Benthic biomass size spectra in shelf and deep-sea sediments

[摘要] The biomass distributions of marine benthic metazoans (meio- to macro-fauna,1 μg–32 mg wet weight) across three contrasting siteswere investigated to test the hypothesis that allometry can consistentlyexplain observed trends in biomass spectra. Biomass (and abundance) sizespectra were determined from observations made at the Faroe–Shetland Channel(FSC) in the Northeast Atlantic (water depth 1600 m), the FladenGround (FG) in the North Sea (150 m), and the hypoxic Oman Margin(OM) in the Arabian Sea (500 m). Observed biomass increased with bodysize as a power law at FG (scaling exponent, b = 0.16) and FSC (b = 0.32),but less convincingly at OM (b = 0.12 but not significantly different from0). A simple model was constructed to represent the same 16 metazoan sizeclasses used for the observed spectra, all reliant on a common detrital foodpool, and allowing the three key processes of ingestion, respiration andmortality to scale with body size. A micro-genetic algorithm was used to fitthe model to observations at the sites. The model accurately reproduces theobserved scaling without needing to include the effects of local influencessuch as hypoxia. Our results suggest that the size-scaling of mortality andingestion are dominant factors determining the distribution of biomass acrossthe meio- to macrofaunal size range in contrasting marine sedimentcommunities. Both the observations and the model results are broadly inagreement with the "metabolic theory of ecology" in predicting a quarterpower scaling of biomass across geometric body size classes.

[学科分类] 地球化学与岩石