Microinvertebrate community response to changing water regimes in the Macquarie Marshes, NSW, Australia

Abstract

Dryland rivers in arid regions of the world support dependant ecosystems under highly variable conditions. The biota of dryland rivers and floodplains has adapted, over time, to the natural cycles of flooding and drying that characterize these environments. Aquatic microinvertebrates form a critical link in the transfer of energy from primary producers to fish and waterbirds that thrive when the rivers rise and floodplains are inundated. Importantly, aquatic microinvertebrates contribute to resiliency of dryland river biota through their ability to form drought-tolerant resting stages during long dry periods. I examined the response of aquatic microinvertebrate communities to changes in environmental conditions, including water regimes, floodplain processes, and habitat availability in the Macquarie Marshes in the arid-zone of western New South Wales, Australia. The Macquarie Marshes are temporary wetlands which have, historically, supported rich and diverse ecological communities such as huge bird colonies of international significance. While these communities have waxed and waned over time with natural flood and drought cycles, anthropogenic changes, in particular modification to the water regime through river regulation and extraction are now altering the normal ecological cycles in the Marshes. ...This study showed that when flooded, the Macquarie Marshes support huge populations of microinvertebrates and correspondingly high numbers of dormant resting stages in dry sediments once the waters have receded. Changes to water regimes that reduce the frequency of flooding and change temporary creeks into semi-permanent water bodies will have a detrimental effect on microinvertebrate communities.