Summer fluctuations of microbial planktonic communities in an eutrophic lake. Cierva Point, Antarctica

IZAGUIRRE, I.; MATALONI, G.; ALLENDE, L.; VINOCUR, A.

JOURNAL OF PLANKTON RESEARCH

Oxford Journals

Lugar: Oxford; Año: 2001 vol. 23 p. 1095 - 1109

0142-7873

Abstract A eutrophic lake at Cierva Point, Antarctic Peninsula was surveyed during summers 1997 and 1998. Phytoplankton size fractions (micro, nano and picoplankton) were analysed, as well as the abundance of bacterioplankton and planktonic ciliates. No permanent vertical stratification was found owing to the shallowness of the lake. Both nutrient concentrations and chlorophyll a values indicated highly eutrophic conditions, which are a consequence of a natural enrichment by seabirds. Significant differences in temperature between the 1997 and 1998 seasons strongly influenced most of the biological features. The phytoplankton community showed a high algal species-richness with important contributions of epilithic, cryobiontic and soil algae. The dominant algal group was Chlorophyta, mainly represented by Chlamydomonas aff. celerrima, followed by Chl.  aff. braunii. Some replacement of phytoplanktonic species took place in summer and was more evident in 1998. Picophytoplankton reached high densities, similar to those reported from other Antarctic lakes. Bacterioplankton abundances were typical of eutrophic and hypereutrophic lakes. There was a positive correlation between bacterial and total phytoplankton abundance. Ciliates reached some very high peaks, with higher figures than those reported for other Antarctic systems with similar trophic status.