Concentrations and sinking rates of transparent exopolymer particles (TEPs) in a coastal sea: the Changjiang River (Yang
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Concentrations and sinking rates of transparent exopolymer particles (TEPs) in a coastal sea: the Changjiang River (Yangtze River) Estuary Shujin Guo2, 3, Jun Sun1* 1 College of Marine Science and Technology, China University of Geosciences (Wuhan), Wuhan 430074, China 2 Jiaozhou Bay Marine Ecosystem Research Station, Institute of Oceanology, Chinese Academy of Sciences, Qingdao
266071, China 3 Center for Ocean Mega-Science, Chinese Academy of Sciences, Qingdao 266071, China
Received 16 October 2019; accepted 14 November 2019 © Chinese Society for Oceanography and Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract
Transparent exopolymer particles (TEPs) are ubiquitous throughout the oceans, and their sedimentation is considered an efficient biological carbon sink pathway. To investigate the role of coastal TEPs in sinking carbon from the upper layer, samples were collected in the spring and summer of 2011 in the Changjiang River (Yangtze River) Estuary, a typical coastal water. The concentrations and sinking rates of TEPs were measured, and potential sedimentation flux of TEPs was estimated. TEPs concentrations ranged from 40.00 μg/L to 1 040.00 μg/L (mean=(209.70± 240.93) μg/L) in spring and 56.67 μg/L to 1 423.33 μg/L (mean=(433.33±393.02) μg/L) in summer, and they were higher at bloom stations than at non-bloom stations during both cruises. A significant positive correlation between TEPs concentration and chlorophyll a (Chl a) concentration was detected, suggesting that phytoplankton was the primary source of TEPs in this area. TEPs sinking rates ranged from 0.08 m/d to 0.57 m/d with a mean of (0.28±0.14) m/d in spring and 0.10 m/d to 1.08 m/d with a mean of (0.34±0.31) m/d in summer. The potential sedimentation flux of TEP-C ranged from 4.95 mg/(m2·d) to 29.40 mg/(m2·d) with a mean of (14.66±8.83) mg/(m2·d) in spring and 6.80 mg/(m2·d) to 30.45 mg/(m2·d) with a mean of (15.71±8.73) mg/(m2·d) in summer, which was ~17.81% to 138.27% (mean=65.15%±31.75%) of sedimentation flux of phytoplankton cells in the study area. Due to the increase of TEPs concentrations and their sinking rates, sedimentation fluxes of TEPs at the bloom station were obviously higher than at the non-bloom station during both cruises. This study indicates that TEPs serve as a carbon sink in the Changjiang River Estuary, especially during bloom events, and their sedimentation should be taken into account when we study the carbon sedimentation in the coastal sea. Key words: transparent exopolymer particles, sinking rates, Changjiang River (Yangtze River) Estuary, coastal sea Citation: Guo Shujin, Sun Jun. 2020. Concentrations and sinking rates of transparent exopolymer particles (TEPs) in a coastal sea: the Changjiang River (Yangtze River) Estuary. Acta Oceanologica Sinica, 39(10): 58–69, doi: 10.1007/s13131-020-1660-7
1 Introduction Transparent exopolymer particles (TEPs) are transparent gellike particles in the ocean that were first identified in the early 1990s (Alldredge et al., 1993). They are formed from polysaccharides
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