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

Analytical solutions to allometric models of predator-prey interaction s in aquatic ecosystems indicate that normalized biomass spectra shoul d consist of a smooth quadratic trend around which periodic oscillatio ns occur. We confirm these assertions by showing that parabolas provid e 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 p elagic community in these lakes can be modelled by a series of parabol as of constant curvature that are aligned along a smooth quadratic bas e, 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 co nversion efficiency estimates of 75-125 kcal . m(-2). yr(-1).