Transparent exopolymer particle (TEPs) dynamics and contribution to particulate organic carbon (POC) in Jaran bay, Korea

Abstract

Transparent exopolymer particles (TEPs) are defined as acidic polysaccharide particles and they are influenced by various biotic and abiotic processes that play significant roles in marine biogeochemical cycles. However, little information on their monthly variation, relationship and contribution to particulate organic carbon (POC) is currently available particularly in coastal regions. In this study, the water samples were collected monthly to determine TEP concentrations and POC concentrations in a southern coastal region of Korea, Jaran Bay from April 2016 to March 2017. The TEP concentrations varied from 26.5 to 1695.4 μg Xeq L-1 (mean standard deviation (S.D.) = 215.9 ± 172.2 μg Xeq L-1) and POC concentrations ranged from 109.9 to 1201.9 μg L-1 (mean ± S.D. = 399.1 ± 186.5 μg L-1) during our observation period. Based on the 13C stable isotope tracer technique, monthly carbon uptake rates of phytoplankton ranged from 3.0 to 274.1 mg C m-2 h-1 (mean ± S.D. = 34.5 ± 45.2 mg C m-2 h-1). The cross-correlation analysis showed a lag-time of 2 months between chlorophyll a and TEP concentrations (r = 0.86, p < 0.01; Pearson's correlation coefficient). In addition, we observed a 2 month lag-phased correlation between TEP concentrations and primary production (r = 0.73, p < 0.05; Pearson's correlation coefficient). In Jaran Bay, the TEP contribution was as high as 78.0% of the POC when the TEP-C content was high and declined to 2.4% of the POC when it was low. These results showed that TEP-C could be a significant contributor to the POC pool in Jaran Bay.