Effects of suspended particles on the growth of two dominant phytoplankton species of Bohai Bay, China

•Suspended particles (SP) inhibit the growth of two marine phytoplankton species.•Higher concentrations of SP show more inhibition on algal growth.•Phaeodactylum tricornutum Bohlin is more tolerant to SP than Gymnodinium sp.•The growth inhibition is due to SP-induced light attenuation and cell aggregation.•Weibull equation is suitable for evaluating algal growth inhibition caused by SP. Suspended particles (SP) are increasing dramatically in Bohai Bay, China and may affect the growth and composition of phytoplankton assembly. To determine the effects of SP on the growth of two dominant phytoplankton species, Phaeodactylum tricornutum Bohlin and Gymnodinium sp., we cultured and tested their growth characteristics under SP concentrations ranging from 0gL−1 to 0.8gL−1. Our results show that the increase in the SP concentrations results in significant decrease in the maximum cell densities and the maximum specific growth rates of these two species. The half maximal inhibitory concentration (IC50) of SP to P. tricornutum and Gymnodinium sp. were 1.07gL−1 and 0.68gL−1 respectively, indicating the inhibitory effect of SP on Gymnodinium sp. was greater than on P. tricornutum. These results suggest that SP inhibits the growth of the two algal species and P. tricornutum is more tolerant to SP than Gymnodinium sp.