Ocean dead zones (often referred to as hypoxic zone) are areas of large bodies of water that have been depleted of the levels of oxygen required to support life. Hypoxia, or hypoxic areas, refer to lowered oxygen levels in a body of water. In aquatic ecosystems, excess nutrients such as phosphorus and nitrogen drive algae overgrowth. Increased plant and algae growth is caused by a process known as eutrophication which is harmful for other non-algae forms of aquatic life. Eutrophication is the process of excess algae growth, which drains oxygen from the ecosystem and depletes the supply available to other forms of life.
What Effect Does Eutrophication and Dead Zones Have Underwater Aquatic Life?
When an aquatic environment becomes saturated with nitrogen and phosphorus, algae in the body of water is given the nutrients to grow excessively. Algae overgrowth consumes oxygen from underwater plants and animals. Large concentrations of algae also obstruct sunlight from reaching other underwater species. Aquatic life will either die, become ill or become ill in underwater hypoxic zones. These areas eventually become biologically desolate.
Ocean dead zones can occur naturally but are exacerbated by agricultural run-off from farmland that carries nutrients from fertilizers and animal manure into rivers and streams, eventually flowing into larger bodies of water. Septic systems and sewage treatment facilities likewise discharge nitrogen that end up groundwater and surface water. Air pollution from cars, factories, gas-powered tools, and power plants also play a role in nitrogen pollution.