289 Is the diversity and functioning of benthic biofilms affected by watershed land use in tropical streams?

Tuesday, May 19, 2009
Ambassador Ballroom
Sofia Burgos , Institute for Tropical Ecosystem Studies, University of Puerto Rico, San Juan, PR
Alonso Ramirez , Institute for Tropical Ecosystem Studies,, University of Puerto Rico, San Juan, PR
Changes in the biodiversity and functioning of stream ecosystems can result from watershed disturbances related to land use. Disturbance is known to eliminate sensitive species from biofilm communities and increase dominance by more resistant groups in impacted sites.  It can also change ecosystem function as not all species are equal. Understanding how land use alters benthic biofilm composition and function is key to understand how streams respond to land use changes. In this study, 15 tropical streams were analyzed in term of their physicochemical parameters, benthic metabolism, and biofilm composition along a land use gradient. Streams formed a clear gradient in conductivity, but were not clearly related to land use as expected. Benthic biofilm metabolism (measured using dark and light chambers) showed that gross primary production and respiration rates ranged from 0 to 55 mg O2/m2/h.   Biofilms biodiversity was analyzed for eukariotes using molecular techniques (e.g. TRFLP). Biodiversity ranged from 36 to 72 species and was highly diverse in all streams irrespectively of land use.  Overall, we found high variability among streams in biofilm diversity and metabolism, suggesting that factors at the watershed level (e.g., land use) are not the main factors controlling them.
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