USE OF IMMOBILIZED ALGAE FOR ESTIMATING BIOAVAILABLE PHOSPHORUS RELEASED BY ZOOPLANKTON

Cells of the green alga Selenastrum capricornutum were immobilized in permeable alginate beads to prevent them from being grazed by zooplank ton. Algae were able to grow in these beads and were used as a new tec hnique to estimate bioavailable phosphorus (P) released by zooplankton . P-limited algal cells were encapsulated in alginate beads and used t o measure P-release by Daphnia pulex feeding on P-saturated and P-limi ted free algal cells. Daphnids grazing on P-saturated cells released 2 0 times more P available for the immobilized algae than animals grazin g on P-limited cells (0.06 versus 0.003 mug P mg-1 Daphnia-DW h-1).