Experimental Study on the Interspecific Interactions Between the Two Bloom-Forming Algal Species and the Rotifer Brachionus plicatilis

The interspecific interactions between the rotifer Brachionus plicatilis and two harmful algal blooms(HAB) species were investigated experimentally by single culture method. B. plicatilis population and the growth of the two algae were compared at different algal cell densities. The results demonstrated that the B. plicatilis obtained sufficient nutrition from Prorocentrum donghaiense to support net population increase. With exposure to 2.5×104 cells mL-1 of P. donghaiense,the number of B. plicatilis increased faster than it did when exposed to other four algal densities(5,10,15 and 20 ×104 cells mL-1),and the increase rate of B. plicatilis population(r) at this algal density was 0.104 ± 0.015 r d-1. Cell densities of P. donghaiense decreased due to the grazing of B. plicatilis. In contrast,Heterosigma akashiwo had an adverse effect on B. plicatilis population and its growth was largely unaffected by rotifer grazing. In this case,B. plicatilis population decreased and H. akashiwo grew at a rate similar to that of the control.