What determines the slope of a plankton biomass spectrum?

Abstract

A number of studies have been performed to understand the characteristics of biomass (size) spectra in aquatic plankton communities around the world. Although the area below a biomass spectrum curve represents the abundance or biomass of a plankton community, it has been hypothesized that the slope and shape of a biomass spectrum are determined by rates of growth, respiration, mortality and trophic dynamics. Observations of biomass spectra indicate that the slope of a biomass spectrum is around −1 on the logarithmic coordinates. Empirical hypotheses of growth-survival and the theoretical framework on biomass conservation based on the rates of individual body growth and abundance change have been developed for interpreting the slope and domes of a biomass spectrum. Here, a mathematical method is developed for estimating specific rates of body growth and abundance change from observations of biomass spectra, and a mathematical model is constructed for the relationship between a biomass spectrum slope, community assimilation efficiency and trophic levels.