Oxygen is a central element of life on the Earth because it helps in aerobic respiration which converts sugar (glucose) C6H12O6 using oxygen, O2 into carbon dioxide, CO2 and water H2O this reaction gives the energy needed for cells to operate. Here, we are giving the meaning of the Oxygen Minimum Zone and Dead Zone, which is very useful for the preparation of competitive examinations like UPSC-prelims, SSC, State Services, NDA, CDS, and Railways etc.
The Oxygen Minimum Zone (OMZ) referring to the zone in the water bodies like Ocean where the oxygen saturation is at its lowest. It is also known as shadow zone. It is a place where no aquatic life is supported due to the low oxygen area in the world's oceans or large lakes. This refers to depths of about 200 to 1000 meters based on the local circumstances. Although, it is found worldwide, but very prevalent along the western coast of continents. It helps in controlling carbon and nitrogen cycling in the oceans.
Oxygen can be dissolved or absorbed into water through eh mixing of surface waters by wind and waves. But the solubility of oxygen or its ability to dissolve in water decreases when the temperature and salinity of the water increases. Changes in ocean temperature and circulation patterns compounded by human activities are leading to oxygen minimum zone (OMZ) expansion with concomitant alteration in nutrient and climate active trace gas cycling.
It is also known as hypoxia, which means reduced level of oxygen in the water. There are 146 dead zones in the world's oceans where marine life could not be supported due to depleted oxygen levels, according to the Global Environment Outlook Year Book, 2003 which is now becoming more than 400 zones. It can occur naturally, but contemporary it is increasing day by day due to the nutrient pollution created by humans.
It is caused by an interaction between biological, chemical and physical factors.
1. Increase in chemical nutrients in the water, leading to excessive blooms of algae that deplete underwater oxygen levels
2. Agricultural runoff of Nitrogen and phosphorous
3. Sewage, vehicular and industrial emissions and even natural factors