CHEMTAX analysis of phytoplankton assemblages revealed potential indicators for blooms of haptophyte Phaeocystis globosa

Harmful algal blooms formed by the haptophyte Phaeocystis globosa have been recorded in the Beibu Gulf since 2011. In this study, the composition and variation of phytoplankton assemblages in the Beibu Gulf were studied during an intense bloom of P. globosa from 2016 to 2017, using the CHEMTAX approach. In phytoplankton samples collected from the Beibu Gulf, chlorophyll a (Chl a, 0.046-2.87 mu g L-1) and fucoxanthin (Fuco, 0.041-13.7 mu g L-1) were the most abundant pigments. Diatoms were the dominant group of phytoplankton, followed by cyanobacteria (mainly Synechococcus), haptophytes, cryptophytes, prasinophytes, dinoflagellates, and chlorophytes. Phytoplankton samples were clustered into four communities characterized by diatoms, cyanobacteria, haptophytes containing 19'-butanoyloxyfucoxanthin (the Hapt-But subgroup of haptophytes), and haptophytes containing 19'-hexanoyloxyfucoxanthin (the Hapt-Hex subgroup of haptophytes). Distribution pattern of the Hapt-But subgroup of haptophyte was consistent with that of P. globosa colonies. Diatoms had positive correlation with P. globosa colony abundance, while cyanobacteria had negative correlation. The diagnostic pigments for colony-forming P. globosa (But-fuco), diatoms (Fuco) and cyanobacteria (zeaxanthin), as well as temperature (<20 degrees C), could serve as potential early-warning indicators for the formation of P. globosa blooms in the Beibu Gulf.

Automated summary

This study investigated the composition and variation of phytoplankton assemblages in the Beibu Gulf during an intense bloom of Phaeocystis globosa using the CHEMTAX approach. The results showed that diatoms were the dominant group of phytoplankton, with a positive correlation between diatoms and P. globosa colony abundance, and a negative correlation between cyanobacteria and P. globosa. Diagnostic pigments and temperature could serve as potential early-warning indicators for the formation of P. globosa blooms in the Beibu Gulf.