A dead zone or hypoxic zone is an area in the ocean that cannot support animal life because of low concentration of oxygen. Dead zones are also found in lake and rivers. Hypoxic zones are caused by the excessive bloom of algae which deplete oxygen concentration in water.
Causes of Hypoxic Zones
Dead zones can occur naturally, but most are caused by human activity especially the dumping of chemicals such as agricultural fertilizer, sewage, and industrial waste. The disposal of these nutrients into the ocean allows for the rapid boom of algae. Agricultural fertilizer is the largest cause of hypoxic zones as it causes algea blooms. When the algae dies, it sinks to the floor of the ocean where it is decomposes. The process consumes massive amount of oxygen leaving the surrounding environment dilapidated. Marine animals feeding on the algae either die or relocate from these zones resulting in more algae that worsen the situation.
Global Dead Zones
No part of the world is in immune to this ecological disaster. There are about 400 known dead zones around the globe, but the Gulf of Oman and the Gulf of Mexico have been affected immensely. In early 2018, researchers found what is thought to be the world’s largest dead zone in the Gulf of Oman in the Arabian Sea. The hypoxic zone is as large as the state of Florida. The area is totally devoid of oxygen and shows minimal present for aquatic animals. The concentration of algae is extremely high that it took the use of underwater robots to map out the exact area affected. The Gulf of Mexico is the perhaps the most famous dead zone as millions of tons of waste is dumped by the Rio Grande and the Mississippi rivers. The condition of the gulf has decimated the once thriving shrimp industry in the regions. Other dead zones in the US are found off the coast of Virginia and Oregon.
Fortunately, the damage caused by dead zones can be reversed by eliminating or reducing the dead zone. In the 1990s, the fall of the Soviet Union led to the disappearance of a dead zone in the black sea due to the spike in the cost of chemical fertilizer in the region. Although this was unintentional, it proved that dead zones are reversible. Since then, the United Nations and policymakers have been pushing for a reduction in industrial emission of fertilizer. Conservation efforts by countries sharing the Rhine River have reduced the size of the North Sea’s dead zone by 35%.