The effects of interaction of rate of food supply and population density on the bioenergetics of the opportunistic polychaete, Capitella capitata (type 1)1

Abstract

Weight‐specific growth rates, population production, and trophic transfer efficiency (worm production/food supply) of different size classes of the polychaete Capitella capitata (type 1) were measured in the laboratory at 20°C under varying conditions of population density and rate of food supply (ration). A hyperbolic tangent function was fitted to the response of individual growth to unit nitrogen of food supply available per unit nitrogen biomass of worm (R : B̄). Maintenance ration, where growth = 0%, occurred at an R : B̄ = 0.08; i.e. a 0.08 g N daily ration of food was needed to maintain 1 g N biomass of C. capitata. Maximum daily individual growth rates of 21, 19, and 15% were predicted for small, medium, and large worms. The individual growth data were combined with long term‐population data collected at three food rations (50, 100, and 150 mg N m−2 d−1) to estimate long term population production. Changes in population density and the presence of meiofauna reduce the actual worm production for a given rate of food supply. Population production and trophic transfer efficiency changed dramatically as a function of rate of food supply, worm size, and biomass.