Light, mixing depth and bacterivory by mixotrophic protists in Andean North-Patagonian lakes.

B. MODENUTTI,; BASTIDAS NAVARRO, M.,

Cordoba

Congreso; 16 International Congress on Photobiology.; 2014

Asociación fotobiología

Light, nutrients, mixing intensity and mixing depth areenvironmental factors that have a large effect on the ecological dynamics ofplankton. Although plankton communities are generally suspended in a well-mixedmedium, within aquatic ecosystems light may have a complex pattern of spatialand temporal variability. Vertical mixing can lead to a shortage of light ifplanktonic organisms are frequently mixed down to the bottom, whereasstratification enhances light supply by decreasing mixing depth. NorthPatagonian Andean lakes from Argentina are high light/low nutrientenvironments, in which mixotrophy appears as a suitable and very commonstrategy for exploiting the extended euphotic zone of the water column. Here wepresented an analysis of different field and laboratory bacterivory experimentscarried out under different light treatments. Bacterivory was assessed inprotists (nanoflagellates and ciliates) by computing fluorescently labeledbacteria (FLB) inside the feeding vacuoles. Result showed that ultraviolet radiation (UVR) reduced bacterivoryalthough the negative effect was more evident in mixotrophic nanoflagellates incomparison with heterotrophic ones. Protists consumption rate on bacteria wasobserved to be reduced up to approximately 70-77 % by UVR.  Finally, we showed that carbon transfer inthe microbial food web would be substantially altered by different temporalheterogeneity in vertical mixing including the UVR effect.