The Role of Detritus at the Land-Sea Boundary

Abstract

Mann, K.H., 1986. The role of detritus at the land-sea boundary. In: P. Lasserre and J.M. Martin (eds), Biogeochemical Processes at the Land-Sea Boundary. Elsevier, Amsterdam. Detritus derived from vascular plants (seagrasses, marsh grasses and mangroves) contains much structural material that is indigestible to most animals. Such detritus must undergo a lengthy period of fragmentation and colonization by bacteria and fungi before it constitutes nutritious food for animals. During the process, a large proportion of its carbon is oxidized to CO 2 . On the other hand the algae (seaweeds, benthic microalgae and phytoplankton) form detritus that is directly usable by animals, though its nutritional value may be further enhanced by microbial colonization. As a result of this difference, rather a small proportion of the carbon production of salt marshes, seagrass beds and mangroves enters coastal food webs. Isotope studies indicate that most of the carbon in coastal animals is derived from algal sources, with minor contributions from vascular marine plants. The dissolved organic matter produced by both phytoplankton and macrophytes is readily taken up by bacteria and these provide an important food source for planktonic and benthic animals. Bacteria associated with detritus food webs are an important mechanism for conserving nitrogen in coastal ecosystems.