A model for acid and alkaline phosphatase activity in a small pond

Acid and alkaline phosphatase activity were determined in a small pond over a period of 24 months (64 samples). Activity of each phosphatase enzyme was positively correlated with chlorophyll concentration, viable bacterial count, total phosphate concentration, inorganic phosphate concentration, and temperature. Multiple regression analysis was used to formulate equations that described phosphatase activity in terms of these physical, chemical, and biotic factors. Corrected coefficients of determination were calculated, and the highest values were obtained when all parameters were included in the equation (r (2)=0.776 and 0.659 for alkaline and acid phosphatase activity, respectively). However, there was little improvement in ther (2) value obtained when only chlorophyll was used in the equation (r (2)=0.654 and 0.624, respectively). Samples were then taken over a further 12 months (25 samples), and observed activity was compared with the activity predicted by application of the previously derived equations. For alkaline phosphatase, the best fit between observed and expected activity was seen with the equation containing all parameters, but for acid phosphatase the best fit was seen with the equation containing only chlorophyll and temperature as the determinants. In both cases there was a good fit between observed and expected data using the equation containing chlorophyll as the sole determinant. From this we have concluded that phytoplankton were the chief producers of phosphatase activity in this pond, although the influence of physical and chemical factors on enzyme activity could not be ignored.