Strong linkages between surface and deep-water dissolved organic matter in the East/Japan Sea
Vertical and horizontal distributions of total dissolved amino acids (TDAAs), dissolved organic carbon (DOC), and dissolved organic nitrogen (DON) were measured in the East/Japan Sea (EJS). The euphotic zone of this sea is N-limited, and the N : P ratio is ∼ 13 below 200 m depth. Elevated TDAA conce...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2017-05-01
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| Series: | Biogeosciences |
| Online Access: | http://www.biogeosciences.net/14/2561/2017/bg-14-2561-2017.pdf |
| Summary: | Vertical and horizontal distributions of total dissolved amino
acids (TDAAs), dissolved organic carbon (DOC), and dissolved organic nitrogen
(DON) were measured in the East/Japan Sea (EJS). The euphotic zone of this
sea is N-limited, and the N : P ratio is ∼ 13 below 200 m depth.
Elevated TDAA concentrations (137 ± 34 nM) and DOC-normalized yields
(0.8 ± 0.2 % of DOC) were observed in deep waters ( ≥ 1000 m)
of the EJS and compared with those in the deep North Pacific Ocean. Significantly
high TDAA concentrations and yields were observed in a region of deep-water
formation, indicating the convection of margin-derived bioavailable dissolved
organic matter (DOM) to deep waters. Declining TDAA concentrations
(36 ± 12 %) and yields (33 ± 13 %) were observed between
1000 and 3000 m throughout the EJS, indicating the utilization of bioavailable
DOM in deep waters. Concentrations of the D-enantiomers of amino acids (Ala,
Glx, Asx, and Ser) were relatively high in deep waters of the EJS, indicating
substantial bacterial contributions to DOM from surface and upper mesopelagic
waters. Climate warming during the past few decades in the EJS is weakening
deep convection during the winter, and one consequence of this reduction in
deep convection is a decline in the supply of bioavailable DOM from surface
waters. |
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| ISSN: | 1726-4170 1726-4189 |