http://reefkeeping.com/issues/2006-04/snn/index.php
read this part
Alkaline phosphatase activity in the phytoplankton communities of Monterey Bay and San Francisco Bay. Nicholson, D., Dyhrman, S., Chavez, F. and Paytan, A. Limnol. Oceanogr., 51(2), 2006, 874-883.
Heres another good read...