Pelagic Food Webs of the East African Great Lakes

Abstract

Abst.act The pelagic food webs of the East African Creat Lales exhibit featurcs lhat suggest continuous, slrong biological interaclions as lvell as strcng interaclions between biota md rheir gcochcnical cnvironncnt. Planldvory by both veftebate md inveftebrate predators appea.s to be a major structuring force affe.ting the animal communnies. The phytoplanlbn appeu to cont ol or modify nutrient chemical conditions during m "erdles summel of stroDg inleracrions wilh lesou.ce leveh. Several case studies illuslrate the roles of these interactions in food web processes. Thc Dipteran lT\a Claobo s appetrs to be an importarl predator whose dhlribulion may be controllcd by intcractions betwccn fish plar*rivory ard tle availability ofoxytenated rctugia. The srrength of biological intcractions k supponcd not only by the patlems of exht dkt.ibutions among Af.ican Grcat Lakcs, but also by thc food \vcb chrnges obsefled when effici€nt planttilorous frsh ae infoduced into lakes. Lake Victoria is given specialalrention asa late that has exhibited changes in limnological condition during de present c€ntury which seem to be driven primdily by chan8es in nuhicnt incomo and regional climate. The neolimnologicalchanges in the lake ale asociated wirh conditions frat lcavc intc.prctablc signals in thc stfatigraphic record of the late sediments. Th'rs Victoria represents acandidate lake forcalibrationofthe tooh and mod€lslhal willbeneeded to infer pastclimaic variarions and ccosystcm changcs in orherEast African lalcs.