The Effects of Interaction of Rate of Food Supply and Population Density on the Bioenergetics of the Opportunistic Polychaete, Capitella capitata (type 1)

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 $20\circ C$ 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: $\bar{B}$). Maintenance ration, where growth = 0%, occurred at an R: $\bar{B}$=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.