Faunal trophic interaction in an oligotrophic-dystrophic lake (Shirakoma-ike, Japan).

The trophic interaction in the pelagic food web of oligotrophic-dystrophic Lake Shirakoma-ike was investigated by a stable isotope technique. Carbon and nitrogen isotope analyses revealed the trophic interaction among Piona carnea (a water mite), Chaoborus sp. (a phantom midge), Daphnia longispina (a cladoceran), and Acanthodiaptomus pacificus (a calanoida copepoda). The δ¹³C values for estimating the relative contributions of D. longispina and A. pacificus to carnivores were used, and they were also used for the constraint of the trophic enrichment factor of δ¹⁵N. Both Chaoborus sp. and P. carnea were suggested to consume D. longispina and A. pacificus at almost the same ratio (1 : 1). However, both carnivores preferred A. pacificus to D. longispina, because D. longispina was much more abundant in the lake than A. pacificus. Omnivory of P. carnea was also analyzed by the mixing model. [ABSTRACT FROM AUTHOR]