Buck, K, R, Monterey Bay Aquarium Research Institute, Moss Landing, USA, buku@mbari.org
Barry, J, P, Monterey Bay Aquarium Research Institute, Moss Landing, USA, barry@mbari.org
Levesque, C, , Monterey Bay Aquarium Research Institute, Moss Landing, USA, levesque@mbari.org
Lovera, C, , Monterey Bay Aquarium Research Institute, Moss Landing, USA, lovera@mbari.org
Kuhnz, L, , Monterey Bay Aquarium Research Institute, Moss Landing, USA, Kuhnz@mbari.org
Carman, K, R, Louisiana State University, Baton Rouge, USA, zocarm@lsu.edu

THE MICROBIAL FOOD-WEB OF THE DEEP-SEA BENTHOS

The structure and function of microbial food webs in deep-sea benthic communities influence greatly the magnitude of carbon remineralization and recycling that occurs at the sediment-water interface. In contrast to epipelagic microbial communities, the surficial sediments of deep-sea communities are dominated by heterotrophic bacteria, which presumably comprise most of the food consumed by higher trophic levels. The biomass of eukaryotic grazers seems to be dominated by metazoans (e.g. nematodes). Protistan bacterial grazers are few but specialized for grazing on surfaces. For several years we have been collecting samples from hadal and bathyl benthos off central California to characterize the trophic structure and rates of carbon flow within the sediment community. Bacteria overwhelmingly (>95%) dominate total biomass. Protists, metazoan meiofauna (principally nematodes) and macrofauna comprise the remaining biomass, with approximately (order of magnitude) equal weight. The effect of these three groups on bacterial biomass, however, is likely disproportionate to their biomass. Smaller organisms will have lower individual metabolic rates, but higher mass-specific carbon consumption. We compare the allometry of faunal fractions to investigate their potential impact on bacterial biomass.