Auckland estuaries
3.2.1 Subtidal and intertidal comparisons
K-dominance curves for the intertidal and subtidal communities of the estuaries Wairoa, Mahurangi, and Waitemata harbour show distinct separations between intertidal and subtidal sites for each estuary (Fig. 11). The cumulative percentage was plotted against the species rank to show the domination of some sites by few taxa compared to those with more even distribution of individuals across taxa. The intertidal curves generally lie above the curves for subtidal communities, implying that intertidal communities are dominated by fewer, more abundant taxa, while subtidal communities have a more even distribution of individuals among species. The curves of the Waitemata intertidal and subtidal locations were least separated, though curves for the Mahurangi locations were less separate than the Wairoa locations. This may be due to the very similar fauna present at the intertidal and subtidal locations within Waitemata, in contrast to the differences in terms of dominant species found at the Wairoa and Mahurangi intertidal and subtidal sampling locations. Depth may also be influencing the faunal differences, as both the Waitemata and Mahurangi subtidal locations were sampled at depths less than 2.0 m chart datum, in contrast to the Wairoa subtidal locations with the largest curve separation from the respective intertidal locations that were sampled at depths between 2.4 and 3.5 m chart datum.
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100
80
60
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20 Wairoa estuary
0
100
80
60
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20 Mahurangi estuary
Cumulative Dominance (%) Cumulative Dominance 0
100
80 intertidal 60 subtidal
40
20 Waitemata harbour
0 110010 Species rank
Figure 11: Mean k-dominance curves for samples from intertidal and subtidal habitats of the estuaries Wairoa, Mahurangi, and Waitemata harbour.
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3.2.2 Across estuary comparisons
Cluster analysis showed three groups with less than 25% similarity (Figure 12A). The first cluster combines samples from the Wairoa and Puhoi estuaries. The second cluster combines samples from intertidal sites of the Okura, Mahurangi, and Henderson (Waitemata) drowned-valley estuaries, as well as from the Waitemata subtidal site and the intertidal site of the Te Matuku (Waiheke Island) coastal embayment. The third cluster encloses samples from subtidal sites of the Wairoa and Mahurangi drowned-valley estuaries, and from the Whitford coastal embayment. Note that the similarity between the subtidal community and the intertidal community of Waitemata harbour is larger than the similarity between the subtidal community of Waitemata harbour and the subtidal communities of other estuaries, as the Waitemata subtidal community is more similar to the other intertidal communities rather than the subtidal communities in terms of community composition and dominant species.
We calculated average similarities in order to determine the species that most contribute to the grouping of samples found in the cluster analysis. We first calculated the contribution of the taxa to the average similarity within the groups 1 – 3 (Table 7). We then calculated the contribution of each taxon to the dissimilarities between group 1 and 2, 1 and 3, and 2 and 3 (Table 8). To identify a set of discriminating or indicating taxa for each group we combined information from the two analyses; that is, we selected taxa with highest contribution to the similarity within the groups and to the dissimilarity between the groups (Table 9). These groupings correspond to macrofaunal groups of three broad-scale habitat types based on prior knowledge of estuarine fauna: 1) upper intertidal habitats with low exposure to tidal currents; 2) intertidal mudflats, exposed to currents; and 3) subtidal mudflats.
The 2-dimensional non-metric multidimensional scaling ordination of the taxa abundances for all samples clearly shows separation of locations from different estuaries and discrimination of intertidal from subtidal communities. Intertidal locations form three sub-groups (at a level of 40% similarity): 1) Wairoa (WAI) & Puhoi (PUI) estuaries, 2) Okura (OKI) estuary and Te Matuku Bay (TMI), and 3) Mahurangi (MHI) estuary & Waitemata harbour (WTI). Subtidal locations form another three groups: 1) Wairoa (WAS) estuary, 2) Whitford embayment (WHS) & Mahurangi (MHS) estuary, and 3) Waitemata harbour (WTS). Overall, there was a statistically significant difference (p = 0.001) between intertidal and subtidal communities;
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however, the dissimilarity (distance in plot) between the intertidal and subtidal communities is highest at the Wairoa estuary (WAI/WAS) and lowest at Waitemata harbour (WTI/WTS). This trend is also evident in the k-dominance curves (Fig. 11), as the difference between intertidal and subtidal curves was smallest for the Waitemata comparison, and largest for the Wairoa comparison.
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0 A 20
40
60 Similarity
80
100 WII WII WII WHS WHS TMI TMI TMI WAS WAS WAS WHS MHS OKI MHI MHI MHS MHS OKI OKI WTS WTS WTS HNI HNI MHI HNI PUI PUI PUI
WII
WII WII MHI PUI HNI PUI HNI PUI
WTS WTS HNI WTS OKI
MHI MHI OKI OKI TMI TMI TMI
WHS
MHS MHS MHS
WHS WHS
WAS WAS WAS B
Figure 12: A: Dendrogram for hierarchical clustering (using group-average linking) of
samples from intertidal (-I) and subtidal (-S) sites of the Hauraki Golf estuaries. The cluster is based
on the Bray-Curtis similarity matrix calculated on standardised, √-transformed abundances of
macrofaunal taxa. B: 2-dimensional MDS of the taxa abundances for all samples, showing
separation into three grouping (estuaries) and discrimination of intertidal from subtidal communities.
Clusters formed at two levels (25 and 40 % similarity) are superimposed on the 2-dimensional MDS
obtained from the same similarities (stress=0.12).
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Table 7: Breakdown of average similarity within groups into contributions from each taxon. Taxa are ordered in decreasing contribution to the average similarity, with a cut-off when the cumulative percent contribution (CPC) is 70 %. The average similarity within groups is put in parentheses.
Group 3 (42.96) Group 2 (39.20) Group 1 (58.33) Taxa CPC Taxa CPC Taxa CPC
Labiosthenolepis 18.2 Heteromastus 24.6 Oligochaeta 35.7 Theora 32.2 Cossura 35.4 Paracorophium 64.8 Cirratulidae 42.8 Macropthalmus 42.8 Helice 92.5 Aotearia 52.6 Nucula 49.8 Arthritica 60.0 Glycera 55.6 Macropthalmus 66.6 Nicon 60.8 Aricidea 73.0 Aricidea 65.4 Aquilaspio 69.7 Boccardia 73.0
Table 8: Breakdown of average dissimilarities between groups into contributions from each taxon.
Taxa are ordered in decreasing contribution to the average dissimilarity, with a cut-off when the cumulative percent contribution (CPC) reaches 60 %. The average dissimilarity between groups is put in parentheses.
Groups 1 & 3 (97.0) Groups 2 & 3 (78.0) Groups 2 & 1 (85.7) Taxa CPC Taxa CPC Taxa CPC
Oligochaeta 10.9 Heteromastus 7.0 Oligochaeta 11.8 Helice 19.9 Labiothenolepis 13.2 Helice 22.4 Paracorophium 26.9 Aotearia 18.5 Paracorophium 30.3 Labiothenolepis 32.6 Nucula 23.7 Heteromastus 37.7 Theora 38.2 Theora 28.0 Cossura 43.9 Aotearia 43.3 Cossura 32.2 Nucula 50.0 Cirratulidae 47.7 Cirratulidae 36.35 Aricidea 53.8 Arthritica 51.6 Aricidea 40.2 Macropthalmus 57.6 Cossura 55.1 Arthritica 43.7 Aquilaspio 60.9 Macropthalmus 58.5 Macropthalmus 46.5 Aricidea 61.9 Aquilaspio 49.3 Paraonidae 51.8 Torridoharpinia 54.1 Phoxocephalidae 56.5 Glycera 58.5 Nicon 60.5
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Table 9: Taxa indicative of three distinct communities within Hauraki Golf estuaries, as determined by the cluster analysis of macrofaunal community data. The taxa were chosen because they most contribute both to similarity within groups and to dissimilarity between groups.
Taxa Estuarine sub-habitats Oligochaetes Group 1: Upper head of estuary, mangrove mudflats, low Paracorophium excavatum inundation time, low tidal current Helice crassa Heteromastus filiformis Group 2: Intertidal mudflats, well supplied with tidal current Cossura sp. Nucula hartvigiana Labiosthenolepis leavis Group 3: Subtidal mudflats Theora lubrica Cirratulidae Aotearia sulcaticeps
3.3 Predicting community composition with environmental data
We computed multivariate statistics using both environmental variables and community (species) data to examine the extent to which the physical data is related to the observed biological pattern. We used environmental (physical) variables based on estuarine variables (Catchment to Estuary Ratio) (Table 2), sediment accumulation rates (SAR) for 137Cs for post-1953 A.D., and other physical descriptions of the sample sites calculated in Phase II (Table 10A, Swales et al. 2002). Analyses by Swales et al. (2002) using PCA to quantify the physical similarities between estuaries showed that mud content and grainsize measurements did not always coincide with high levels of sedimentation, for example the Puhoi estuary with high infilling of relatively sand-rich sediments as opposed to the Wairoa estuary, infilling with muddier pasture-derived sediment.
Before reporting results of our statistical analyses using the physical data, we note some of the challenges in relating the physical data to our macrofaunal community data. As discussed in Hume et al. (2002), net sedimentation rates do not describe actual mortality of communities from catchment development and increased sedimentation rates, and they are not event-based (i.e., they do not report the number of mortality-causing sedimentation events per year). Thus, relating this data to current macrofaunal communities is difficult as these communities live in the upper 5 - 10 cm of the sediment surface. Most sediment is delivered to estuaries during flood events,
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though this sediment may have been deposited in few large events or many small events, or a mixture of both large and small events. The physical data does not allow us to distinguish sediment between these forms of deposition, or to distinguish sediment amounts that have been deposited in recent years (e.g., the past decade). This limits our ability to relate the time scale of sedimentation to macrofaunal community responses. In particular, the stratigraphic data collected in the Phase II portion of this study give net sedimentation rates at best as averages over the 1953 to present period, using the 137Cs indicator. These rates are based on the maximum depth at which 137Cs is detected in the cores, and represent a minimum rather than maximum amount of sedimentation. For example, the two of the intertidal sites (Puhoi and Wairoa) with the highest rates of sedimentation had Cs present throughout the core, implying either that 1) the sediment at the bottom of the 30 cm stratigraphic core was placed in 1953; or 2) more likely, that the 1953 marker is below the depth surveyed for the stratigraphic cores, and instead the 30cm core represents a much shorter length of time, and thus much higher rates of sedimentation than the maximum of 5.9 mm/yr detected by the 137Cs dating method in Swales et al. (2002). Further analyses of the dataset in Phase II may define a more accurate temporal horizon for these cores using 210Pb dating; however, these analyses were not available at the time this report was written. Regardless, for this report we use the SAR recommended by the Phase II report (137Cs) which is also the only SAR dating method with results available for all core locations. Our analyses of this data are limited, in terms of a gradient in SAR; 8 (27%) of these values are at the maximum SAR of 5.9mm/yr and 6 (20%) of these reported values are at the minimum SAR calculated of 3.02 mm/yr.
To overcome these issues we used a rank-order approach to contrast SAR at the different sites. We first used a non-parametric Kruskal-Wallis analysis of variance test to analyse between-site differences, using ranked data. Results showed significant differences between sites, and post-hoc Bonferroni comparison tests suggested a gradient with the distinctive end groups being Puhoi Intertidal and Wairoa Intertidal (as the sites with highest SAR) and the Waitemata Subtidal site (as the site with the lowest SAR) (Table 10B).
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Table 10: A. Physical data from phase II report (see Swales et al. 2002 for description and calculation of these rates). B. Significant differences between sites and pair-wise multiple comparison tests (SAR (137Cs)). Sites connected by the same line are not significantly different from each other.
Max. Mean Median Mud SAR Depth of particle particle content Estuary Core (137Cs) 137Cs (cm) [Zn] diameter diameter (%) Mahurangi MHI1 5.5 26.5 21.95 116.55 96.84 26.26 MHI2 5.9 26.5 24.04 128.91 122.38 10.15 MHI3 4.7 22.5 26.38 157.38 139.80 4.69 MHS1 4.7 22.5 27.47 151.10 108.86 16.79 MHS2 3.9 10.5 25.71 106.70 100.47 15.91 MHS3 3.9 18.5 22.51 113.11 102.77 13.37 Puhoi PUI1 5.9 >29.5 14.05 146.66 129.56 11.40 PUI2 5.5 >29.5 14.40 176.90 133.66 7.41 PUI3 5.9 >29.5 16.11 146.28 125.95 11.81 Okura OKI1 3.0 14.5 17.32 108.16 99.61 28.32 OKI2 5.9 >29.5 17.84 125.77 116.27 15.97 OKI3 3.0 14.5 19.86 112.34 109.83 10.70 Henderson WTI1 3.9 18.5 83.01 143.49 123.34 6.88 WTI2 3.9 18.5 82.19 171.98 138.67 4.62 WTI3 5.9 >29.5 83.13 201.21 147.66 7.74 Waitemata WTS1 3.0 14.5 97.52 293.93 202.89 8.95 WTS2 3.0 14.5 88.28 172.62 154.77 2.67 WTS3 3.0 14.5 100.79 121.71 115.91 9.29 Whitford WHS1 3.9 18.5 34.87 139.32 69.75 48.27 WHS2 4.7 22.5 37.96 190.92 73.68 45.87 WHS3 4.7 22.5 31.83 120.66 81.50 32.66 Wairoa WAI1 5.9 >29.5 33.79 85.56 72.96 39.63 WAI2 5.9 >29.5 37.74 90.36 71.19 41.80 WAI3 5.9 >29.5 40.14 79.70 65.10 46.51 WAS1 3.9 18.5 33.44 172.45 104.78 22.14 WAS2 4.7 22.5 32.68 607.83 642.14 13.31 WAS3 3.0 14.5 24.53 159.62 125.45 13.66 Te Matuku TMI1 4.7 22.5 20.37 154.26 135.66 14.89 TMI2 5.5 26.5 26.38 104.35 97.80 24.13 TMI3 4.7 22.5 18.93 94.92 88.31 27.67
.P = 0.294 18.54 = 2א :Kruskal Wallis test
Highest Lowest B. ______PUI WAI MHI OKI WTI TMI MHS WHS WAS WTS
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Canonical correspondence analysis (ter Braak 1986) results using all physical variables and SAR alone both showed separation of Puhoi and Wairoa Intertidal samples, and Waitemata Subtidal samples from the other sample locations. While 19.5 % of the variation in community composition is explained by the first 2 axes when including all physical variables (p = 0.005), 5.2 % is explained by SAR alone (p = 0.045). A PCCA that removed the effect of all physical variables (except SAR) and used SAR and dummy variables representing estuary type (coastal embayment, drowned valley, tidal lagoon) explained 24.6 % of the variance in community composition with the first two axes (p = 0.005).
This analysis implies that irrespective of estuary type and major site environmental characteristics SAR is causing long-term changes in the structure of the macrobenthic community.
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4. Conceptual Model
We created a conceptual model of long-term changes in macrobenthic community composition with increasing rates of sedimentation based on data collected in this and other research performed in the Auckland estuaries. In our model, we predict diverse communities for each of the estuary types (coastal embayment, drowned valley and tidal lagoon) at early stages of estuarine infilling, and low rates of SAR (Figure 13). These communities will consist of many different species, at intertidal and subtidal locations. The species consist of varied life history stages, (physiological tolerances) and represent many different functional roles. The organisms will live at varying depths in the sediment, with some forming permanent structures (e.g., tubes) and other being mobile (e.g., errant predatory polychaetes). Biogenic modification of the sediment will occur. As these communities are subject to greater levels of sedimentation, communities will converge to a low diversity type community type regardless of estuary type (Figure 13). This low diversity community will be similar to those found at Puhoi (tidal lagoon) and Wairoa Intertidal (drowned valley) and consist of primarily small opportunistic species like oligochaetes and the amphipod Paracorophium excavatum, and some large disturbance tolerant, highly mobile species like the mud crab Helice crassa.
Based on our macrofaunal analyses from Auckland estuaries (Fig. 12 Tables 7-9), we would expect community groupings similar to the following as sedimentation rates increase:
Group 1: Communities of subtidal sediments, farthest from sediment source. This community is distinguishable from group 2 and 3 by presence of the polychaete species Aotearia, Labiosthenolepis, and species of the family Cirratulidae.
Group 2: Communities present in less-disturbed intertidal sediments, exposed to tidal current, and with low or moderate exposure to catchment runoff. This community is composed of a diverse community, with numerous functional roles, distinguished at our sampling locations by the presence of the polychaete species Heteromastus filiformis, Cossura sp., and species of the family Glyceridae, the bivalve Nucula hartvigiana, and the mud crab Macrophthalmus hirtipes.
Group 3: Communities present in intertidal mud flats in the upper head of the estuary with little exposure to tidal currents. This community is distinguished by the dominance of both disturbance or stress-tolerant species like the crab Helice crassa,
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and opportunistic species including the amphipod Paracalliope novizealandiae, and oligochaetes.
The communities in group 3 are representative of highly infilled estuaries, with high rates of sedimentation, encompassing multiple estuary types, all with high disturbance rates and stress tolerant communities. Conversely, groups 1 and 2 are representative of different intertidal (group 2) and subtidal (group 1) habitats, with diverse species assemblages, and healthy functioning communities. These community groupings in our analysis show more discernable differences between those with high sedimentation rates, in contrast to those with low or medium rates of sedimentation. Further separation is noted based on physiological tolerances of organisms to subtidal and intertidal habitats. While our samples were unable to distinguish sub-groupings within Groups 1 and 2 of intertidal and subtidal communities based on different estuary types, as most of our sampling locations occurred within drowned valley estuaries, it is predicted that sub-groupings based on further replicate sampling of estuaries of different types with varying levels of sedimentation would reflect communities of intertidal and subtidal sediments specific to tidal lagoons, coastal embayments.
Figure 13: Conceptual model of macrobenthic community structure as sediment deposition increases, ranging from ‘young’ estuaries with low SAR to ‘mature’, highly infilled estuaries with high SAR. Each of the three types of estuaries in this study (coastal embayment, drowned valley, tidal lagoon) consists of a diverse community with high functional diversity and varied ecosystem roles under low SAR. High SAR (combined with natural aging of estuaries) results in a convergence of all estuarine types to a single, low diversity community of disturbance-tolerant species with similar functional roles.
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5. Conclusions and Recommendations
Sedimentation due to both natural infilling of estuaries, as well as that due to human modification of catchments, results in modifications to benthic communities, following a community trajectory from younger estuaries with diverse habitats, large proportions of subtidal habitat, and low rates of sedimentation accumulation, to mature, infilled estuaries with primarily intertidal habitat and little habitat diversity. Sedimentation rates are greatest at the upper head of the estuary (e.g., tidal creeks, mangroves) and lowest at subtidal areas of coastal bays. Mangrove flats at the upper head of the estuary with large fluctuations in abiotic parameters (temperature, water content of the sediment, water depth, salinity, pore water oxygen concentration, depth of oxic layer, supply of colonists via waves and tidal currents) are very different from subtidal habitats which offer a less fluctuating environment. These differences and the differences in community structure are linked, as sedimentation affects the physical condition of an estuary, modifying the sediment characteristics including mud content and grainsize, as well as modifying the amount of suspended particulates which in turn changes communities to those that are tolerant of these new conditions. Sedimentation can also influence colonisation of these affected areas as increased infilling can change tidal current velocity and channel morphology with concomitant, changes to the probability of colonisation by larvae, post-settlement juvenile, or adult colonisers.
Periods of high sedimentation rates (“catastrophic sedimentation”) may be accompanied by temporary or permanent changes in the composition of the benthic macrofauna (Norkko et al. 1999, Berkenbusch et al. 2001, Lohrer et al. 2003, Thrush et al. 2003). The structure (and function) of the sediment community can shift permanently if the sedimentation event permanently changes the local hydrodynamic conditions and the physicochemical sediment properties. However, the degree of alteration in community structure depends on the original composition of the community concerned. Species like oligochaetes and the amphipod Paracorophium excavatum are well adapted to frequent disturbance, and are opportunistic species with high mobility, larval and post-larval dispersal. Other species are less tolerant, requiring more constant physical conditions, and are less tolerant of stresses like sedimentation. Lower sedimentation rates over long time periods can also modify communities, for example long-term decreases in species less tolerant of sedimentation such as Atrina or specific to other sediment types (Aquilaspio) have been detected in long-term monitoring programmes (Cummings et al. 2003).
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Increased rates of sedimentation due to catchment development are clearly impacting our estuaries. Our research implies that Auckland estuaries initially consist of diverse communities comprised of various functional groups and life history strategies at the early stages of estuarine infilling (and at low rates of sedimentation). However, increased sedimentation reduces these diverse communities to a stress-tolerant community made up of few disturbance tolerant and opportunistic species. While high sedimentation rates often result in transformation of estuaries to muddier rather than sandier sediments, sedimentation history, not just grainsize, will determine community structure. Healthy, diverse communities do exist in muddier sediments, as our study shows. However, when muddy sediments are subject to high rates of sediment loading, a single stress-tolerant community of low diversity remains. The stress-tolerant communities that we found in the sites with highest SAR were similar to those predicted to result from a number of stressors, including anoxia, metal or organic contamination, and stormwater discharge. It is important that we are aware of the multiple stressors affecting our estuarine communities as well as the consequences of individual stressors of macrofaunal community assemblages.
Further analyse the effects of different estuary types (coastal embayments, drowned valleys, tidal lagoons) was not possible in the current study due to the lack of a number of each estuary type with varying levels of sediment accumulation. Instead, seven of our sampling locations were from drowned valleys, allowing us to expand our knowledge of the relationship of sedimentation on macrofaunal communities in these estuaries, showing a community gradient from high to low diversity, and many to few functional roles, as sedimentation increases. To confirm our prediction that these community changes are similar across estuary types, a number of each estuary type at different levels of sedimentation would be required to be studied.
Each of the estuaries studied in this report were sampled from muddier locations. As organisms in these muddy locations are likely the most tolerant of high levels of suspended sediment concentrations and low mean grainsize, it is likely that the communities are least susceptible to sedimentation. Further study of communities in sandier environment that are less tolerant of muddy sediments and increased suspended sediment concentrations associated with increased sedimentation rates are warranted to determine effects. While this study concentrated on muddy habitats as being places where sediment accumulation rates could be measured, studies in sandy habitats could be based on the premise that estuaries with higher SARs in muddy areas would also have higher SARs (or associated indirect effects in their sandy habitats).
Finally, fundamental research is necessary to address the collection of physical data on sedimentation at scales relevant to the temporal scale of macrofaunal
TP 222 - Evidence for the physical effects of catchment sediment runoff preserved in estuarine sediments: Phase III macrofaunal communities 40
communities. While the physical measurements used in the Phase II report detail valuable information about sedimentation rates in Auckland estuaries due to catchment development, macrofaunal communities do not directly respond to decadal time scales and net sedimentation rates. Instead, benthic organisms respond to event-based sedimentation. Changes in community structure brought about by direct mortality events due to sediment deposition events after storms and flooding, as well as changes in sediment composition and suspended sediment concentration that modify the environment in which these organisms live. Bioturbation by these macrofaunal communities, as well as physical removal of sediments by tidal currents and erosion, reduces our ability to describe more recent sedimentation events. Further study detailing both gross and net sedimentation, as well as frequency of events of sediment deposition will further enable us to determine community trajectories with predicted increases in sedimentation rates.
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6. Acknowledgements
We thank Dominic McCarthy for assistance with choice of sampling locations. We thank Judi Hewitt for statistical advice. We thank Judi Hewitt, Terry Hume, and Drew Lohrer for assistance with development of the conceptual model.
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7. References
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Gibbs, M.; Thrush, S.; Sukias, J.; Berkenbusch, K.; Thompson, D.; Bury, S. (2002). Evaluation of terrestrial sediment spatial patterns throughout the Whitford embayment and its benthic food web using stable isotope techniques. NIWA Client Report ARC01270, 30 p.
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Hume, T. & Herdendorf, C.E. (1992). Factors controlling tidal inlet characteristics on low-drift coasts. Journal of Coastal Research 8(2): 355–375.
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Norkko, A.; Thrush, S.F.; Hewitt, J.E.; Norkko, J.T.; Cummings, V.J.; Ellis, J.I.; Funnell, G.A.; Schultz, D. (1999). Ecological effects of sediment deposition in Okura estuary. NIWA Client Report ARC90243, 39p.
Oldman, J.O. & Swales, A. (1999). Maungamaungaroa Estuary numerical modelling and sedimentation. NIWA Client Report ARC70224.
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Swales, A.; Hume, T.M.; Oldman, J.W.; Green, M.O. (1997). Sedimentation history and recent human impacts. NIWA Client Report ARC60201, 90p.
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Swales, A.; Hume, T.; McGlone, M.S.; Pilvio, R.; Ovenden, R.; Zviguina, N.; Hatton, S.; Nicholls, P.; Budd, R.; Hewitt, J.; Pickmere, S.; Costley, K. (2002). Evidence for the effects of catchment sediment runoff preserved in estuarine sediments: Phase II (field study). Unpublished report prepared for the Auckland Regional Council. NIWA Client Report No. HAM2002-067. ter Braak, C.J.F. (1986). Canonical correspondence analysis: a new eigenvector technique for multivariate direct gradient analysis. Ecology 67: 1167-1179. ter Braak, C.J.F.; Smilauer, P. (1998). CANOCO release 4 reference manual and user's guide to Canoco for Windows-Software for canonocal community ordination. Microcomputer Power, Ithaca.
Thrush, S.F.; Cummings, V.J.; Norkko, A.; Hewitt, J.E.; Budd, R.; Swales, A.; Funnell, G.A. (1998). Response of horse mussels (Atrina zelandica) to sediment loading. Unpublished report for Auckland Regional Council. NIWA client report No. ARC80230. 20pp.
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Appendix I: Table of GPS Co-ordinates for sediment core locations.
Estuary Environment Core Water Depth Latitude Longitude (m C.D.) Mahurangi Intertidal MH-I1 36°26.184’S 174°43.087’E MH-I2 36°26.423’S 174°43.078’E MH-I3 36°26.596’S 174°43.076’E Subtidal MH-S1 -2.0 36°28.114’S 174°43.514’E MH-S2 -0.7 36°28.114’S 174°43.514’E MH-S3 -0.5 36°28.116’S 174°43.688’E Puhoi Intertidal PU-I1 – – PU-I2 36°31.528’S 174°41.351’E PU-I3 36°31.537’S 174°41.402’E Okura Intertidal OK-I1 36°40.470’S 174°42.801’E OK-I2 36°40.473’S 174°42.860’E OK-I3 36°40.479’S 174°42.930’E Henderson Intertidal HN-I1 36°48.665’S 174°39.432’E HN-I2 36°48.646’S 174°39.437’E HN-I3 36°48.617’S 174°39.515’E Waitemata Subtidal WT-S1 -0.2 36°49.915’S 174°40.926’E WT-S2 -1.4 36°50.164’S 174°41.517’E WT-S3 -0.5 36°50.349’S 174°40.647’E Whitford Subtidal WH-S1 -5.0 36°52.598’S 174°56.537’E WH-S2 -6.8 36°52.111’S 174°56.932’E WH-S31 -5.0 36°52.630’S 174°57.390’E Wairoa Intertidal WI-I1 36°56.810’S 175°05.207’E WI-I2 36°56.826’S 175°05.261’E WI-I3 36°56.837’S 175°05.319’E Subtidal WA-S1 -2.4 36°54.824’S 175°06.969’E WA-S2 -3.5 36°53.919’S 175°07.189’E WA-S3 -2.8 36°54.602’S 175°08.105’E Te Matuku Intertidal TM-I1 36°49.896’S 175°07.895’E TM-I2 36°49.939’S 175°07.846’E TM-I3 36°49.986’S 175°07.777’E
Note: (1) Actual position not recorded – the intended location is given.
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Appendix 2: List of macrofaunal taxa found at the intertidal and subtidal sites sampled in October 2001 and January 2002. A check designated that a taxa was identified from that location.
Order Family Genera Species MHI MHS OK PUI TMI W WA WT WTS WHS I AI S I Crustacea: Amphipoda Corophiidae Corophium sp. X Crustacea: Amphipoda Corophiidae Paracorophium excavatum X X X X Crustacea: Amphipoda Lysianassidae Parawaldeckia suzae X Crustacea: Amphipoda Melitidae Maera mastersi X Crustacea: Amphipoda Melitidae Melita awa X Crustacea: Amphipoda Melitidae Melita inaequistylis X Crustacea: Amphipoda Paracalliopiidae Paracalliope novizealandiae X X X X X Crustacea: Amphipoda Phoxocephalidae Phoxocephalidae sp. X X X X X Crustacea: Amphipoda Phoxocephalidae Torridoharpinia hurleyi X X X X X Crustacea: Amphipoda Urothoidae Urothoidae sp. X Mollusca: Bivalvia Erycinidae Arthritica bifurca X X X X X X X X Mollusca: Bivalvia Pinnidae Atrina zelandica X Mollusca: Bivalvia Veneridae Austrovenus stutchburyi X X X X Mollusca: Bivalvia Veneridae Dosinia lambata X Mollusca: Bivalvia Tellinidae Macomona liliana X X X X X Mollusca: Bivalvia Mactridae Mactra ovata X X X X (Cyclomactra) Mollusca: Bivalvia Mytilidae Musculista senhousia X Mollusca: Bivalvia Nuculidae Nucula hartvigiana X X X X X X Mollusca: Bivalvia Mesodesmatidae Paphies australis X Mollusca: Bivalvia Carditidae Pleuromeris zelandica X Mollusca: Bivalvia Galeommatidae Scintillona zelandica X
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Order Family Genera Species MHI MHS OK PUI TMI W WA WT WTS WHS I AI S I Mollusca: Bivalvia ?Semelidae Theora lubrica X X X X X X Mollusca: Polyplacophora Polyplacophora sp. X Mollusca: Gastropoda Cominella glandiformis X Crustacea: Malacostraca Cumacea Colurostylis lemurum X X Crustacea: Malacostraca Caridea Alpheus sp. X X X X X X Crustacea: Malacostraca Caridea Caridea sp. X Crustacea: Malacostraca Brachyura Halicarcinus whitei X Crustacea: Malacostraca Brachyura Helice crassa X X X X X Crustacea: Malacostraca Brachyura Macrophthalmus hirtipes X X X X X X X X Crustacea: Malacostraca Brachyura Brachyura sp. X X X X Crustacea: Isopoda Anthuridae Anthuridae sp. X X X Crustacea: Isopoda Flabellifera Cirolanidae sp. X Crustacea: Isopoda Flabellifera Exosphaeroma ?chilensis X Crustacea: Isopoda Flabellifera Isopoda sp. X Crustacea: Cirripedia Cirripedia sp. X Crustacea: Malacostraca Mysida sp. X Crustacea: Malacostraca Nebaliacea sp. X X Crustacea: Cirripedia Cirripedia sp. X Crustacea: Malacostraca Tanaidacea sp. X Annelida: Polychaeta Polychaeta sp. X Annelida: Polychaeta Capitellidae Heteromastus filiformis X X X X X X X X X Annelida: Polychaeta Cirratulidae Aphelochaeta sp. X X X X X Annelida: Polychaeta Cossuridae Cossura sp. X X X X X X X X Annelida: Polychaeta Glyceridae Glycera ovigera X X X X X X X Annelida: Polychaeta Goniadidae Glycinde dorsalis X X X X X
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Order Family Genera Species MHI MHS OK PUI TMI W WA WT WTS WHS I AI S I Annelida: Polychaeta Hesionidae Hesionidae sp. X X Annelida: Polychaeta Lumbrineridae Aotearia sulcaticeps X X X (Lumbrinereis) Annelida: Polychaeta Maldanidae Asychis sp. X X X X X Annelida: Polychaeta Maldanidae Euclymene insecta X Annelida: Polychaeta Maldanidae Macroclymenella stewartensis X X Annelida: Polychaeta Maldanidae Maldane theodori X Annelida: Polychaeta Nephtyidae Aglaophamus macroura X X X Annelida: Polychaeta Nereidae Nereidae sp. X Annelida: Polychaeta Nereidae Ceratonereis sp. X X Annelida: Polychaeta Nereidae Nicon aestuariensis X X X X X X X Annelida: Polychaeta Nereidae Perinereis sp. X X Annelida: Polychaeta Opheliidae Armandia cirrhosa X Annelida: Polychaeta Orbiniidae Naineris sp. X Annelida: Polychaeta Orbiniidae Orbinia papillosa X Annelida: Polychaeta Orbiniidae Phylo sp. X X Annelida: Polychaeta Orbiniidae Scoloplos cylindrifer X Annelida: Polychaeta Orbiniidae Scoloplos leadamas X X X Annelida: Polychaeta Paraonidae Aricidea sp. X X X X X X X Annelida: Polychaeta Paraonidae Levinsenia gracilis X Annelida: Polychaeta Paraonidae Paraonella sp. X X Annelida: Polychaeta Pectinariidae Pectinaria australis X X X X X Annelida: Polychaeta Pillargidae Ancistrosyllis sp. X X Annelida: Polychaeta Polynoidae Lepidonotinae sp. X X X X Annelida: Polychaeta Sigalionidae Labiosthenolepis laevis X X X X
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Order Family Genera Species MHI MHS OK PUI TMI W WA WT WTS WHS I AI S I Annelida: Polychaeta Spionidae Aquilaspio aucklandica X X X X X X X Annelida: Polychaeta Spionidae Boccardia syrtis X X X X X X Annelida: Polychaeta Spionidae Minuspio sp. X X X X X X
Annelida: Polychaeta Spionidae Polydora sp. X X Annelida: Polychaeta Spionidae Scolecolepides sp. X X X X X X Annelida: Polychaeta Syllidae Exogone sp. X X X X Annelida: Polychaeta Syllidae Syllidae sp. X Annelida: Polychaeta Terebellidae Euthelepus sp. X Annelida: Polychaeta Terebellidae Polycirrus sp. X Annelida: Polychaeta Terebellidae Terebellides sp. X Nemerteana Nemerteana sp. X X X X X X X Oligochaeta Oligochaete spp. X X X X X Echinodermata: Ophiuroidea Ophiuroidea sp. X X X X Echinodermata: Holothuroidea Trochodota dendyi X
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