© 1982 by The Society for Integrative and Comparative Biology
Bacterial—Invertebrate Interactions in Uptake of Dissolved Organic Matter1
Biologische Anslalt Helgoland (Zentrale) Notkestraße 31, D-2000 Hamburg-52, Federal Republic of Germany
SYNOPSIS. AS compared to integumentary uptake systems of soft-bodied marine invertebrates, bacterial systems, in terms of transport constants, are much better adapted to the low concentrations of dissolved organic nutrients encountered in coastal and offshore waters. Bacteria respond to the presence of suitable dissolved organic substrates with induction, uptake and multiplication, maintaining the concentrations of dissolved organic matter (DOM) permanently low. At realistic in situ concentrations, epidermal uptake by pelagic and epibenthic animals proceeds at such low rates that scarcely a substantial proportion of their metabolic needs is provided by absorption. In marine sediments, where the life processes of bacteria and animals are closely interrelated, the macrofauna is sheltered by shells, firm tubes and burrows, which are irrigated by means of overlying water of the water column. Hence, interstitial water with its sometimes higher concentrations of DOM is scarcely available to sediment-dwelling larger metazoans. The meiofauna mainly inhabits the few millimeters of the upper sediment layers and the thin halos surrounding irrigated macrofaunal burrows, where sufficient oxygen is available. Unless the magnitude of horizontal water movement, the amounts of diffusional nutrient supply and the percentages, by which nutrient concentrations are reduced by meiofaunal uptake, are known, estimations of nutritional benefits from uptake of DOM by meiofauna cannot be made. For all infaunal taxa, bacteria appear to represent a major food supply.