The Bering Sea and western Arctic Ocean, as high production areas, play a key role in the Arctic Ocean biological pump, and are vulnerable to abrupt climate change, especially sea water warming and sea ice melt. Alterations in biological pump can influence the sources and degradation of sedimentary organic matter, and thus can be indicated by fatty acid (FA) content and composition of sediment. FA analysis of surface sediments, collected during the 5th and 6th Chinese Arctic Research Expeditions, showed that the total FA of the Chukchi Shelf was exceptionally high ((97.15 ± 55.31) μg/g), while the Bering Basin was the lowest ((15.00 ± 1.3) μg/g), and the Canada Basin, the Chukchi Shelf and the Bering Shelf were intermediate ((88.65 ± 3.52) μg/g, (70.35 ± 11.32) μg/g and (38.28 ± 14.89) μg/g, respectively). Marine FAs (short chain saturated FA + unsaturated FA) accounted for the most abundant (86.82% ± 7.08%), terrestrial FAs (long chain saturated FA) as the second abundant (8.45% ± 6.62%), while bacterial FAs (odd FA) as the least (4.63% ± 2.24%); diatom index (16:1ω9/16:0) was high at the southern and northern Chukchi Shelf (> 0.82) and the Bering Shelf edge (> 0.65), while it was low at the rest areas. These results indicated that: (1) marine source was the major contributor of sedimentary organic matter of the Bering Sea and the western Arctic Ocean, while terrestrial one contributes minor; diatom predominates was the primary producers of the southern and northern Chukchi Shelf and the Bering Shelf edge; percentage of bacterial FAs was remarkably low, comparing with tropical and temperate seas, suggesting a suppressed bacterial activity under low temperature; (2) labile organic matter accumulation rate was extremely high at the Chukchi Shelf, and was extremely sensitive to sea water warming and sea ice melt; (3) chlorophyceae and prymnesiophyceae dominate phytoplankton community at the Canada Basin and the Chukchi Slope. In conclusion, FA of surface sediment can be used to indicate sources and degradation of organic matter in the Bering Sea and the western Arctic Ocean; further, combining with other samples and biomarkers, FA was viable to shed light on the response of biological pump under the abrupt Arctic climate change.
| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |