Effect of UVR on Lake Water and Macrophyte Leachates in Shallow Andean-Patagonian Lakes: Bacteria Responses to Changes in Optical Features.

MARCELA BASTIDAS; BALSEIRO, E.G; MODENUTTI, BE

Photochemistry and Photobiology

Wiley Interscience

Año: 2009 vol. 85 p. 332 - 340

0031-8655

The aim of this study was to identify bacterial responses in twoshallow lakes from Patagonia to UV-irradiated dissolved organicmatter (DOM) coming from different sources. We carried outlaboratory experiments in which natural lake water andPotamogeton linguatus leachates were irradiated (UVA-340fluorescent tubes Q-Panel) or kept in darkness. Natural bacterialassemblages were then incubated in four treatments: natural lakewater, irradiated lake water, macrophyte leachate and irradiatedmacrophyte leachate. We estimated bacterial abundance, compositionand activity, and changes in the optical features ofDOM. Our results showed that the addition of leachates causedan increase in the DOM mean molecular size. After UVexposure, a high bacterial activity was observed in lake watertreatments. On the contrary, carbon uptake by bacteria wasreduced in the irradiated leachate treatment. The degree ofaromatization in the leachate treatments increased and thus maycontribute to a dissolved carbon less available for bacterialactivity. Regarding the bacteria assemblage we observed thatb-Proteobacteria outcompete the other groups in the leachatetreatments, this group being more efficient at utilizing the highmolecular weight DOM. These results highlight the importanceof UVR interacting with different DOM sources in bacteriaresponses of shallow lakes.