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Communication at the NABS Annual meeting, Keystone, 2000
(116) GRAZER INTERACTIONS IN A TROPICAL LOWLAND STREAM.
N.C. Barbee. Department of Ecology, Evolution and Marine Biology, University of California, Santa Barbara, CA, USA 93106
I examined the interaction between Glossosomatid caddisflies and Sicydium gobies in a tropical lowland stream on the Pacific Coast of Costa Rica to assess the effects of these two abundant grazers on periphyton abundance and sediment accumulation, as well as the effects of Sicydium on Glossosomatid distributions. I manipulated the presence/absence of Glossosomatids and gobies in riffles using a cross-classified experimental design. Glossosomatids were allowed to naturally colonize pre-conditioned artificial substrata within small (30cm2) in situ cages that were either open or closed to gobies. To exclude Glossosomatids, substrata in half of the cages were raised off the surrounding streambed. After 4 weeks, both Glossosomatids and Sicydium had a significant negative effect on periphyton biomass (as measured by chl a and AFDM). However, only Sicydium were able to keep sediment from accumulating on caged substrata. Furthermore, there were more Glossosomatids in +Sicydium cages than in –Sicydium cages, suggesting that gobies facilitate the colonization of substrata by Glossosomatids by either removing sediment from hard substrata or by improving their access to algal resources.
Presented at 10:15 AM on Tuesday, May 30, 2000 in Species Interactions II
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