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Western Treatment Plant This publication may be cited as: Loyn, R., Norman, I, Papas, P., Potts, J., Dixon, B. (unpublished) Possible effects of increased salinity on waterbirds, invertebrates and phytoplankton at the old lagoons (85W, 145W and Walsh’s Lagoon), Western Treatment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. 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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.