| Summary: | Ecological studies of the freshwater lakes at the Schirmacher Oasis have been reported. Physical variables such as atmospheric temperature, solar radiation, winds, etc. showed that the environment at Schirmacher Oasis is less extreme than near the coast. Lakes showed similarities in structure and were classified as proglacial lakes in the rock basins. NO sub(3) and PO sub(4) in lake waters were low ranging from 0 to 3.08 mu M and 0.06 to 0.4 mu M (except for one value of 1.07) respectively. These values were comparable to other freshwater lakes in Antarctica. SiO sub(3) concentration showed large fluctuations between lakes. Urea, ammonia, total nitrogen (TN) and dissolved organic phosphorus (DOP) attained maximum values of 1.39, 1.79, 16 and 0.52 mu M in surface waters and contributed as an important N and P substitute to the algal growth. While chlorophyll a was low, surface values was lower than 0.7 mg m sup(-3) , the primary productivity was variable. Thick moss beds and benthic algal mats were dominant in some lakes. Based on these characteristics the lakes were grouped as oligotrophic in nature. Organic carbon content of sediment was low, ranging from 0.05 to 1.8% and consequently the faunal density was also low. Protozoans, Nematodes, Turbillaria, Tardigrades and Rotifers were dominant faunal groups. Bacteria and yeasts were predominant in soils and lake sediments. Detritus and associated bacteria form an important source of food for the opportunistic feeders such as metazoans. Long term studies of the lake environment from 1981 to 1994 have shown fluctuation in nutrients and chlorophyll without any signs of eutrophication. POC, sediment bacterial counts and microfaunal density showed an increasing trend. Survival of Phoromidium sp. for several years in lake waters was noted as a remarkable feature which supported the view that the reproductive cycle in these lakes maintains a steady state, in spite of harsh changes in the environmental conditions
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