MODENUTTI Beatriz Estela
congresos y reuniones científicas
Deep chlorophyll máxima in North-Patagonian Andean lakes: strategies in a strong light gradient.
B. MODENUTTI,; BASTIDAS NAVARRO, M.,; E. BALSEIRO,
Congreso; ASLO MEETING; 2011
North Patagonian Andean lakes from Argentina are high light/low nutrient environments, in which mixotrophy appears as a suitable and very common strategy for exploiting the extended euphotic zone of the water column. During summer stratification these lakes exhibit the development of a Deep Chlorophyll Maxima (DCM) at the metalimnetic layers, near 1% of surface PAR irradiance. Here, we combined data form field surveys and laboratory experiments in order to analyze how organisms cope with a strong physical gradient of light. Picocyanobacteria, mixotrophic ciliates and flagellates are the main components of most DCM found in Andean-Patagonian lakes. The vertical distribution of phototrophic species is driven by a trade-off between light availability and damage by UVR. In particular, the mixotrophic ciliate Ophrydium naumanni exhibited high photosynthetic efficiency at low light intensities and further experiments showed that there is a positive correlation between light intensity and ingestion rates. Therefore, in environments where light is not limiting, an increase in light availability should increase particle uptake because phagotrophy provides essential substances for growth. These results may also indicate that changes in carbon/nutrient uptake may have important consequences for elemental (carbon:nitrogen:phosphorus) ratios.