Braarudosphaera bigelowii morphotypes in the surface sediments of the southwestern South China Sea.

The present study reports on the distribution and occurrence of Braarudosphaera bigelowii in the surface sediments of the western part of the South China Sea (SCS), along the coast of Vietnam. This part of the SCS is a known upwelling region, characterized by low salinity conditions due to high annual rainfall and river run-off, confirming the results of earlier studies regarding the occurrence of B. bigelowii in shallow bays, nearshore, low salinity marine waters and upwelling areas. Morphometric analysis of B. bigelowii pentaliths in the western SCS revealed the presence of the 3 morphotypes proposed by Takano et al. (2006) based on the pentalith side lengths from coccospheres encountered in surface water samples. This paper also reports the occurrence of a new B. bigelowii morphotype in the SCS, corresponding to specimens with a pentalith side length of 3.5-4.0µm. An attempt to relate the distribution of these morphotypes with temperature and salinity proved to be inconclusive, suggesting the possibility that other factors could be influencing the occurrence of the morphotypes in the study area. [ABSTRACT FROM AUTHOR]