HR: 09:45h
AN: NB41A-06    [Abstracts]
TI: Diatom Assemblages as Indicators of Solute Levels in Lowland Neotropical Streams, Costa Rica
AU: * Bixby, R J
EM: bbixby@uga.edu
AF: Institute of Ecology, University of Georgia, Athens, GA 30602 United States
AU: Wydrzycka, U
EM: ursula_maria@hotmail.com
AF: Escuela de Ciencias Biol ógicas, Universidad Nacional, Heredia, Costa Rica
AU: Pringle, C
EM: cpringle@uga.edu
AF: Institute of Ecology, University of Georgia, Athens, GA 30602 United States
AB: Previous research in streams draining lowland rainforests of La Selva Biological Station, Costa Rica, has shown that the invertebrate species composition does not differ between solute-poor [soluble reactive phosphorus (SRP) < 10 μg L^-1] versus solute-rich (SRP > 100 μg L^-1) streams that receive groundwater enriched with solutes from geothermal activity. In contrast, algal community analyses shows that solutes play important roles in structuring diatom assemblages in these high- and low-solute streams. Periphyton samples were collected in the wet and dry seasons from epipelic and epilithic substrates in light gaps in streams along a solute gradient. High- solute streams were dominated by taxa associated with high conductivity [i.e., Seminavis sp. and Bacillaria paxillifer (O.F. Müll.) Hendey]. In contrast, cosmopolitan and acidophilic taxa (i.e., Nupela praecipua Reichardt, Navicula longicephala Hustedt, and Frustulia spp.) were most common in low-solute, poorly buffered streams. These results suggest that diatom assemblages in high-solute streams are most likely influenced by a suite of solutes, including phosphorus; low-solute streams have diatom assemblages characteristic of poorly buffered, oligotrophic conditions, and, more importantly, low pH. While these low-solute streams generally have circumneutral pH, diatom response illustrates their poor buffering capacity.
DE: 1806 Chemistry of fresh water
DE: 9360 South America
SC: North American Benthological Society [NB]
MN: 2005 Joint Assembly