A Quantitative Analysis of Alkaline Phosphatase Activity in He‘eia Fishpond

Abstract

Dissolved organic phosphorus (DOP) is a potentially significant source of bioavailable P to primary producers in aquatic systems. The presence of the alkaline phosphatase (APase) enzyme indicates inorganic P deficiency and the potential for utilization of the DOP pool. Seasonal and spatial variability of alkaline phosphatase activity (APA) was quantified in He‘eia Fishpond, a coastal brackish-water pond adjacent to Kaneohe Bay, Hawaii. Whole community APA (> 0.7 µm), normalized to chlorophyll a, revealed changes in APA in concert with varying nutrient inventories and ratios. Specifically, we observed elevated dissolved organic nitrogen to phosphate ratios (DIN:DIP) following a major storm event, accompanied by elevated APA and alterations in phytoplankton community. Taken together, these data suggest that storm pulses of fluvial material into the coastal ocean can significantly perturb the resident phytoplankton community. Ultimately, investigating the potential bioavailability of DOP increases our understanding of controls on primary production and phytoplankton community structure.