Net tow and surface sediment distributions of pteropods in the South China Sea region: Comparison and oceanographic implications

Abstract

The purpose of this work is to compare the sediment distributions of pteropod species and species groups with their known distributions in the plankton of the Southeast Asian region. Generally, the limits of net tow and sediment distributions of pteropod species on the Sunda Shelf and in the Java Sea are very similar, but there are several significant exceptions. Diacria quadridentata extends much farther into shallow water in Gulf of Thailand and Java Sea sediments than predicted from net tows. Although they were nearly absent from the Gulf of Thailand plankton, Creseis virgula virgula and C. virgula conica are present in upper-Gulf sediments. The occurrence of several oceanic pteropod species (and one oceanic planktonic foraminifer) in shallow-water sediments south of Singapore provides evidence that oceanic waters are at least occasionally transported through the Malacca Strait from the Andaman Sea toward Singapore. Hydrographic data and transport directions suggest that the occurrences of Clio convexa (a pteropod) and Euphausia sibogae (a euphausiid) only in the eastern South China Sea represent “spill over” from the Sulu Sea at the eastern end of their Indian Ocean distribution rather than preference for the eastern South China Sea environment. Karimata Strait between the southern South China Sea and the Java Sea seems to act as a filter for zooplankton species and apparently only the most tolerant shallow-water species communicate through the Strait.