Comparative ecology of plankton communities in seven Antarctic oasis lakes

Similarities and differences in the biological limnology ofseveral perennially ice-covered, amictic lakes within a 100x 100 km grid of an Antarctic desert oasis have been identified.Most of the lakes possessed the cryptophyte Chroomonas lacustrisas the dominant phytoplankter which was accompanied by otheralgae, bacteria, yeasts, and ciliates. Maximum phytoplanktondensities and extractable particulate chlorophyll a usuallyoccurred well below the poorly transparent ice covers. The sevenlakes varied among themselves but all displayed more oligotrophicthan eutrophic values for five trophic state indicators. Thehigh dissolved O₂/CO₂ ratio in these lakes caused by supersaturatedoxygen and the previously reported high proportion of extracellularphotosynthate production by the phytoplankton raise the possibilityof a significant amount of photorespiration compared to inorganiccarbon incorporation for growth. In addition to the supersaturatedoxygen, the plankton communities could be limited by low lightintensities, hypersalinity (in some lakes), available nutrients,and grazing by protozooplankton.