9407159 Edmondson The purpose of this project is to conduct the last phase of a log-term study of Lake Washington that started in 1955. The lake has been subjected to a series of external disturbances, four of which have been studied as they developed. Earlier ones have been studied in cores by paleolimnological methods. An abrupt increase in the alkalinity of the lake (acid neutralizing capacity or content of alkaline substances) in 1988 is attributed to the probable effect of land development on the chemical content of streams draining the developed areas. The change was accompanied by an inconspicuous but significant change in the phytoplankton. The aim of this project is to pursue two goals: 1. Characterizing the condition of the lake by measuring on a regular schedule features that are relevant to the change in alkalinity. These are a set of chemical properties and a set of biological properties that are affected by chemical conditions. Focus is on the abundance and species composition of the phytoplankton and on the abundance and reproduction of the zooplankton. Data on some species of fish are available from State agencies and University studies. 2. Characterizing the chemical content of the streams entering Lake Washington, and relating it to the degree of development in the drainage areas. Samples are taken along streams above and below developed and undeveloped areas and places where developments are planned. These schedules are repeated at intervals during varied conditions of stream flow and weather. The area of land developed at different times in the past in each drainage area is being determined by analysis of aerial photographs. The data will be related to known chemical changes in the streams.
