Global Ocean Darkening ( UPSC Prelims)

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News Context

A research study discovered that 21% of the global ocean experienced a darkening trend from 2003 to 2022, with significant changes observed particularly in the Arctic, Antarctic, and Gulf Stream areas.

About Darkening of the Ocean

The content discusses a decrease in light penetration into the world's oceans, resulting in a reduction of the photic zone. The photic zone is the sunlit layer, approximately 200 meters deep, where the majority of marine life, about 90%, exists.
 Causes:
      ○ In Coastal Oceans: This is due to a combination of nutrient, organic material, and sediment accumulation from agricultural runoff and increased rainfall.
      ○ In Open Oceans: The warming of surface waters leads to algal blooms, and climate-induced changes in ocean circulation patterns contribute to the issue.
 Effects: The reduction in light penetration limits ocean productivity by restricting light-dependent processes such as reproduction and photosynthesis. This decline in fish populations impacts the fisheries industry and affects climate regulation.