|Title||Production of dissolved organic carbon enriched in deoxy sugars representing an additional sink for biological C drawdown in the Amazon River plume|
|Publication Type||Journal Article|
|Year of Publication||2014|
|Authors||Meador T.B, Aluwihare LI|
|Journal||Global Biogeochemical Cycles|
|Type of Article||Article|
|Keywords||biocomplexity; chemical-composition; DOC advection; Marine snow; matter; neutral sugars; nitrogen; north-atlantic ocean; pacific; polysaccharides; remineralization; Richelia; sea; seawater; transformations|
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.