Phosphatase activity in the sea

Phosphatase is a key-enzyme in the marine environment, although life in the sea is normally not P limited. Expression of phosphatase in algae is generally regulated by the prevailing external concentration of inorganic phosphate, but the internal N: P ratio may also play a role. For bacteria, additional mechanisms like their C and N demands may be important. This is suggested by high phosphatase activities occasionally measured in eutrophic or deep water in the presence of relatively high phosphate concentrations. The distribution of phosphatase activity among the particulate and the dissolved fractions is highly variable. In particular, the dissolved fraction can contribute considerably to the total phosphatase activity ( up to 70%), which differs from the pattern of other hydrolytic ectoenzymes. Parts of this fraction may originate from marine protozoa. The contribution of bacteria and phytoplankton to the particle-associated fraction of phosphatase is extremely variable, depending on P-availability, the dominant organisms, water depth and environmental factors. Community analysis revealed that bacteria attached to marine snow and N-2-fixing cyanobacteria were frequently strong producers of phosphatase. Field studies carried out on a great variety of marine regions suggest that phosphatase activity is generally a good indicator of the P status of phytoplankton. Several heat-stable or heat-labile phosphatases, isolated from marine organisms living in extreme or other environments have been recommended for biotechnological applications.