Possible effects of increased salinity on waterbirds, invertebrates and phytoplankton at the old lagoons (85W, 145W and Walsh’s Lagoon), Western Treatment Plant

R. Loyn, I. Norman, P. Papas, J. Potts and B. Dixon

August 2006

Possible effects of increased salinity on waterbirds, invertebrates and phytoplankton on old lagoons, Western Treatment Plant

This publication may be cited as: Loyn, R., Norman, I, Papas, P., Potts, J., Dixon, B. (unpublished) Possible effects of increased salinity on waterbirds, invertebrates and phytoplankton at the old lagoons (85W, 145W and Walsh’s Lagoon), Western Treatment Plant. Report for Melbourne Water. Arthur Rylah Institute for Environmental Research. Department of Sustainability and Environment, Heidelberg.

© The State of Victoria Department of Sustainability and Environment 2006 This publication is copyright. Apart from any fair dealing for private study, research, criticism or review allowed under the Copyright Act 1968, no part of this publication may be reproduced, stored in a retrieval system or transmitted in any forms or by any means, electronic, photocopying or other, without the prior permission of the copyright holder.

Disclaimer This publication may be of assistance to you but the State of Victoria and its employees do not guarantee that the publication is without flaw of any kind or is wholly appropriate for your particular purposes and therefore disclaims all liability for any error, loss or other consequence, which may arise from you relying on any information in this publication.

Arthur Rylah Institute for Environmental Research, DSE i Possible effects of increased salinity on waterbirds, invertebrates and phytoplankton on old lagoons, Western Treatment Plant

Contents

Summary ...... iii 1 Introduction ...... 1 2 Methods...... 2 3 Waterbirds using the old lagoons...... 4 3.1 Methods...... 4 3.2 Results...... 4 3.2.1 Numbers of waterbirds...... 4 3.2.2 Breeding waterbirds ...... 4 4 Effects of brine disposal on waterbirds...... 8 4.1 Waterbirds and salinity, a review...... 8 4.1.1 Salination...... 8 4.1.2 Salination and biotic effects...... 9 4.1.3 Wetland utilisation by waterbirds occurring at the old lagoons...... 11 4.1.4 Utilisation of saline waters by waterbirds...... 12 4.1.5 Shorebirds ...... 15 4.1.6 Comments on salinity in Victoria...... 20 4.1.7 Overview of likely effects on waterbirds in Victoria...... 20 4.2 Multivariate analysis using recent data from the WTP...... 23 4.2.1 Methods ...... 23 4.2.2 Results and discussion ...... 23 4.2.3 Responses of waterbirds to other aspects of water chemistry ...... 24 4.3 Data on waterbirds and salinity from 465 Victorian wetlands...... 26 4.3.1 Methods ...... 26 4.3.2 Results and discussion ...... 27 4.4 Recent data on waterbirds, zooplankton and salinity from 52 wetlands in the Wimmera of western Victoria...... 39 4.4.1 Methods ...... 39 4.4.2 Results and discussion ...... 39 4.5 Data on waterbirds and salinity from 54 wetlands near Kerang...... 42 4.5.1 Methods ...... 42 4.5.2 Results...... 42 4.6 Data on waterbirds and zooplankton from the RAAF Lake at Point Cook, in relation to cycles of filling and drying with increased salinity...... 44 4.6.1 Methods ...... 44 4.6.2 Results and discussion ...... 44 4.7 Overview by waterbird species...... 48 5 Aquatic invertebrates in the 85W Lagoon, and models of effects of brine disposal....49 5.1 Methods...... 49 5.2 Results and discussion ...... 50 5.2.1 Invertebrates present in the ponds ...... 50 5.2.2 Salinity tolerance ...... 51 5.3 Conclusion and recommendations...... 55 6 Phytoplankton, and effects of brine disposal...... 57 7 Acknowledgments ...... 60 8 References ...... 61

Arthur Rylah Institute for Environmental Research, DSE ii Possible effects of increased salinity on waterbirds, invertebrates and phytoplankton on old lagoons, Western Treatment Plant

Summary

Melbourne Water Corporation (MWC) commissioned the Arthur Rylah Institute for Environmental Research to compile data from various sources to help determine likely impacts of increased salinity at the “old lagoons” (85W, 145W and Walsh’s Lagoon) at the Western Treatment Plant (WTP) near Werribee. The increased salinity is expected to occur in association with brine disposal from a proposed salt reduction plant, designed to produce recycled water suitable for use in offsite irrigation of vegetable crops. MWC has obligations to conserve waterbirds at the WTP, which is listed as a wetland of international importance under the Ramsar Convention. Data were compiled on waterbirds and their responses to salinity from the literature, personal experience of the authors, and from a number of published studies from south- eastern Australia. Data were also compiled on responses of aquatic invertebrates and phytoplankton, as these contribute to the food-chains on which the waterbirds depend. Data on waterbirds numbers at the old lagoons were tabulated from a current monitoring project, to show the species for which the old lagoons are most important. A wide range of waterbirds feed in the old lagoons, which are also used for breeding by Black Swans and small numbers of other species. Limited sampling was conducted in the 85W Lagoon to determine which taxa of phytoplankton, zooplankton and zoobenthos were most abundant. Data on waterbirds and salinity were examined from a broad set of 465 Victorian wetlands, assessed in the 1980s. Data were also examined from recent studies at the WTP (over a narrow range of salinities), at a set of 52 wetlands in the Wimmera, and at a set of 54 wetlands near Kerang. Data were examined from a coastal wetland near Point Cook, which varied in salinity as it dried out over a two-year period. Data on zooplankton were also examined from some of these studies. Collectively the results suggest that the old lagoons may currently be too saline for some waterbird species (Dusky Moorhen, Australian Wood Duck). Most of the waterbirds that occur there can tolerate a wide range of salinities, some even using marine waters (35,000 mg/L). However, Hardhead and Freckled Duck are likely to decline substantially or disappear if salinities exceed ~4000 mg/L, and Blue-billed Duck, Pink-eared Duck, Pacific Black Duck and Eurasian Coot are also likely to decline as salinities reach or exceed 5000 mg/L. Breeding conditions for Black Swans may be affected, as young waterbirds of many species need access to fresh water. The old lagoons do not provide important breeding habitat for other waterbird species. Some of the ponds in the old lagoons support thousands of shorebirds when water levels are low (including one that is managed as a conservation pond to provide shorebird habitat). Most of these species can tolerate a range of salinities, including tidal mudflats. Some may benefit from increased salinity, especially if this reduces encroachment by terrestrial vegetation. Species confined to freshwater habitats are generally uncommon on the old lagoons. However, small numbers of one species, the Black-tailed Godwit, regularly visit drying ponds in the system, and may be affected adversely by expected increases in salinity. Invertebrates were sampled in three habitats in three ponds from the old lagoons in January 2006. The most abundant taxa were microcrustacean and midge larvae grazers (animals that graze on algae) and detritivores (feeding on small detritus that may be plant or animal in origin). Salinity risk modelling using data from a salt sensitivity database, was

Arthur Rylah Institute for Environmental Research, DSE iii Possible effects of increased salinity on waterbirds, invertebrates and phytoplankton on old lagoons, Western Treatment Plant

used to assess the risk of increasing salinity from 1000 to 5000 mg/L on the aquatic invertebrate present in the ponds. The modelling showed that the predicted increase is likely to affect taxa present in the ponds detrimentally. Given the uncertain and variable nature of the data it is difficult to determine at what level effects will occur and to be confident that effects will actually occur with each species. Phytoplankton data from Water EcoScience collected in September 2003 were used to estimate the phytoplankton community on the old lagoons. Fifty-three taxa were collected from this study, of which many are likely to be consumed by invertebrate grazers and detritivores. Little is known about the response of phytoplankton taxa to salinity; however some taxa have been found to be relatively salt-tolerant in some studies. As there are many uncertainties in our predictions, a monitoring program is recommended with its main focus on waterbirds and selected groups of invertebrate species.

Arthur Rylah Institute for Environmental Research, DSE iv Possible effects of increased salinity on waterbirds, invertebrates and phytoplankton on old lagoons, Western Treatment Plant

1 Introduction

The Western Treatment Plant (WTP) is one of two main sewage treatment plants for Melbourne. It covers 11,000 ha near Werribee, between Melbourne and Geelong on the shores of Port Phillip Bay. The WTP attracts large numbers of waterbirds (ducks, swans, coots and grebes) and international migratory shorebirds (Lane and Peake 1990; Loyn et al. 2002a, b), and is listed as an integral part of a wetland of international importance under the Ramsar Convention on Wetlands 1982. Hence the needs of waterbirds must be considered in changes to the site’s management. Melbourne Water Corporation (MWC) manages the WTP, and has obligations for sewage treatment and conserving waterbirds. MWC has implemented an Environment Improvement Project (EIP) at the WTP in order to comply with its Victorian Environment Protection Authority accredited licence for discharging effluent into Port Phillip Bay. The Government of Australia listed the EIP as a controlled action under its Environment Protection & Biodiversity Conservation Act 1999, and approved the EIP with conditions on conserving Ramsar values and monitoring effects. Recent State Government initiatives (“Our Water Our Future”) have highlighted the need to conserve fresh water and reduce the use of potable water for industrial and agricultural purposes. One opportunity to do this is to make greater use of treated effluent from the WTP for offsite irrigation of local vegetable crops. Unfortunately the effluent carries a load of salt (mainly sodium chloride, ~1000-1500 mg/L) and some of the local crops (especially lettuce) are sensitive to salinity. Hence MWC proposes to build a salt reduction plant, to produce a stream of recycled water suitable for sustainable use in irrigating vegetable crops. An inevitable by-product of the process is a stream of more saline water. Part of this stream can be drained directly to Port Phillip Bay, but some will need to be recirculated through the sewage treatment system to reduce nitrogen loads. The proposal is to recirculate the saline stream through the “old lagoons”, consisting of 85W Lagoon, 145W Lagoon and Walsh’s Lagoon. This is expected to increase the salinity of the old lagoons from their current levels (1000-1500 mg/L) to ~3000-5000 mg/L (note that sea water is ~35,000 mg/L). However, the level of salinity will vary seasonally (being higher in summer) and increase towards the end of the pool sequence. A mean salinity value of c. 3000 mg/L is anticipated for ponds about two-thirds through the system (T. Otimi, pers. comm.). Increases in salinity of this order may be expected to have effects on the waterbird populations and the aquatic biota on which they depend for food. Hence MWC commissioned the Arthur Rylah Institute (ARI) to review the literature and examine other sources of information to help predict likely changes, so that they can be managed appropriately. This report presents the relevant information we have gathered for this project.

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2 Methods

Several approaches were identified that could provide information to help predict effects of expected changes, each with its own strengths and limitations. The following discrete tasks were undertaken in order to provide a useful set of data for prediction: 1. Data on waterbirds currently using the old lagoons were compiled from waterbirds monitoring over the whole WTP in recent years (unpublished data collected by ARI for MWC, 2000-2005). These showed which species made most use of the lagoon, and the mean numbers of those species over 27 counts. Data were also compiled on numbers of these species over the whole WTP, so that the value of the old lagoons could be viewed in the broader context. The emphasis was on waterbirds because these are the species that carry specific obligations under the international Ramsar Convention, and in consequence the Australian EPBC Act. However, the zooplankton constitute the main food of the waterbirds, and the phytoplankton are likely to be the main source of primary productivity. 2. Samples of aquatic invertebrates were collected from three ponds within the 85W Lagoon on 17 January 2006 (85WA pond 5, 85WB pond 7 and 85WC pond 7), to give an indication of the most common species present. At each pond, invertebrates were sampled from the littoral zone (water close to the shore), and from the water and benthos (i.e. sediment) ~2m out from the shore. Data on aquatic invertebrates were modelled to assess the chances that each species would persist through the expected changes in salinity.

3. Information on phytoplankton was compiled from samples collected at nearby Walsh’s Lagoon and 145W Lagoon by Water EcoScience as part of a joint project with ARI for MWC, 2002-05.

4. Literature reviews were conducted to ascertain what was known about likely effects of increasing salinity on the respective taxa of waterbirds, zooplankton and phytoplankton. The authors also drew on personal experience in predicting likely effects: in some cases this supplemented deficiencies in the formal literature. 5. Data on waterbird numbers and water chemistry on 23 ponds at the WTP, collected together on eight occasions from November 2001 to July 2004, were compiled from a separate study conducted by ARI and Water EcoScience for MWC. Waterbirds densities on these ponds were modelled with respect to suites of potential explanatory variables as part of that study, using Bayesian model-averaging. Water conductivity was one of these variables, and is commonly used as a surrogate for salinity. Hence the models were examined to see the predicted effects of salinity in conjunction with other variables, all assessed at the WTP (though not at the old lagoons). 6. Data were compiled from studies of waterbirds and salinity at multiple wetlands in Victoria in the 1980s (A.H. Corrick, pers. comm.) and stored in the Victorian Wetland Database. These included 517 records from 465 wetlands where waterbird numbers and salinity or conductivity were assessed at the same time. On large wetlands salinity readings were often taken from several points, each corresponding to a single count of waterbirds. Waterbird densities were calculated and graphed against salinity readings. Inspection of the graphs allowed good visual interpretations of likely responses, and the range of salinities that can support relatively high densities of each species. Correlation matrices were also generated for the pertinent range of

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salinities (800-6500 mg/L) to assess whether salinity was generally a positive or negative influence over this range. Logistic regression was used to model responses of species to salinity in terms of presence or absence over a slightly wider range (800-7500 mg/L), and in terms of abundance if present. Further modelling of the dataset can be done if required. 7. Data regarding waterbird numbers, zooplankton (ostracods) and salinity levels at 50 wetlands in the Wimmera of western Victoria, based on snapshot samples collected by ARI teams in November 2005 (M. Smith, G. Cheers et al. pers. comm.) were reviewed. This provides an up-to-date dataset from a clearly defined set of wetlands, collected by a single team over a short time-frame. 8. Information on waterbird numbers and salinity at 52 wetlands near Kerang in north- western Victoria, collected in 1988-89 (Lugg 1990) was reviewed. As above, this provides a set of data from a constrained set of sites and times, in contrast to the more diffuse and variable data from the Victorian Wetland Database. Salinity levels varied from fresh to hypersaline. 9. Data on waterbird numbers, zooplankton and salinity on a natural land-locked saline coastal lake (the RAAF Lake, 71 ha) near Point Cook, 15 km north-east from the northern boundary of the WTP (Loyn et al. 2003) were also examined. Waterbirds were counted and zooplankton recorded over two years (2001-03) during which the lake filled and then dried. This gives some idea of the extent of change that may occur on a single wetland in response to changing water levels and salinity. Salinity increased as water levels dropped, exceeding 10,000 mg/L for much of the latter part of the study.

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3 Waterbirds using the old lagoons

3.1 Methods Waterbirds numbers have been counted over the entire WTP six times per year since 2000 (Loyn et al. 2002a and unpublished data). These counts were mostly conducted by Bob Swindley for ARI on behalf of Melbourne Water Corporation. This database provides a good record of the waterbirds using the old lagoons in recent years, and puts it in context with the rest of the WTP. The data have been compiled and tabulated for this purpose. Shorebirds have also been counted regularly during this period. However, sewage treatment lagoons generally provide little habitat for shorebirds except when water levels are dropped to expose substantial muddy shores. One pond in the 85W Lagoon provided important shorebird habitat in 2003-04 when water levels were dropped to allow construction activities (Rogers et al. 2004). Another pond (85WC pond 9) is currently managed as a conservation pond to supply shorebird habitat during summer. Counts of shorebirds have been made at these ponds, but may not give a good guide to their potential to provide habitat in the longer term as this management is relatively new. Hence these data have not been presented in detail.

3.2 Results 3.2.1 Numbers of waterbirds Numbers of waterbirds counted on the old lagoons over five years are shown in Table 1 along with numbers counted in the entire WTP. Table 1 only considers waterbirds that use operating sewage ponds as a major habitat. Birds such as shorebirds (which use sewage ponds mainly when water levels are low) are considered elsewhere in this report. In the context of the entire WTP, the old lagoons support >30% of the mean count population of seven native waterbird species (Hoary-headed Grebe, Australasian Shoveler, Hardhead, Australian Shelduck, Eurasian Coot, Black Swan and Australasian Grebe) (Table 1). Two other species (Blue-billed Duck and Pink-eared Duck) gathered seasonally at the old lagoons in numbers that exceeded 30% of the totals for the WTP. In winter 2006, all of the Freckled Ducks that remained over winter at the WTP (50 birds) inhabited the old lagoons. Some of these species also feed in marine habitats (Hoary-headed Grebe and Black Swan on a regular basis; Australasian Shoveler mainly close to freshwater outlets), so they can tolerate levels of salinity much higher than anticipated to occur at the old lagoons (Table 2). Several other species are known to use highly saline wetlands elsewhere (notably Australian Shelduck and Banded Stilt). However, several species that used the old lagoons rarely occur on the sea or highly saline waters (Table 2). They include Hardhead, Blue-billed Duck, Pink- eared Duck, Freckled Duck and two species that were found only in very low numbers (Australasian Grebe and Australian Wood Duck). To determine the potential sensitivity of these species to proposed changes, we need to examine data from wetlands of known salinity elsewhere. This is done in subsequent sections.

3.2.2 Breeding waterbirds Most of the waterbirds recorded at the old lagoons were using the ponds for feeding and loafing rather than breeding. Black Swans were the main exception, and they breed in small numbers throughout the WTP including the old lagoons. However, the peak breeding season

Arthur Rylah Institute for Environmental Research, DSE 4 Possible effects of increased salinity on waterbirds, invertebrates and phytoplankton on old lagoons, Western Treatment Plant for Black Swans at the WTP is winter and early spring (Loyn et al. 2002), when salinity changes are not expected to be high. Waterbirds are often more sensitive to salinity when breeding than at other times, because the young need access to fresh water. However, this will mainly be an issue for Black Swans at the old lagoons. Pairs of other duck species occasionally nest among long grass on banks between sewage ponds, but the numbers involved are small and this issue does not appear to warrant further consideration. The shorebirds for which the WTP is most important are migratory species (most nesting in the Northern Hemisphere, one in New Zealand). Of the shorebirds that nest in Australia, five nest regularly at the WTP: Pied Oystercatcher on the coast, Black-winged Stilt on shallow freshwater wetlands, Masked Lapwing in various grassland habitats, Red-capped Plover on flat open ground and Black-fronted Dotterel on strips of open stony substratum, often beside gravel roads. The old lagoons are not known to be a major breeding habitat for these species, but they can provide breeding habitat at times. Two of these species are normally found in freshwater habitats (Black-winged Stilt and Black-fronted Dotterel) and could be adversely affected by any increase in salinity. Black-winged Stilts specialise at breeding in vegetated freshwater wetlands, but occur more widely when not breeding: this may indicate that they have more need for fresh water when breeding than at other times.

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Table 1. Numbers of waterbirds counted on the old lagoons and in the whole of the Western Treatment Plant, 2000-05. Non-native species are marked *. Data for the whole farm are shown only for waterbird species that use the ponds as a major habitat (ducks, geese, swans, grebes and coot). Species are listed in descending order of mean abundance on the old lagoons.

Family or Guild Mean Max Whole- Mean as % (27 counts) (27 counts) farm whole-farm mean 2000-05 Guilds Waterbirds (all ducks, geese & swan) 16687 35174 67819 24.6 Filterers 4347 15203 28459 15.3 Grebes 4157 15091 10297 40.4 Diving ducks 2866 5456 11075 25.9 Dabblers 1964 6066 9047 21.7 Hardhead 1589 4240 4085 38.9 Stiff-tails (sub-set of diving ducks) 1277 4145 6990 18.3 Grazing ducks 1264 6252 3275 38.6

Species Hoary-headed Grebe Grebe 4148 15088 10262 40.4 Australasian Shoveler Filterer 2194 8653 6211 35.3 Pink-eared Duck Filterer 2150 9270 22127 9.7 Hardhead Diving duck 1589 4240 4085 38.9 Australian Shelduck Grazing duck 1262 6251 3264 38.7 Grey Teal Dabbler 1123 3083 4595 24.4 Eurasian Coot 1117 2288 2853 39.1 Blue-billed Duck Diving duck 1039 3642 5937 17.5 (stiff-tail) Black Swan Swan 973 3232 2813 34.6 Chestnut Teal Dabbler 592 2237 3489 17.0 Pacific Black Duck Dabbler 249 746 962 25.8 Musk Duck Diving duck 238 772 1052 22.6 (stiff-tail) Silver Gull Gull 142 1593 575 24.7 Whiskered Tern Tern 130 1425 801 16.2 Australian Pelican Pelican 16 124 Australasian Grebe Grebe 9 234 20 45.4 White-winged Black Tern Shorebird 6 72 35 17.9 Freckled Duck Filterer 3 17 122 2.4 Purple Swamphen Waterhen 1 37 Black-tailed Native-hen Waterhen 1 35 Domestic Goose * Goose 1 2 1 100 Australian Wood Duck Grazing duck 0 6 7 6.6 Great Crested Grebe Grebe 0 4 15 2.2 Cape Barren Goose Goose 0 2 2 14.8 Northern Shoveler Filterer 0 1 0 Mallard * Dabbler 0 1 0 Domestic Duck * Dabbler 0 1 0 Black Duck-Chestnut Teal hybrid Dabbler 0 1 0

# Note that this table does not include shorebirds and other wading birds, which occur mainly when water levels are reduced in particular ponds, eg certain ponds on Walsh’s Lagoon and 85WC pond 9 (managed as a conservation pond for shorebirds since 2005).

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Table 2. Use of saline habitat by waterbirds recorded on the old lagoons, 2000-05, based on published and unpublished personal observations at WTP or elsewhere in southern Australia. Totals show the sum of 27 counts at the old lagoons, and species are arranged in decreasing order of this value (as in Table 1). An assessment based on literature is given in Table 3. Species Mean Use of marine or saline habitats elsewhere Hoary-headed Grebe 4148 Often feeds on sea or saline waters Australasian Shoveler 2194 Sometimes in estuaries Pink-eared Duck 2150 Rarely on sea Hardhead 1589 Rarely on sea Australian Shelduck 1262 Often feeds from tidal mudflats; visits hypersaline waters Grey Teal 1123 Often feeds in estuaries or sheltered marine bays Eurasian Coot 1117 Rarely on sea Blue-billed Duck 1039 Rarely on sea Black Swan 973 Often feeds on sea or saline waters Chestnut Teal 592 Often feeds on sheltered sea or saline waters Pacific Black Duck 249 Often feeds in estuaries Musk Duck 238 Often feeds on sheltered sea Silver Gull 142 Often on seashore or saline wetlands Whiskered Tern 130 Sometimes feeds over estuaries Red-necked Avocet 25 Often on tidal mudflats or shores of saline wetlands Australian Pelican 16 Often on sheltered sea Australasian Grebe 9 Mainly on fresh water Black-winged Stilt 8 Mainly on vegetated freshwater wetlands White-winged Black Tern 6 Sometimes feeds over estuaries Banded Stilt 3 Often on hypersaline waters Freckled Duck 3 Rarely on sea Purple Swamphen 1 Dense vegetation, not on seashore Black-tailed Native-hen 1 Dense vegetation, not on seashore Glossy Ibis 1 Mainly freshwater wetlands Australian Wood Duck 0 Avoids saline water Black-fronted Dotterel 0 Avoids saline water; uses fresh streams Great Crested Grebe 0 Often on sea Small migratory shorebirds 150 Often on tidal mudflats or shores of saline wetlands; see (many spp.) Table 5 for individual species

Note: Some species are notable by their absence from sewage lagoons generally, e.g. Dusky Moorhen, which occurs at the WTP only on fresh water (e.g. vegetated creeks and an ornamental pond).

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4 Effects of brine disposal on waterbirds

4.1 Waterbirds and salinity, a review Since European occupation, the landscape of much of Australia has undergone substantial modification, which has profoundly affected terrestrial and aquatic ecosystems. As native vegetation has been cleared, and replaced with relatively short rooted, often essentially annual agricultural species, there have been consequential changes in hydrological processes at scales varying from local levels to entire catchments or series of catchments. At the same time, and often in direct association, significant diversions (or modifications) of river flows have occurred for human consumption or for the development of irrigation-based agriculture. Such changes have also had effects on wetland salinities and on dependent flora and fauna. In this review, it was considered important to examine aspects of salination which may affect aquatic ecosystems, dependent flora and fauna and hence waterbirds using them.

4.1.1 Salination In some catchments, and in some regions of Australia, salinisation of inland waters may be considered as a natural process. Thus, where water flows into terminal wetlands, it is inevitable that dissolved salts (often sodium chloride) concentrate within that wetland (e.g. Lake Eyre, some western Victorian wetlands; see Hart et al. 1991 for further details).1 This primary salinisation leads to salt lakes which may have an associated, specialised and restricted biota. In this discussion (based extensively on Hart et al. 1990, 1991, Bailey and James 2000 and Clunie et al. 2002), although the effects of natural salinisation will be briefly mentioned, most attention is paid to secondary forms of salinisation, essentially the consequences of anthropogenic activities. For simplicity, all forms of salting are considered to involve sodium chloride (although this salt is not always the most abundant). Secondary salinisation is recognised as having two separate forms, namely dryland salinity and irrigation-induced salinity. Dryland salinity, widespread across parts of Victoria, is initiated by removal of native vegetation and its replacement by (usually) alien, short-rooted species. Such activities result in a rising groundwater table which includes the associated mobilisation of salts (often, or even predominantly, sodium chloride) which may invade the root systems and cause widespread damage to, if not death of, plants. Additionally, this form of salinity liberates salts into lower-lying wetlands and drainage systems, particularly when flows are modified or reduced. Accumulation of salts then occurs when evaporation reduces available water (e.g. Nielsen and Hillman 2000). Regulation of water supply leads to reduced variability of flows and may ultimately include periods of no flow. In a similar fashion, increased agricultural development and widespread irrigation results in a raised water table, and the consequent upwards movement of salts, which affects crops and influences local drainage systems (see Hart et al. 1990, 1991; NLWRA 2001 for details). Within Victoria, it is now considered that there are some five rivers (Avoca, Campaspe, Lindsay, Loddon and Wimmera) ‘at risk’ of increased salt loading (MDBMC 1999). At the same time, MDBMC (1999) noted that, of the 1 million ha of irrigable land in Victoria there were some 440 000 ha which already had a high water table, a figure which would increase

2 In this review, there is some variation in units used to express ‘salinity’. However, total soluble (or dissolved) salts (tds), as mg/L, are considered equivalent to µS/cm x 0.68 (Hart et al. 1991), i.e. EC units.

Arthur Rylah Institute for Environmental Research, DSE 8 Possible effects of increased salinity on waterbirds, invertebrates and phytoplankton on old lagoons, Western Treatment Plant to around 600 000 ha without further management. These estimates were increased (to 843 000 ha) in MDBMC (1999) and to over 3 million ha by 2050 (NLWRA 2001; see also (http://audit.ea.gov.au/anra/land/land_frame.cfm?region_type=VIC®ion_code=VIC… for further details). Similarly, salt accumulation in dryland catchments was increasing and, in some areas, expected to do so for the next 100 years (MDBMC 1999). This loading was, according to the Salinity Audit, greatest in the Avoca catchment but discharge to the Murray River was in fact higher from the Goulbourn-Broken catchment. Without any amelioration, well over 50 % of agricultural land will be in moderate to high risk of increasing salinities. High risk areas occur or will occur, particularly in the Goulbourn-Broken area (>58%) and north central Victoria, in the Glenelg-Hopkins (>40%) and Corangamite (>48%) regions in south west (SCC 2001). Some of these rivers (e.g. Goulbourn, Campaspe, Loddon) have extensive diversions of water for irrigation and, as with the Avoca River, salt loads do not necessarily reach the Murray River (MDBMC 1999). To an extent, dryland salinity management plans have been established for major Murray-Darling Basin catchments. Nevertheless, inflows of saline groundwater (up to 34,000 mg/L) occur downstream and compound problems associated with waste water from irrigation schemes and associated elevation of ground waters. The situation is, of course, further exacerbated by the extensive clearing previously undertaken in such areas and the continued application of excessive amounts of water in irrigation-based agricultural pursuits. In general, it is considered that all irrigated areas in the southern Murray-Darling Basin will have water tables within 2 m of the surface by 2010 (for details see http/www.mdbc.gov.au/naruralresources/env_issues/water_and_land_salinity.htmp, and included references). Within the Goulbourn-Broken and Corangamite regions, some 40% of wetlands are expected (given current trends) to be within areas of shallow water tables by 2050: additionally, there will be a 200-300% increase in stream length, or perimeter of lake or wetland within such areas (see http://audit.ea.gov.au/ANRA/land/sal_context… for details).

Of all wetlands, those on riverine plains are most likely to be directly affected by rising water tables. Hence, floodplain wetlands associated with the Murray are increasingly threatened and c. 25% in the lower Murray floodplain are already affected (Hillman and Nielsen 2000). For wetlands the long term trend is generally considered to show similar problems (SCC 2001). Thus existing Ramsar wetlands will increasingly be affected by rising water tables as will other wetlands. There is, however, only a ‘very limited understanding of the ecological effects of salination on wetlands’, and the same is true for flows in streams and other water courses which maintain wetlands.

4.1.2 Salination and biotic effects There is a decreasing diversity of aquatic (and littoral) vegetation and attendant fauna with increasing salt loading of wetland habitats (Norman and Corrick 1988, Hart et al. 1990, 1991). Moreover, even relatively small increases in salinity can affect fauna and flora, and those taxa represented in higher salinities tend to be specialised for such regimes. Salinity sensitivity data presented in Hart et al. (1990) indicate, generally, the paucity of such information. Further, they also show that generalisations are not necessarily possible even within the same taxonomic grouping. As such, the implications for predictive possibilities across a range of salinity levels are apparent, and the requisite improvements in available data have not occurred (Clunie et al. 2002). In particular, details regarding the influence of increased salt on specific life stages and on ecosystems generally remain severely deficient. It is, however, possible to reiterate or develop some themes from the reviews of Hart et al.

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(1990, 1991), Bailey and James (2000) and Clunie et al. (2002), which have particular relevance to wetlands and waterbirds utilising them. First, since the timing (season) and frequency of inputs of salt (i.e. continuous, intermittent or cyclical) will vary depending on the source, and on local rainfall and or flooding, so too will the effect on biota within different drainage systems. It is also apparent that, while during flood events salt may be diluted or indeed flushed from individual wetlands, residual solutions will concentrate as the drying cycle progresses. Residual salts are, therefore, likely to accumulate and the individual wetland generally show a trend towards increased salinity. The process, which for many wetlands is likely to be irregular rather than have a seasonal frequency, has implications for the ensuing productivity which may vary not only in relation to salinity levels, but also ambient temperature, daylength and inputs of nutrients, including deleterious anions and cations (Bailey and James 2000; Clunie et al. 2002). Secondly, Hart et al. (1990) indicated the paucity of information regarding the basic distribution of species (plants or animals) within Victorian wetlands. This situation has not changed materially since that time. Thirdly, and despite some recent initiatives (e.g wetlands conservation program, Anon 1988a), there have been few long term studies of physico-chemical changes in Victorian wetlands; these changes can be substantial and may have varying influence on the local infauna or inflora. While it is accepted that plant communities might be the most obvious index of changing salinities, it is equally clear that there are ‘seasonal’ successions which also occur (Hart et al. 1990); these may obscure changes due to salinity.

Fourthly, changes to the composition of the plant associations occur when salinities reach or exceed about 1000 mg/L (Hart et al. 1990, 1991). While little is known about sub-lethal effects of increased salinity, or indeed on its influence on differing stages of development, the majority of macrophytes are not salt tolerant and often have limits around 4000 mg/L (Brock 1981). Similarly, microalgae show sensitivity to salt, with numbers and taxa reducing with increased levels: more particularly, the reduction in vascular plant representation may remove substrates required by various diatoms (Bailey and James 2000), and presumably other taxa. Bailey and James (2000) also noted that a large proportion of submergent macrophytes were likely to suffer sublethal effects (including reduced ‘vigour’) or die when salinity reached c. 2000 mg/L. More recent studies, reviewed in Clunie et al. (2002), indicate i) some stimulation of growth in E. camaldulensis seedlings at salinities of around 2400 mg/L, ii) reduction of sensitivity following pre-incubation at non-lethal levels and iii) that, apart from Lamprothamnium spp., charophytes do not tolerate the dramatic changes of salt and water levels often experienced in local wetlands. Bailey and James (2000) noted that some riparian species may, through root uptake adjustment, not be as seriously affected by increased salt loads as previously thought. Nevertheless, high salinity levels in association with varying water regimens can affect riparian communities and, if flooding is infrequent, saline groundwater can induce poor health (see Clunie et al. 2002 for further details). Changes to macrophytic vegetation, and to associated littoral species (which may include nest sites or foraging areas), as a consequence of increased salinity will all have some impact on waterbird utilisation of affected areas. Fifthly, following the review by Hart et al. (1990), which indicated i) that invertebrate species (particularly some insect and mollusc groups), could include some of the most salt-sensitive species, ii) that some crustaceans were the most salt-tolerant species, and iii) that there were serious data deficiencies, Bailey and James (2000) and Clunie et al. (2002) added further comments, based on more recent literature. Thus, Bailey and James (2000) considered that

Arthur Rylah Institute for Environmental Research, DSE 10 Possible effects of increased salinity on waterbirds, invertebrates and phytoplankton on old lagoons, Western Treatment Plant some species would suffer ‘adverse’ effects with salinity increases as low as 800 mg/L., and that these occurred in each invertebrate group including crustaceans. In this regard Keighery et al. (2000) considered that mass extinctions would occur in the wheatbelt region of Western Australia if salinity was to increase; studies there had already shown that the diversity of invertebrates declined with increased salt loading. Clunie et al. (2002) emphasised many earlier conclusions, and noted (again) that data were still poor, and those regarding sublethal effects were generally lacking. They noted too that salinity reduces species richness and changes community structures with inevitable consequences for predatory species (including birds). They repeated earlier comments and reinforced the prospect that synergistic effects, between salinity, oxygen concentration, pH and various ions, may be important even if salinity represents the most obvious agent. Sixth, there is a general view that many fish species are salt tolerant particularly if acclimation is gradual. Nevertheless, even within this well-studied group, the effects on various life stages are poorly known, sublethal effects are not understood and sensitivity may vary between catchments (Clunie et al. 2002). Conclusions for amphibians and reptiles have remained generally speculative, and are based on inadequate data. However, some studies suggested that frogs may act as an indicator species at low salt levels but both they, and fish species, would be affected by loss of macrophytes (Clunie et al. 2002). Clunie et al. (2002) also suggested that previous, and more recent, studies on waterbirds indicated a reduced diversity with increased salinities, most broods occurred where salinities were less than 15,300 mg/L and that growth rates would be affected by ‘elevated’ salinity.

Finally, Bailey and James (2000), in following Hart et al. (1991), considered that any effects on suites of taxa would result in effects on ecological processes themselves. They also commented on i) the general dearth of information regarding effects on communities and processes, ii) the prospect that temporary wetlands would be affected not only by increased loading during drying cycles but also by increased temperatures and reduced dissolved oxygen in summer; iii) the prospect that pH would play a significant role in determining representation; iv) loss of invertebrate biomass would reduce foods available to other taxa; and v) while some invertebrate species might be tolerant to increased salinity, their diversity would decline. Clunie et al. (2002), reviewing more recent literature, also indicated that waterlogging together with increased salination had a greater effect on survival and growth of seedlings than did either factor in isolation. Further, the increased salinity has an effect not only on foods used by waterbirds but also on the vegetation (e.g. reeds, trees) used for roosting, nesting ,and foraging; all are compounded by water depth and other physico- chemical factors. In this review, the potential influence of changing salinities on waterbirds using part of the Western Treatment Plant at Werribee (namely the old lagoons), is considered both in terms of literature reviewed above, and in terms of observations made during 2000-2006. Particular attention is paid to utilisation of saline and hypersaline waters.

4.1.3 Wetland utilisation by waterbirds occurring at the old lagoons It is possible to summarise, in general terms, wetland utilisation by waterbirds of varying taxa. Here, using habitat utilisation details from Marchant and Higgins (1990, 1993) and personal observations, waterbirds recorded at the old lagoons (Table 1 above, plus selected shorebirds and wading birds that occur there) have been considered as using wetlands of varying salinities (from freshwater to hypersaline): their use of marine waters is also noted (Table 3).

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It is clear that, for the 30 taxa under consideration, wetlands of a range of salinities are used either occasionally or routinely by most species. For seven species (mostly waterbirds), freshwater wetlands are apparently preferred while two species (Red-necked Avocet and Banded Stilt) saline to hypersaline wetlands are used extensively. For the most part observational data indicate presence (and absence), but it is unclear for some species whether foraging occurs or whether birds are merely roosting in the categorised habitats. Certainly some species feed regularly and extensively in marine habitats (e.g. Hoary-headed Grebe) without any apparent need for freshwater sources, while others (e.g. Grey and Chestnut Teal) require access to sources of freshwater to remove or reduce excessive salt loads (see Table 3). Nevertheless, some species, for example, Black Swan, Chestnut and Grey Teal, are known to have salt glands which allow extra-renal removal of excessive salt (Lavery 1972, Hughes 1976, Baudinette et al. 1982). In contrast, some species (e.g. Hardhead, Pink- eared Duck, Blue-billed Duck) occur infrequently on marine waters if at all. In general, waterbirds at the old lagoons use the area for feeding (or loafing) during non- breeding periods. However, Black Swan and Chestnut Teal breed in and around several wetlands within the WTP and, since flightless young need access to freshwater (Swanson et al. 1984, Stolley et al. 1999), might be affected by changes in salinities. Changes in salinities will also affect potential food species present, and hence vary the potential use by waterbirds.

4.1.4 Utilisation of saline waters by waterbirds Some species (e.g. Chestnut Teal, Grey Teal, Black Swan) utilise marine areas, particularly embayments, feeding and roosting there during non-breeding periods. Local waterbirds also occur on coastal and inland wetlands of varying salinities (see, for example, Marchant and Higgins 1990), but a detailed understanding of the use of such areas is generally lacking. Further, dietary information for some waterbird species is poorly understood (see Table 4) although Cape Barren Geese do not necessarily depend on access to fresh water, apparently being able to obtain obligatory water requirements from their diet (Marchant and Higgins 1990). Other waterbirds, such as Black Swans, Chestnut and Grey Teal, may forage in marine areas but they do need to have fresh water available to assist in the removal of excess salt (Lavery 1972, Norman 1983, Baudinette et al. 1982).

Halse (1987), in reviewing the probable changes in local avifauna at a wetland where salinity was increasing, suggested that the number of resident and breeding species would decline by ‘at least 50 per cent’ if the trend continued. Species using the included or surrounding vegetation for nesting would no longer do so since, presumably, the vegetation would die with increased salt loading. In a more detailed study in south-western Western Australia, Goodsell (1990) found that, though 90% of broods were recorded on waters with salinities less than 15,300 mg/L, there was an increased use associated with pH at low or medium salt levels: he suggested that a combination of high or low pH and salinity was associated with successful breeding. Halse et al. (1991) extended sampling in the area covered by Goodsell, and examined a greater range of wetlands. In their study, more waterbird species were associated with brackish waters than any other salinity range and it was concluded that salinity was an important factor in wetland utilisation. In these brackish (or even saline) wetlands local productivity may be high, and provide enhanced foraging opportunities

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Table 3. Utilisation of wetlands by waterbird species observed at the old lagoons (and ranked according to count totals on 85W): categorisation following HANZAB 'Habitat' sections and references cited, and pers. obs. (Here information is summarised for generalised wetland categories: (+) = rarely; + = occasional; ++ = usual; +++ = preferred; * = range of embayments, shores and inshore waters). Species Freshwater Estuarine Saline Marine* Hypersaline Comments Hoary-headed Grebe ++ ++ ++ ++ + Hardhead +++ + + (+) Pink-eared Duck +++ + + Australasian Shoveler +++ + + + Australian Shelduck ++ + + + ++ Presumably needs source of freshwater nearby Grey Teal ++ ++ + ++ + Presumably needs source of freshwater nearby Blue-billed Duck ++ + (+) + Black Swan ++ ++ + ++ + Presumably needs source of freshwater nearby; saline Wetlands usually < 60 o/ooo = limits of aquatic food plants Eurasian Coot ++ + + + + Chestnut Teal ++ ++ + ++ + Presumably needs source of freshwater nearby Pacific Black Duck ++ + + + Musk Duck ++ + + + Red-necked Avocet + + +++ + +++ Whiskered Tern ++ + + (+) Silver Gull + ++ ++ ++ + Black-winged Stilt ++ + + + Salinities 10,000 – 145,000 mg/L Banded Stilt (+) + ++ +++ Salinities 40,000 – 145,000 mg/L Red-necked Stint + ++ ++ ++ + Freckled Duck +++ + Purple Swamphen +++ + Black-tailed Godwit + + + + + Black-fronted Dotterel ++ (+) Marsh Sandpiper + + ++ + Australasian Grebe +++ (+) Great Crested Grebe ++ + ++ ++ + Australian Wood Duck +++ + Cape Barren Goose (+) + Grazing species, breeding on offshore islands Great Egret + + + + White-winged Black Tern + + + (+) + Black-tailed Native-hen ++ + (+)

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Table 4. Major food sources taken by Australian waterbirds. (source Marchant and Higgins 1990 and references cited; ? = extent not determined).

Species Major foods taken Comments Plant material Invertebrates Australian Shelduck Extensive Extensive Poorly known Australasian Shoveler ? extent Extensive Poorly known Australian Wood Duck Extensive in dry periods Chestnut Teal Extensive Extensive, includes molluscs Grey Teal Extensive Includes molluscs Hardhead Extensive Extensive, particularly Poorly known molluscs Pacific Black Duck Extensive ? extensive Pink-eared Duck Extensive – mainly larvae Poorly known and plankton Black Swan Extensive Blue-billed Duck Extensive Extensive Poorly known Cape Barren Goose Extensive Freckled Duck ? extent Extensive Poorly known Magpie Goose Extensive Musk Duck ? extent Extensive Also takes small fish, and ducklings Plumed Whistling-Duck Extensive Poorly known

(Halse et al. 1991). Usage of wetlands in drier areas of Western Australia, where saline wetlands predominate, was further examined by Chapman and Lane (1997). Waterbirds were more abundant, in terms of species and numbers, following rainfall events when there were high water levels, flooding and low salinities. While numbers of species declined as water levels declined, some species (Grey Teal, Australian Shelduck) remained in large numbers on some wetlands which provided breeding habitat and appropriate resources even as salinities increased. Similarly, in inland Australia, Kingsford and Porter (1994) found that the saline Lake Wyara (9400 mg/L in August 1989, but reaching up to 30,000 mg/L) held more than ten times the number of waterbirds (including ducks) than the nearby fresh Lake Numalla (c. 1600 mg/L in 1989, <3000 mg/L at other times). Wyara supported considerably more Grey Teal and Pink-eared Duck than did Numalla, and more nests and broods of Black Swan were also found there. Kingsford and Porter (1994) indicated that the differences in utilisation were a reflection of available foods: planktonic invertebrates and macrophytes were more numerous in the salt waterbody, whereas the freshwater contained shrimp and fish communities, communities perhaps restricted by higher salinities. The saline lake did, however, hold fewer invertebrate taxa. Of note was their suggestion that salt flocculated suspended clay particles; these dropped to the substrate and allowed penetration of light which then supported macrophyte development and subsequent invertebrate production. These authors (and those listed above) did not, however, indicate that movement between the two wetlands and associated freshwater systems, for those species (and age groups) requiring fresh water, was not occurring. In Victoria, where most natural waterbodies have high levels of salinity (Williams 1980), there have been few studies on effects of increasing salinities on wetland communities. Weber (1979) noted that natural water courses were used to drain irrigation water, changing the irregular nature of inundation to one of permanency and increased salinity; many local plant species could not tolerate high salt levels. In western Victorian lakes benthic invertebrates decreased both in species richness and abundance with increased salinities,

Arthur Rylah Institute for Environmental Research, DSE 14 Possible effects of increased salinity on waterbirds, invertebrates and phytoplankton on old lagoons, Western Treatment Plant and waterbird taxa showed similar declines (Missen and Timms 1974, Timms 1983). Maher (1991) too, working on wetlands in arid Australia, also found a reduced representation of invertebrate taxa as salinity levels rose. Nevertheless, while some species may ingest water with dissolved salt when feeding, salt levels do not extend much beyond 35,000 mg/L (e.g. Black Swan, Hughes 1976) unless fresh water sources are available (Riggert 1977, Norman 1983). The situation in young waterbirds, as opposed to adults discussed above, is more complex. Riggert (1977) indicated that Australian Shelduck ducklings are 6 days old before they can eliminate salt through nasal glands and Halse (1987) also noted the need for potable water for ducklings using saline wetlands, with seepages being used in the period shortly after hatching. Swanson et al.(1984) and Stolley et al. (1999, and references cited) summarised previous studies, indicating that there were lethal or sublethal effects which occurred following the provision of saline water to ducklings or goslings. Typically, the sublethal consequences were decreased growth rates, which were depressed with increasing salinities. These authors also noted that ducklings were closely associated with seepages of fresh water and considered that a knowledge of the feeding ecology of flightless ducks was required to understand salt tolerances. Nevertheless, there were additional problems with other ions (such as Mg++, or SO4--), even with functioning salt glands.

4.1.5 Shorebirds Muddy shores constitute the main habitat used by most shorebird species, including the transequatorial migrants that visit the WTP in internationally significant numbers. Sewage treatment lagoons are normally kept too full to offer significant habitat for more than a few shorebirds. However, one of the ponds in the 85W Lagoon (85WC pond 9) has become surplus to treatment requirements, and is being managed as a conservation pond with varying water levels for the express purpose of providing shorebird habitat. Hence shorebirds need to be considered to some extent in the context of the current proposal. Use of this pond for this purpose is relatively recent, so knowledge of species that used it in recent years may not give a full picture of its potential to support shorebird species over time. Some shorebird species favour tidal mudflats and others favour non-tidal wetlands, and many species make use of both tidal and non-tidal mudflats (Lane 1987; Marchant and Higgins 1993). Red-necked Stints, Curlew Sandpipers and Sharp-tailed Sandpipers are the three most numerous transequatorial migrant species at the WTP, and all feed extensively from tidal and non-tidal habitats (Loyn et al. 2002b; Beazley 2004). Sharp-tailed Sandpipers often select vegetated shores, and may spend much of their time on non-tidal wetlands, though large flocks also feed from tidal mudflats at the WTP, especially where there are accumulations of beach-washed algae or sea-grass. Red-necked Stints and Curlew Sandpipers seem to prefer feeding from tidal mudflats, moving there as the tide drops and using non-tidal wetlands at the WTP partly to extend their feeding period over the high tide. However, this simple picture does not explain all the intricacies of movement between tidal and non-tidal wetlands, especially for Curlew Sandpipers. Current research at the WTP is endeavouring to elucidate some of these complexities. Habitats used by other shorebird species at the WTP are summarised in Table 5. In the context of the current study, the important point is that the most numerous shorebird species make extensive use of marine tidal mudflats, and hence are unlikely to be disadvantaged by the small increases in salinity expected in the old lagoons. Of the species that make little use of tidal habitats (Table 5), some are widely distributed in Australia, and

Arthur Rylah Institute for Environmental Research, DSE 15 Possible effects of increased salinity on waterbirds, invertebrates and phytoplankton on old lagoons, Western Treatment Plant relatively common in suitable freshwater wetlands (e.g. Black-fronted Dotterel, Red-kneed Dotterel and the migratory Latham’s Snipe). The WTP cannot be considered a major habitat for these species, except possibly for Red-kneed Dotterels during droughts. Four non-tidal species are associated mainly with vegetated freshwater wetlands, and are uncommon or rare in south-eastern Australia (Wood Sandpiper, Ruff, Pectoral Sandpiper and Long-toed Stint). More than half of Victoria’s records of these species come from the WTP or nearby wetlands (Emison et al. 1987). These four species have occurred quite often at conservation ponds at 35E, Paradise Road and the T-section Lagoon, but rarely at the old lagoons, which may already be too saline for these species. Five other species favour non-tidal habitats partly because they feed by wading in shallow water, and need to avoid habitats with substantial wave action (Black-tailed Godwit, Marsh Sandpiper, Black-winged Stilt, Banded Stilt and Red-necked Avocet): the latter two species often feed while swimming in calm water. One of these species, the Banded Stilt, is renowned for its regular occurrence on hypersaline wetlands, up to 145,000 mg/L, where dense flocks of many thousands gather to feed on brine shrimps (Marchant and Higgins 1993). They are known to breed erratically and mysteriously on ephemeral lakes in inland Australia soon after they fill with flushes of fresh water. A breeding event recently occurred on a highly saline part of the Coorong in South Australia, but the species does not usually breed in coastal habitats and has not been recorded in such areas in Victoria. Red-necked Avocets can clearly tolerate salinities up to 35,000 mg/L, as they often feed from calm shallow seas at the WTP (Loyn et al. 2002b) and elsewhere (e.g. Western Port, Loyn et al. 2002c). Black-winged Stilts rarely use tidal waters except where there are soaks of fresh water, and they breed mainly in vegetated freshwater wetlands. These three species can all be found feeding in wetlands with salinities substantially greater than expected to occur at the old lagoons. Hence they are not likely to suffer greatly from expected increases in salinity, in terms of non-breeding populations. Marsh Sandpipers and Black-tailed Godwits rarely use tidal waters in southern Australia, but they do so quite often in northern Australia (Marchant and Higgins 1993). In northern Australia, Black-tailed Godwits favour mudflats with very soft sediments (e.g. at creek outlets) and in southern Australia they occur much more often in freshwater wetlands than saline wetlands (D. Rogers, pers. comm.). Five shorebird species breed regularly at the WTP (Pied Oystercatcher, Masked Lapwing, Black-fronted Dotterel, Red-capped Plover and Black-winged Stilt). All may breed from time to time at or near the old lagoons, generally as simple pairs, but the old lagoons are not known to be an important breeding habitat for any of these or other shorebird species. Two of these species (Pied Oystercatcher and Red-capped Plover) breed commonly in marine coastal or hypersaline environments, with little or no access to fresh water. Masked Lapwings breed in an extremely wide range of habitats, usually with access to fresh water. Black-fronted Dotterels always breed close to fresh water, but the needs of the young birds are not known to be more demanding than those of the adults. Black-winged Stilts specialise at breeding in vegetated freshwater wetlands, and this may indicate that they have more need for fresh water when breeding than at other times. Freshwater wetlands generally remain close to full capacity, and macrophytic terrestrial or aquatic vegetation grows on any shore that remains exposed. Hence little open habitat is left for use by shorebirds. Wetlands with intermediate salinity levels tend to provide more habitat for shorebirds, partly because they tend to dry out more frequently (becoming more saline in the process) and offer greater expanses of mudflat as habitat. This is clearly demonstrated at the WTP, where one of the main difficulties in maintaining shorebird

Arthur Rylah Institute for Environmental Research, DSE 16 Possible effects of increased salinity on waterbirds, invertebrates and phytoplankton on old lagoons, Western Treatment Plant habitat in conservation ponds is to prevent undue growth of vegetation as they dry out (Loyn et al. 2002b). If salinity increases at the 85WC pond 9, this may make it easier to control vegetation and maintain open mudflats for shorebirds. In conclusion, increases in salinity at 85WC pond 9 are likely to have little effect on the shorebirds that are most numerous there currently apart, perhaps, from the Black-tailed Godwit. They may reduce the potential of the conservation pond to support breeding populations of Black-winged Stilts and possibly other species, but it may become easier to control vegetation for the benefit of shorebirds generally.

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Table 5. Shorebird species recorded at the Western Treatment Plant (other than rare vagrants), with details of their breeding range, habitat use and frequency of occurrence at the WTP (revised from Loyn et al. 2002b). Species regularly observed on the old lagoons (in ponds with low water levels) are marked #. Species are listed in taxonomic order (Christidis and Boles 1994).

Common name Scientific name Main breeding Main Local Comments range1 habitats at status3 WTP2 Latham's Snipe Gallinago hardwickii NE Asia ntf U dense aquatic vegetation Black-tailed Godwit # Limosa limosa NE Asia b U mainly non-tidal; formerly rare, now regular Bar-tailed Godwit Limosa lapponica NE Asia t U formerly regular, now rare Eastern Curlew Numenius madagascariensis NE Asia t U formerly regular, now few Marsh Sandpiper # Tringa stagnatilis NE Asia nt C mainly wades in shallows Common Greenshank # Tringa nebularia NE Asia b C mainly wades in shallows Wood Sandpiper Tringa glareola NE Asia ntf U few individuals, vegetated wetlands Terek Sandpiper Xenus cinereus NE Asia b R mainly wet mud, rocks Common Sandpiper Actitis hypoleucos NE Asia b U drains; rocks; narrow shores Grey-tailed Tattler Heteroscelus brevipes NE Asia t R rocky shores Ruddy Turnstone Arenaria interpres NE Asia t U often among rocks Great Knot Calidris tenuirostris NE Asia t R often wades in shallows Red Knot Calidris canutus NE Asia t U often wades in shallows Sanderling Calidris alba NE Asia t R mainly on ocean beaches Red-necked Stint # Calidris ruficollis NE Asia b A mainly wet mud Long-toed Stint Calidris subminuta NE Asia ntf R prefers vegetated wetlands Pectoral Sandpiper Calidris melanotus NE Asia ntf U few individuals, vegetated wetlands Sharp-tailed Sandpiper # Calidris acuminata NE Asia b A prefers vegetated wetlands Curlew Sandpiper # Calidris ferruginea NE Asia b A often wades in shallows Broad-billed Sandpiper Limicola falcinellus NE Asia b R mainly wet mud Ruff Philomachus pugnax NE Asia nt R prefers vegetated wetlands Red-necked Phalarope # Phalaropus lobatus NE Asia nt R swims on water (on sea elsewhere) Pied Oystercatcher Haematopus longirostris Australia t C,b coastal mudflats Sooty Oystercatcher Haematopus fuliginosus Australia t R rocky or sandy shores Black-winged Stilt # Himantopus himantopus Australia nt C,b breeds in vegetated fresh water Banded Stilt # Cladorhynchus leucocephalus Australia nts U large flocks in some years; swims or wades in saline wetlands

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Table 5. Continued.

Common name Scientific name Main breeding Main Local Comments range1 habitats at status3 WTP2 Red-necked Avocet # Recurvirostra Australia nt C,b wades or swims; few breeding records at WTP novaehollandiae Pacific Golden Plover Pluvialis fulva NE Asia t C often among rocks, or roosting in saltmarsh Grey Plover Pluvialis squatarola NE Asia t U few, some years, now rare Red-capped Plover # Charadrius ruficapillus Australia b C,b broad dry flats Double-banded Plover # Charadrius bicinctus New Zealand b C often in pasture or saltmarsh Lesser Sand Plover Charadrius mongolus NE Asia t R formerly regular at Spits Black-fronted Dotterel # Elseyornis melanops Australia ntf U,b fresh water margins Red-kneed Dotterel # Erythrogonys cinctus Australia ntf U,b vegetated marshes Banded Lapwing Vanellus tricolor Australia o U,b mainly pasture Masked Lapwing # Vanellus miles Australia b A,b mainly pasture & banks

Notes: 1. Most species breeding in NE Asia also breed in western Alaska, and some have broad ranges in northern Eurasia and North America. Many species not shown here have been recorded as vagrants. 2. t=tidal mudflats; b=both tidal and non-tidal mudflats; ntf=non-tidal freshwater wetlands; nts=non-tidal saline wetlands; nt=non-tidal wetlands generally; o=open country such as pasture. Species marked nt or nts feed occasionally on sheltered tidal areas at the WTP 3. A=abundant, C=common, U=uncommon (<30, or larger flocks occasionally), R=rare, b=breeding (usually just a few pairs at the WTP). Codes taken from Melbourne Water Bird Checklist for WTP.

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4.1.6 Comments on salinity in Victoria Dryland salinity is an expression of major water imbalances within a catchment (Anon. 1998b) but, since there may be a long lead time (some 20 – 50 years; SCC 2001) between clearing, one of the causative factors, and the eventual appearance of salinity, its effects may be manifest well before remedial action is considered, let alone implemented. In Australia there has been extensive land clearing, replacement of deep-rooted native vegetation with alien, short-rooted plants (usually crops or pasture). These widespread land use changes, involving the clearing of deep-rooted native species, has resulted in rising water tables which are now within 1 – 2 m of the surface in many areas. The effects are magnified when the predominantly alien (often fertilised) pasture dies; the water table rises further and creates more damage or the potential for such damage (SCC 2001). This modification has, locally, been exacerbated by the accompanying, and increasing, use of (often) impounded water for irrigation, effects further magnified by those of water diversions. One consequence has been an increase in salinity levels in rivers, including the Murray River (MDBMC 1999). Changes to vegetation, alteration of water movement and development of irrigation in Victoria has resulted in a rising water table over much of the state. Indeed, currently there are already five catchments identified as being at risk of increased salinity current estimates for areas with a high water table exceed 400 000 ha, and it is thought that this will increase to over 840 000 ha (e.g. MDBMC 1999). While wetlands in lower lying portion of the landscape are subject to the direct effects of increased salinisation, since drainage into them is direct, other wetlands will be affected by run-off from salinisation in higher areas. Such a process will inevitably have effects on dependent biota, such as waterbirds.

4.1.7 Overview of likely effects on waterbirds in Victoria Each waterbird species occurring in Victoria has its own habitat requirements, and each is likely to respond to salinity in a different way (e.g. Kingsford and Norman 2002 and references cited). Nevertheless, relatively large numbers of some species are known to occur in saline areas (e.g. marine embayments) or on wetlands with increased salinities (Lavery 1972, Norman 1983, Emison et al. 1987, Halse et al. 1991; Loyn et al. 1994). What is usually not clearly reported, and certainly not yet quantified in any Victorian wetlands, is the actual use that particular species make of the wetlands on which they are reported. This is similarly the case for a range of other waterbirds. Most species are highly mobile and may be able to access fresh water at some distance from where they may be recorded feeding or resting. Some species may require access to such sources of fresh water, as discussed above. In this regard, it is of note that the influence of increased salt concentrations on waterbirds differs within a species depending on the age of individuals concerned (and or previous exposure to higher salinities). While some waterbird species, such as the Grey Teal, are reported from saline or even hypersaline areas, they may use such areas for foraging only if the salt glands are sufficiently developed or acclimated and there is access to fresh water (Lavery 1972, Norman 1983). Salt glands, at least in a range of species, show a considerable increase in size and, presumably, capability when the bird uses saline areas (e.g. California Gull Larus californicus, Mahoney and Jehl 1985a). Further, ducklings of probably all waterbird species require access to fresh water for a period after hatching hence precluding use of hypersaline wetlands for feeding in the absence of freshwater. Indeed decreased growth, if not death, has been reported when young waterbirds have been reared on hypersaline water (Riggert 1977, Swanson et al. 1984). In young waterbirds there is not the prospect of avoiding intake of salt water by using ingested foods as a source of fresh

Arthur Rylah Institute for Environmental Research, DSE 20 Possible effects of increased salinity on waterbirds, invertebrates and phytoplankton on old lagoons, Western Treatment Plant water, by manipulation of foods to prevent inflows as in eared grebe Podiceps nigricolis (Mahoney and Jehl 1985b) or by flying to sources of drinking water. Details summarised in this review indicate that salinity increases (and indeed decreases) can affect waterbirds directly, and indirectly, through their effects on dependent flora and fauna which may form all or part of the birds' diet. Generally there is a poor understanding of the effects of salination on wetlands (and the dependent flora and fauna). There have been few long-term studies of physico-chemical changes in wetlands locally in relation to inflora and infauna. Plant communities (and dependent fauna) might reflect changing salinities but this can be confounded by seasonal successions. Certainly changes to composition of plant succession occur when salinities reach or exceed about 1000 mg/L (Hart et al. 1990, 1991); the majority of macrophytes are not salt tolerant and often have limits around 4000 mg/L (Brock 1981). A reduction of vascular plants may also remove substrates and changes to macrophyte representation may affect waterbirds nesting/feeding in them. Further, in affecting suites of taxa there may be effects on ecological processes. However, although it appears that diversity of aquatic and littoral vegetation declines with increased salt loading, sensitivity data are restricted and generalisations are not necessarily possible even within the same taxonomic grouping. Further, timing and frequency of salt inputs will have variable effects, with dilution occurring during flood events and concentration increasing as the wetland dries out. Both have influence on ensuing productivity, which is also affected by ambient temperature, daylength and chemical (including nutrient) concentrations. Other factors also complicate estimation of the potential effects of increasing salinities. Thus some insect and mollusc groups may include some of the most salt-sensitive invertebrates: in contrast, some crustaceans are the most salt-tolerant. Nevertheless adverse effects may occur with low increases in salinity (c. 800 mg/L Bailey and James 2000). In Victorian wetlands those authors found that invertebrate richness and abundance declined with increased salinities. Waterbird representation generally follows a similar pattern (although the relationship is not necessarily linear and some saline wetlands can have more species, and greater numbers, than fresher areas as a consequence of available foods and access to fresh water). While waterbirds may forage on brackish or hypersaline wetlands, some species may do so only if fresh water is accessible (e.g. Hughes 1976). In saline waters, the range of potential food taxa may be restricted since it is well understood that changes in wetland salt regimes have an array of effects on taxa, whether flora or fauna, and that an increased salt load within a wetland leads to a decreasing number of taxa (Hart 1990, 1991, Bailey and James 2000, Clunie et al. 2002). Since some waterbird species (e.g. Pink-eared Duck, Australasian Shoveler) are more specialised foragers than others (Pacific Black Duck, Chestnut or Grey Teal), a decreasing availability of some prey species will in turn ultimately affect the suite of waterbirds present at a wetland, although numbers of some may increase. Such changes reflect, then, both the response of food species and the consumer. Other changes may also influence species present at wetlands, but at a different temporal and spacial scales. Increased salinities lead to a changed macrophytic vegetation and certainly, if prolonged, and associated with extensive waterlogging of substrate, influences specific representation of emergent and littoral species: indeed entire communities can be replaced. All such changes will affect utilisation by waterbirds, whether the wetland is used as a foraging area or for other behavioural processes (such as breeding, moulting or brood care). These processes are dynamic, in terms of the varying periodicity of breeding events (which may vary considerably from species to species) but also in terms of the changing salinities determined by varying stages in the wetting and drying cycle of the wetland itself: there are too local and concurrent physico-chemical changes associated with waterlogging, and

Arthur Rylah Institute for Environmental Research, DSE 21 Possible effects of increased salinity on waterbirds, invertebrates and phytoplankton on old lagoons, Western Treatment Plant changing ionic representations. In addition, such variations are also overlain by changing wetland distributions elsewhere, which, for some species, may include the continental landscape. Shorebirds raise some different issues because most species need open wet mudflats, and this feature tends to occur most extensively in wetlands of intermediate salinity. Increases in salinity at 85WC pond 9 are likely to have little effect on the shorebirds that are most numerous there currently. They may reduce the potential of the conservation pond to support breeding populations of Black-winged Stilts and possibly other species, but it may become easier to control vegetation for the benefit of shorebirds generally.

Arthur Rylah Institute for Environmental Research, DSE 22 Possible effects of increased salinity on waterbirds, invertebrates and phytoplankton on old lagoons, Western Treatment Plant

4.2 Multivariate analysis using recent data from the WTP 4.2.1 Methods Data on waterbird densities and various physico-chemical variables were available for 23 ponds at the WTP, for eight occasions between November 2001 and July 2004, from current projects by ARI and Water EcoScience for Melbourne Water Corporation. These are being analysed as part of that monitoring program. The ponds were from six treatment lagoons (115E, 55E, 25W, Lake Borrie North, Lake Borrie South and Walsh’s Lagoon). The old lagoons lie between 25W and Little River, and include Walsh’s Lagoon, along with 85W and the adjacent 145W Lagoon. One of the physico-chemical variables was conductivity, which has a roughly linear relationship with salinity (with a conversion factor of 0.68, Hart et al. 1991). Salinity levels ranged from 884 to 2584 mg/L on individual pond-date combinations during this period, with a mean value of 1403.3 mg/L (1300-3800 EC units, with a mean of 2064 EC units). Hence the dataset provides an opportunity to assess the relative influence of salinity on variations in waterbird numbers at the WTP, in combination with other variables. However, it should be noted that the range of salinity levels is quite narrow, and does not go as high as expected when the old lagoons are used for brine disposal. Multivariate regression models were developed for densities of the main waterbird species and some groups of species (e.g. dabbling ducks; filter-feeding ducks; diving ducks), in terms of physico-chemical variables and estimates of phytoplankton and zooplankton abundance. A Bayesian model-averaging approach was used, recognising that multiple alternative models could each contain important elements of “truth”, which could get lost in the traditional approach of selecting “best” models (Raftery 1997; Wintle et al. 2003). The models were based on 184 observations (23 x 8) as indicated above. A feature of Bayesian analysis is that prior understanding can be used as an input to the modelling process. In this case, we developed models with or without prior information, and elected to present coefficients for the models that did not take prior information into account. The modelling exercise will be reported more fully elsewhere.

4.2.2 Results and discussion The model-averaging approach gave strong indications that Black Swans and Hoary-headed Grebes would respond positively to changes in salinity over the fairly narrow ranges observed during the study (884-2584 mg/L), and that diving ducks as a group would respond negatively (Table 6). Models for two of the diving ducks (Blue-billed Duck and Musk Duck) suggested that they would not respond to salinity over this range (probability >90%) while models for the third species (Hardhead) gave ambivalent evidence of a negative response (Table 6). Models for Pacific Black Duck gave ambivalent evidence of a negative response and those for Chestnut Teal gave ambivalent evidence of a positive response (Table 6). As Chestnut Teal was the most numerous species of dabbling duck, this was also reflected in ambivalent evidence for positive responses by dabbling ducks and waterfowl in general. Other species showed no evidence of effects of salinity over this narrow range (probability <10%).

Arthur Rylah Institute for Environmental Research, DSE 23 Possible effects of increased salinity on waterbirds, invertebrates and phytoplankton on old lagoons, Western Treatment Plant

Table 6. Probability values refer to the probability that salinity contributed to explanatory models, and are not equivalent to P values in frequentist statistics. High probability values (>80%) give strong evidence that salinity and bird numbers were related over this salinity range (884-2584 mg/L). Low values (<20%) give strong evidence that they were not related. Intermediate values (20-80%) give ambivalent evidence.

Coefficient (x 1000) Probability (%) that variable contributes Bird species Uninformed Informed Uninformed Informed Eurasian Coot 0 0 0 0 Hoary-headed Grebe 5.188 5.072 100 100 Australian Wood Duck too few data too few data too few data too few data Black Swan 2.102 2.066 100 100 Australian Shelduck 0.0045 0.0067 2.8 2.5 Pacific Black Duck -0.317 -0.426 35.8 41.8 Chestnut Teal 2.837 2.725 57.2 55.0 Grey Teal 0.062 0.045 3.9 2.9 Australasian Shoveler 0.039 0.030 6.0 4.6 Pink-eared Duck 0.129 0.092 3.9 2.7 Freckled Duck # -0.008 -0.007 5.1 4.5 Hardhead -1.210 -1.451 37.7 44.7 Blue-billed Duck -0.045 -0.136 4.1 13.0 Musk Duck -0.010 -0.011 3.0 3.5

Bird group Grebes 5.2 5.1 100 100 Dabbling ducks 2.0 3.8 35.5 73.7 Diving ducks -2.9 -2.7 51.6 100 Filter-feeding ducks 0.21 0.15 5.3 3.8 Grazing ducks 0.005 0.007 2.8 2.5 Stiff-tail ducks -0.15 -0.32 7.5 19.2 Ducks, geese and swans 19.2 19.5 79.6 86.2 # Data on Freckled Duck were analysed for just three of the six treatment lagoons (25W, Lake Borrie North and Lake Borrie South, four ponds on each = 12 ponds and 96 records) as there were few records from elsewhere (total positive records = 27).

4.2.3 Responses of waterbirds to other aspects of water chemistry The same Bayesian modelling averaging process also considered the impact of other aspects of water chemistry, including ammonia, nitrate and phosphorus, in combination with other variables. Full results will be reported elsewhere, but the following summary may help to predict effects of any changes in nutrients in the old lagoons when the desalinisation plant is active. It is expected that this will result in small increases in levels of ammonia, nitrate and phosphorus. Three species (Black Swan, Pink-eared Duck and Musk Duck) showed strong evidence of negative relationships with ammonia (probabilities >80%), and one species (Eurasian Coot) showed ambivalent evidence of such a relationship (probability 41.7%). Two guilds (filter- feeders and diving ducks) also showed evidence of negative relationships with ammonia (probabilities of 88% and 67% respectively). No species showed evidence of a positive relationship with ammonia, and any increase in ammonia is likely to result in reduced numbers of waterfowl. Two species (Black Swan and Hardhead) showed strong evidence of negative relationships with nitrate (probabilities of 100% and 77.8% respectively). These species would probably decline if nitrate levels increased. One species (Blue-billed Duck) showed strong evidence of

Arthur Rylah Institute for Environmental Research, DSE 24 Possible effects of increased salinity on waterbirds, invertebrates and phytoplankton on old lagoons, Western Treatment Plant a positive relationship with nitrate (probability of 100%). It would probably increase if nitrate levels increased, and other variables remained constant. No species showed clear evidence of a relationship with phosphorus, probably because phosphorus did not vary greatly between ponds or time periods during the study. Just one species (Pacific Black Duck) showed weak evidence of a negative relationship with phosphorus (probability 55.3%). Other variables that influenced numbers of particular species included:

• pond area (positively for Pink-eared Duck, Australasian Shoveler and Australian Shelduck; negatively for Musk Duck); • cumulative retention time (positively for Australian Shelduck, Pacific Black Duck and Chestnut Teal); • water temperature (positively for Australian Shelduck and negatively for Musk Duck); • CBDO5, a measure of bacterial activity (positively for Australian Shelduck); • Chlorophyll a, a measure of algal activity (positively for Grey Teal and negatively for Australian Shelduck); • dissolved oxygen (negatively for Black Swan), and • salinity as discussed above.

Previous modelling (Loyn et al. 2002a) showed a significant positive relationship with nitrate for Blue-billed Duck (as in this study), and also for most other duck species (in contrast to this study). This discrepancy emphasises the uncertainty involved in making predictions about effects of changes in complex systems. The previous work indicated a general tendency towards negative relationships with ammonia, as in this study.

Other literature gives little further guidance on likely effects of small changes in ammonia, nitrate, or phosphorus levels on waterbirds at the WTP. No relevant empirical information was found on interactions between salinity and nutrient levels, though it is well known that such interactions are possible because any nutrient can influence the uptake of other nutrients by plant or animal species.

Arthur Rylah Institute for Environmental Research, DSE 25 Possible effects of increased salinity on waterbirds, invertebrates and phytoplankton on old lagoons, Western Treatment Plant

4.3 Data on waterbirds and salinity from 465 Victorian wetlands 4.3.1 Methods Data on waterbird numbers and salinity levels were extracted from the Victorian Wetland Database. Most of the field data had been collected by Andrew Corrick and his colleagues in the 1980s. The database also included information on wetland area (when full) and the extent of various wetland habitat categories. Some of the waterbird counts considered only a subset of species, and this was indicated. In those cases, we regarded data on other species at those wetlands as missing. Many records included data on the percentage of wetland covered in water, and the percentage counted during partial counts. However, this information was missing from many records, and we elected to calculate waterbird densities in relation to the full area of each wetland (number of waterbirds divided by full area in hectares, then multiplied by 100 to give numbers per square kilometre). Salinity was recorded sometimes in terms of conductivity and sometimes as mg salt per litre. Conductivity values were converted to salinity by multiplying by 0.68, after Hart et al. (1991). If no valid salinity measures were taken, or other data were highly incomplete, records were excluded from further consideration. Our final dataset included 517 counts of waterbirds from 465 Victorian wetlands. Data were examined mainly by species. Two broad groups of birds were also considered, by summing densities for individual species in each group. One group contained the true waterbirds (Anatidae: ducks, geese and swans) and the other group contained shorebirds (Charadriidae: plovers, sandpipers and allies). Other groups have been used elsewhere (e.g. Loyn et al. 2002a) but were not considered appropriate for the current purpose, because responses to salinity can vary greatly at the species level. The data on densities of waterbird species and groups were examined in relation to salinity in three ways (summary graphs and table, correlation and regression). Firstly, waterbird densities were plotted against salinity values for the 455 wetlands where salinity was less than 11,000 mg/L, since few waterbirds were common at higher salinity levels. This was done for species that were common at the old lagoons (Table 1) and also for a few species that are common on freshwater habitats and currently rare at the old lagoons, presumably because they are currently too saline. Secondly, a correlation matrix was generated between waterbird densities and salinity values, for 234 records with salinity values between 800 and 6500 mg/L (Table 7). This range was chosen to embrace all likely scenarios for the old lagoons, from below current levels to values slightly higher than expected if the lagoons are used for brine disposal. This showed which species showed positive or negative trends with salinity over this range, and the strength of those relationships in terms of correlation coefficients. Thirdly, a more formal analysis was undertaken to investigate relationships between waterbird occurrence or density and salinity. A two-stage approach was needed (Barry and Welsh 2002; Potts and Elith in press) because the data were zero-inflated: many species were absent from high proportions of the wetlands. The first stage was to analyse presence or absence as a function of salinity using logistic regression. The second stage was to analyse density in relation to salinity, for those wetlands where the species was recorded. This involved regressing waterbird densities against salinity values (generating simple linear models) and against linear combinations of salinity and salinity squared (generating quadratic models). This was done for 230 records with salinity values between 800 and 7500 mg/L. The slightly broader range was considered appropriate because the quadratic term could account for expected negative responses to salinity at higher levels, even if

Arthur Rylah Institute for Environmental Research, DSE 26 Possible effects of increased salinity on waterbirds, invertebrates and phytoplankton on old lagoons, Western Treatment Plant responses were positive at lower levels. This approach identified which species showed significant linear or curvilinear responses to salinity within this range.

4.3.2 Results and discussion Summary graphs and table The graphs show that many species were common on at least some wetlands with a broad range of salinities up to ~7000 mg/L, and generally scarce when salinities exceeded that level (Figures 1-9). However, the pattern varied greatly between species. Several species were strongly associated with freshwater wetlands, becoming rare in wetlands with salinities > 1000 mg/L. This applied in particular to Australian Wood Duck and Dusky Moorhen (Table 7 and Figure 9), in accord with our prior expectations (Table 2). These species are respectively rare or absent from sewage treatment lagoons throughout the WTP (Loyn et al. 2002a). Similar patterns were observed for Plumed Whistling-Duck and White-necked Heron (Table 7). Two other species believed to be freshwater specialists (Australasian Grebe and Black-fronted Dotterel, Table 2) showed higher than expected levels of tolerance, occurring on some wetlands with salinities of 1-5000 mg/L. Many records of Black-fronted Dotterels in saline environments refer to birds feeding in local sources of fresh water, such as channels or freshwater outlets (Emison et al. 1987; Dann et al. 1994). One species of diving duck (Hardhead) was common on many freshwater wetlands, and rarely recorded on wetlands with salinities >4000 mg/L (Figure 1). The two other diving ducks (Blue-billed Duck and Musk Duck, collectively known as “stiff-tails”) also showed declining trends with increasing salinity, but appeared much less sensitive than Hardhead. Freckled Duck were reported rarely, and were only numerous on two wetlands, with salinities between 1000 and 2000 mg/L (Figure 4). The species often occurs in company with Hardhead (pers. obs.) and both species may share a general intolerance to high levels of salinity. Several species showed an apparent aversion for freshwater wetlands. These included most of the shorebird species and shorebirds as a collective group (Figure 2). This may be due to their need for extensive open mudflats, a habitat unlikely to develop in freshwater swamps where water levels are stable and muddy margins are quickly colonised by aquatic vegetation. More surprisingly, the pattern was also shown by Purple Swamphen, a bird that needs mosaics of open mud and dense aquatic vegetation. Purple Swamphens and Dusky Moorhens co-exist in many wetlands (Marchant and Higgins 1990, 1993, pers. obs.), but the present evidence raises the possibility that salinity levels may be an important partial segregating factor determining whether one or the other species will occupy a particular wetland. Overall, several species showed evidence that densities would peak at salinity levels between 1000 and 5000 mg/L (e.g. Australasian Shoveler and Blue-billed Duck). Some others tended to be more numerous in wetlands with salinity levels of 5000 mg/L than 1000 mg/L, including Hoary-headed Grebe, Silver Gull, most shorebirds, Cape Barren Goose, Magpie Goose, Pink-eared Duck and Musk Duck (Table 7). Another group tended to be more numerous in wetlands with salinity levels of 1000 than 5000 mg/L, including Black Swan, Grey Teal, Hardhead and Freckled Duck (Table 7).

Arthur Rylah Institute for Environmental Research, DSE 27 Possible effects of increased salinity on waterbirds, invertebrates and phytoplankton on old lagoons, Western Treatment Plant

Ducks, geese & swans

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Figure 1. Mean densities (birds per square kilometre) of ducks, geese and swans from 517 counts in 465 Victorian wetlands in relation to salinities of those wetlands (mg/L) (data from Victorian Wetland database, A.H. Corrick, pers. comm.). This group of birds can be numerous on wetlands with a wide range of salinities, but are generally scarce on wetlands more saline than ~10,000 mg/L. Individual species vary greatly in their tolerance levels (see subsequent figures).

Shorebirds

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Figure 2. Mean densities (birds per square kilometre) of shorebirds from 517 counts in 465 Victorian wetlands in relation to salinities of those wetlands (mg/L) (data from Victorian Wetland database, A.H. Corrick, pers. comm.). Freshwater wetlands tend to be colonised by dense growth of vegetation along the shore, and hence provide little open muddy habitat for shorebirds. Furthermore, wetlands that recede periodically (providing open muddy habitat for shorebirds) tend to become more saline as they dry. Shorebirds clearly can tolerate a range of salinities, but tend to be most numerous on wetlands with intermediate levels of salinity.

Arthur Rylah Institute for Environmental Research, DSE 28 Possible effects of increased salinity on waterbirds, invertebrates and phytoplankton on old lagoons, Western Treatment Plant

Hoary-headed Grebe

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Figure 3. Mean densities (birds per square kilometre) of two waterbird species that dive for food (Hoary-headed Grebe and Hardhead), from 517 counts in 465 Victorian wetlands in relation to salinities of those wetlands (mg/L) (data from Victorian Wetland database, A.H. Corrick, pers. comm.). These were among the four most numerous species at the old lagoons. Note that Hoary-headed Grebes tolerate a wide range of salinities, whereas Hardhead rarely inhabit waters where salinity exceeds 4000 mg/L.

Arthur Rylah Institute for Environmental Research, DSE 29 Possible effects of increased salinity on waterbirds, invertebrates and phytoplankton on old lagoons, Western Treatment Plant

Pink-eared Duck

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Freckled Duck

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Figure 4. Mean densities (birds per square kilometre) of three filter-feeding ducks, from 517 counts in 465 Victorian wetlands in relation to salinities of those wetlands (mg/L) (data from Victorian Wetland database, A.H. Corrick, pers. comm.). Some outlying high values may be erroneous. Note that Australasian Shoveler tolerate a wide range of salinities; Pink-eared Duck appear to avoid waters more saline than ~5000 mg/L; and the limited data on Freckled Duck suggest they may need fresh water (cf Hardhead, Figure 2).

Arthur Rylah Institute for Environmental Research, DSE 30 Possible effects of increased salinity on waterbirds, invertebrates and phytoplankton on old lagoons, Western Treatment Plant

Blue-billed Duck

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Figure 5. Mean densities (birds per square kilometre) of two “stifftails” (diving ducks) from 517 counts in 465 Victorian wetlands in relation to salinities of those wetlands (mg/L) (data from Victorian Wetland database, A.H. Corrick, pers. comm.). One outlying high value was considered erroneous and removed from the graph for Musk Duck. Note that Musk Duck tolerate a wide range of salinities, whereas Blue-billed Duck tend to be most numerous in fresh or brackish water.

Arthur Rylah Institute for Environmental Research, DSE 31 Possible effects of increased salinity on waterbirds, invertebrates and phytoplankton on old lagoons, Western Treatment Plant

Chestnut Teal

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Figure 6. Mean densities (birds per square kilometre) of three dabbling ducks, from 517 counts in 465 Victorian wetlands in relation to salinities of those wetlands (mg/L) (data from Victorian Wetland database, A.H. Corrick, pers. comm.). Note that all appear to tolerate a wide range of salinities, although weak negative trends are evident for Grey Teal and Pacific Black Duck. Other evidence suggests that Pacific Black duck may be more sensitive than these data indicate (e.g. they are rare on nearby saltworks, where Chestnut Teal are abundant).

Arthur Rylah Institute for Environmental Research, DSE 32 Possible effects of increased salinity on waterbirds, invertebrates and phytoplankton on old lagoons, Western Treatment Plant

Australian Shelduck

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Figure 7. Mean densities (birds per square kilometre) of three waterbirds that feed extensively from vegetation,, from 517 counts in 465 Victorian wetlands in relation to salinities of those wetlands (mg/L) (data from Victorian Wetland database, A.H. Corrick, pers. comm.). Some of the outlying high counts may be erroneous. Note that all appear to tolerate a wide range of salinities, but the Eurasian Coot were substantially more common in fresh or brackish wetlands than elsewhere.

Arthur Rylah Institute for Environmental Research, DSE 33 Possible effects of increased salinity on waterbirds, invertebrates and phytoplankton on old lagoons, Western Treatment Plant

Australian Wood Duck

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Figure 8. Mean densities (birds per square kilometre) of three waterbird species that favour freshwater habitats, from 517 counts in 465 Victorian wetlands in relation to salinities of those wetlands (mg/L) (data from Victorian Wetland database, A.H. Corrick, pers. comm.). None of these species are common on the old lagoons at the WTP.

Arthur Rylah Institute for Environmental Research, DSE 34 Possible effects of increased salinity on waterbirds, invertebrates and phytoplankton on old lagoons, Western Treatment Plant

Dusky Moorhen

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Figure 9. Mean densities (birds per square kilometre) of Dusky Moorhens from 517 counts in 465 Victorian wetlands in relation to salinities of those wetlands (mg/L) (data from Victorian Wetland database, A.H. Corrick, pers. comm.). This species appears to be less tolerant of salinity than any other common waterbird species. At the WTP, it only occurs regularly on freshwater creeks and the ornamental pond at the main office. These are similar to the habitats it favours throughout the state (vegetated rivers, creeks, billabongs and freshwater lakes).

Correlations Correlations with salinity between 800 and 6500 mg/L were generally weak (Table 7), reflecting the wide range of random factors that can affect waterbird densities at a diverse suite of wetlands. Of the 20 species considered, trends appeared to be positive over this range for ten species (Hoary-headed Grebe, Whiskered Tern, Silver Gull, Banded Stilt, Red- necked Avocet, Red-necked Stint, Cape Barren Goose, Chestnut Teal, Blue-billed Duck and Musk Duck). Trends appeared to be negative for seven species (Eurasian Coot, Australian Wood Duck, Black Swan, Pacific Black Duck, Grey Teal, Freckled Duck and Hardhead). Three species showed extremely weak negative correlations with salinity over this range (<0.020, Table 7) (Australian Shelduck, Australasian Shoveler and Pink-eared Duck). Three species were omitted from this and subsequent analysis, because of possible errors in the data (Australasian Grebe, Black-fronted Dotterel and Black-winged Stilt): these species are not numerous on the old lagoons (Table 1). When groups were considered collectively, shorebirds correlated positively with salinity and waterbirds (ducks, geese and swans) showed weak negative correlations with salinity over this range (Table 7).

Arthur Rylah Institute for Environmental Research, DSE 35 Possible effects of increased salinity on waterbirds, invertebrates and phytoplankton on old lagoons, Western Treatment Plant

Table 7. Correlations for densities of waterbird species (birds per square kilometre) with salinity (mg/L) from Victorian wetlands with salinity levels between 800 and 6500 mg/L (n=234).

Bird species or group Correlation Comments coefficient r Eurasian Coot -0.129 Dives for aquatic vegetation Hoary-headed Grebe 0.079 Dives for aquatic fauna Whiskered Tern 0.048 Picks insects from surface Silver Gull 0.168 Uses muddy shores Banded Stilt 0.066 Also inhabits hypersaline waters, upending for brine shrimps Red-necked Avocet 0.073 Takes invertebrates while wading or swimming Red-necked Stint 0.051 Needs muddy shores Cape Barren Goose 0.083 Grazes on nearby grassland Australian Wood Duck -0.078 Grazes on nearby grassland; needs fresh water Black Swan -0.028 Reaches for aquatic vegetation below surface Australian Shelduck -0.006 Also occurs on hypersaline waters Pacific Black Duck -0.066 Avoids hypersaline waters Chestnut Teal 0.061 Favours tidal waters Grey Teal -0.086 Favours inland wetlands Australasian Shoveler -0.008 Filters food from water surface Pink-eared Duck -0.003 Filters food from water surface Freckled Duck -0.126 Filters food from water surface Hardhead -0.023 Dives for food in fresh water Blue-billed Duck 0.032 Dives for food Musk Duck 0.118 Dives for food Shorebirds 0.123 Need muddy shores Ducks, geese & swans -0.027 Varied needs as above Species 0.103 Numbers of shorebird species contribute to this relationship Total 0.038

Regression Logistic regression models identified significant relationships between presence or absence of species and salinity (over the range 800-6500 mg/L) for 12 species and one group of species (p<0.6, Table 8). These effects were positive for six species (Purple Swamphen, Eurasian Coot, White-faced Heron, Royal Spoonbill, Yellow-billed Spoonbill and Australian Shelduck) and for shorebirds considered collectively. The positive relationship for Yellow- billed Spoonbill was unexpected as the species generally favours freshwater wetlands and estuaries (Emison et al. 1987; Marchant and Higgins 1990, 1993; Loyn et al. 1994), and may relate to the availability of shallow water as ephemeral wetlands dry out and become more saline. The same process may also help drive the observed relationship for shorebirds. The positive relationship for Eurasian Coot was also unexpected, as the species is known to be less tolerant of high salinities than many duck species (Tables 2 and 3), but this did not manifest itself within the current dataset. Significant negative effects were observed for six species (Dusky Moorhen, Hoary-headed Grebe, White-necked Heron, Straw-necked Ibis, Pink-eared Duck and Hardhead) (p<0.6, Table 8). The negative relationship for Hoary-headed Grebes was unexpected as flocks commonly gather on saline waters or the sea (Tables 2 and 3). However, the species may need fresh water for breeding, and flocks tend to disperse to access suitable breeding habitat. The data

Arthur Rylah Institute for Environmental Research, DSE 36 Possible effects of increased salinity on waterbirds, invertebrates and phytoplankton on old lagoons, Western Treatment Plant suggest that Hoary-headed Grebes are more likely to be present on freshwater wetlands (albeit in low numbers) than on saline waters, but models of abundance tell a different story (see below). Linear models of abundance (for sites where each species was present) showed that densities of Chestnut Teal increased with salinity over the range 800-6500 mg/L, but no significant linear relationships were found for other species (p<0.6, Table 9). This reflects the great variability of the dataset, with many unmeasured variables potentially contributing to observed densities. It also reflects the non-linear nature of the relationships, with many species appearing to increase and then decrease with salinity over this range (Figures 1-9). However, quadratic models explained little extra variance for any species except Hoary- headed Grebe, and even for that species, the quadratic model explained only 9.6% of variance (Table 10). The model for Hoary-headed Grebes implied that on waters where they were present, densities would tend to increase with salinity to a maximum at ~4300 mg/L, and then decline as salinity increased further. Quadratic models for other species were too weak to deserve further comment.

Table 8. Logistic regression models for probability that a species is present on a wetland in relation to salinity (logit Probability = Constant + (Estimate x Salinity in mg/L)). Note that estimates have been multiplied by 1000 for display, and the values shown need to be divided by 1000 for use in this equation. Relationships where P<0.06 are shown in bold.

Bird species or group Constant Estimate (x 1000) P (re salinity) Dusky Moorhen 0.117 -1.694 0.008 Purple Swamphen -1.242 0.323 <0.001 Eurasian Coot -0.059 0.152 0.055 Hoary-headed Grebe 0.283 -0.202 0.010 Whiskered Tern -2.027 0.056 0.590 Silver Gull -0.712 0.060 0.426 Banded Stilt -6.860 0.342 0.523 Red-necked Avocet -3.215 0.034 0.846 Red-necked Stint -5.02 0.340 0.125 Great Egret -1.924 -0.079 0.529 White-faced Heron -1.670 0.205 0.012 White-necked Heron -1.637 -0.352 0.056 Royal Spoonbill -4.422 0.500 <0.001 Yellow-billed Spoonbill -3.092 0.338 0.001 Australian White Ibis -2.407 -0.073 0.629 Straw-necked Ibis -1.501 -0.375 0.039 Australian Wood Duck -2.540 -0.242 0.280 Black Swan 1.007 0.023 0.790 Australian Shelduck -0.080 0.181 0.023 Pacific Black Duck -0.623 0.030 0.691 Chestnut Teal -1.011 0.041 0.633 Grey Teal -0.328 -0.085 0.274 Australasian Shoveler -1.149 -0.110 0.268 Pink-eared Duck -0.806 -0.457 0.003 Freckled Duck -1.360 -1.314 0.096 Hardhead -0.811 -0.277 0.016 Blue-billed Duck -1.356 -0.160 0.167 Musk Duck -0.766 0.105 0.160 Shorebirds -0.608 0.201 0.008 Waterbirds (ducks, geese & swans) 3.830 -0.134 0.487

Arthur Rylah Institute for Environmental Research, DSE 37 Possible effects of increased salinity on waterbirds, invertebrates and phytoplankton on old lagoons, Western Treatment Plant

Table 9. Linear models of waterbird density (birds per square kilometre, if present on a wetland) in relation to salinity (mg/L). (Density = Constant + Estimate x Salinity)). Note that estimates have been multiplied by 1000 for display, and the values shown need to be divided by 1000 for use in this equation. Relationships where P<0.06 are shown in bold.

Bird species or group Direction of presence- Direction of Constant Estimate P (re (dependent variable) absence response density (x 1000) salinity) (from Table 8: bold if relationship P<0.06) (bold if P<0.06) Eurasian Coot positive negative 626 -75.9 0.153 Hoary-headed Grebe negative positive 74 30.4 0.097 Silver Gull positive positive 26.5 16.5 0.088 Black Swan positive negative 152 -6.7 0.648 Australian Shelduck negative negative 165 -14.9 0.205 Pacific Black Duck positive negative 136 -1.70 0.902 Chestnut Teal positive positive 38.6 38.1 0.058 Grey Teal negative negative 477 -38.8 0.424 Australasian Shoveler negative positive 38.2 2.55 0.735 Pink-eared Duck negative positive 52 48 0.382 Hardhead negative positive 129 14.7 0.735 Blue-billed Duck negative positive 8.6 4.84 0.389 Musk Duck positive positive 9.7 0.39 0.609 Shorebirds positive positive 16 51.7 0.324 Waterbirds (ducks, geese negative negative 532 -5.7 0.891 & swans)

Table 10. Quadratic models of waterbird density (birds per square kilometre, if present on a wetland) in relation to salinity (mg/L) (Density = Constant + Estimate1 x Salinity) + (Estimate 2 x Salinity squared)). Note that estimates have been multiplied by 1000 for display, and the values shown need to be divided by 1000 for use in this equation. Relationships where P<0.06 are shown in bold. For most species, data were inadequate for modelling, or residual variance exceeded the variance explained by the model.

Bird species or group Explanatory Constant Estimate P Variance (dependent variable) variable (x 1000) explained by model

Hoary-headed Grebe Whole model 0.004 9.6 Constant -190 Salinity 221.1 0.002 Salinity squared -0.0255 0.005 Implied salinity for 4300 maximum density mg/L

Silver Gull Whole model 0.064 4.1 Constant -65 Salinity 78.7 0.049 Salinity squared -0.008 0.108

Pink-eared Duck Whole model 0.277 3.2 Constant -265 Salinity 299 0.130 Salinity squared -0.035 0.182

Arthur Rylah Institute for Environmental Research, DSE 38 Possible effects of increased salinity on waterbirds, invertebrates and phytoplankton on old lagoons, Western Treatment Plant

4.4 Recent data on waterbirds, zooplankton and salinity from 52 wetlands in the Wimmera of western Victoria 4.4.1 Methods Data were obtained from 50 wetlands in the Wimmera in spring 2004, with measurements made of salinity, waterbird numbers, zooplankton and other elements of the biota, as part of an ARI study under the National Action Plan for salinity control. The waterbird data were collected by Garry Cheers, Ed McNabb and Phoebe Macak. The zooplankton data were collected by teams organised by Sabine Schreiber and Mike Smith, and identified to species level by selected specialists. For the present analysis, waterbird numbers were converted to densities using the full area of each wetland. The data were tabulated to show mean waterbird densities and indices of zooplankton abundance for five levels of salinity. Salinities ranged from 37 to 120,000 mg/L.

4.4.2 Results and discussion Similar patterns emerged for waterbirds as with previous data (Table 11). The data highlight the aversion of Australian Wood Duck for saline water, and the tolerance of many species for a wide range of salinities. Hardhead also emerged as favouring fresh or brackish but not saline water, in accord with the analysis of state-wide data. Data on zooplankton showed that ostracods were common on all wetlands, across the very broad range of salinities examined (Table 12). Total zooplankton showed reached their maximum abundance over two salinity ranges, 3000-5000 and 10,000-22,000 mg/L, and were less abundant in fresh or hypersaline wetlands. Several taxa showed bimodal distributions, suggesting that they may have included more than one species, each adapted to different levels of salinity.

Table 11. Densities of waterbird (birds per square kilometre) in relation to salinity (mg/L) on 50 wetlands in the Victorian Wimmera, spring 2004 (M. Smith, G. Cheers et al., pers. comm.).

Salinity (mg/L): <680 900-2720 3000-5000 5300- 61200+ 15000 Birds/100ha N: 27 11 8 8 10 Eurasian Coot 47 229 490 659 0 Australasian Grebe 0 2 0 6 0 Hoary-headed Grebe 29 67 115 25 0 Black-fronted Dotterel 1 4 2 0 0 Australian Wood Duck 36 4 0 11 0 Black Swan 7 13 24 184 0 Australian Shelduck 5 8 33 124 9 Pacific Black Duck 35 16 2 81 0 Chestnut Teal 0 0 0 3 0 Grey Teal 123 187 140 1042 1 Australasian Shoveler 2 4 4 2 0 Pink-eared Duck 4 4 18 0 0 Freckled Duck 1 0 0 0 0 Hardhead 38 88 11 27 0 Blue-billed Duck 1 2 1 0 0 Musk Duck 1 3 0 0 0

Arthur Rylah Institute for Environmental Research, DSE 39 Possible effects of increased salinity on waterbirds, invertebrates and phytoplankton on old lagoons, Western Treatment Plant

Table 12. Relative abundances of zooplankton (mainly ostracods) in relation to salinity (mg/L) on 50 wetlands in the Victorian Wimmera, spring 2004 (M. Smith et al., pers. comm.).

Change fresh to Mean Mean Mean Mean Mean Mean brackish Salinity 200- 1000- 3000- 10000- (mg/L): <200 999 2999 9999 22000 44000+ N: 33 17 16 16 11 18 Sample (mL) 29.27 33.24 29.44 30.94 35.45 21.72 Subsample (mL) 1.14 1.35 1.78 1.25 0.91 2.00 neg Asplanchnidae 0.18 0.06 0.00 0.00 0.00 0.00 Ascomorpha 2.09 0.59 0.00 0.00 0.00 0.00 Ascomorphella 2.82 0.00 0.00 0.00 0.00 0.00 Bdelloidea 4.82 5.41 3.19 3.81 0.00 0.11 pos Brachionus 5.52 0.94 19.81 0.94 47.64 6.33 neg Cephalodella 2.30 3.06 9.00 1.25 0.09 0.11 neg Colletheca 1.64 0.59 0.06 0.00 0.00 0.06 Colurella 15.91 1.71 0.13 0.75 0.09 0.00 pos Conochilus 0.06 0.12 0.13 0.00 0.00 0.06 neg Dicranophorus 1.36 2.53 0.81 0.00 0.00 0.22 neg Dipleuchlanis 0.21 0.06 0.00 0.00 0.00 0.00 Encentrum 1.03 0.06 0.06 0.00 0.00 0.00 neg Eosphora 0.18 0.29 0.25 0.00 0.00 0.00 neg Epiphanes 0.06 0.18 0.00 0.00 0.00 0.00 Euchlanis 12.15 5.65 1.63 0.00 0.09 0.00 neg Filinia 0.24 0.24 0.00 0.00 0.00 0.00 Floscularia 0.09 0.12 0.00 0.00 0.27 0.00 Gastropus 0.21 0.00 0.00 0.00 0.00 0.00 Hexathra 0.06 0.35 0.06 0.63 218.27 0.00 pos Horaella 0.00 0.06 0.00 0.00 0.00 0.00 Itura 0.36 0.06 0.06 0.00 0.00 0.00 Keratella 22.00 8.06 0.06 0.63 0.00 0.33 pos Lecane 24.73 33.82 86.31 8.44 1.27 0.50 neg Lepadella 6.61 7.12 66.13 11.75 29.91 0.22 neg Lindiia 0.33 0.00 0.00 0.00 0.00 0.00 Lophocharis 0.12 2.06 0.00 0.00 0.00 0.00 Macrochaetus 0.03 0.00 0.00 0.06 0.00 0.00 pos Monommata 0.45 0.00 0.00 0.00 0.00 0.00 Mytilina 0.88 0.53 0.13 0.00 0.00 0.00 neg Notommata 1.27 0.47 0.13 0.00 0.00 0.00 neg Platyias 0.12 0.59 0.00 0.00 0.00 0.00 Plationus 0.06 0.12 0.00 0.00 0.00 0.00 Polyathra 3.94 0.94 0.00 0.00 0.00 0.00 Proales 0.58 0.00 0.13 1.44 0.00 0.00 pos Scaridium 0.27 0.71 0.00 0.00 0.00 0.00 Sinantherina 12.30 1.00 1.94 0.13 0.00 0.00 neg Squatinella 0.15 0.35 0.00 0.00 0.00 0.00 Synchaeta 0.61 0.00 0.00 0.00 0.00 0.00 Taphrocampa 1.06 0.53 0.00 0.00 0.00 0.00

Arthur Rylah Institute for Environmental Research, DSE 40 Possible effects of increased salinity on waterbirds, invertebrates and phytoplankton on old lagoons, Western Treatment Plant

Table 12. Continued.

Change fresh to Mean Mean Mean Mean Mean Mean brackish Salinity 200- 1000- 3000- 10000- (mg/L): <200 999 2999 9999 22000 44000+ N: 33 17 16 16 11 18 Sample (mL) 29.27 33.24 29.44 30.94 35.45 21.72 Subsample (mL) 1.14 1.35 1.78 1.25 0.91 2.00 neg Testudinella 3.15 1.24 3.63 2.63 0.00 0.06 neg Trichocerca 4.00 2.41 4.63 9.63 0.00 0.00 pos Trichotria 0.64 0.00 0.00 0.00 0.00 0.11 Notommata 0.06 0.00 0.00 0.00 0.00 0.00 Enteroplea 0.03 0.00 0.00 0.00 0.00 0.00 Wolga 0.00 0.00 0.00 0.00 0.00 0.00 Calanoida 4.91 2.94 2.40 6.63 2.36 11.44 pos little Chydoridae 13.67 9.59 21.00 21.94 21.91 9.89 difference Cyclopoida 15.30 38.29 19.27 30.06 52.45 29.22 pos Daphniidae 1.70 2.71 2.73 5.38 1.82 1.22 pos Harpacticoida 2.55 9.53 14.40 2.00 0.82 6.44 neg Ilyocryptidae 0.00 0.00 0.07 0.00 0.00 0.00 neg Macrothricidae 2.85 29.29 10.53 2.63 35.73 5.33 neg Moinidae 0.09 0.12 0.00 0.94 0.00 0.17 pos Nauplii 82.88 78.41 41.20 128.00 95.09 94.61 pos Ostracoda 7.97 12.94 22.67 10.44 9.36 15.83 neg **Ostracoda 0.82 0.18 0.67 0.19 0.00 0.44 neg Sididae 0.06 0.00 0.40 0.06 0.00 0.06 neg Total 267.48 266.00 333.58 250.31 517.18 182.78

Arthur Rylah Institute for Environmental Research, DSE 41 Possible effects of increased salinity on waterbirds, invertebrates and phytoplankton on old lagoons, Western Treatment Plant

4.5 Data on waterbirds and salinity from 54 wetlands near Kerang 4.5.1 Methods A pertinent case-study examined waterbird numbers and salinity levels on 54 wetlands in the Kerang region of north-west Victoria, in 1988-89 (Lugg 1990). Each major wetland was counted five or six times from September 1988 to July 1989. Reporting rates (% of counts where each species was recorded) were documented for 54 waterbird species in relation to five salinity levels (Table 3). The levels fortuitously included two of great relevance to the current situation (fresh=1,500-4,000 EC and brackish=4,000-10,000 EC). These ranges are equivalent to 1000-2720 mg/L (fresh) and 2720-6800 mg/L (brackish). Data were collected on bird densities (numbers per hectare) as well as presence-absence, but unfortunately not presented in the published report.

4.5.2 Results The species of greatest relevance to the old lagoons are the ducks and possibly shorebirds. Reporting rates of ducks collectively and shorebirds collectively were higher on brackish than fresh wetlands, and substantially lower on wetlands classed as very fresh (<1020 mg/L), saline (14,706-147,060 mg/L) or hypersaline (>147,060mg/L). Very few species occurred on hypersaline wetlands, and the species list was highest for fresh or brackish wetlands with little difference between the two groups (Table 13).

The same pattern was shown by most individual species. Two exceptions were Australian Wood Duck (=Maned Duck) and Pacific Black Duck, which were slightly more common on fresh or very fresh wetlands than on brackish wetlands, as expected from our Table 2. All other duck species showed higher reporting rates on brackish wetlands than fresh or very fresh wetlands (Table 13). These included the species identified as not using marine waters, but common on the old lagoons (Table 13). The same pattern was also shown by Hoary- headed Grebe and Black Swan, and even (surprisingly) by Australasian Grebe (Table 13).

Arthur Rylah Institute for Environmental Research, DSE 42 Possible effects of increased salinity on waterbirds, invertebrates and phytoplankton on old lagoons, Western Treatment Plant

Table 13. Reporting rates for waterbirds in Kerang Lakes, in relation to salinity ranges (from Lugg 1990).

Very fresh Fresh Brackish Saline Hypersaline < 1020 1020-2720 2720-6800 6800- > 68,000 mg/L mg/L mg/L 68000 mg/L mg/L Great Crested Grebe 4 19 35 21 0 Hoary-headed Grebe 2 13 41 53 0 Australasian Grebe 11 7 18 0 0 Australian Pelican 71 54 65 11 0 Great Cormorant 46 30 41 0 0 Little Black Cormorant 35 22 35 6 0 Pied Cormorant 9 6 12 0 0 Little Pied Cormorant 39 39 65 12 0 Darter 41 22 47 0 0 Pacific Heron 2 7 12 0 0 White-faced Heron 22 31 65 11 0 Rufous Night Heron 9 4 6 0 0 Great Egret 17 31 18 0 0 Intermediate Egret 1 2 0 0 0 Little Egret 0 2 0 0 0 Sacred Ibis 37 30 24 0 0 Straw-necked Ibis 22 19 18 0 0 Glossy Ibis 0 6 0 0 0 Royal Spoonbill 20 20 29 0 0 Yellow-billed Spoonbill 9 13 18 4 0 Black Swan 35 59 88 60 0 Australian Shelduck 11 59 70 66 13 Pacific Black Duck 48 52 41 6 0 Grey Teal 39 63 94 42 0 Chestnut Teal 0 6 23 4 0 Australasian Shoveler 2 17 52 2 0 Pink-eared Duck 0 19 29 6 0 Hardhead 4 22 29 4 0 Maned Duck 7 4 6 0 0 Blue-billed duck 0 0 12 11 0 Musk Duck 0 19 47 30 0 Freckled Duck 1 11 12 0 0 Dusky Moorhen 30 20 12 2 0 Purple Swamphen 41 46 0 0 0 Eurasian Coot 15 30 65 9 0 Black-tailed Native-hen 0 22 24 0 0 Masked Lapwing 9 39 59 40 26 Banded Lapwing 0 0 0 0 3 Red-kneed Dotterel 2 19 29 6 0 Red-capped Plover 0 4 6 36 23 Black-fronted Plover 0 7 12 0 0 Black-winged Stilt 2 24 41 23 0 Banded Stilt 0 0 0 6 0 Red-necked Avocet 0 6 6 36 5 Greenshank 2 9 29 15 0 Red-necked Stint 0 2 6 19 0 Curlew Sandpiper 0 4 6 17 0 Marsh Sandpiper 0 6 12 0 0 Sharp-tailed Sandpiper 0 7 23 23 0 Latham’s Snipe 2 2 0 0 0 Bar-tailed Godwit 0 2 0 0 0 Silver Gull 11 43 47 51 13 Whiskered Tern 15 22 35 6 0 Caspian Tern 4 4 24 0 0 Number of species 40 54 46 32 7

Arthur Rylah Institute for Environmental Research, DSE 43 Possible effects of increased salinity on waterbirds, invertebrates and phytoplankton on old lagoons, Western Treatment Plant

4.6 Data on waterbirds and zooplankton from the RAAF Lake at Point Cook, in relation to cycles of filling and drying with increased salinity 4.6.1 Methods Waterbirds were counted at the RAAF Lake (Pont Cook Coastal Park) on 23 days from April 2001 (when the lake had filled from recent heavy rains) to March 2003, when water levels had been low and water highly saline for many months (Loyn et al. 2003). Approximate measurements were made of salinity (published as specific gravity, but converted here to mg/L) and zooplankton abundance on many of these dates. This report examines the data descriptively, as an example of changes that can happen at a single wetland.

4.6.2 Results and discussion Numbers of waterbirds were very high soon after the lake filled, and declined as water levels dropped and became more saline (Table 14). Species composition changed over this time. Initially the common ducks were filter feeders (Pink-eared Duck and Australasian Shoveler) and they disappeared early while numbers of dabbling ducks increased (Grey Teal and Chestnut Teal). A few Hardhead were present on the first two counts and none were seen subsequently. No Pacific Black Duck were seen at all. The decline of filter feeders preceded the main increase in measured salinity, but the measurements were made from a single sampling station and may not be accurate reflections of the true salinity over the rest of the lake. The general decline in waterbirds numbers coincided with an increase in measured salinity from 4400 to 8000 mg/L (Table 14). Shorebirds were initially scarce, as the lake was full to capacity and few mudflats remained exposed (Table 15). They became common on later visits as water levels fell, and extensive mudflats became exposed. They remained common as the lake dried and became more saline, but made little use of it when the lake was virtually dry (Table 15). Silver Gulls made most use of the lake when it was full, and tolerated higher levels of salinity than most waterbirds (Table 15). Only four zooplankton species were found in the small water samples collected. They were common at salinities up to ~5000 mg/L, and declined substantially as salinity rose to 8000 and then above 10000 mg/L (Table 16). Just one species of ostracod was represented in the most saline samples.

Arthur Rylah Institute for Environmental Research, DSE 44 Possible effects of increased salinity on waterbirds, invertebrates and phytoplankton on old lagoons, Western Treatment Plant

Table 14. Numbers of waterbirds in relation to salinity at the RAAF Lake, Point Cook Coastal Park, 2001-03 (from Loyn et al. 2003).

Hoary- Blue- Salinity headed Black Australian Australasian Pink-eared Chestnut Grey billed Musk All Survey Date mg/L Grebe Swan Shelduck Shoveler Duck Teal Teal Hardhead Duck Duck ducks Waterbirds 8-Apr-01 * 6 12 0 263 3500 22 0 8 0 0 3793 3811 30-Jun-01 4960 250 8 0 300 1100 200 350 2 0 0 1952 2210 2-Aug-01 4960 175 45 0 200 530 120 180 0 0 4 1034 1254 21-Aug-01 4960 200 2 0 250 700 60 200 0 0 0 1210 1412 2-Sep-01 3300 92 2 38 0 850 35 200 0 0 1 1124 1218 18-Sep-01 * 51 4 0 14 0 0 350 0 0 0 364 419 13-Oct-01 4500 79 4 51 0 0 1100 800 0 0 1 1952 2035 7-Nov-01 4400 85 0 60 0 0 1300 1000 0 0 0 2360 2445 17-Nov-01 4400 191 0 76 0 0 700 500 0 0 1 1277 1468 15-Dec-01 * 0 0 76 0 0 80 50 0 0 0 206 206 18-Jan-02 8000 0 0 126 0 0 0 3 0 0 0 129 129 7-Feb-02 * 0 0 33 0 0 0 0 0 0 0 33 33 27-Feb-02 10400 0 1 3 0 0 0 3 0 0 0 6 7 12-Mch-02 13000 0 0 0 0 0 0 0 0 0 0 0 0 10-Apr-02 16000 1 0 0 0 0 0 0 0 0 0 0 1 5-May-02 13400 0 0 0 0 0 0 0 0 0 0 0 0 26-Jun-02 20120 0 0 0 0 0 0 0 0 0 0 0 0 12-Jul-02 * 0 0 0 0 0 0 0 0 34 0 34 34 4-Aug-02 11700 0 0 0 0 0 0 0 0 0 0 0 0 5-Sep-02 12800 0 0 0 0 0 0 0 0 0 0 0 0 23-Oct-02 * 0 0 0 0 0 0 0 0 0 0 0 0 24-Oct-02 13400 0 0 0 0 0 0 0 0 0 0 0 0 4-Mch-03 * 0 0 0 0 0 0 0 0 0 0 0 0

Arthur Rylah Institute for Environmental Research, DSE 45 Possible effects of increased salinity on waterbirds, invertebrates and phytoplankton on old lagoons, Western Treatment Plant

Table 15. Numbers of shorebirds and Silver Gulls in relation to salinity at the RAAF Lake, Point Cook Coastal Park, 2001-03 (from Loyn et al. 2003).

Black- Red- Salinity Water Masked winged Banded necked All Silver Waterbird Survey Date mg/L level Lapwing Stilt Stilt Stint# waders Gull s Total 8-Apr-01 * 6 0 0 0 6 0 3811 3857 30-Jun-01 4960 4 2 0 0 6 350 2210 2600 2-Aug-01 4960 4 4 0 0 8 200 1254 1491 21-Aug-01 4960 4 2 0 0 6 250 1412 1673 2-Sep-01 3300 8 3 0 0 11 0 1218 1244 18-Sep-01 * 4 5 0 0 9 14 419 442 13-Oct-01 4500 4 2 0 0 6 20 2035 2133 7-Nov-01 4400 4 0 0 0 4 9 2445 2607 17-Nov-01 4400 3 6 0 100 109 2 1468 1586 15-Dec-01 * 8 * 120 300 428 50 206 739 18-Jan-02 8000 14 * 150 300 476 153 129 768 7-Feb-02 * 0 * 30 0 30 0 33 63 27-Feb-02 10400 21 0 0 0 21 14 7 47 12-Mch-02 13000 28 0 0 125 153 1 0 154 10-Apr-02 16000 4 0 0 0 4 16 1 25 5-May-02 13400 29 0 0 0 31 0 0 31 26-Jun-02 20120 5 0 0 50 55 0 0 57 12-Jul-02 * 26 0 0 4 117 0 34 153 4-Aug-02 11700 0 0 0 36 39 0 0 39 5-Sep-02 12800 0 0 0 69 69 0 0 69 23-Oct-02 * 0 0 0 150 152 1 0 154 24-Oct-02 13400 7 0 0 140 147 0 0 147 4-Mch-03 * 0 0 0 0 6 0 0 6

Arthur Rylah Institute for Environmental Research, DSE 46 Possible effects of increased salinity on waterbirds, invertebrates and phytoplankton on old lagoons, Western Treatment Plant

Table 16. Relative abundances of zooplankton in relation to salinity at the RAAF Lake, Point Cook Coastal Park, 2001-03 (from Loyn et al. 2003). Zooplankton abundance was scored on a logarithmic scale from 0 (absent) to 4 (abundant).

Salinity Survey Date mg/L Ostracoda sp. 1 Ostracoda sp. 2 Calenoida sp.1 Calenoida sp.2 Total 8-Apr-01 * 4 1 0 0 5 30-Jun-01 4960 * * * * * 2-Aug-01 4960 2 0 3 2 7 21-Aug-01 4960 3 0 3 2 8 2-Sep-01 3300 * * * * * 18-Sep-01 * 2 0 4 3 9 13-Oct-01 4500 * * * * * 7-Nov-01 4400 3 1 3 3 10 17-Nov-01 4400 4 1 4 0 9 15-Dec-01 * * * * * * 18-Jan-02 8000 3 1 0 0 4 7-Feb-02 * * * * * * 27-Feb-02 10400 4 1 2 0 7 12-Mch-02 13000 3 1 1 0 5 10-Apr-02 16000 1 0 0 0 1 5-May-02 13400 2 0 0 0 2 26-Jun-02 20120 1 0 0 0 1 12-Jul-02 * * * * * * 4-Aug-02 11700 * * * * * 5-Sep-02 12800 * * * * * 23-Oct-02 * * * * * * 24-Oct-02 13400 * * * * * 4-Mch-03 * * * * * *

Arthur Rylah Institute for Environmental Research, DSE 47 Possible effects of increased salinity on waterbirds, invertebrates and phytoplankton on old lagoons, Western Treatment Plant

4.7 Overview by waterbird species Some of the studies above provide conflicting evidence for particular waterbird species, and a more consistent picture for other species. The reliability of particular studies varies to some extent between species, but in general the state-wide database (section c above) provides the most solid set of data. This is despite the large number of zero counts on particular wetlands (Figures 1-9). The prevalence of zero counts is expected for data concerning highly mobile waterbirds which come and go from particular wetlands in response to rainfall and other events at local and continental scales (Kingsford and Norman 2002). Using the most reliable data for each species, the waterbird species can be considered in several groups, according to their likely responses to salinity, as shown in Table 17. Monitoring is needed to determine the extent of change that actually occurs.

Table 17. Likely responses of waterbird species to increasing salinity in the old lagoons, based on all evidence above.

Habitat and response to salinity Waterbird species Shorebird species Fresh water wetlands, old lagoons are Dusky Moorhen# currently too saline to provide regular Australian Wood Duck# habitat Fresh or brackish wetlands, old lagoons Australasian Grebe Long-toed Stint# currently marginal Wood Sandpiper# Pectoral Sandpiper# Fresh or brackish wetlands, old lagoons Hardhead Black-fronted Dotterel suitable now but not if salinity reaches Freckled Duck 5000 mg/L Old lagoons suitable now but much less Eurasian Coot Black-tailed Godwit so if salinity reaches 5000 mg/L Pacific Black Duck Blue-billed Duck Old lagoons suitable now but less so if Pink-eared Duck Red-kneed Dotterel# salinity reaches 5000mg/L Declines likely if salinity exceeds 6000 Grey Teal mg/L Australasian Shoveler Declines likely if salinity exceeds 8000 Many species mg/L Species marked # are currently uncommon on the old lagoons.

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5 Aquatic invertebrates in the 85W Lagoon, and models of effects of brine disposal

5.1 Methods Invertebrates were sampled in the littoral zones (edges of the pond), benthos (bottom of the ponds) and plankton (surface water to depth 30 cm) at three sites in lagoon 85W pond 5, lagoon 85WB pond 7 and lagoon 85WC pond 7 on January 17, 2006. The littoral zone was sampled using a sweep net (mesh size 250 microns) by sweeping the net along 10 m of pond edge from the surface to the bottom. Two sweep samples were collected at each site. Plankton was sampled using a plankton tow net (mesh size 180 microns). The net was thrown 10 m perpendicular to the pond edge and towed back to the pond edge. Three plankton samples were collected at each site. Benthos was sampled by scraping the substratum using a container secured to the end of a 3 m pole (access further into the lagoon was not possible). Three benthos samples were collected from each site. Samples in each habitat type were combined together to increase the sample area/volume and they were preserved in 80% ethanol for identification in the laboratory. Plankton net tow samples are semi-quantitative and sweeps and the benthic techniques are qualitative. Taxa were identified to the lowest practicable level in the allocated timeframe using keys contained in Hawking (2000). The microcrustacea were identified by Russel Shiel, a taxonomist specialising in the identification of these taxa. Due to the qualitative and semi quantitative nature of the sampling methods, abundances are estimates only and the following categories were used (Table 18).

Table 18. Categories used for estimation of abundances.

Number of Abundance individuals category 1-10 1 11-100 2 101-1000 3 1001+ 4

Salinity tolerance information (minimum, maximum and median salinity tolerances) for each taxon was obtained primarily from the Salt Sensitive Database (Bailey et al. 2002) and other literature. Data in the Salt Sensitive Database originate from laboratory/field-based experiments or, and for most cases, field observations. The field data indicate the salinity ranges at which the taxa were reported, from one or more studies or data sources. The maximum value does not, therefore, represent the maximum salinity tolerance of the taxon. Species sensitivity risk models were developed for each pond based on tolerances reported in Land and Water Australia’s Salt Sensitivity Database (Bailey et al. 2002). Where multiple records were present for a species or taxonomic resolution was only to genus or family level, the median for that species or group was used as the tolerance value in the risk model. Likewise, the upper and lower bounds on the risk model were based on the maximum and minimum reported ranges for each species or group. Risk models were based on non-parametric cumulative mixture distributions, derived using RiskCalc 4.0 (RAMAS corp.). This approach, described in Dixon and Wilson (2006), has the advantage that there is no assumption of an underlying distribution and that it is possible to

Arthur Rylah Institute for Environmental Research, DSE 49 Possible effects of increased salinity on waterbirds, invertebrates and phytoplankton on old lagoons, Western Treatment Plant

incorporate uncertainty bounds from any source, unlike other approaches to this type of risk assessment.

5.2 Results and discussion 5.2.1 Invertebrates present in the ponds Twenty-four taxa (genera, subfamilies and suborders) were collected across all habitats and ponds. Crustaceans, dipterans (flies) and hemipterans (true bugs) comprised the bulk of the invertebrate abundance. The most common taxa in the plankton were small crustaceans including Daphnia carinata that grazes on phytoplankton, Mesocyclops notius that predates on small insect larvae (e.g. midges) and Candonocypris novaezelandiae that feeds on detritus and phytoplankton (Table 19).

Table 19 Relative abundance of invertebrate taxa collected in the plankton at each lagoon. Ordered by decreasing relative abundance with trophic status shown. Abundance categories are reported in Table 18.

Lagoon 85W 85WB 85WC Pond 5 5 7 Order Genus/Species Trophic status Cladocera Daphnia carinata Grazer 4 4 4 Copepoda Mesocyclops notius Predator 3 4 3 Candonocypris Detritivore Ostracoda novaezelandiae 3 2 2 Hemiptera Notonectidae sp.. Predator 2 1 1 Hemiptera Anisops sp. Predator 2 Cladocera Moina micrura Grazer 1 1 Diptera (Chironomidae) Polypedilum sp. Detrivore 2 Diptera (Chironomidae) Chironomus sp. Detritivore 2 Hemiptera Micronecta sp. Detritivor/Predator 1

The most common taxa on the surface of and within the top few centimetres of the benthos were the same small crustaceans present in the plankton as well as two midge larvae: Polypedilum sp. and Chironomus sp. that both feed on detritus (Table21).

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Table 20. Relative abundance of invertebrate taxa collected from the benthos at each lagoon. Ordered by decreasing relative abundance. Abundance categories are reported in Table 18.

Lagoon 85W 85WB 85WC Pond 5 5 7 Order Genus/Species Trophic status Ostracoda Candonocypris novaezelandiae Detritivore 4 4 3 Diptera (Chironomidae) Polypedilum sp. Detritivore 4 3 4 Cladocera Daphnia carinata Grazer 4 3 3 Copepoda Mesocyclops notius Predator 4 3 2 Diptera (Chironomidae) Chironomus sp. Detritivore 2 2 3 Cladocera Leydigia sp. nov. Grazer 2 Hemiptera Notonectidae unident. Predator 2 Platyhelminthes Turbellaria sp.. Detritivore 1 1 Nematoda Unidentified Predator 1 1 Diptera (Chironomidae) Procladius sp. Predator 1 1 Oligochaeta Tubificidae Group B Detritivor 1

The most common taxa in the littoral zone were also the small crustaceans present in the plankton and benthos (D. carinata, M. notius and C. novaezelandia) and the two midges present in the benthos (Polypedilum sp. and Chironomus sp.) as well as a true bug of the family Notonectidae. Notonoectidae are predators of small insect larvae (Table 21).

Table 21. Relative abundance of invertebrate taxa present in the littoral habitat at each lagoon. Ordered by decreasing relative abundance. Abundance categories are reported in Table 18.

Lagoon 85W 85WB 85WC Pond 5 5 7 Order Genus/Species Trophic status Ostracoda Candonocypris novaezelandiae Detritivore 4 4 4 Cladocera Daphnia carinata Grazer 3 4 4 Copepoda Mesocyclops notius Predator 3 4 4 Hemiptera Notonectidae sp.. Predator 3 3 2 Diptera (Chirinomidae) Polypedilum sp. Detritivore 3 2 4 Diptera (Chirinomidae) Chironomus sp. Detritivore 3 2 3 Hemiptera Anisops sp. Predator 3 1 Hemiptera Agraptocorixa sp. Predator 2 2 1 Predator/Detritiv Hemiptera Micronecta sp. or 1 2 2 Hemiptera Sigara sp. Predator 1 1 Grazer/Detritivor Diptera (Chirinomidae) Kiefferulus sp. e 2 Diptera (Chirinomidae) Cricotopus sp. Grazer 1 Diptera (Chirinomidae) Procladius sp. Predator 1 Platyhelminthes Turbellaria sp.. Predator 1 Mollusca Physa acuta Grazer 1 Coleoptera Paracymus sp. Predator 1 Coleoptera Scirtidae sp. Detritivore 1

5.2.2 Salinity tolerance Literature reviews by Hart et al. (1991) and Bailey et al. (2000), based on a combination of field and laboratory data, indicate that typically invertebrates are impacted by a salinity increase above 1000 mg/L. There are, however, halotolerant (salt tolerant) and halointolerant species but since many taxa were only recorded at a small numbers of sites

Arthur Rylah Institute for Environmental Research, DSE 51 Possible effects of increased salinity on waterbirds, invertebrates and phytoplankton on old lagoons, Western Treatment Plant

(just one in some cases); their true range of tolerance is poorly known. Other than the studies used in the Salt Sensitivity Database, there were few available salinity data for the taxa collected in this study. A summary of the field and/or laboratory salinity ranges for the taxa collected in the ponds is provided (Table 22). It is evident from the table that for all but one species, the expected salinity increase to 5000 mg/L will exceed the median of their reported salinity tolerances. Salinity risk models (Figures 10-12) show the cumulative proportion of taxa affected by the predicted salinity increase from 1000 to 5000 mg/L. Given the uncertain and variable nature of the data and situation under examination it is difficult to determine at what level effects will occur. Varying degrees of adaptation and endemism may mean that organisms at a particular site display markedly different susceptibilities to members of the same species at other sites. For these reasons it is informative to consider both the mean or median tolerance levels and the range of expected tolerances reported for each species.

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Table 22: Salinity tolerance information for taxa collected in the ponds, ordered from lowest to highest median salinity tolerance. References to studies from which the data has been calculated are contained in the reference section of the Attachment. The red line represents the new salinity level – 5000 mg/L.

Min Max Median Data Order Family Genus/species (mg/L) (mg/L (mg/L) source Reference number (see Attachment 1)

Diptera Orthocladiinae Cricotopus sp. 82 1900 128 field 79, 96 Ostracoda Cyprididae Candonocypris novaezelandiae 400 400 400 field 94 Oligochaeta Oligochaeta Unidentified 108 58000 437 field 10, 66, 67, 68, 94, 100, 106, 107 Cladocera Moinidae Moina micrura 470 4800 540 field 96, 106 Cladocera Chydoridae Leydigia sp. nov. 476 680 578 field 33 Diptera Chironominae Polypedilum sp. 82 5500 751.5 field 66, 67, 68, 79, 107 Cladocera Daphniidae Daphnia carinata 110 17800 1106 field 94, 96, 106 Copepoda Cyclopoida Mesocyclops notius 600 2000 1300 field 106 Diptera Chironominae Kiefferulus sp. 109 51700 1402 field 66, 67, 68,, 79, 107 Trichoptera Leptoceridae Triplectides australis 1402 1402 1402 field 66, 67, 68 Coleoptera Scirtidae Unidentified 434 3900 1600 field 66, 67, 68, 107 Diptera Chironominae Chironomus sp. 82 57400 1804 field 66, 67, 68, 79, 94, 96, 106, 107 Platyhelminthes Turbellaria Unidentified 400 8000 1885 field 66, 67, 68, 85, 94, 107 Nematoda Unidentified Unidentified 201 19000 2120 field 20, 101 Hemiptera Notonectidae Unidentified 100 30400 2312 field 101,106, 107 Hemiptera Corixidae Micronecta sp. 100 53800 2420 field 10, 54 Hemiptera Corixidae Unidentified 82 53800 2900 field 9, 10, 54, 71, 79 Diptera Chironominae Unidentified 337 58000 3120 field 55, 66, 67, 68, 79, 95, 96, 106, 107 Mollusca Physidae Physa acuta 400 5800 3200 field 71,94,106,107 Diptera Tanypodinae Procladius sp. 200 59800 3481.5 field 5, 94, 96, 106, 107 Hemiptera Notonectidae Anisops sp. 100 30400 3600 laboratory71 Hemiptera Corixidae Agraptocorixa sp. 100 27100 3600 field 10, 54 Hemiptera Corixidae Sigara sp. 100 25700 4350 field 94 Coleoptera Hydrophilidae Paracymus sp. 4200 6200 5916 field 5, 106

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1

m2 Min Tolerance Max Tolerance

pred

0.5 Median m1 Tolerance

now

affected of species Proportion

Current Salinity New Salinity (1,000mg/L) (5,000mg/L) 0 0 10000 Salinity (mg/L)

Figure 10. Species sensitivity risk model for Lagoon 85W pond 5. Note the maximum tolerance has been truncated for display purposes.

1

Min Tolerance Max Tolerance

Median 0.5 Tolerance

pred

Proportion of species affected affected of species Proportion m2

m1 now

Current Salinity New Salinity (5,000mg/L) (1,000mg/L) 0 0 10000 Salinity (mg/L)

Figure 11. Species sensitivity risk model for Lagoon 85WB pond 7. Note the maximum tolerance has been truncated for display purposes.

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1

Min nowTolerance Max Tolerance

0.5 Median Tolerance

pred

Proportion of species affected affected of species Proportion m2 m1

Current Salinity New Salinity

(1,000mg/L) (5,000mg/L)

0 0 10000 Salinity (mg/L)

Figure 12. Species sensitivity risk model for Lagoon Pond 85WC pond 7. Note the maximum tolerance has been truncated for display purposes.

The plots show non-parametric cumulative probabilities of effects of increasing salinity. The minimum and maximum tolerances represent the lowest and highest salinities in which the t the taxon has been found in the field or through laboratory/field-based experiments. The individual studies from which the data have been sourced are listed in Table 22. The black solid line represents the median of the reported maximum salinity occurrence for that taxon. Figures 10-12 show that in 85W pond 5, the new salinity is higher than the median of the salinity maxima for all taxa and higher than the maximum reported value for approximately 17% of species. For 85WB pond 7, the new salinity is higher than the median of the salinity maxima for all taxa and for approximately 27% of species, the change will be above their maximum reported tolerance. For 85WC pond 7, the new salinity is higher than the median of the salinity maxima for approximately 92% of species and for approximately 20% of species, the change will be above their maximum reported tolerance.

5.3 Conclusion and recommendations The risk modelling indicated that the new salinity level would exceed the median of the maximum recorded salinity values for 87-99% of taxa across the three ponds. Some of these taxa could be expected to decline in abundance or disappear as salinities increased to 5000 mg/L. For approximately 14% of taxa in 85WC pond 7, the change will be above their maximum reported tolerance level – a strong indication of expected adverse effects on populations at this salinity level.

Arthur Rylah Institute for Environmental Research, DSE 55 Possible effects of increased salinity on waterbirds, invertebrates and phytoplankton on old lagoons, Western Treatment Plant

There are uncertainties involved in this type of risk assessment and it is therefore recommended that any changes in salinity that should occur be gradual and regular monitoring and reporting be undertaken in order to detect effects at this time before significant impact may occur. The monitoring frequency would depend on the rate of salinity increase in the ponds; however, a provisional frequency of bi-monthly sampling/data collection is suggested. A monitoring program can be developed if the brine disposal is planned but data collection should occur for a minimum of three occasions before brine disposal is initiated. In sum, an impact on invertebrate populations is likely if salinity is increased to 5 000 mg/L; however, the nature and severity of the impact is indeterminate. Further, the salinity should be increased gradually to reduce the severity of impacts on the invertebrate populations. Finally, monitoring invertebrate populations to detect changes during the salinity increase is highly advisable.

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6 Phytoplankton, and effects of brine disposal

Phytoplankton samples were not collected from Walsh, 145W and 85W lagoons during the time of the invertebrate sampling, however data collected by WSL Pty Ltd in September 2003 was used to provide an estimate of the taxa present across the lagoons. Fifty-three taxa were collected in this sampling event, comprising blue-green algae, green algae, euglanoids, cryptomonads and diatoms. The mean cell concentrations for each taxon from all samples and ponds (i.e. ponds 12, 14and 18) was calculated (Figure 12). Taxa with cell concentrations greater than 1000 cells/mL, together with their classification (taxonomic Division) are shown in Table 6. It is likely that the invertebrate grazers and detritivores (Table 23) are feeding on most of these taxa. Only two of the taxa found in Walsh’s Lagoon are recorded in the salt sensitivity database: the green algae Ankistrodesmus sp., which has a recorded salinity range of 82-163 mg/L and Sphaerocystis sp., which has a recorded salinity range of 82-156 mg/L (Bailey et al. 2002). These values are from one study only, however (Norris et al 1993) and therefore there is a high degree on uncertainty with their actual salinity tolerance. Ankistrodesmus has been shown in at least one study to be favoured by increased salinity (Kessler 1980). A species of Scendesmus (S. armatus) has been found to grow well in experiments using salinities of up to 8000 mg/L (Russell and Veltkamp 1997).

With respect to diatoms, Bailey and James (2000) propose a simple general classification whereby taxa with a salinity tolerance of less than 13600 mg/L are considered sensitive. This level is far greater the expected increase in the lagoons from 1000 to 5000 mg/L.

Due to the lack of salinity tolerance information available for these phytoplankton taxa, monitoring of invertebrates is considered more appropriate as part of the assessment of impacts associated with the proposed salinity increase.

Arthur Rylah Institute for Environmental Research, DSE 57 Possible effects of increased salinity on waterbirds, invertebrates and phytoplankton on old lagoons, Western Treatment Plant

40000.0

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Figure 12. Mean cell concentrations for each taxon from all samples and ponds (12, 14 and 18).

Arthur Rylah Institute for Environmental Research, DSE 58 Possible effects of increased salinity on waterbirds, invertebrates and phytoplankton on old lagoons, Western Treatment Plant

Table 23. Phytoplankton taxa with mean cell concentrations greater than 1000 cells/mL.

Classification (Division) Mean concentration across all ponds Taxa (cells/mL) Chlamydomonad Green algae 34329.8 Planktolyngbya sp. (filaments) Blue-green alga 28595.0 Chlorococcoids Green alga 11098.8 Scenedesmus sp. Green alga 9689.3 Centrales Diatoms 5902.2 Cryptomonads Crytpomonads 4879.8 Merismopaedia sp. (quads) Blue-green alga 3682.6 Pseudanabaena sp. (filaments) Blue-green alga 3226.5 Microcystis sp. Blue-green alga 2861.9 Dictyosphaerium sp. Green alga 2860.9 Aphanocapsa sp. (colonies) Blue-green alga 1702.2 Ankistrodesmus sp. Green alga 1671.3 Coelastrum sp. (cells) Green alga 1458.4 Pediastrum sp. (cells) Green alga 1393.6 Sphaerocystis sp. (cells) Green alga 1228.7 Lepocinclis sp. Euglenoids 1033.4 Pennales Diatom 1029.8

Arthur Rylah Institute for Environmental Research, DSE 59 Possible effects of increased salinity on waterbirds, invertebrates and phytoplankton on old lagoons, Western Treatment Plant

7 Acknowledgments

Many thanks to Tohi Otimi and Will Steele (Melbourne Water Corporation) for inviting us to prepare this review. Many thanks also to Andrew Corrick, Mike Smith, Garry Cheers, Ed McNabb, Phoebe Macak, Shanaugh McKay, Alan Lugg, Eric Savage and others for generating some of the data used in various analyses.

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8 References

Anon. 1988a. Wetlands conservation program for Victoria. Department of Conservation Forests and Lands, Melbourne. Anon. 1998b. Dryland salinity and its impacts on rural industries and the landscape. Science, Engineering and Innovation Council, Canberra. Bailey, P., Boon, P. and Morris, K. 2002. Salt Sensitivity Database. http://www.rivers.gov.au/research/contaminants/saltsen.htm Bailey, P.C. and James, K.R. 2000. Riverine and wetland salinity impacts: assessment of R & D needs. Land and Water Resources Research and Development Corporation. Occasional Paper No. 25/99. Barry, S. C. and Welsh, A.H. 2002. Generalised additive modelling and zero inflated count data. Ecological Modelling 157: 179-188. Baudinette, R.V., Norman, F.I. and Roberts, J. 1982. Salt gland secretion in saline- acclimated Chestnut Teal, and its relevance to release programs. Australian Journal of Zoology 30, 407-415. Brock, M.A. 1981. The ecology of halophytes in the south-east of South Australia. Hydrobiologia 81, 23-32.

Chapman, A. and Lane, J.A.K. 1997. Waterbirds usage of wetlands in the south-east arid interior of Western Australia. Emu 97, 51-59. Christidis, L. and Boles, W. E. 1994. The taxonomy and species of birds of Australia and its territories, RAOU Monograph 2 Royal Australasian Ornithologists Union, Melbourne, 112 pp. Clunie, P., Ryan, T., James, K. and Cant, B. 2002. Implications for rivers from salinity hazards: scoping study. Report produced for Murray-Darling Basin Commission, Strategic investigations and riverine program – Project R2003. Dixon, W.J. and Wilson, J.A. 2006. Draft Report on the Refined Approaches to Predictive Modelling of the Risks of Increasing Salinity on Biodiversity Assets. DSE Victoria. Goodsell, J.T. 1990. Distribution of waterbird broods relative to wetland salinity and pH in south-western Australia. Australian Wildlife Research. 17, 219- 229. Halse, S.A. 1987. Probable effect of increased salinity on the waterbirds of Lake Toolibin. Western Australian Department of Conservation and Land Management, Technical Memo. No. 15. Halse, S.A., Williams, M.R., Jaensch, R.P. and Lane, J.A.K. 1991. Wetland characteristics and waterbird use of wetlands in south-western Australia. Wildlife Research 20, 103-126. Hart, B.T., Bailey, P., Edwards, R., Hortle, K., James, K., McMahon, A., Meredith, C. and Swadling, K. 1990. Effects of salinity on river, stream and wetland ecosystems in Victoria, Australia. Water Research 24, 1100-1117.

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Hart, B.T., Bailey, P., Edwards, R., Hortle, K., James, K., McMahon, A., Meredith, C. and Swadling, K. 1991. A review of the salt sensitivity of the Australian freshwater biota. Hydrobiologia 210, 105-144. Hawking, J.H. 2000 Key to Keys, A guide to keys and zoological information to identify invertebrates from Australian inland waters. Identification Guide No.2, 2nd Edition Cooperative Research Centre for Freshwater Ecology: Albury. Hughes, M.R. 1976. The effects of salt-water adaptation on the Australian Black Swan Cygnus atratus (Latham). Comparative Biochemistry and Physiology 55, 271-277. Keighery, XX, Halse, S., McKenzie, N., Gibson, N., Burbidge, A. and Gomboso, J. 2000. Salinity: driving the catastrophic collapse of our ecosystems. Department of Conservation and Land Management (CALM Science Division, Nature Conservation Division) [Not seen, quoted from SCC 2001.] Kessler, E. 1980 Mass culture of Chlorella strains under conditions of high salinity, acidity and temperature. Archives of the Hydrobiological Supplment 60: 80- 86

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