ABSORPTION OF DISSOLVED OXYGEN BY THE UPPER LAYER OF BOTTOM SEDIMENTS IN A SMALL LAKE DURING LATE WINTER

Abstract

The results of measurements of dissolved oxygen in the vicinity of the water-sediment interface in a small mesotrophic Lake Vendyurskoe (Southern Karelia) at the end of the ice-covered period are reported. The measurements were carried out in April 2008 on 18 slope sites (depths from 2.5 m to 9.3 m), with a predominance of water-saturated silt. The content of dissolved oxygen decreased sharply at the contact with silt. The maximum oxygen gradient reached 9 (mgO2/l)/cm on the silt surface . The rate of oxygen consumption by the sediment was maximal at a depth of 6-8 m. This rate was 1.5 times lower in shallower and deeper areas. The amount of dissolved oxygen absorption by sediments was estimated based on the lake’s bathymetric curve. A comparison of our estimates with the measured dissolved oxygen content in the water column suggests that over 60 % of oxygen reduction is the result of absorption by silt and less than 40 % is due to the destruction of labile organic matter in the water column at the stage of winter stagnation.

Keywords

• dissolved oxygen
• bottom sediments
• absorption of dissolved oxygen
• shallow lake
• ice-covered period