Ocean 'dead zones,' areas with critically low or no oxygen, continue to pose a significant threat to marine life in 2025. These zones, which can be perennial or seasonal, severely impact aquatic life, particularly on the seabed and in deeper waters. The first dead zones were discovered in the 1970s, and their prevalence has increased significantly since then.
A 2008 study identified over 400 dead zones worldwide, including areas in America, China, Japan, and Australia. The Gulf of Mexico, near the Mississippi River's mouth, remains one of the most severely affected areas. These zones are caused by a combination of natural processes and human activities, primarily the discharge of waste and agricultural runoff, which leads to oxygen depletion.
Excessive nutrients, especially nitrogen and phosphorus, cause eutrophication, stimulating excessive algae growth. When this algae dies and decomposes, it consumes oxygen, creating hypoxic conditions. Fortunately, dead zones can be reversed by mitigating or eliminating their causes. For example, collaborative efforts are underway in 2025 to reduce nutrient pollution in the Chesapeake Bay, although meeting all reduction goals remains a challenge. The application of programs like Costa Rica's Ecological Blue Flag Program globally can foster a culture of protecting water resources and oceans.