Abstract
The dinoflagellates Alexandrium pacificum and Prorocentrum donghaiense are two well-known harmful algal blooms (HABs)-forming species, both were usually found in the same sea areas in form of HABs in China. To date, there is no mechanistic model that can fully explain the occurrence of P. donghaiense blooms with A. pacificum. We found that different strains of P. donghaiense had different intrinsic growth rates of 0.107-0.215/d, and these strains exhibited different responses to the allelopathic action from A. pacificum. Some strains of P. donghaiense could grow well despite some degrees of inhibition in a short period, suggesting the two algal species P. donghaiense and A. pacificum could coexist, even if A. pacificum was allelopathic. Our findings may advance the understanding of phenotypes in P. donghaiense and provide a potential mechanism involved in the coexistence of P. donghaiense and A. pacificum in the same area.