Spatial and temporal variations in algal blooms in the coastal waters of the western South China Sea

Algal blooms occur frequently in the coastal waters of the western South China Sea (SCS). This paper reports spatial and temporal variations of algal bloom events in these waters from 1993 to 2007. Twenty-five algal bloom events occurred in summer in the coastal waters of South and Central Vietnam where they were associated with wind-induced, coastal, nutrient upwelling and river discharges; a further eight events occurred in the coastal waters of North Vietnam. A greater number of algal bloom events were observed in 1999 and 2002, and were accompanied by several previously unobserved species for the study period. These events may be related to the El Niño events of 1998 and 2002. Furthermore, the bloom-causative species Trichodesmium erythraeum (Cyanophyta) entirely dominated the phytoplankton community of algal blooms during 1993–1999 whereas the species Phaeocystis globosa (Haptophyta) dominated blooms after 2002. This study establishes a basis for further long-term research of algal bloom event variations, and provides a compiled scientific reference that may be used for later prediction of Harmful algal blooms (HABs).

► Algal blooms occur frequently in western coast of South China Sea in the summer.
► In 1993–2007, 1999 and 2002 were two peak-years of algal bloom occurrence.
► The blooms are associated with wind-induced upwelling; causative species changed.
► Trichodesmium erythraeum (Cyanophyta) dominated algal blooms in 1993–1999.
► Phaeocystis globosa (Haptophytes) dominated algal blooms in 2002–2007.