Genetic Analysis of a Large-Scale Bloom Offshore Qingdao, China.

A sudden large-scale bloom event of the haptophyte that lasted over one month in the winter of 2021 was observed offshore Qingdao, China. This bloom event was unusual as it was the first bloom recorded in Qingdao offshore. Furthermore, the temperature at which this event occurred was much lower than that of previous blooms in China. We hypothesize that the strains that drove the development of this bloom offshore Qingdao were genetically unique and have a competitive advantage in the environmental conditions. To test this hypothesis, we analyzed genetic diversity and the temporal dynamics of the bloom, using the high-resolution molecular markers and that we developed recently. The analysis revealed that the genetic compositions of offshore Qingdao were rather limited, containing two dominant genotypes and other rare genotypes with low abundance, representing a small portion of the genetic diversities identified in coastal waters in China, and were rather different from the genotypes outside of the Jiaozhou Bay before the bloom in the winter of 2021. This suggested only certain strains contribute to the development of blooms under certain environmental conditions. The genetic composition may indicate the unusual timing and scale of this event.