Seasonal contrast of particulate organic carbon (POC) characteristics in the Geum and Seomjin estuary systems (South Korea) revealed by carbon isotope (δ13C and Δ14C) analyses

Abstract

In this study, we newly investigated surface water samples collected in two contrasting Korean estuary systems (i.e., closed Geum and open Seomjin estuaries) along a salinity gradient in winter (December) in 2016. The main objectives were to determine the source of particulate organic carbon (POC) in winter and to assess the environmental factors inducing seasonal differences in POC characteristics. Concentrations and dual carbon isotopes ( δ13 C and 14 C) of POC were analyzed together with concentrations and stable carbon isotopes ( δ13 C) of dissolved inorganic carbon (DIC) and compared with those obtained in summer (August) in 2016. Our study provided a new insight that for both estuarine systems, the seasonal contrast in POC characteristics was associated with stronger wind-induced estuarine sediment resuspensions in winter than in summer providing a greater contribution of aged POC to the total POC pool in winter.