Spatial variation of phytoplankton community from Malacca Strait to southern South China Sea in May of 2011

Phytoplankton community and its relationships with environmental factors were investigated in the surface waters from Malacca Strait (MS) to the connected South China Sea (SCS) in May of 2011. Salinity was significantly lower in MS. No significant spatial variations were found for most of the nutrients (except silicate) between MS and connected SCS. Silicate gradually increased from Andaman Sea to the southern MS, and then declined from the southern MS to SCS. Phytoplankton mainly belonged to diatoms and dinoflagellates. The dominant species of diatoms were Skeletonema, Pseudo-nitzschia, Navicula, and Thalassionema. Dinoflagellates were mainly presented by Prorocentrum, Scrippsiella and nano-dinoflagellate. Diatoms contributed to most of the phytoplankton abundance in the middle and south MS. However, dinoflagellates predominated in the side of Andaman Sea or SCS. Chlorophyll a concentration and phytoplankton abundance were the highest in the shallowest sampling station of middle MS. CCA results suggested that salinity and silicate were the most important environmental variables influencing the phytoplankton spatial variation. The prosperity of diatoms in the middle MS may be promoted mainly by the sufficient nutrients brought by the deep-water intrusion or river inflow. Silicate can be considered as an indicator for high phytoplankton biomass, but could not be the limited factor for the phytoplankton growth in MS.