Phosphatase activity in Eutrophic Tokyo Bay

Alkaline phosphatase activity in seawater samples taken from Tokyo Bay was measured by both spectrophotometric and fluorometric methods. A stratified distribution pattern of the enzyme was observed in August, a vertically mixed pattern in December. The distribution of phosphatase activity in the eutrophic seawater was paralleled by variations in other parameters, such as viable counts of bacteria, chlorophyll a content, inorganic and total phosphorus concentrations, amounts of seston, particulate deoxyribonucleic acids (DNA) and protein. A significant correlation between phosphatase activity and these measurements indicated that the enzyme was a good indicator of the degree of eutrophication. The positive relationship between phosphatase and inorganic phosphorus indicates that enzyme activity was not inhibited at inorganic phosphorus levels present in the bay and that production of phosphatase by microorganisms inhabiting the bay was not repressed at the inorganic phosphorus levels in the bay. Culture experiments revealed that the formation of repressible phosphatase by bacteria isolated from the bay was not affected by the inorganic phosphorus levels in the bay.