Dual carbon isotope (δ13C and Δ14C) characterization of particulate organic carbon in the Geum and Seomjin estuaries, South Korea

Kang, Sujin; Kim, Jung-Hyun; Ryu, Jong-Sik; Shin, Kyung-Hoon

Dual carbon isotope (δ13C and Δ14C) characterization of particulate organic carbon in the Geum and Seomjin estuaries, South Korea

2020

Kang, Sujin | Kim, Jung-Hyun | Ryu, Jong-Sik | Shin, Kyung-Hoon

We investigated the source, composition, and reactivity of particulate organic carbon (POC) in two contrasting Korean estuary systems, a closed estuary (Geum) (i.e., with an estuary dam at the river mouth) and an open (Seomjin) estuary. A dual isotope (δ¹³CPOC and Δ¹⁴CPOC) approach was applied to surface water samples collected along a salinity gradient in August 2016. Our results indicate that phytoplankton-derived POC was the main contributor to the total POC pool in the reservoir of the Geum estuary, while terrestrial-derived POC predominated the upper Seomjin estuary. A simple binary mixing model using Δ¹⁴CPOC revealed a higher modern POC contribution (87–90%) in the Geum estuary reservoir than that (77%) of the upper Seomjin estuary. Accordingly, it appears that an estuary dam can alter the source and reactivity of POC in a reservoir, which can be transferred to the adjacent coastal ecosystem.

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