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Title: An ultrahigh-resolution mass spectrometry index to estimate natural organic matter lability: FTICRMS organic matter molecular lability index
Award ID(s):
1141978 0838970 0338342
NSF-PAR ID:
10021658
Author(s) / Creator(s):
; ; ;
Date Published:
Journal Name:
Rapid Communications in Mass Spectrometry
Volume:
29
Issue:
24
ISSN:
0951-4198
Page Range / eLocation ID:
2385 to 2401
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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  1. Abstract

    Decomposition of particulate organic matter (POM) plays a key role in the formation of hypoxia in subsurface waters of coastal ocean, yet little is known about the lability and transformation of POM in the hypoxic zone. Suspended particles were collected from surface waters to overlying waters (~30 cm above the sediment‐water interface) along the shelf of northern Gulf of Mexico (nGOM) in late spring/early summer of 2010–2013. Total hydrolyzable amino acids (THAA) and pigments were measured in these particulate samples to trace organic matter lability. The degradation indices, derived from the THAA and chloropigments, were positively correlated with dissolved oxygen (DO) concentrations in the shelf region, suggesting that decomposition of POM contributed greatly to DO utilization. Bacterial degradation appears to be the major pathway for POM decomposition on both inner and mid shelves, while zooplankton grazing played a minor role. POM samples in the overlying water on the inner shelf were the most degraded from the THAA and pigment results, and they also had high C/N ratios (9–14) and depleted δ13C values (−29‰ to −24‰), pointing to a source of terrestrial C3 plant material. This distinct terrestrial signal of POM in the overlying water suggests strong selective degradation of marine‐sourced organic matter, but how the terrestrial organic matter is settled to this layer and its ultimate fate remain unclear. Taken together, these data offer new angles looking into the lability and degradation pathways of POM, and mechanisms of hypoxia formation in coastal waters.

     
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