The ways in which the community of algae and bacteria, the periphyton community, at the sediment surface in lakes controls the fluxes of oxygen, carbon and phosphorus at the water-sediment interface will be studied. The research is organized around four tasks: 1) elucidation of the mechanisms involved in producing the day-night fluctuations of phosphorus afflux from the sediments to the overlying water; 2) determination of the importance of algal heterotrophy and tolerance of suboxic conditions in the maintenance of the algal community under the seasonally changing conditions present at the sediment-water interface; 3) identification and quantification of the roles of the biological and physiochemical factors at the sediment-water interface that are involved in the control of oxygen dynamics of lake hypolimnia; and 4) determination of the various sources of nutrients for the algae and bacteria of the periphyton community. The research will be conducted at two sites: an alkaline lake, Lawrence Lake, in Michigan; and an acidic lake in the vicinity of Orno, Maine. State-of-the-art systems will be used for the isolation and manipulation of periphyton that permits variations in light levels and the chemical composition of the "porewater" solutions in which the periphyton is grown. Extremely detailed measurements of chemical conditions at the boundary layer between sediment and the water column will be made with a computer-aided microelectrode data acquisition system. Dr. Klug's research team has pioneered in the use of this system in studies of lake biogeochemistry. The significance of this research is its focus on phosphorus dynamics of lakes. Phosphorus has been identified as the nutrient responsible for the euthrphication of many lakes and rivers. Understanding factors that control phosphorus dynamics in these water bodies is clearly important to their management. Dr. Klug is a world leader in the study of lake biogeochemistry. The institutional support for this research is outstanding. The Ecosystem Studies Program recommends award of this grant.
