What are Ocean Dead Zones?

The ocean is a life source that we cannot afford to be without. Imagining the ocean, we tend to think of the hypnotizing sounds of crashing waves and the sight of birds in flight. From the shores, the seas seem like an ending oasis of beautiful waters to the human eye. There is also adventure to be found in the ocean, both above and below the water. We love exploring the depths of the ocean below by means of snorkeling and scuba diving to see the coral reefs and schools of fish.

Now, imagine if below the water, there was no more beauty to behold. Everything would be still and lifeless with overgrown algae surrounded by dead fish and other dying plants and aquatic species. These sorts of areas do exist and they are called the dead zones.

According to NOAA,

Hypoxic zones can occur naturally, but scientists are concerned about the areas created or enhanced by human activity. There are many physical, chemical, and biological factors that combine to create dead zones, but nutrient pollution is the primary cause of those zones created by humans. Excess nutrients that run off land or are piped as wastewater into rivers and coasts can stimulate an overgrowth of algae, which then sinks and decomposes in the water. The decomposition process consumes oxygen and depletes the supply available to healthy marine life.


A dead zone in the ocean is created by hypoxia and is also known as a hypoxic region, caused by insufficient amount of oxygen. These spots are found in oceans and in other large bodies of water all over the world, and can be caused by natural occurrences such as the shifting of the routine patterns of water and wind. Still, these changes have much less of an impact than human activity. Caused mainly by pollution from irresponsible industrial practices, marine animals are unable to live in these underwater areas because there is not enough oxygen circulating to allow them to survive.

Causes and Effects of Ocean Dead Zones

(Lack of Sunlight, Algae Overgrowth, and Excess Nutrients)

1. As the water heats up from climate change, there are more dead zones that are forming because of eutrophication. Eutrophication is how the underwater environment reacts to pollutants from runoff that comes from the land and leads to the overabundance of nutrients, encouraging the overgrowth of algae.

2. The algae overgrowth blocks the light from the sun, and the blocking of sunlight is harmful to creatures underwater. Plants still go through photosynthesis underwater and they also produce carbon for breathing. Animals need these plants to live underwater just as they do on land for oxygen.

3. Sunlight is especially vital in the littoral zones. These are the zones that are closest to the edge of the waters by the shores. When sunlight hits these areas of water, it absorbs deeply into the ground, encouraging plants in the ocean to grow. As this process is disrupted, the cycle of life below the water comes to a halt, causing death to species and adding to the pollution of the Earth.

4. As life ceases to exist and there is less oxygen circulating underwater, oxygen minimum zones (OMZ) are the result. These regions are a permanent disparity that have a damaging effect on the underwater ecosystem.

5. While nutrients can be healthy, too many nutrients are a form of pollution that lead to the death of organic food sources and destroys natural habitats. Phosphorus and nitrogen are already present in the water in small quantities, but too much of these elements is far from a good thing. Too much nitrogen and phosphorus in the water causes algae to grow faster than ecosystems can handle. Nitrogen can also go back into the atmosphere and create more pollution that is damaging to people and the environment and ruins our drinking water.

6. Excess nitrogen and other chemicals in the ocean lead to extreme imbalances underwater, with algal bloom resulting from the existence of these elements and being a major contributor to the creation of dead zones. Algal bloom is the formal definition for the rapid growth of algae in the water and this excess of algae can be toxic to sea creatures and plants.

7. The algae that is most responsible for dead zones is called cyanobacteria, a type of algae that is allowed to flourish because of nitrogen and phosphorus material that continue to fill up in the ocean. This algae also grows beyond the capacity of the ecosystem because, as a type of bacterial algae, it is self-reliable and can grow without undergoing the process that other plants typically depend on. Additionally, fish and other underwater species cannot eat this sort of algae.

Effects of dead zones have a major effect on what happens in the life of aquatic species.

1. A ocean dead zone is an invisible trap that there is no escaping from for marine life. Fish can’t detect dead zones before entering the areas. Unfortunately, once fish wander into a dead zone, it’s hard to escape and survive. The oxygen shortage causes the fish to lose consciousness and die shortly after. Other sea dwellers, such as lobsters and clams, are also unable to get away because they naturally move slowly.

2. Fish suffer greatly from dead zones because the extreme changes in the oxygen level changes their entire biology. Their organs become smaller, meaning they can’t reproduce or function in the necessary ways that allow them to flourish. The females are unable to produce as many eggs and the males can’t properly impregnate the females to keep the species alive.

The less biodiversity that exist underwater, the more the balance of the entire ocean is disrupted. This also leads to economic instability for local fisherman. Local fisherman do not cause as much devastation to the population of fish by catching them in small quantities instead of overfishing. They often sell the fish locally or simply prepare fish as part of healthy meals for their family.

3. We should also consider the fact that many of us choose to eat seafood instead of meat for health purposes. Generally, eating seafood causes less of a strain on the natural resources that are used to produce and distribute meat. If sea animals are poisoned in their natural habitat, then they will become unsafe for consumption and will no longer be a viable option for food. As result, our economy would be forced to place a strain on other food sources.


Solutions to Ocean Dead Zones

1. Better practices and accountability must be put in place to protect the ocean. A major step would be to stop letting so many chemicals find their way into the ocean. Oftentimes, chemicals are not disposed of properly and our oceans are not made for these materials. Every day, we pour chemicals into the drain or throw them away in the trash can. Liquid chemicals poured down the drain flow into bodies of water and cannot be filtered out. The chemicals that we combine with water for cleaning and other purposes are also part of the runoff that destroys the life cycle of the ocean.

2. As humans, we need to pay attention to where we let our sewage direct itself and to what we allow to absorb into the ground. One of the main causes of the cyanobacteria that accumulates and contributes to dead zones is our use of fertilizers that include harmful chemicals. We should use much less fertilizer when farming anywhere that is close to bodies of water as industrial farming practices encourage the existence of dead zones. Some may assume that if you’re not close by the ocean, it’s not affected by the use of fertilizers, but this isn’t always true. Fertilizing ingredients travel more easily than you may think, and can find their way from a small body of water to the ocean.

3. Far too much trash is found in the ocean as well. Treating the ocean like a large trash negatively affects us all because it creates toxicity. As previously mentioned, many of the underwater inhabitants that die due to dead zones and pollution also provide us with fresh and healthy food sources. Similarly, more pollution goes out into air and changes its quality for the worst. Because the ocean can’t break down much of the trashed material, the water is polluted. Animals choke on unfamiliar material, and because the water is poisoned, it kills various marine animals.

4. Farmers use phosphorus and nitrates to grow their crops, which eventually seeps into large rivers and this runoff is poisonous. While the waters rely on nutrients such as nitrogen and phosphorus to stimulate the growth of underwater plants, we know that excessive amounts are harmful. Naturally, a portion of excess nutrients are removed by some marine animals. If we would find additional ways to move this process along, things would go much more smoothly and balance could be achieved. Furthermore, if farmers knew the damage that is done to agriculture as a result of poisoning the ocean, they could change the way they work and find alternative approaches that don’t contribute to ruining the environment.

5. Another solution is to raise awareness. Explaining to others the importance of keeping the ocean clean can help to encourage positive habits. On a personal level, if we adhere to a sustainable lifestyle, then we can reduce the dead zones that are created. We should use less water by being conscious of our daily habits because this helps less water to go into the sewage system and the ocean. As we recycle, many of the items that are discarded of in landfills or in other random areas will not be able to go into the ocean and alter the balance of the water.

Image credit: Unspalsh , diego


A true environmentalist by heart ❤️. Founded Conserve Energy Future with the sole motto of providing helpful information related to our rapidly depleting environment. Unless you strongly believe in Elon Musk‘s idea of making Mars as another habitable planet, do remember that there really is no 'Planet B' in this whole universe.