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A Stable Isotope Study on Seasonal Food Web Dynamics in a Eutrophic Lake
Author(s) -
Yoshioka Takahito,
Wada Eitaro,
Hayashi Hidetake
Publication year - 1994
Publication title -
ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.144
H-Index - 294
eISSN - 1939-9170
pISSN - 0012-9658
DOI - 10.2307/1941739
Subject(s) - trophic level , food web , zooplankton , phytoplankton , pelagic zone , benthic zone , plankton , environmental science , eutrophication , ecology , copepod , smelt , isotope analysis , δ15n , stable isotope ratio , oceanography , biology , δ13c , nutrient , fishery , crustacean , physics , quantum mechanics , geology , fish <actinopterygii>
Phytoplankton, zooplankton, benthic invertebrates, and pond smelt were collected in a eutrophic lake (Lake Suwa, Japan) from spring to autumn in 1986 and 1987. Their stable carbon and nitrogen isotope ratios were analyzed together with conventional examination of the gut contents of pond smelt. Temporal variations in isotope rations were similar among the organisms other than benthic animals. The @d 1 5 N values of diet for several animals in the pelagic food web were estimated, assuming a stepwise enrichment in 1 5 N with increasing trophic level. A calanoid copepod, Eodiaptomus japonicus, seemed to feed on the predominant phytoplankton, including Microcystis spp., while Microcystis did not seem to be important as an organic source for other zooplankton and pond smelt. The temporal variation of the isotope ratios of pond smelt was well explained by visual gut content analysis. It is suggested that intensive measurements of carbon and nitrogen isotope ratios of each species serve to effectively assess the yearly dynamics of the food web structure in eutrophic lakes when productivity and species composition of plankton change seasonally.