THE CHEMICAL COMPOSITION OF BOTTOM SEDIMENTS IN NORTHERN LAKE LADOGA AS AN INDICATOR OF LONG-TERM VARIATIONS IN THE LAKE ECOSYSTEM

Abstract

The chemical composition of Lake Ladoga sediments was studied. Nutrients were found to accumulate in the oxidized top layer of the sediments in the deep-water part of the lake. The content of P, N, Fe, Mn increased with water depth and where the sediments had a finer particle size composition. Bays exposed to considerable human impact contained sediments formed under reducing conditions, with higher oxygen demand and high rates of organic matter decomposition. Nutrient flows from the sediments to the water column corresponded to the level typical of eutrophic lakes. Changes in the distribution of nutrients down the sediment suggest that human activities in the catchment, even if short-term, are comparable in effect with the action of natural-climatic and tectonic factors.

Keywords

• sediments
• nutrients
• eutrophication