SIZE-BASED STRUCTURE AND PRODUCTION IN THE PELAGIA OF LAKES ONTARIO AND MICHIGAN

Analytical solutions to allometric models of predator-prey interactions in aquatic ecosystems indicate that normalized biomass spectra should consist of a smooth quadratic trend around which periodic oscillations occur. We confirm these assertions by showing that parabolas provide good models of normalized biomass as a function of body mass within homogeneous trophic groupings oi organisms (phytoplankton, zooplankton, or fish) in the pelagic food webs of Lakes Ontario and Michigan. In addition, we show that the normalized biomass spectrum for the whole pelagic community in these lakes can be modelled by a series of parabolas of constant curvature that are aligned along a smooth quadratic base, as predicted by theory. Total secondary production in Lake Ontario is predicted from these models to be 234 kcal . m(-2). yr(-1) (1 kcal = 4.19 kJ), which compares favourably with sampling estimates of about 154 kcal . m(-2). yr(-1) for the whole community except rotifers and some hypolimnetic organisms, but both are higher than particle-size conversion efficiency estimates of 75-125 kcal . m(-2). yr(-1).