Observations on the formation and breakdown of the oxidized microzone at the mud surface in lakes

Evidence is presented indicating that the winter thickness of the oxidized microzone at the surface of lake muds may depend upon turbulent displacement of the uppermost sediments into the overlying aerated water, as well as upon the reducing power of the sediments themselves. It is also suggested that this winter oxidized layer may disappear mainly from the surface downward, owing to the greater oxygen consumption there brought about by decomposition of sedimented plankton. Lastly, evidence for a final evolutionary phase of lake sterility, due to development of extremely reducing conditions in the bottom mud, is examined and rejected.