Effects of Cochlodinium bloom in Pearl River Estuary in China on the growth of other harmful algal bloom species

A large scale bloom of Cochlodinium,covering over 300 km2,occurred in coastal waters of Pearl River Estuary in China in October 2009.Water samples in the bloom patches were collected during the bloom.Phytoplankton was analyzed,and the effects of bloom sample on the growth of the other three phytoplankton species Skeletonema costatum,Prorocentrum micans and Heterosigma akasiwo were studied.Cochlodinium was the predominant species in the phytoplankton community in the bloom samples,with the cell density of 3.15×106 cells/L and percentage proportion of 73.3%.The growth of P.micans and H.akasiwo was significantly inhibited by the bloom water.However,the bloom water did not inhibit the growth of S.costatum,even accelerated the growth to some extend.The inhibition substances were mainly in cell-free filtrate,and tended to be hot-resistive.