Over the past 20 years, the world’s oceans have gotten significantly darker. This trend could have catastrophic consequences for the planet’s marine ecosystems, fisheries and climate. The researchers came to this conclusion after analyzing satellite data and climate models. It turned out that between 2003 and 2022, 21% of ocean waters were affected by the darkening – an area equal to the landmass of Europe, Africa, China and North America combined.
About 90% of marine species live in the upper layers of the ocean where sunlight penetrates. This is where photosynthesis of phytoplankton, the microscopic algae that are the basis of food chains and produce almost half of the earth’s oxygen, takes place. However, due to decreased water transparency, the light zone has risen 50-100 meters in some regions, forcing organisms to fight for survival.
“Marine creatures use light to hunt, reproduce and navigate. If it disappears, they have to go higher up where there is less space,” explains Dr. Thomas Davies of the University of Plymouth, author of the study in the journal Global Change Biology.
Causes: from climate to currents
Darkening is most noted near coasts due to annual water runoff, or pollution. In the open ocean, however, global warming is the key factor. For example, in the Gulf Stream region near Greenland, changes in water circulation and heating lead to the formation of denser layers that block light penetration.
Interestingly, 10% of the ocean, on the contrary, became lighter. Thus, a large “light spot” appeared near Ireland, but scientists are not yet ready to explain this phenomenon.
On the verge of collapse
Professor Oliver Zielinski of the Baltic Sea Institute cautions: darkening disrupts food chains, shifts species’ ranges and reduces the ocean’s ability to absorb carbon. “Coastal areas that are most vulnerable due to pollution may lose their resilience, which will affect people as well,” he adds.
Scientists are calling for accelerated research and strategies to protect the oceans. One thing is still clear: darkening waters are not only an environmental problem, but also a direct threat to the stability of the entire biosphere.
Previously, scientists learned when Earth’s oceans were green.
According to oceanographicmagazine.com
