Primary production in ten reservoirs in southern Brazil

The growth and phosphatase activity during phosphorus starvation of cultures of Nodularia spumigera Mertens were examined. Stationary phase was reached much sooner in phosphorus-deficient cultures than in phosphorus-sufficient cultures; the growth rate did not change. Phosphatase activities were greatly increased in stationary phase. Diurnal patterns were established for phosphorus-sufficient cultures, but they were not light related. In phosphorus-deficient cultures, an increase in phosphatase activities over a 24 h period was superimposed on a diurnal pattern. Both phosphorus and nitrogen additions lowered the relative phosphatase activities in long term studies, but the effect of phosphorus was much more pronounced. In short term studies, phosphorus appeared to cause an immediate decrease in phosphatase activity, but did not affect phosphatase activity after that for up to 24 h. Nitrogen did not have any short term effect on phosphatase. Phosphatase activity was correlated with changes in the proportion of TCA-insoluble phosphorus (polyphosphates).