Phytoplankton vertical distribution in a South Andean Lake (Argentina) during a deep chlorophyll maximum

QUEIMALIÑOS, CP

Montecatini

Congreso; 2nd European Phycological Congress; 1999

Vertical profiles of phytoplankton were measured in a deep (90m), ultraoligotrophic lake of South andes (Patagonia, Argentina), during the stratifying period. These profiles were analysed in relation with light intensity, temperature and the presence of a recently described Deep Chlorophyll Maximum, which is caused by endosymbiotic Chlorella. Phytoplankton community of Lake Moreno Oeste was largely dominated by nanoflagellates belonging to Prymnesiophyceae, Cryptophyceae and Dinophyceae. Almost all species were present during the whole studied period and showed a rather event distribution in the water column. However, it was noticeable that Rhodomonas lacustris was the only species that presented its highest values in coincidence with the DCM. These peaks were registered just below the thermocline, where light intensity was about 1% of surface irradiance, always measured at noon. This evidence accords with the cryptomonad ability to grow and reproduce under low light intensities, due to the particular photosynthetic system within this group.