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Presented at the NABS Annual meeting, Pittsburgh, Pennsylvania, 2002
in Disturbance Ecology III
ROCK ARCHITECTURE MEDIATES DISLODGMENT AND MORTALITY OF LOTIC INVERTEBRATES IN HIGH-FLOW EVENTS.
J.R. Holomuzki1 and B.J.F. Biggs2. 1Department of Evolution, Ecology and Organismal Biology, The Ohio State University, 1680 University Dr., Mansfield, OH 44906 USA, 2National Institute of Water and Atmospheric Research, P.O. Box 8602, Christchurch, New Zealand
We examined how the leptophlebiid mayfly Deleatidium spp., the mudsnail Potamopyrgus antipodarum, and the stony-cased caddisfly Pycnocentrodes aeris, each with different flow habitat preferences and motilities, respond to elevated flows in a large recirculating flume. Our goal was to learn more about how rock size, sorting and shape interact with life-history traits to affect species persistence along the flow disturbance gradient. Dislodgment and mortality varied among taxa and depended on rock characteristics. Dislodgment rates were highest in caddisflies and were related to their propensity to occupy epibenthic surfaces. Mayflies exhibited the lowest tendency to dislodge. However, dislodgment of all taxa was significantly lower from poorly sorted patches of stones (gravel + cobble) than from well sorted patches (gravel or cobble alone). Manipulations of rock shape showed that dislodgment was significantly greater from round/smooth rocks than from flat/smooth and jagged (angular) rocks. Mortality rates were uniform among taxa, except in round/smooth gravel where mayfly mortality was significantly higher than that of the other taxa. These stones also had the highest tendency to erode. Our results suggest that rock architecture plays a key role in allowing these species to persist in flow-variable habitats.
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