The unifying principal of this research is the linkage between ecosystem-level processes and the community ecology of streams. Geothermal activity associated with volcanism is significant in determining regional landscape patterns in surface water chemistry and biota along the volcanic spine of Central America. Geothermal processes introduce natural chemical discontinuities into streams e.g. high levels of soluble reactive phosphorus (SRP) that interrupt the stream continuum and influence basic ecological processes. The main objective of this work is to test how geothermally- introduced chemical discontinuities structure lowland tropical stream communities. The investigators (1) determine if geothermal nputs affect algal primary production and community composition in different light environments (in light gaps and shaded sections of an interior forest stream and in an open pasture stream); (2) evaluate community- and ecosystem-level response to simulated geothermal inputs of SRP using flow- through bioassays and whole-system manipulations, respectively; and (3) determine how fish influence net primary production and algal community structure above and below sites of geothermal discontinuities and examine interacting effects of fish and phosphorus amendments on primary production. //
