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Presented at the NABS Annual meeting, Pittsburgh, Pennsylvania, 2002
in Disturbance Ecology III
HIDING OUT: DOES CREVICE SIZE MATTER?
E.A. Bergey and J.F. Weaver. Oklahoma Biological Survey and Department of Zoology, University of Oklahoma, Norman, OK 73069
Substrate crevices can be effective refuges for benthic algae from disturbances such as grazing and the abrasion associated with spates. But crevices are not all the same; in particular, crevices vary in size. The size of crevices may influence both the size range of algae that are sheltered and the degree of protection from disturbance. In our experiment, we tested a wide range of crevice sizes as refuges for benthic algae against grazing by the central stoneroller, a native minnow. We tested the hypothesis that crevices of a particular size range are protective, but that larger crevices are no longer protective because the disturbance agent is no longer excluded. Replicate clay stones were made using a set of eight molds with rounded depressions. Additional crevice treatments included smooth clay stones and natural limestone. Stones were inoculated with a stream derived algal slurry. The experiment was run in eight large plastic pools, which each contained three grazer treatments: fish exclusion, cage control, and open. After one month's exposure to grazers, smaller crevices contained higher algal densities than larger crevices, supporting the crevice size hypothesis.
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