A scientist has discovered some regions called “dead zones” in the tropical North Atlantic, off the West African coast.
These dead zones are actually regions which lack oxygen, making it practically impossible for any living creatures to exist.
The scientists discovered a dead zone that has the lowest level of oxygen in the Atlantic ocean and where marine animals could not live.
According to the experts, a dead zone is created when swirling masses of water known as “eddies” move westwards.
Johannes Karstensen, researcher at GEOMAR and the Helmholtz Centre for Ocean Research Kiel and one of the scientists who discovered the dead zones, explained that before this recent study it was generally believed that the open water of the Atlantic had very little concentrations of oxygen: approximately 40 micromole per liter of seawater, or about one milliliter of dissolved oxygen per liter of sea water.
The concentration of oxygen described by Karstensen is very low but still can allow animals to survive in the ocean waters.
The oxygen level measured in the recently discovered dead zones is about 20 times lower than what the scientists previously measured. This means that the regions called “dead zones” are basically void of oxygen and are not habitable for marine animals.
According to the scientists, the dead zones were created by eddies that are about 90 miles in diameter.
Karstensen explained that the eddies move so fast that is very difficult for the sea water to exchange oxygen between the surrounding ocean and the rotating current.
This water circulation produces a shallow layer that is a dozen meters on top of the swirling water, where there is intense marine vegetation growth.
The scientists managed to measure the extent and the properties of these dead zones and studied how they can affect the surrounding ecosystem.
According to their findings, the zoo planktons that are inside the eddies stay at the surface of the water during the day. The scientists said that the zoo planktons usually hide in deep water in order to avoid predators.
Karstensen explained that another important aspect that is close connected to the impact on the ecosystem has also a socioeconomic dimension.
The study revealed that the dead zones observed by the scientists propagated less than 100 kilometers north of the Cape Verde archipelago.
The researchers say that it’s possible for such a dead zone to move close to the islands in the near future.
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