This project was initiated in 1969 to identify and study processes that were contributing to accelerated eutrophication of Lake Michigan.^Results of several different types of nutrient enrichment experiments showed that inputs of phosphorus to the lake accelerated phytoplankton growth and eutrophication.^It was also shown that there was an imbalance in the inputs of phosphorus and silica to the lake relative to the amounts required by diatoms.^As a result silica concentrations decreased over a 30- to 40-y period to levels that limited diatom production and favored the growth of blue-green and green algae, a generally undesirable environmental change.^These findings indicated that additional research should be conducted on effects of phosphorus and silica on phytoplankton growth and on effects of tributary inputs, which supply large amounts of phosphorus.^In addition research was conducted on the silica cycle to understand processes involved in changing the geochemical environment from silica replete to silica limited for diatom growth.

November 1, 1969 to September 30, 1981. Prepared for the U.S. Department of Energy under contract no. DE-AC02-76EV02003.