BAFFICO gustavo Daniel
Community structure and photosynthetic activity of epilithon from a highly acidic (pH <= 2) mountain stream in Patagonia, Argentina
BAFFICO, G.; DIAZ, M.; WENZEL, M.; KOSCHORRECK, M.; SCHIMMELE, M.; NEU, T.; PEDROZO, F.
Lugar: Tokyo; Año: 2004 vol. 8 p. 463 - 473
We explored the benthic community living on stones in an acidic(pH ≤ 2) stream of active volcanic origin from Patagonia, Argentina, by combining in situ measurements (temperature, pH, conductivity, dissolved oxygen), Photosynthesis of intact biofilms (measured with microsensors by the light-dark shift method), pure culture experiments on isolated algae, and confocal laser scanning microscopy on the biofilms. The epilithon of the Agrio River was dominated (99% of total biomass) by one species: Gloeochrysis sp (Chrysophyceae). This species was observed as brown, mucilaginous, 200 µm thick films on stones, growing in clumps in a dense matrix of fungal hyphae, bacteria and inorganic particles held together by extracellular polymeric substances. Gloeochrysis was isolated and cultivated. The photosynthetic rate measured at saturation irradiance was 120 µmol O2 (mg Chl a)-1 h-1 under lab conditions and the saturation rate of photosynthesis by CO2 was 90 µmol O2 (mg Chl a)-1 h-1 for oxygen evolution. Photosynthetic activity of the biofilm was light dependent and saturated above 200 µmol photons m-2 s-1. In the dark, the stone surface became anoxic. Our data suggest that primary production in Agrio River was not limited by light, carbon, or phosphorous but instead, nitrogen limited.