Spatial distributions of δ13C, δ15N and C/N ratios in suspended particulate organic matter of a bay under serious anthropogenic influences: Daya Bay, China

Stable isotopic signatures (delta C-13 and delta N-15) and C/N ratios of suspended particulate organic matter (POM) were investigated from the surface water of Daya Bay during summer and winter of 2015. The relatively high 813Crom values suggested the input of C-13-depleted terrigenous organic matter was low in Daya Bay. There were significant correlations between delta C-13(POM) values and chlorophyll a concentrations both during summer and winter, suggesting the delta C-13(POM) values were mainly controlled by the phytoplankton biomass in the surface water. The distribution of delta N-15(POM) values was more complicated than that of delta C-13(POM) and displayed low values in the outer bay and the Dan'ao River estuary. N-15-depleted ammonia originating from industrial wastewater might have strongly influenced the water quality and stable isotopic signatures of POM near the Dan'ao River estuary. The delta C-13(POM) and delta N-15(POM) values strongly reflect the influences of anthropogenic activity and eutrophication in Daya Bay. (C) 2016 Elsevier Ltd. All rights reserved.