海洋低氧現象

海洋低氧現象是由於人為活動^[1]而導致的海洋氧含量降低的現象，這是人為排放的二氧化碳^[2][3]和富營養化日益嚴重造成的結果。主要表現為在沿海和河口缺氧區域（或死亡區）的數量不斷增加，以及全球海洋中最低氧含量區域的擴大。海洋中氧含量的下降相當迅速，全球低氧海域以每年5.54%的速率增長^[4]，對所有有氧海洋生物以及依賴海洋生物獲取營養或生計的人們構成了威脅^{[5] [6][7][8]}。

全球海洋低氧區域圖

一般而言，水中溶解氧濃度小於2mg/L時，就被認為處於低氧狀態^[9]。可分為周期性低氧、季節性低氧和持續性低氧^[10]。

當前波羅的海是全球最大的死亡區，20%的海域至少有40年一直處於缺氧狀態^[11]，而黑海在150-250米水層處有90%的海域出現低氧現象^[12]。

參看

• 缺氧事件

參考文獻

1. Laffoley, D; Baxter, JM. Ocean deoxygenation : everyone’s problem. Switzerland: Gland. 2019: 562 [2020-11-14]. ISBN 978-2-8317-2013-5. （原始內容存檔於2021-04-13）.
2. Stramma, L; Johnson, GC; Printall, J; Mohrholz, V. Expanding Oxygen-Minimum Zones in the Tropical Oceans. Science. 2008, 320 (5876): 655–658. doi:10.1126/science.1153847.
3. Mora, C; et al. Biotic and Human Vulnerability to Projected Changes in Ocean Biogeochemistry over the 21st Century. PLOS Biology. 2013, 11 (10): e1001682. doi:10.1371/journal.pbio.1001682.
4. Vaquer-Sunyer, Raquel; Duarte, Carlos M. Thresholds of hypoxia for marine biodiversity. Proceedings of the National Academy of Sciences. 2008-10-07, 105 (40): 15452–15457. doi:10.1073/pnas.0803833105.
5. Oceans suffocating as huge dead zones quadruple since 1950, scientists warn. The Guardian. 2018-01-04 [2020-11-14]. （原始內容存檔於2021-04-13）.
6. Niina Heikkinen, ClimateWire. Ocean's Oxygen Starts Running Low. Scientific American. 2016-05-02 [2020-11-14]. （原始內容存檔於2021-02-26） （英語）.
7. Long, Matthew C.; Deutsch, Curtis; Ito, Taka. Finding forced trends in oceanic oxygen: TRENDS IN DISSOLVED OXYGEN. Global Biogeochemical Cycles. 2016-02, 30 (2): 381–397. doi:10.1002/2015GB005310.
8. Guest post: How global warming is causing ocean oxygen levels to fall. Carbon Brief. 2018-06-15 [2020-11-14]. （原始內容存檔於2021-02-04） （英語）.
9. Gray, Js; Wu, Rs; Or, Yy. Effects of hypoxia and organic enrichment on the coastal marine environment. Marine Ecology Progress Series. 2002, 238: 249–279. doi:10.3354/meps238249.
10. Diaz, R. J.; Rosenberg, R. Spreading Dead Zones and Consequences for Marine Ecosystems. Science. 2008-08-15, 321 (5891): 926–929. doi:10.1126/science.1156401.
11. Conley, Daniel J.; Humborg, Christoph; Rahm, Lars; Savchuk, Oleg P.; Wulff, Fredrik. Hypoxia in the Baltic Sea and Basin-Scale Changes in Phosphorus Biogeochemistry. Environmental Science & Technology. 2002-12, 36 (24): 5315–5320. doi:10.1021/es025763w.
12. Diaz, Robert J. Overview of Hypoxia around the World. Journal of Environmental Quality. 2001-03, 30 (2): 275–281. doi:10.2134/jeq2001.302275x.