Underwater Eclipse: How Darkening Oceans Disrupt Ecosystems

Image Source: Sigma Earth

Recent scientific findings reveal a startling trend: more than one-fifth of the world’s oceans have darkened significantly over the past two decades. This phenomenon, known as "ocean darkening," is shrinking vital light-dependent habitats and putting marine life at risk. Researchers warn that the consequences for ocean health, fisheries, and planetary well-being could be profound.

Extent of Ocean Darkening

Over 20% of Oceans Affected: According to new research, 21% of the global ocean has become darker, an area larger than Asia.
Photic Zone Contraction: The upper region of the ocean in which light penetrates (the photic zone) has contracted by up to 50 meters in nearly 10% of the ocean, and over 100 meters in some parts.

Impact on Marine Life

Habitat Compression: Some 90% of marine life depends on the photic zone for survival, food, and reproduction.
Increased Competition: When the photic zone is compressed, sea life is forced into shallower, more concentrated waters, increasing competition for food and putting them at greater predation risk.

Causes of Darkening

Coastal Causes: Agricultural land runoff, sediment, and organic matter are covering coastal waters, restricting light penetration.
Open Ocean Changes: Changes in plankton community, rising sea surface temperature, and ocean circulation are driving darkening in deeper waters.

Ecological and Global Implications

Turbulent Ecosystems: Reduced light disrupts photosynthesis, migration, and reproduction patterns, threatening the integrity of marine food webs.
Climate and Fisheries: Oceans' darkening might jeopardize the ocean's ability to regulate the climate and supply global fisheries, with implications for biodiversity and livelihoods of people.

Notable Findings

Regional Severity: Darkening is especially strong in polar regions, the North Atlantic, and the North Pacific—areas already suffering catastrophic ecosystem shifts with climate change.
Some Areas Lightening: About 10% of the ocean has actually lightened over the same time frame, reflecting the complexity of global changes.

Sources: New Atlas, The Indian Express, Earth.com