Effect of detritus supply on trophic relationships within experimental benthic food webs. I. Meiofauna-polychaete ( capitella capitata (Type I) Fabricius) interactions

Abstract

In a long-term (40–55 wk) microcosm experiment, the presence of the polychaete Capitella capitata (Type I) Fabricius reduced population densities and trophic transfer efficiencies (detritivore production per amount of detritus supplied) of the nematode Diplolaimella chitwoodi Gerlach at high (150 mg N · m −2 · day −1) detritus ration and of the harpacticoid copepod Tisbe holothuriae Humes at low (50 mg N · m −2 · day −1) detritus supply. The rarer nematodes Theristus ostentator Wieser & Hopper and Paracyatholaimus pesavis Wieser & Hopper fed at depth on fungal hyphae attached to polychaete fecal pellets thereby minimizing contact with the other metazoa. In a series of short-term (4-day) growth experiments, the presence of either Diplolaimella chitwoodi or Tisbe holothuriae reduced daily weight-specific growth (g increase · g worm −1 · day −1) of Capitella capitata on separate diets of mixed cereal and red seaweed, Gracilaria foliifera (Harvey) Taylor, detritus. Both sets of experiments suggest that Capitella capitata competes for food with Diplolaimella chitwoodi and Tisbe holothuriae. Meiofauna-polychaete interactions were dependent, in part, upon the degree of similarity among species in food requirements and habitat preferences, and may incorporate a variety of regulatory mechanisms other than competition or predation.