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Title: Sargassum sp. Act as a Large Regional Source of Marine Dissolved Organic Carbon and Polyphenols
Abstract

Dissolved organic carbon (DOC) plays critical roles in marine carbon cycling, but its sources and sinks remain uncertain. In this study, we monitored DOC exudation rates ofSargassum natansunder visible light (λ > 390 nm) and solar radiation. DOC release rates ranged from 7 to 10 μg C g−1biomasshr−1(wet weight) under visible light, but increased to 23 to 41 μg C g−1biomasshr−1when exposed to natural sunlight. Results indicate that DOC released bySargassumcould amount to 0.3 to 1.2 Tg C/year, potentially contributing significantly to the marine DOC pool in the Gulf of Mexico and Western North Atlantic. We employed the Folin‐Ciocalteu phenolic content method, nuclear magnetic resonance (NMR) spectroscopy, and ultrahigh resolution Fourier transform ion cyclotron resonance mass spectrometry (FT‐ICR MS) to characterize the diverse pool of organic compounds exuded fromSargassum. Results from these complementary methods showed thatSargassumrelease large quantities of phlorotannins, a class of polyphenols that have very similar properties to terrestrial DOC. These phlorotannins and their oxygenated phenolic derivatives exhibit a high hydrogen deficiency and functionalization (i.e., 4 to 6 oxygen atoms per aromatic ring), representing 5 to 18% of the released DOC isolated by solid phase extraction. Thus,Sargassumis the largest biological source of open ocean polyphenols recorded to date. The amount of polyphenolic DOC released bySargassumchallenges previous beliefs that all polyphenols found within the oceans are remnants of terrestrial organic matter, although the stability of phlorotannins and their derivatives needs to be further evaluated.

 
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NSF-PAR ID:
10459806
Author(s) / Creator(s):
 ;  ;  ;  ;  ;  ;  
Publisher / Repository:
DOI PREFIX: 10.1029
Date Published:
Journal Name:
Global Biogeochemical Cycles
Volume:
33
Issue:
11
ISSN:
0886-6236
Page Range / eLocation ID:
p. 1423-1439
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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