The influence of iron and manganese on nutrient cycling in shallow freshwater Antarctic lakes.

Abstract

Mesotrophic Heywood Lake and oligotrophic Sombre Lake, Signy Island, were studied over 1 full yr. The development of deep water anoxia in Sombre Lake is accompanied by release, from the sediments, of N, Si, P, Fe and Mn. There are strong seasonal correlations between the vertical profiles of Fe and P, under the ice cover in Heywood Lake. Nitrogen profiles appear independent of the other determinants, Si, P, Fe and Mn. Towards the end of the period of bottom-water anoxia, during the spring melt, high concentrations of ferrous, released from the anoxic sediments, have been detected in oxygenated waters. This apparent stability, in the presence of oxygen, may be attributable to a combination of low pH and the possible influence of high concentrations of humic acids from the melt inflows. -from Author