Exploring origin of oxygen-consuming organic matter in a newly developed quasi-hypoxic coastal ocean, the Bohai Sea (China): A stable carbon isotope perspective.
Sci Total Environ
; 837: 155847, 2022 Sep 01.
Article
in En
| MEDLINE
| ID: mdl-35550889
ABSTRACT
The Bohai Sea, adjacent to the Northwest Pacific, is a semi-enclosed shallow-water marginal sea that was considered on a critical path of eutrophication and environmental degradation. To better understand the Bohai Sea metabolism-induced summertime dissolved oxygen (DO) decline, five field surveys were conducted between July 2019 and July 2021 to investigate the seasonal/interannual and spatial variations in DO, dissolved inorganic carbon (DIC), and stable isotopic composition of DIC (δ13CDIC). Although the water-mixing scheme was subject to spatial variation, a uniform apparent ratio of δ13CDIC versus apparent oxygen utilization was estimated at -0.0122 per µmol O2 kg-1 in the Bohai Sea in summer. Based on a three-endmember water-mixing model and the mass balance of DIC and its stable isotopic composition, the assumed uniform δ13C values of oxygen-consuming organic matter in the Bohai Sea DO-deficient areas was estimated to be -19.47 ± 1.85 in 2020 and between -20.6 and - 18.1 in 2021. This isotopic composition is very similar to the δ13C value of organic matter from marine diatoms, but different to that of terrestrial organic matter sources surrounding the Bohai Sea. Our results indicate that nearly all the organic matter consumed by community respiration in the Bohai Sea is produced in situ by marine plankton. To mitigate the seasonal DO shortage in the Bohai Sea, reduction of allochthonous nutrients is crucial.
Key words
Full text:
1
Collection:
01-internacional
Database:
MEDLINE
Main subject:
Oxygen
/
Carbon
Country/Region as subject:
Asia
Language:
En
Journal:
Sci Total Environ
Year:
2022
Document type:
Article
Affiliation country:
China