ABSTRACT
The general biochemical role of extracellular enzymes in the sea is similar to that in other aquatic environments. However, in order to understand the ecological significance of enzymes in the sea specific marine environmental factors have to be considered, e.g., a) seawater is a highly diluted medium interspersed with hot spots of organic matter concentration, aggregation, and decomposition (1). b) as a result of hydrographic conditions, the oceans are characterized by distinct horizontal and vertical zonations. The deep sea, in particular, with its enormous volume, depends entirely on substrate supply from sinking material produced in the surface layer (2). c) in the sea, low-molecularweight organic matter that persists as dissolved organic carbon (DOC) is less bioreactive and more strongly diagenetically altered than the bulk of high-molecular-weight matter (3,4). d) the deep seabed receives very little of the total surface-derived primary productivity, and much of this organic matter is strongly altered. Finally, at chemical and hydrographic discontinuities in the sea (e.g., fronts, boundary layers, and oxygen, nutrient, and salinity gradients), drastic changes occur in microbial species diversity and enzymatic properties.
