Abstract: The authors investigated stable carbon isotopes of surface sediments from three typical bays in Guangdong Province, namely, Zhanjiang Bay, Shenzhen Bay and Liusha Bay, collected in 2009. The results showed that the δ¹³C values in the surface sediments from Zhanjiang Bay ranged from ?25.9 to ?23.9‰ with an average of ?25.2‰; those from Shenzhen Bay were from ?25.9 to ?23.2‰ with an average of ?25.1‰; and the those from Liusha Bay were from ?23.2 to ?20.0‰ with an average of ?20.9‰. Based on the classic binary mode, the proportion of terrestrial organic matter was in a range of 0.57?0.90 with an average of 0.78 in Zhanjing Bay, was in a range of 0.45?0.90 with an average of 0.76 in Shenzhen Bay, while that in Liusha Bay was small, and the proportion of its marine organic matter was high. The organic matters in the surface sediments of Zhanjiang Bay and Shenzhen Bay were mainly originated from the continental shelf, including the mixed organic matters from C3 plants and from marine planktonic microalgae, with the C3 plants playing the leading role. However, the organic matters in the surface sediments of Liusha Bay were almost all originated from macroalgae and shellfish’s excreta. Their distributions showed no obvious regularity, which was mainly affected by continental runoff, shipping and tides, as well as by the primary productivity in the sea water and aquaculture.

Key words: stable carbon isotope, surface sediment, typical bay, Guangdong Province