Bacteria in the cold deep-sea benthic boundary layer and sediment-water interface of the NE Atlantic

This is a short review of the current understanding of the role of microorg anisms in the biogeochemistry in the deep-sea benthic boundary layer (BBL) and sediment-water interface (SWI) of the NE Atlantic, the gaps in our know ledge and some suggestions of future directions. The BBL is the layer of wa ter, often tens of meters thick, adjacent to the sea bed and with homogenou s properties of temperature and salinity, which sometimes contains resuspen ded detrital particles. The SWI is the bioreactive interface between the wa ter column and the upper 1 cm of sediment and can include a large layer of detrital material composed of aggregates that have sedimented from the uppe r mixed layer of the ocean. This material is biologically transformed, over a wide range of time scales, eventually forming the sedimentary record. To understand the microbial ecology of deep-sea bacteria, we need to apprecia te the food supply in the upper ocean, its packaging, passage and transform ation during the delivery to the sea bed, the seasonality of variability of the supply and the environmental conditions under which the deep-sea bacte ria grow. We also need to put into a microbial context recent geochemical f indings of vast reservoirs of intrinsically labile organic material sorped onto sediments. These may well become desorped, and once again available to microorganisms, during resuspension events caused by deep ocean currents. As biotechnologists apply their tools in the deep oceans in search of uniqu e bacteria, an increasing knowledge and understanding of the natural proces ses undertaken and environmental conditions experienced by deep-sea bacteri a will facilitate this exploitation. (C) 2000 Federation of European Microb iological societies. Published by Elsevier Science B.V. All rights reserved .