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Article

Characterization of Marine-Surface-Dissolved Organic Matter via Amino Acid Enantiomers and Its Implications Based on Diel and Seasonal Observations

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School of Oceanography, Shanghai Jiao Tong University, Shanghai 200030, China
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State Key Laboratory of Estuarine and Coastal Research, East China Normal University, Shanghai 200241, China
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Department of Statistics and Actuarial Sciences, East China Normal University, Shanghai 200241, China
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Key Laboratory of Marine Chemistry Theory and Technology Ministry of Education, Ocean University of China, Qingdao 266100, China
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Key Laboratory of Marine Ecosystem Dynamics, Ministry of Natural Resources & Second Institute of Oceanography, Ministry of Natural Resources, Hangzhou 310012, China
*
Author to whom correspondence should be addressed.
Academic Editor: Slađana Strmečki Kos
Water 2021, 13(5), 685; https://doi.org/10.3390/w13050685
Received: 5 January 2021 / Revised: 24 February 2021 / Accepted: 26 February 2021 / Published: 3 March 2021
Due to the essential roles of dissolved organic matter (DOM) in both microbiol food loop and marine carbon cycling, changes in marine DOM composition have an important impact on the marine ecosystem and carbon cycling. In October 2014 and June 2015, two field investigations for the DOM in the upper 200 m were conducted in the slope region of the northern South China Sea to characterize the DOM composition via amino acid enantiomers. In June, our sampling locations were under upwelling impact induced by an eddy-pair event, whereas in October there were no eddies. High-frequency sampling (a few hours interval) over 24 h reveals that the variability of the amino acid carbon yield (min. 0.2%) and the D/L alanine ratio (min. 0.02) is larger than its corresponding analytical and propagated errors, suggesting solid short-term changes for these two molecular-based indicators. Section samples from June showed a lower D/L alanine ratio (0.43 vs. 0.53) and a GABA mol% (1.0% vs. 1.6%) relative to the section samples from October, suggesting that DOM in June is more fresh (less degraded) compared to that in October. A higher serine mol% (19.5% vs. 13.2%) and lower D/L serine ratio (0.06 vs. 0.24) from the diel observation in June relative to October further indicates that phytoplankton, rather than bacteria, plays an more important role in DOM composition alternation. This is consistent with the higher phytoplankton biomass found in June, promoted by the eddy-pair. View Full-Text
Keywords: Amino acid; diel variability; dissolved organic matter; propagated error; South China Sea Amino acid; diel variability; dissolved organic matter; propagated error; South China Sea
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MDPI and ACS Style

Zhu, Z.-Y.; Zhou, Y.-C.; Ma, W.-C.; Wu, Y.; Li, M.; Liu, S.-M.; Xu, X.-W.; Zhou, M. Characterization of Marine-Surface-Dissolved Organic Matter via Amino Acid Enantiomers and Its Implications Based on Diel and Seasonal Observations. Water 2021, 13, 685. https://doi.org/10.3390/w13050685

AMA Style

Zhu Z-Y, Zhou Y-C, Ma W-C, Wu Y, Li M, Liu S-M, Xu X-W, Zhou M. Characterization of Marine-Surface-Dissolved Organic Matter via Amino Acid Enantiomers and Its Implications Based on Diel and Seasonal Observations. Water. 2021; 13(5):685. https://doi.org/10.3390/w13050685

Chicago/Turabian Style

Zhu, Zhuo-Yi, Ying-Chun Zhou, Wen-Chao Ma, Ying Wu, Ming Li, Su-Mei Liu, Xue-Wei Xu, and Meng Zhou. 2021. "Characterization of Marine-Surface-Dissolved Organic Matter via Amino Acid Enantiomers and Its Implications Based on Diel and Seasonal Observations" Water 13, no. 5: 685. https://doi.org/10.3390/w13050685

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