Production of dissolved organic carbon enriched in deoxy sugars representing an additional sink for biological C drawdown in the Amazon River plume

TitleProduction of dissolved organic carbon enriched in deoxy sugars representing an additional sink for biological C drawdown in the Amazon River plume
Publication TypeJournal Article
Year of Publication2014
AuthorsMeador T.B, Aluwihare LI
JournalGlobal Biogeochemical Cycles
Volume28
Pagination1149-1161
Date Published2014/10
Type of ArticleArticle
ISBN Number0886-6236
Accession NumberWOS:000344797500009
Keywordsbiocomplexity; chemical-composition; DOC advection; Marine snow; matter; neutral sugars; nitrogen; north-atlantic ocean; pacific; polysaccharides; remineralization; Richelia; sea; seawater; transformations
Abstract

In North Atlantic waters impacted by discharges from the Amazon and Orinoco Rivers, where planktonic diatom-diazotroph associations (DDA) were active, we observed that an average ( standard deviation) of 6112% of the biological drawdown of dissolved inorganic carbon (DIC) was partitioned into the accumulating total organic carbon pool, representing a flux of up to 94 Tg C yr(-1). This drawdown corresponded with chemical alteration of ultrafiltered dissolved organic matter (UDOM), including increases in stable C isotopic composition (C-13) and C:N. The dissolved carbohydrate component of UDOM also increased with biological DIC drawdown and diatom-associated diazotroph (i.e., Richelia) abundance. New carbohydrates could be distinguished by distinctively high relative abundances of deoxy sugars (up to 55% of monosaccharides), which may promote aggregate formation and enhance vertical carbon export. The identified production of non-Redfieldian, C-enriched UDOM thus suggests a mechanism to explain enhanced C sequestration associated with DDA N-2 fixation, which may be widespread in mesohaline environments.

DOI10.1002/2013gb004778
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