Succession and controlling factors of phytoplankton assemblages during a period with recurrent outbreaks of Phaeocystis globosa blooms in Qinzhou Bay, China

Qinzhou Bay is a tropical semiclosed bay with the highest phytoplankton diversity and high frequency of harmful algal blooms (HABs) in Guangxi coastal area, located north Beibu Gulf. Phaeocystis globosa typical HAB species mainly occur autumn winter. The causes these succession assemblages related to are complicated not fully understood. Therefore, continuous survey was conducted monthly from October 2018 March 2019 study community its relationship environmental variables this area. results revealed that dynamics varied significantly time, P. most frequent dominant five voyages, cell density 3.79 ± 1.34 × 10 6 cells/L January. Chaetoceros had were associated early stage, while they replaced by Guinardia striata when increased rapidly January, abundance dinoflagellates after decline . index indicated structure more stable December, sharp increase January caused diversity. redundancy analysis (RDA) variation affected hydrological chemical factors, including DIN/DIP, temperature, DSi, DIP DSi/DIP. Furthermore, we inferred phosphorus (P) key factor limiting colony formation , P limitation prevented outbreak blooms. This research may provide insight into mechanisms driving prevention