The first benthic harmful dinoflagellate bloom in China: Morphology and toxicology of Prorocentrum concavum.

More frequent events and geographic expansion of benthic harmful algal blooms have been reported in recent years. An unexpected bloom of benthic P. concavum occurred in Xincun Bay, Hainan Island, the South China Sea was monitored in August 2018. Species identification, toxin analysis and toxicity test were conducted in the study. Quantitative study revealed that P. concavum had a high cell density on the surface of substrates and in water column. The bloom forming species was identified based on the morphology and phylogeny. Toxin analysis indicated that there were no detectable DSP toxins either in algae or in shellfish samples. The result of toxicity test revealed that the extracts of P. concavum caused the mortality of brine shrimp larvae (Artemia salina). The results from this study may provide more insight into the rising threats of harmful dinoflagellate blooms to marine benthic ecosystems.