Variability in δ<sup>13</sup>C and δ<sup>15</sup>N Stable Isotope Signatures in Mangrove Ecosystem of Hainan, China

Abstract

δ13C and δ15N dual stable isotope signatures were used to determine the impact of mangrove materials and other organic carbon sources to fish, crab (Scylla paramamosain) and land use communities in an ecologically significant mangrove ecosystem of Hainan Island in the southern part of China. The mean δ13C values of the leaves ranges from-36.72 to 32-89‰ suggesting that mangrove trees follow the C3 type photosynthetic pathway. The analyzed specimen on the crab was found to have δ13C and δ15N values ranging from-21.41 to-19.74‰ and 7.60 to 7.78‰ respectively, and that of fish from-12.92 to-13.02‰ and 7.01-7.53‰. Crabs showed low δ13C values as compared to the fish. The δ13C revealed that the mangrove crabs directly relied on the mangrove materials. The variation of carbon and nitrogen concentration respectively showed considerable difference in the ultimate sources of carbon and trophic level. It was observed that mangrove leaves contribute to the food sources. The land usage that contributes to pollution and the nutrient distribution reflects anthropogenic loading of nitrogen in the mangrove area. Thus, this calls for the need to conserve the mangrove ecosystem at Hainan.