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Presented at the NABS Annual meeting, Pittsburgh, Pennsylvania, 2002
in Disturbance Ecology I
THE POTENTIAL INFLUENCE OF PHYSICAL DISTURBANCE ON MACROINVERTEBRATE COMMUNITIES BY SALMON REDD DIGGING.
A.J. Hewertson1 and A.M. Milner1,2. 1School of Geography and Environmental Sciences, University of Birmingham, Birmingham, B15 2TT, 2Institute of Arctic Biology, University of Alaska, Fairbanks, AK 99775, USA
Stonefly Creek in Glacier Bay National Park, Alaska, is a recently formed stream consisting of three main reaches of contrasting temperatures and turbidities. The two lower reaches support relatively high numbers of adult spawning salmon while a set of cascades prevents salmon migration further upstream. Previous studies in Glacier Bay have indicated that redd digging by adult spawning salmon can create macroinvertebrate downstream drift, resulting in the reduction of species and abundance. Salmon redds which are not subsequently over-dug by other fish constitute a pulse disturbance, and an experiment was designed to simulate this disturbance type within these contrasting reaches. Patches were manually disturbed on specified dates, and sampled to determine community response over time. Contrasting communities were found at each reach, with differing diversities, species richness and dominance, and with low similarity to each other. Response to disturbance varied between the reaches, with those regularly disturbed by salmon showing greater resilience to disturbance with more rapid recovery. Some chironomid species groups were highly resilient and cosmopolitan, while other related species were fugitives, rapidly colonising recently disturbed patches. Twenty-one days after disturbance the macroinvertebrate communities were still substantially different from the control communities.
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