Benthic macroinvertebrate production

Abstract : Lake Washington is one of a system of three lakes located in northwestern Washington State (Figure 1 - 1). The lake provides a textbook example of eutrophication remediation through reduction of nutrient loads. The decline and recovery of the lake are the subject of a series of classic works by W. T. Edmondson, his students, and co-workers (Edmondson 1972; Edmondson and Lehman 1981; Edmondson 1991; Edmondson 1994). The description of the lake in this chapter is derived from these sources as well as from a Web site maintained by the King County Department of Natural Resources and Parks (http ://dnr/metrokc. gov/wlr/waterres/lakes/Monitor. htm). Lake Washington was formed at the end of an ice age roughly 12,000 years ago. Within historic times, the lake had one major inflow at its northern end, the Sammamish River, which drains Lake Sammamish. The outlet was the Black River at the southern end. The Black River flowed into the Cedar River, which led to Puget Sound. In 1916, a locked ship canal was constructed that connected Lake Washington with Puget Sound through Lake Union to the west. The level of Lake Washington was lowered by 3.3 m, and the Cedar River was converted from an outflow to an inflow. The major outflow was now through the Chittenden locks at the western end of Lake Union.

(1994). Lake Washington Fish: A Historical Perspective. Lake and Reservoir Management: Vol. 9, No. 1, pp. 148-151.

Selected major lakes and reservoirs of Washington State are depicted as polygons. Major reservoirs on the Columbia and Snake Rivers, and Lake Washington are excluded.

Coniferous Forest Biome studies of benthic communities in Lakes Washington, Sammamish, Chester Morse, and Findley include research projects on sedimentation, mineralization, macroinvertebrate populations, periphyton and oxygen uptake. Past studies suggest that oxygen uptake by sediments can be related to such trophic indicators as primary production, temperature, and nutrient fluxes (Hargrave 1969a, 1969b, Mortimer 1971, Pamatmat 1968, 1969, 1971a,1971b, and 1973).

Grazing rates and density of the crustacean zooplankton were measured in Findley and Chester Morse Lakes and Lake Sammamish, Washington. Sample analysis is incomplete at reporting time, thus estimates of production from examination of life stage biomass changes was not possible. Maximum density of crustacean zooplankton was about 10/1 in the water column of oligotrophic Findley and Chester Morse Lakes and 70/1 in mesotrophic-eutrophic Lake Sammamish during 1972. Densities averaged about 10 times greater in Lake Sammamish than in the other lakes. Copepods comprised most of the numbers in all three lakes. Grazing apparently represents a sizable loss to phytoplankton in the three lakes feeding rates experimentally determined in situ from changes in 14C tagged phytoplankton ranged from nearly one half to over six times the algal biomass per day. However, feeding rate was always less than phytoplankton productivity