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Lehman, J.T. and C.E. Caceres, 1993. Food-Web Responses to Species Invasion by a Predatory Invertebrate: Bythotrephes in Lake Michigan, University of Michigan. Reprinted from Limnology and Oceanography (1993) 38(4): 879-891 Food-Web Responses to Species Invasion by a Predatory Invertebrate: Bythotrephes in Lake MichiganSeveral developments in the offshore plankton community accompanied the invasion of Bythotrephes cederstroemi Schoedler (Crustacea: Cladocera: Cercopagidae) into Lake Michigan. A native predatory cladoceran, Leptodora kindti, became significantly reduced in abundance and biomass in the presence of Bythotrephes. The offshore Duphnia assemblage, which had consisted of three species before the arrival of Bythotrephes, was reduced to dominance by only D. galeata mendotae. Abundances of Daphnia species exhibited reciprocal relationships to Bylhotrephes abundance in both space and time. The surviving Daphnia populations offshore exhibited altered daytime vertical distributions which reduced spatial overlap with the invading predator. Model calculations indicate that energetic requirements by Bytho trephes equaled or exceeded replacement production by Duphniu during midsummer of the first years of species invasion. Decreases in midsummer Duphnia biomass did not produce significant increases in midsummer algal biomass, measured as particulate chlorophyll a. Instead, physical mixing depth and epilimnetic temperature, a correlate of the intensity of density stratification, exhibited the strongest statistical relationship to Chl a over the years studied. Contact: John Lehman, University of Michigan,
Department of Biology, Center for
Great Lakes and Aquatic Sciences, Ann
Arbor, MI 48109-1048 |