INTEGRATED CULTIVATION OF THE RED ALGA KAPPAPHYCUS-ALVAREZII AND THE PEARL OYSTER PINCTADA-MARTENSI

The effect of simultaneously cultivating the pearl oyster Pinctada mar tensi and the red alga Kappaphycus alvarezii on growth rates of both s pecies was investigated in laboratory and field studies conducted from December 1993 to June 1995. The two study sites were in subtidal area s 100 km apart off the east coast of Hainan Island, China. Pearl oyste rs were cultivated in the center of an algal farm and red alga was cul tivated in the center of the pearl oyster farm. These field experiment s showed higher growth rates of both P. martensi and K. alvarezii in a co-culture system than in a monospecies culture system. Laboratory st udies showed that the algae removed nitrogenous wastes released by pea rl oysters. Algae treated with pearl oyster wastes grew much faster th an those without oyster wastes. Algae treated with the seawater to whi ch NH4Cl, NaNO3 and NaNO2 were added grew at the same rate as those tr eated with natural seawater containing oyster nitrogenous wastes, sugg esting that enhanced growth of algae in the co-culture system was larg ely due to nitrogenous metabolites of the pearl oysters. In the co-cul ture, growth of pearl oysters was positively influenced by the presenc e of rapidly growing algae but when seawater temperature decreased bel ow 20 degrees C, the algae grew slowly and there was no measurable ben efit of mixed culture to either algae or pearl oyster.