Hypolimnetic aeration intensifies phosphorus recycling and increases organic material sedimentation in a stratifying lake : Effects through increased temperature and turbulence
Juha Niemistö, Köngäs, Petrina, Laura H. Härkönen, Jukka Horppila
Abstract
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.