The availability and utilization of nutrients by algae and rooted aquatic plants was measured in laboratory studies using both sorption and algal growth assays. The tests were conducted to evaluate contributions of phosphorus to the Madison (Wisconsin) lakes from septic tanks, agricultural runoff, and urban drainage and to measure changes in the nutritional status of six lakes which were manipulated for water quality improvement by nutrient inactivation or hypolimnetic aeration. The assay techniques are described and results are compared with chemical determinations of plant nutrients. Comparative rates of phosphorus sorption by different types of aquatic plants were determined by three methods in order to understand how the plants compete for limited phosphorus sources. In situ and laboratory experiments indicated that naturally layered lake muds in three lakes release soluble phosphate-phosphorus when disturbed and will be competitively sorbed by both muds and plants in aerobic conditions.

"February 1974." "Project Officer, Mr. Thomas E. Maloney, National Environmental Research Center." "U.S.G.P.O. sales statement incorrect in publication." Includes bibliographical references. " Grant R-801361, Program Element 1BA031."