title: Nutrient variations and isotopic evidences of particulate organic matter provenance in fringing reefs, South China.
abstract: Nutrient over-enrichment is considered to be one of the causes of coral decline. Increase in traditional fishing in the Xuwen National Coral Reefs Reserve tract (XW) and tourism around the Sanya National Coral Reefs Reserve tract (SY) are causing this coral decline. This study reviews the current state of knowledge of the nutrient status of coastal fringing reefs in South China and evaluates the primary sources of nutrients using stable isotope method. Surveys of seawater nutrients showed that the seawater remained clean in both the XW and SY coastal coral reef areas. Based on the isotopic differences between anthropogenic sewage and naturally occurring aquatic nutrients, the isotopic values of particulate organic matter (POM) and the C/N ratios were successfully used to identify the presence of anthropogenic nutrients in aquatic environments. The δ(13)C, δ(15)N and C/N compositions of POM from XW and SY (-21.18±2.11‰, 10.30±5.54‰, and 5.35±0.69 and -20.80±1.34‰, 7.06±3.95‰, and 5.77±2.15, respectively) showed statistically significant variations with the season. The δ(13)C and δ(15)N values of POM suggest marine and terrestrial-derived nutrient sources. Organic carbon is a mixture of marine phytoplankton, marine benthic algae and terrestrial-derived plants. The δ(15)N values suggest terrestrial-derived sewage and upwelling-dominated nitrogen sources. In the presence of natural upwelling and coastal currents, coastal coral reef areas are more vulnerable to the increasing anthropogenic nutrient inputs. Anthropogenic activities might lead to large increases in the nutrient concentrations and could trigger the shift from coral- to macroalgae-dominated ecosystems, which would ultimately result in the degradation of the coastal coral reef ecosystem. These results provide some understanding of the declining coral reef ecosystem and the importance of conservation areas and coastal coral reef resource management.
authors.affiliation: State Key Laboratory of Marine Environmental Science, Key Laboratory of the Ministry of Education for Coastal and Wetland Ecosystems, College of the Environment and Ecology, Xiamen University, South Xiangan Road, Xiangan District, Xiamen City, Fujian Province 361102, China.
authors.forename: Di
authors.initials: D
authors.lastname: Cao
authors.affiliation: State Key Laboratory of Marine Environmental Science, Key Laboratory of the Ministry of Education for Coastal and Wetland Ecosystems, College of the Environment and Ecology, Xiamen University, South Xiangan Road, Xiangan District, Xiamen City, Fujian Province 361102, China. Electronic address: wzcao@xmu.edu.cn.
authors.forename: Wenzhi
authors.initials: W
authors.lastname: Cao
authors.affiliation: State Key Laboratory of Marine Environmental Science, Key Laboratory of the Ministry of Education for Coastal and Wetland Ecosystems, College of the Environment and Ecology, Xiamen University, South Xiangan Road, Xiangan District, Xiamen City, Fujian Province 361102, China.
authors.forename: Ying
authors.initials: Y
authors.lastname: Liang
authors.affiliation: State Key Laboratory of Marine Environmental Science, Key Laboratory of the Ministry of Education for Coastal and Wetland Ecosystems, College of the Environment and Ecology, Xiamen University, South Xiangan Road, Xiangan District, Xiamen City, Fujian Province 361102, China.
authors.forename: Zheng
authors.initials: Z
authors.lastname: Huang
mesh_terms: D002247:Carbon Isotopes / Q000032:analysis*; D002681:China; D003247:Conservation of Natural Resources; D057894:Coral Reefs; D004784:Environmental Monitoring; D009587:Nitrogen Isotopes / Q000032:analysis*; D052638:Particulate Matter / Q000737:chemistry*; D012623:Seawater / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000032:analysis*
chemical_list: D002247:Carbon Isotopes; D009587:Nitrogen Isotopes; C000615243:Nitrogen-15; D052638:Particulate Matter; D014874:Water Pollutants, Chemical; C000615229:Carbon-13
keywords: C/N ratio; Coral reefs; Particulate organic matter; δ(13)C; δ(15)N