The Phosphorus Status of Eutrophic Lake Sediments as Related to Changes in Limnological Conditions—Total, Inorganic, and Organic Phosphorus

Abstract

AbstractTo aid in the assessment of the role of sediments as a source of P to lake waters and to provide insight into the factors which may influence sediment P release, changes with time in the P status of noncalcareous sediments of a eutrophic lake were related to changes in sediment C and N, surface water composition, pH, temperature, and phytoplankton growth.The nature and extent of changes in sediment P status and the relationship of these changes to limnological conditions differed with location in the lake. Changes in sediment composition were greatest in a bay which received agricultural runoff in the early spring. This additional supply of nutrients apparently provided the initial impetus for increased surface water biological activity in the spring relative to other locations as reflected in increased surface water organic C and N, turbidity, and phytoplankton growth. At this location, total sediment P, C, and N decreased during the late spring and early summer. These changes corresponded to the period of exponential growth of the lake phytoplankton population. During the late summer and early fall when plankton growth entered the stationary and declination phases, sediment organic C, total N and P increased, evidently as a result of the deposition of detritus containing these elements.Changes in inorganic P accounted for most of the changes in total sediment P. Combining data from all sampling locations in the lake, sediment inorganic P was not correlated with changes in surface water temperature or pH, but was inversely correlated with surface water organic C. The results thus indicate that sediment inorganic P was directly related to the biological productivity of the surface waters, and in at least one location, sediments served as a significant source of P to these waters supporting increased biological growth.