Sources and degradation of organic matter in the surface sediments of the Chukchi Sea: insights from amino acids
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Abstract: In the context of global warming and rapid environment change in the Arctic, the supply of organic matter (OM) has increased significantly and a large amount of OM are buried on the Arctic shelf. Studying the fate of OM in Arctic shelf sediments is crucial to understanding the global carbon sink. As a marginal sea of the Arctic Ocean, the Chukchi Sea is one of the most critical areas where OM is buried. Based on the surface sediment samples collected during the sixth Chinese National Arctic Research Expedition in the summer of 2014 and the Sino-Russian joint Arctic Research Expedition in the summer of 2016, this study takes amino acids (AAs) as the primary tool to explore the source and degradation of OM in the surface sediments of the Chukchi Sea. This study shows that total hydrolyzable amino acid (THAA) concentrations (dry weight) are high, with a mean value of (32.7 ± 15.8) μmol/g. Their spatial distribution is related to primary productivity, hydrodynamic conditions, sediment properties and other factors. The source of OM in the surface sediments of the Chukchi Sea is dominated by diatom-dominated marine productivity, with some input from terrestrial sources. Bacteria, as the main source of the D-enantiomer of AA (D-AA), not only have transforming effect on OM, but their cell walls and remnants likewise supply the OM pool. Based on a series of diagenetic indicators, we conclude that the OM in the surface sediments of the Chukchi Sea has undergone extensive degradation [DI (degradation index) = −0.59 ± 0.44], and the degradation degree in the slope is higher than that in the shelf. This study uses AA to explore the sources and degradation of OM in the sediments of the Chukchi Sea, which facilitates our understanding of OM transport and transformation on the Arctic shelf.
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Key words:
- Chukchi Sea /
- amino acids /
- degradation indicator /
- organic matter
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Table 1. Location, water depth, THAA content, OC content, specific surface area, carbon stable isotopes, THAA-C and DI of the Chukchi Sea surface sediments
Sample station Latitude/°N Longitude/°E Water depth/m THAA/(μmol·g−1) OC/% SSA/(m2·g−1) $ \text{δ} $13C/‰ THAA-C/% DI Shelf sediments LV77−2 68.57 190.09 52.70 51.5 1.68 15.68 −22.4 15.63 −0.20 LV77-3 68.88 187.85 51.00 44.4 2.03 22.11 −21.9 10.75 −0.40 LV77-4 69.20 185.09 48.70 66.1 2.64 27.08 −21.5 12.31 −0.27 LV77-5 69.71 186.79 50.60 49.2 1.93 22.25 −21.8 12.83 −0.34 LV77-6 72.20 186.38 52.72 44.2 2.08 29.61 −21.7 10.64 −0.26 LV77-7 71.18 186.51 43.00 22.1 0.98 12.97 −22.7 11.24 −0.48 LV77-8 69.59 182.52 47.00 32.2 1.00 − −22.2 15.97 −0.36 LV77-9 69.60 179.85 44.71 22.8 0.53 12.06 −22.7 21.45 −0.25 R02 67.67 −169.00 50.00 34.0 − − − − −0.51 R03 68.62 −169.00 53.70 49.1 1.11 12.17 −22.7 22.62 −0.06 R05 71.00 −169.00 44.00 23.0 − − − − −0.54 R06 72.00 −168.98 51.35 43.5 1.47 20.29 −22.1 14.68 −0.53 R07 73.00 −168.97 73.76 46.2 1.47 22.60 −22.0 15.68 −0.38 R08 74.00 −169.00 82.69 29.8 1.27 26.53 −22.3 11.42 −1.12 S02 71.92 −157.46 73.00 48.3 1.72 25.42 −22.7 14.14 −0.49 C01 69.22 −168.14 50.00 30.4 0.89 13.82 −23.6 16.99 −0.54 C03 69.03 −166.48 33.00 18.7 1.06 4.05 −24.4 8.83 −0.40 C05 70.76 −164.74 33.00 3.1 0.10 − −23.2 15.86 −0.21 Slope sediments R09 74.61 −169.03 190.00 20.6 0.86 29.59 −21.9 11.55 −1.15 R10 75.43 −167.90 164.36 13.2 0.56 26.70 −23.8 11.33 −1.55 R11 76.15 −166.20 352.43 18.0 0.79 37.45 −21.6 10.78 −1.62 R12 77.00 −163.89 438.86 9.6 0.50 24.32 −22.7 9.32 −1.33 Note: − represents no data. -
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