Macroinvertebrate cycles of decline and recovery i

Authors: Bea Sommer Pierre Horwitz

Publish Date: 2009/01/28

Volume: 624, Issue: 1, Pages: 191-203

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Abstract

Management of wetlands influenced by the Gnangara groundwater mound Western Australia is becoming increasingly challenging due to an ongoing decline in the regional groundwater table A number of these groundwaterdependent wetlands have acidified with adverse effects on the extant macroinvertebrate fauna due to the oxidation of pyritic sediments One management option in such cases is artificial augmentation of surface water in order to maintain or reinstate anaerobia in the sediments This paper documents cycles of macroinvertebrate decline and recovery over 12 years of monitoring in three Gnangara mound wetlands affected by droughtinduced acidification one of which is being artificially augmented Acidification did not result in a reduction of the total number of macroinvertebrate families present however there were clearly identifiable groups of acidsensitive taxa amphipods and isopods ostracods chydorid and daphnid cladocerans mayflies oligochaetes clams and snails and acidtolerant taxa sandfly larvae macrothricid cladocerans and water boatmen In the artificially augmented wetland the effects of acidification were reversed acidsensitive taxa reappeared and acidtolerant taxa decreased in numbers Moreover there were a number of taxa that appeared for the first time since augmentation and summer family richness increased markedly This study has shown that artificial augmentation of wetland water levels can be a successful recovery strategy for recently acidified systems but this will depend on a number of factors and the ‘recovered’ state will be at least slightly different from the original stateThe authors wish to thank the Western Australian Department of Water and its predecessors for providing the initiative and funding for the Gnangara Mound Macroinvertebrate Monitoring Program Thanks are also extended to The National Heritage Trust the National Action Plan for Salinity and Water Quality and the Western Australian Department of Water for providing funding for the Strategic Reserve Project on Acid Sulphate Soils which allowed the production of this paper We are also grateful to Dr Richard Norris Dr Robert Bailey and an anonymous reviewer for their constructive comments on the manuscript

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