Characteristic Size Distributions of Integral Benthic Communities

Abstract

Uniform size spectra comprising bacteria through macrofauna characterize six intertidal communities when biomass concentration is expressed as a function of logarithmic intervals of organism size. Although total community biomass ranged from 70 cm 3 /m 2 to 1283 cm 3 /m 2 , biomass distribution patterns are consistent over the entire size spectrum. Three biomass peaks, at 0.5–1 μm equivalent spherical diameter (29–81 cm 3 /m 2 ), 64–125 μm (0.5–4 cm 3 /m 2 ), and > 2 mm (2.4–1283 cm 3 /m 2 ) were separated by typically low biomasses near 8 μm (0–0.04 cm 3 /m 2 ) and 500 μm–1 mm (0–1.5 cm 3 /m 2 ). The peaks correspond to bacteria, interstitial meiofauna, and macrofauna, respectively. Size discontinuities between grain colonizers and interstitial microfauna or epibenthic microflora near 8 μm, and between interstitial meiofauna and burrowing or sedentary macrofauna near 500–1000 μm, are reflected in low biomass values in these size intervals. Comparison of the data with recast published data for other locales shows that similar size distributions characterize a wide variety of benthic communities, including estuarine to abyssal. This study is the first to describe quantitatively, in detail, the size composition of marine benthic communities.Key words: benthic, community, bacteria, meiofauna, macrofauna, size, biomass, Sheldon spectrum