Molecular Approaches to Microbial Biomass Estimation in the Sea

Abstract

The marine environment is the largest contiguous habitat on Earth. It is composed of several distinct ecosystems including high-latitude (polar) zones, mid-latitude open-ocean gyres, equatorial upwelling systems and a diverse assemblage of coastal habitats (e.g. continental shelves, bays, coral reefs, mudflats and estuaries). These individual ecosystems have characteristics that collectively influence both their populations (e.g. types of organisms present, trophic structures) and their in situ rates of biogeochemical processes (e.g. primary production, respiration and nutrient cycling). This diversity makes broad generalizations about microbial processes in the sea impossible. It is also important to remember that our current understanding of ecological processes in the largest marine habitat (by volume), the deep sea, is rudimentary. An excellent example of our lack of general understanding of deep-sea processes was the unexpected discovery, in 1977, of luxuriant communities of previously unknown organisms surrounding regions of hydrothermal fluid discharge (Corliss et al., 1979). This discovery challenged our basic views on the obligate role of sunlight in global ecology, and presented a new paradigm for the existence of life in the biosphere (Karl, 1995a).