Distributions of particulate and dissolved phosphorus in aquatic habitats of Peninsular Malaysia.

Particulate phosphorus was the dominant phosphorus species and accounted for 72 ±â€¯5% of total phosphorus in coastal habitats, 63 ±â€¯4% in estuaries, 58 ±â€¯6% in lakes and 80 ±â€¯7% in aquaculture farms whereas dissolved inorganic phosphorus (DIP) and dissolved organic phosphorus (DOP) were minor components. Correlation analyses (DIP vs Chl a; R2 = 0.407, df = 31, p < 0.001) suggested phosphorus limiting conditions in lakes, which was corroborated with the highest alkaline phosphatase activity (APA) that fluctuated from 0.38 to 41.14 nmol L-1 min-1. In contrast, APA was elevated in coastal habitats and estuaries only when DIP concentration decreased below 0.9 µM. Moreover size-fractionation experiment showed that the highest APA was detected in the 0.2-2 µm pico-size fraction. Our results suggested that the main APA in coastal habitats and estuaries was from phototrophic pico-eukaryotes and heterotrophic bacteria, and regulated largely by DIP availability.