Aquatic macroinvertebrate communities on wood in an Australian lowland river: experimental assessment of the interactions of habitat, substrate complexity and retained organic matter
J. A. Scealy A , S. J. Mika A and A. J. Boulton A BA Ecosystem Management, University of New England, Armidale, NSW 2350, Australia.
B Corresponding author. Email: aboulton@une.edu.au
Marine and Freshwater Research 58(2) 153-165 https://doi.org/10.1071/MF06105
Submitted: 20 June 2006 Accepted: 2 November 2006 Published: 8 February 2007
Abstract
Since European settlement, vast amounts of wood have been removed from Australian rivers. In recognition of its ecological value, including as habitat for aquatic invertebrates, wood is being reintroduced but with little understanding of optimum placement (pools v. riffles) or structural complexity to enhance invertebrate diversity. We hypothesised that complex woody debris would support higher numbers and more macroinvertebrate taxa, especially in riffles. Wood substrates of two complexities but similar surface areas were introduced into pools and riffles at three sites along the Hunter River, Australia. After 30 days, more taxa and individuals occurred on the complex substrates in pools and riffles at all sites. Substrates in riffles usually supported more taxa and individuals but responses were site-specific. Community composition varied among sites, substrates and habitats. Complex substrates, especially in riffles, trapped drifting organic matter that increased abundance and taxa richness but did not alter overall trends among substrates or habitats within sites. However, densities of rheophilic (flow-loving) taxa were reduced by entrained organic matter. Our results indicated that complex woody debris introduced into riffles could enhance diversity and abundance of macroinvertebrates in the Hunter River. However, these conclusions from a short-term, small-scale experiment need validation from longer-term, large-scale river rehabilitation projects.
Additional keywords: habitat complexity, invertebrate ecology, patchiness, river management.
Acknowledgements
This project was funded by the Australian Research Council, and we thank the industry partners Mt Arthur Coal, Bengalla Mining, Macquarie Generation, Hunter-Central Rivers Catchment Management Authority and Department of Natural Resources for funds and access to the study sites. We are grateful to Dr Mark Sanders for project management, Dan Keating for technical support in the field, Paul Lisle for assistance in the laboratory, and B. Lackman for inspiration. Useful comments on earlier drafts of this manuscript were provided by Mark Dahm, Darren Ryder and three anonymous referees.
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