bio155_edmondson_lakewashington_94 - ~~ f)p~tJDfCt.) W. T....

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Unformatted text preview: ~~ f)p~tJDfCt.) W. T. Edmondson Department 0/ Zoology. N]-15. u~" o/Washington. Seattle, WA 98195. ABSTRA cr , Edmondson, W. T. 1994. Sixtyyean of Lake Washington: a curriallwn \itae. Lake and Resew. Manage. 10 (2):75-84. The purpOle ollhl. paper II to list known diStUrbances of Lake Washington, to desaibe the eaea on the lake of several of them. and to dilcutl resultS In tenns of whole-lake qualioexperimena. Eutrophication with treated sewage eBluent and the divenion of diluent are created as experimeoa, with nuutent manipulation, whidt change the phytoplankton convnuoitySU11CQJ reo A later unexpecled increase in uansparenq is traced through a chain of predatoR to flood control measures In the iargest Inlet. An inaease In alkalinity, accompanied by dtanges in phytoplankton, 11 ataibuted to real estate land development. The role of ~eolimnologica1lnfom1adon is UiUlU2ted. Key Words: whole-lake quali-experimenu, land-lake InteracUons, eulrophlauon. plankton community lUUCture. predadoo. the PleistOCene. For a shon time it was conneCted to PugetSotind. asmdenced by the presence insedimenlS of diatoms characteristic of brackish water (5. Eo B. Abella, pen. comm.). During its existence the Jake has been subjected to many disturbances. m~t made by people living in its drainage area (Table 1). Each disblrbance that has been studied had a measurable effect on the lake (Table 2). In 63,000 B. P. (Before Present), Lake Washington received considerable ashfalIfrom the explosion ofML M2~_'!!a tha.tformed Crater Lake. The sedimentary record shows distinct, temporary effects on planktonic and littoral diatoms (Abella 1988. see also Edmondson 1984). Evaluation of the effect on the lake community and the terreSbiai community around it b complicated by a simultaneous change in climate (Abella 1988, Leopold et a1.1982). In about 1100 B. P. ( = 850 AD.), a large area of the Pacific Northwestwas shaken by earthquakes. Forested hillsides slid into Lake Washington, creating sunken foreslS of standing trees (KarlinandAbeUa 1992). Aby.. product of this event was a widely distributed layer of silt in the sediment that selVes as a dear time mark (Abella, pen. comm.). A transitory effect on the plankton is shown by a change in the proportions of diatom species. Limited activities of the small native human population probably had little effect on the lake. but that changed with the arrival of European settlers (Bagley 1916). Some of the disturbances included in Table I were not accompanied by limnologiCalsrudies. but probable The title of this paper refen to the fact that exactly 60 yean ago the first genuine limnologial study of Lake Washington was made. from 14January 19S5 to 20January 19S4 (Scheffer and Robinson 19S9). RexJ....
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bio155_edmondson_lakewashington_94 - ~~ f)p~tJDfCt.) W. T....

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