Alkaline phosphatase activity and utilization of dissolved organic phosphorus by algae in subtropical coastal waters

Alkaline phosphatase activity (APA) and the availability of dissolved organ ic phosphorus (DOP) to marine algae were determined in Xiamen Bay and in al gal batch culture systems. Results showed that APA changed with seasons, in creasing to the highest value in summer and decreasing to the lowest in aut umn and spring in Xiamen Bay. Tests on natural populations of planktonic al gae and bacteria community showed that algae were mostly responsible for DO P utilization, while bacteria could not take up DOP compounds. Results from algal batch cultures also supported the above conclusion. Relationships be tween APA and environmental factors indicated that APA was negatively corre lated with phosphorus level such as phosphate and small molecular DOP, and APA played an important role in utilization of DOP by algae. All the result s emphasized the ecological significance of DOP in subtropical coastal wate rs. (C) 1999 Elsevier Science Ltd. All rights reserved.