Phytoplankton structure and dynamics in a turbid Antarctic lake (Potter Peninsula, King George Island)

UNREIN, F.; VINOCUR, A.

POLAR BIOLOGY

Springer

Año: 1999 vol. 22 p. 93 - 101

0722-4060

Qualitative and quantitative changes in thefreshwater phytoplankton from one of the largest lakesin Potter Peninsula were studied during the summerperiod of 1995/1996. The main limnological featureswere analysed. This research constitutes the first studydealing with the phytoplankton structure and dynamicsfrom lakes in Potter Peninsula. Due to the mixing of thewater column by the constant wind action during theice-free period, neither physical, chemical nor biologicalparameters showed di€erences between depths. Solublereactive phosphorus remained low (26 ug l-1) while totalphosphorus concentrations were up to 232 lg l)1. Sus-pended solids and total phosphorus di€ered significantlybetween the two basins in which the lake is divided.Sixty-five taxa were identified. The Bacillariophyceaewas the dominant class followed by Chrysophyceae.Achnanthes lanceolata var. haynaldii and Hydrurus foe-tidus (cysts) were the dominant species. Tychoplanktonicspecies were the best represented in terms of abundanceand species richness. The principal component analysiscarried out with abiotic variables showed a temporalgradient characterised by the augmentation of sus-pended solids, total phosphorus, conductivity, pH andNH4-N to the end of the summer period. The PrincipalComponent Analysis performed with biotic variablesalso showed a temporal trend related to a decline inphytoplankton density and an enhancement of chloro-phyll-a despite a slight increase of light limitation duringthe study period. This inverse relation may be due to thepresence of picoplankton in chlorophyll-a samples. Thepotential e€ect of grazing on the phytoplankton struc-ture is a subject to be tested in future studies.