In contrast to the popular interest and "scientific" discussion of "food-chains", "balance of nature", and "community development", factual data concerning these basic ecological relationships are amazingly scant. The details of aquatic succession are as yet largely unknown. While numerous aquatic ecologists have described qualitative food cycles, practically no attempt has been made to correlate food-cycle analysis and productivity with lake succession. In an attempt to explore some of the quantitative aspects of these basic processes, a series of studies have been initiated on a senescent lake near Minneapolis for the purpose of analysing the contemporary food cycle or metabolism, of the lake in relation to its utilization of nutrient and its disposition of metabolic products. These products, becoming semi-fossilized at the lake bottom, serve as indices for evaluating the lake metabolism during the earlier periods of its development. Since this ambitious project is not yet completed, this dissertation does not cover the entire program; rather, it presents the results thus far obtained on four distinct, though related, aspects of the general problem of ecological dynamics in a senescent lake.