It is the oceanic equivalent of Armageddon and does not support most life forms. The Gulf of Mexico dead zone covers an area larger than Connecticut. This zone is getting bigger each year.
The Gulf of Mexico dead zone is fed by the Mississippi River, the 3rd biggest river basin behind the Amazon in South America, and the Congo in Africa. The Mississippi River runs 2,350 miles across the heart of the US before emptying into the Gulf of Mexico.
But the river is also a part of the reason for the Gulf of Mexico dead zone. Countless marine animals are killed or forced out in the summer from the oxygen-starved region. This year might be the worst, according to the National Oceanic and Atmospheric Administration (NOAA).
The Immense Size Of The Gulf Of Mexico Dead Zone
The Gulf of Mexico dead zone remains the second largest among the 400 plus such zones worldwide and the largest within US territory. Other dead zones within US territory include Lake Eire, Long Island Sound, and Puget Sound, Chesapeake Bay, plus many stretches of the coastline.
The Gulf of Mexico dead zone is growing in size and this year will have reached 7,829 square miles. Runoff from the Mississippi River is responsible for the size of the patch. These come from the vast urban and agricultural lands of the Midwestern farmlands of America and also waste from cities like St. Louis, Minneapolis, Baton Rouge, New Orleans, and Memphis.
These runoffs feed and invigorate the algae bloom leading to extremely low levels of oxygen, or ‘hypoxia.’ This makes this water unable to support any form of marine life.
Each year the Mississippi River is getting more toxic as the use of synthetic fertilizers, cattle waste, plus other pollutants rich in pollutants flow south, feeding the Gulf of Mexico dead zone.
Nancy Rabalais, a marine scientist and an expert on dead zones, said that the chemical-rich waters gushing into the Gulf of Mexico dead zone feeds the algae and leads to further lowering of the oxygen levels.
She says that the nitrate load in the river in May is the best indicator of the extent of that year’s dead zone. And this year it is turning into the worst ever.
And the fishermen living in these waters are the worst affected. they are forced to cross the dead zone to reach the deeper ocean in search of fish. Hypoxic water with oxygen below 2 parts per million.
The Increase In Size Is Affecting Livelihoods As Well
The zone for fishing is shrinking by the day. Inshore fisheries with smaller boats not fit for the high sears are forced to stay idle.
The hypoxic zone spanning the Gulf of Mexico dead zone is a center of rich and productive fishery. The increase in the frequency and area of the hypoxic zone has turned into a cause of economic and environmental concern.
Ironically, the cause of the dead zones is phytoplankton, the basis of the food web of the ocean. They produce close to half the oxygen on earth and are a crucial part of the ocean ecosystem. But overfeeding them can cause sudden changes that can have disastrous consequences.
But their conversion into an algae bloom can spell disaster for marine life in the region. Algae bloom doesn’t always cause a dead zone. But the change into a destructive bloom can happen suddenly.
A portion of the algae bloom turns toxic and can be quite dangerous to live in the vicinity. One of the most dangerous algae blooms is those that cause red tides. They begin as rosy plumes, giving off the smell of rotting fish.
They cause eye and skin irritation among swimmers. They even let off a stinging gas, drifting to the beaches at times.
Such poison can also permeate the food chain and travel up through bioaccumulation. They can cause various ailments like poisoning from the toxic ciguatera fish, which causes vomiting and neurological problems.
Even non-toxic algae blooms can also interfere with fishing due to their volume. They affect the feeding routines of even the whales. They overwhelm seagrass beds and coral reefs, threatening the marine life living there. They include some commercially significant fish.
Algae Bloom Not Solely Responsible For Spots Such As The Gulf Of Mexico Dead Zone
Several factors combine to lead to the formation of a dead zone. Sudden algae bloom eventually sink to the bottom of the ocean where they get digested by bacteria deep in the waters. This process consumes a vast amount of oxygen and leads to a sudden shortage of it.
But under normal conditions, churning driven by ocean winds balance out the lack of oxygen in the water. Other conditions, such as a rise in temperatures, and alternate layers of salty and fresh layers of water also combine to create places such as the Gulf of Mexico dead zone.
A warm layer of water at the surface and the cold water underneath form separate layers and prevent vertical churning capable of carrying oxygen to the depths.
Additionally, freshwater infusion from the rivers forms an upper layer that traps saltwater, starved of oxygen, below the surface.
But the biggest cause of the Gulf of Mexico dead zone is the excess nutrients that flow into the sea from the Mississippi River. These excess 1.7B tons cause algae blooms. These nutrients are part of the agricultural runoffs, manures, fertilizers, and soil. There are also fossil-fuel discharges, and industrial and household pollutants.
Fish swim out to the open oceans when faced with such a depletion. But some varieties, like the carp that stay behind, have been found to possess reduced reproductive organs that drastically affect their population. The worst affected are the marine creatures dwelling at the bottom of the sea. They cannot move out and perish.
The Mississippi River is not the only source of the problem but remains a major one. Fear of affecting the farming economy of Midwestern America has prevented any regulation to regulate nutrient runoffs.
An increase in wetland cover, and boosting the presence of shellfish, no-till farming, and a better drainage system in farms can limit nutrient pollution to some extent.