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Presented at the NABS Annual meeting, La Crosse, Wisconsin, 2001
HABITAT EFFECTS ON DRIFT AND BENTHIC RESETTLEMENT OF LARVAL HYDROPSYCHID CADDISFLIES (CERATOPSYCHE SPARNA)
J. R. Holomuzki1,2 and A. Van Loan2. 1The Ohio State University at Mansfield, Department of Evolution, Ecology, and Organismal Biology, 1680 University Dr. , Mansfield, OH 44906, 2University of Michigan Biological Station, 9008 Biological Rd. , Pellston, MI 49769
We conducted 2 experiments in flow-through artificial streams to examine the effects of habitat heterogeneity on drift and benthic resettlement of larval hydropsychid caddisflies (Ceratopsyche sparna). In the first experiment, we examined transport distance and drift re-entry in relatively large channels (9 x 1 m) with connecting patches of biofilm-covered gravel, biofilm-covered cobbles, and Cladophora-covered cobbles. In the second experiment, we focused on benthic movements and behaviors of larvae in each habitat type after settlement. In experiment 1, transport distance and number of drift re-entries varied among habitats, both being highest in gravel and lowest in Cladophora-covered cobbles. In fact, no larvae re-entered the drift after settling in Cladophora. Cladophora patches also had the highest turbulence intensity at 0.6 x depth. Findings from the second experiment revealed that drift rates were significantly higher from biofilm-covered rocks than from Cladophora-covered cobbles. Distance moved on substrates by non-drifting larvae was greatest in gravel and lowest in Cladophora patches. Moreover, larvae laid fewer and shorter draglines in gravel compared to the other substrates. Our findings indicate that habitat strongly affects dispersal decisions, transport distance, and benthic activity of these hydropsychid larvae, and hence their population distributions.
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