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Presented at the NABS Annual meeting, Pittsburgh, Pennsylvania, 2002
in Disturbance Ecology III
EFFECTS OF WATER REMOVAL ON INTRODUCED TRICHOPTERA COMMUNITY BIOMASS IN IAO STREAM, MAUI, HAWAII.
M.D. McIntosh1, M.E. Benbow1, and A.J. Burky2. 1Department of Entomology, Michigan State University, East Lansing, Michigan 48824-1115, 2Department of Biology, University of Dayton, Dayton, Ohio 45469-2320
Numerous streams throughout the Hawaiian Islands have diversions that remove freshwater for human use; however, little research has addressed the effects of this on aquatic insect communities. We studied the effect of water removal by a stream diversion on density and biomass of two introduced Trichoptera, Chematopsyche pettiti (Banks) (Hydropsychidae) and Hydroptila arctia (Ross) (Hydroptilidae), in Iao Stream, Maui, from April-August 2000. We found that both species have multivoltine lifecycles. The mean total instar biomass for each species was significantly reduced below the diversion (38% and 54% reduction for C. pettiti and H. arctia, respectively). The pooled Trichoptera biomass was significantly greater above the diversion (178.3 mg m-2 and 112.86 mg m-2 for upstream and downstream, respectively). Both species had greater densities above the diversion; however, individual mass of H. arctia 5th instars, but not C. pettiti instars, was significantly lower below the diversion. Our results suggest that reduced habitat due to lowered stream flow limits the densities of both species below the diversion, whereas lowered food quantity and quality may differentially affect H. arctia biomass through smaller body sizes. These data suggest water removal significantly affects the biomass of this introduced Trichoptera community, affecting the trophic energetics of Hawaiian stream ecosystems.
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