Water blooms life; yet, how many of us realise how vital it really is? To truly understand the importance of water, ask a thirsty person, or the researchers and scientists obsessively trying to find it on other planets to fuel the hope of life away from Earth.
Environmentalists, activists, experts, and others are gearing up for the Capitol Hill Ocean Week (CHOW) from June 4 to 6, just ahead of World Oceans Day on June 8. The CHOW is a premier annual conference examining policy issues on the current situation of oceans, coasts, and the Great Lakes.
The need for ocean conservation was proposed in 1992 at the Rio de Janeiro Earth Summit, to raise awareness about the importance of waterbodies, specifically, oceans. Every year, the UN Division for Ocean Affairs and the Law of the Sea coordinates different activities for the protection of oceans around the globe.
The fact of the matter, however, is that humans and their activities have been, over the years, killing this source of lifethere has been an over 400% increase in ocean dead zones over the last 50 years.
The Chicago Tribune reported on May 19 that the floods in Louisiana are likely to form a dead zone on the coast of the state by this summer; it will likely be the second-largest dead zone in the world.
What are ocean dead zones?
According to the National Geographic, dead zones are low-oxygen or hypoxic areas in oceans and lakes.
Dead zones form through eutrophication. It is defined as an increase in chemical nutrients in the water, leading to excessive growth of algae that deplete the level of oxygen underwater. The primary culprits are phosphorus and nitrogen from agricultural runoff. However, sewage, burning of fossil fuels, and vehicular and industrial emissions, besides some natural factors, such as churning of oceans, also act as catalysts to this process.
In the previous decade, an estimated 26% of the total carbon dioxide in the oceans came from fossil fuels; this concentration is expected to double over the next decade.
Ocean dead zones tend to form in areas where there is heavy agricultural and industrial activity, because industries discharge their chemical waste into the waterbodies.
Since the 1970s, dead zones have been detected in the Chesapeake Bay off Maryland, Scandinavias Kattegat Strait, the mouth of the Baltic Sea, the Black Sea, and the northern Adriatic, indicating the magnitude of the damage caused by human activities.
According to a 2008 study in Science, there were 405 identified dead zones worldwide, up from 49 in the 1960s.
Why are ocean dead zones dangerous?
The overgrowth of the cyanobacteria or the blue-green algae leads to the algae consuming more water and, in turn, blocking sunlight, causing a depletion in the level of oxygen in the water.
Such oxygen-less pockets underwater have been depleting marine life. Organisms that can flee the dead zones leave the area, while those that cannot are stressed or die of suffocation.
If some types of algae blooms are large, they produce chemicals and toxins, which is known as a harmful algal bloom. These toxins not only deteriorate aquatic life but are also harmful to humans, as they contaminate the water.
Where are the largest dead zones located?
Since 1985, when dead zone mapping began, the biggest was the Gulf of Mexico dead zone, which is about 22,000 square kilometres; to give you some perspective, that is as big as New Jersey.
One of the main reasons for its spread has been fertilisers and pesticides discarded in the Mississippi River. The other major contributor is the popular US grocery chain Whole Foods. The store gets its meat supply from some of the worst polluters in agribusiness, namely Tyson Foods and Cargill. The animal waste and fertilisers that are used to preserve and process the meat end up in the Gulf of Mexico, contaminating the waterbody and spreading the dead zone wider.
Such dead zones also cause food problems. More than 2,12,000 metric tons of food is lost due to the presence of hypoxia in the Gulf of Mexico, says Marine biologist Robert Diaz.
Last year though, scientists found the biggest. This dead zone is located in the Gulf of Oman, an important strait spanning 181,000 square kilometres that connects the Arabian Sea and the Persian Gulf; bordered by Iran, Pakistan, UAE, and Oman, it is nearly the size of Tamil Nadu.
Late last year, scientists sent remote-controlled submarines to the strait. Their findings suggest that the lack of oxygen is not due to plastic pollution or volcanic eruptions underwater. It is, in fact, an Oxygen Minimum Zone, as such areas are officially called.
Their study shows that there has been a rapid growth of almost 20,000 square kilometres of the dead zone since the 1990s. Burning of fossil fuels has exacerbated the rate of oxygen depletion.
In the Baltic Sea, there exists a dead zone of over 60,000 square kilometres (about twice the size of Belgium) at a depth of 70 metres. Only microorganisms can survive here, as the deep water contains high concentrations of toxic hydrogen sulphide.
Evolution in dead zones
Over the years, scientists have noticed certain changes in dead zones. They believed these zones were inhabitable; however, at the beginning of 2019, an unusual species of fish was discovered.
We observed cusk-eels, grenadiers, and lollipop sharks swimming in areas where the oxygen concentration was less than one per cent of the typical surface oxygen concentrations, said biological oceanographer Natalya Gallo. Usually, fish do not survive in oxygen-depleted areas; hence, it was all the more shocking.
Experts, however, caution against premature celebration, saying most species dont survive in dead zones for long. National Geographic reveals that such low-oxygen zones are causing deformities in a lot of fish. Between 2006 and 2007, nearly a quarter of female Atlantic croaker fish caught in the northern Gulfs dead zone had developed deformed testes-like organs, instead of ovaries.
Whats swirling in the Indian waters?
India is no stranger to ocean dead zones eitherone in the Indian Ocean has led to a loss of nearly 80% of the shrimp population on the coast of Goa.
New research published in the journal Nature Geosciences shows that Bay of Bengal, too, has a dead zone spanning 60,000 square kilometres, at a depth of 100-400 metres. Nearly 200 million peoples livelihoods are dependent on this Bay, which has seen a loss of two per cent in the level of oxygen over the last 50 years.
Fishing is the most common occupation in the area, and this increase in the dead zone has continued to reduced fishermens catch and put pressure on the sector.
Sailors once feared the bay for its man-eating sharks; these are now hardly ever seen in the waters. Numbers of other predators, such as grouper, croaker, and rays also have dwindled. Catches now mainly consist of sardines, which are at the bottom of the marine food web.
The Mergui Island in the Bay of Bengal, towards the Thai-Myanmar border, is one of the most secluded parts in the area. The depleting catch due to cyanide poisoning has affected the lives of the islanders, forcing them to flee to less affected zones, such as Myanmar or Thailand.
With climate change set to worsen, scientists also fear a nutrient alteration in the fish available in the Bay of Bengal.
Time will tell, but the Bay of Bengal is at a tipping point, and we currently need models to illuminate how human activities will impact the nitrogen cycle in the area and across the world, warns Laura Bristow, a scientist at the Max Planck Institute for Marine Microbiology in Bremen and The National Institute of Oceanography of India.
The way forward
It is, however, possible to reverse dead zones through concentrated efforts. Since the discovery of the first one, around 160 dead zones have recovered due to improved management of sewage and agricultural runoff. But increase in the use of fertilisers has slowed down the rate of recovery.
This year, in a first, both the BJP and Congress addressed climate change in their respective manifestos for the Lok Sabha election 2019.
The BJP promised to focus on renewable energy and talked about Green Bonus, a scheme for the protection of forests in the Himalayan region to achieve the minimum 33% green cover from the current 22%. The Congress, on the other hand, proposed two major schemesone for the restoration of the soil quality and the other for the conservation of waterbodies.
Globally, mathematical models have been developed to stop the spread of these zones. Also, studies are being conducted on how to make an oxygen-deprived waterbody oxygen-rich again. In principle, such a recovery is possible, but if the waters become warmer, the recovery will take longer.
Furthermore, 190 countries have pledged compliance to the Sustainable Development Goals, which includes a call to halve untreated wastewater by 2030 and reduce marine pollution by 2025. The UN Environment Assembly committed to a Pollution-Free Planet and cleaning up a third of the worlds coastlines by 2030; and last year, the International Nitrogen Initiative announced a global goal to cut nitrogen waste in half by 2030.
Global warming is having a deep impact on ocean dead zones, while the dead zones themselves are hastening climate change. It is a vicious cycle, and we dont have a lot of time to right it.
Amrita Deshmukh is a Writing Analyst at Qrius