Dead zones are a result of eutrophication. These lifeless water regions are characterized by low oxygen levels otherwise known as hypoxia. Hypoxia is primarily caused by increased microbial respiration that goes along with the breakdown of organic matter. While the name implies otherwise, the microorganisms that live on the decomposing debris prevent dead zones from being without life.

Animals and plants suffocate to death being in dead zones because they require dissolved oxygen to survive. Unfortunately, human-caused impacts like exacerbated eutrophication and climate change are only continuing to contribute to an unprecedented rise in the occurrence and intensity of dead zones. There are, however, natural dead zones as well.

• Natural Dead Zones 

While most of the dead zones are primarily caused by pollution, there are natural dead zones as well. The lower Black Sea, for example, contains the largest dead zone on earth developed organically.

• The Severity of Dead Zones  

There are warning signs of dead zones, for example, Red Tide algal blooms are an ominous sign for marine life. Red tides and vast areas of dead zones are mostly caused by nutrient runoff into the water, destroying wildlife in the process.

More fish, crabs, and other species perish every year as dead zones increase globally. Chemical fertilizers, untreated sewage, and other waste dumped into earth’s water bodies are the main offenders. Currently, there are around 415 coastal dead zones throughout the world. The documented cases of hypoxic areas have sharply increased from 1960 with at least 169 documented cases between then and 2007. Most of the world's dead zones are found along the eastern coast of the United States, as well as the Baltic, Japanese, and Korean Peninsular coastlines. 

Conventional agricultural operations, among other factors are largely responsible for the dead zone mayhem.

Nutrient Pollution from Conventional Agriculture  

The problematic sequence of coastal water pollution, ironically, starts on land. A significant source of freshwater nitrate pollution is caused by agriculture. Around 50% of the nitrogen sprayed on crops often goes unutilized because it leaches into the groundwater. Land erosion runs off the extra fertilizer into smaller water tributaries before being led out to sea and settling in coastal bays. These sources release nitrogen and phosphorus into rivers and marine areas or transfer them from the atmosphere, leading to distressing and often irreparable impacts. Numerous rivers, lakes, and oceans are impacted by eutrophication and dead zones brought on by nutrient runoff. The crude water quality has negative impacts on fishery outputs, drinking water sources, and agricultural production itself.

Fixing The Issue of Dead Zones 

The only way to mitigate dead zones is to address their sources. Given that agriculture and industrial processes are largely responsible for causing the problem, it is imperative to rectify the wrongs in these sectors.

The most obvious step is reducing the use of fertilizers and runoff of surplus nutrients from croplands. Along with it, preventing animal feces from entering the waterways. We also need to be more prudent in industrial procedures, including minimizing the release of chemicals, organic matter, and nutrients from production sites. Further, managing sewage treatment plants more efficiently to lessen nutrient runoff into groundwater and surface waters.

The coastal waters would receive much less nitrogen and phosphorus from these changes, slowing down the spread of dead zones across the world.  

Final Thoughts  

As of now, the Arabian Sea has the largest dead zone where marine life cannot flourish because of a persistent lack of oxygen. North of the Gulf of Mexico has the second-largest dead zone. This is alarming given that The Gulf of Mexico provides 65% of the harvested oysters, 72% of the harvested shrimp, and 16% of the commercial fish caught in the United States. A dead zone in such a crucial region not only threatens a significant loss of goods that are highly sought after by consumers but also disrupts the country’s sizable commercial economy. With dead zones rapidly expanding, it's time to get our priorities straight.