SPATIAL VARIATION IN ELEMENTAL AND ISOTOPIC COMPOSITIONS OF CARBON AND NITROGEN IN A COASTAL LAGOON REVEALS NATURAL AND ANTHROPOGENIC INFLUENCESDang Thi Nhu Y.
Increased delivery of particulate organic matter (POM) to coastal lagoons has caused disturbance in nutrient cycling, water quality and aquatic biodiversity. Therefore, the major concern in coastal management is assessment of sources and pathways of POM in order to maintain ecosystem health. Elemental and isotopic of POM compositions are being increasingly used as useful markers for sources of POM in coastal ecosystems to obtain understanding of the nutrient sources and anthropogenic influences. In this study, variation in elemental and stable isotope compositions of carbon (C) and nitrogen (N) were measured in Cau Hai lagoon, Central Vietnam to characterize the possible sources of C and N. Variations in values of C/N ratios (8.17 Â± 0.14) and ï¤13C (-22.00â° Â± 0.13) indicated that POM was mainly of autochthonous origin due to high microalgae productivity. The values of ï¤15N (3.83â° Â± 0.08) were likely inferred from potential input of POM from aquaculture practices. These results suggest that main sources of POM in the lagoon were derived from autochthonous microalgae and slightly anthropogenic impacts through aquaculture activities. Control POM load should be taken into account in maintaining water quality and biodiversity in the lagoon to inhibit microalgae biomass and shading due to nutrient enrichment.