Hypolimnetic aeration intensifies phosphorus recycling and increases organic material sedimentation in a stratifying lake : Effects through increased temperature and turbulence

The effect of hypolimnetic aeration on the sedimentation of inorganic and organic material as well as phosphorus was examined in a spatially comprehensive investigation in a dimictic northern temperate lake in southern Finland.Two years of aeration strongly increased the gross sedimentation of dry matter (68% 2%, mean SD) and phosphorus (87% 7%) in the aerated, deep areas.Although the organic content of the settling material decreased, the total amount of organic matter reaching the lake bottom increased by 53% 6%.Also the shallow areas were affected, although to a lesser extent.We suggest that the observed increases were due to an aeration-induced increase in the hypolimnetic water temperature and turbulence, which not only increased the mineralization of organic matter but also phosphorus recycling, and consequently the production of excess organic material.