A "dead zone," or a region of low to no oxygen, has grown larger than Connecticut in the Gulf of Mexico, making it unsuitable for certain commercial marine species, and experts believe the lack of tropical activity is to blame.

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Imbalance Nutrient Levels

When surplus nutrients such as nitrogen and phosphorus from agriculture and sewage from towns and farms upstream wash into the Gulf, a hypoxic zone, also known as a dead zone, forms. During the warmer months, algae feed on these nutrients, and as the algae die and sink to the Gulf's floor, bacteria feed on the vast tangled masses, depleting the oxygen in the surrounding water.

Low Oxygen

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The ensuing low-oxygen zone is known as a hypoxic zone or a dead zone since it cannot support marine life, and it occurs every year in the Gulf. It may not only endanger local animals, but it may also have a financial impact on fisheries.

According to the National Oceanic and Atmospheric Administration (NOAA), hypoxic environments affect fish diets, growth rates, reproduction, habitat usage, and availability of economically harvested species like shrimp.

Fisheries along the Louisiana coast will now have to contend with a larger-than-normal dead zone.

Dr. Nancy Rabalais, professor at Louisiana State University and LUMCON, and the principal investigator told AccuWeather, "Basically half of the Louisiana coast for several miles, many miles offshore, the oxygen was too low to support the occurrence of penaeid shrimp, which is one of our biggest economic fisheries in that area." "As a result, that region was no longer available as a viable home for those shrimps. I'm not sure how it will translate into catches in money in the next month or two."

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Hypoxic Area

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The hypoxic area was expected to cover 4,880 square miles. Still, scientists from Louisiana State University and the Louisiana Universities Marine Consortium discovered a few abnormalities during the yearly survey, from July 25 to August 1.

For starters, the dead zone ended up being 6,334 square miles in size, which, although not huge, is about the size of Rhode Island in terms of square miles.

The scientists ascribed the larger-than-expected size to the Mississippi River's higher-than-average summer production, which meant more algae-feeding nutrients as well as more fresh water pushed into the basin.

"More freshwater increased the differential between the upper and lower layers, preventing oxygen from reaching from the surface to the bottom," Rabalais stated.

Low oxygen levels were distributed differently this year than in previous years, with the region west of the Atchafalaya River being bigger than in previous years. According to Rabalais, southerly winds and the resultant currents would have forced the discharge of fresh water back toward the shore and west of the Atchafalaya Delta.

In early July, Hurricane Elsa, which hit Florida's west coast, was the most recent tropical system to hit the Gulf. However, during late June, Tropical Storm Claudette was the only storm that came close enough to cause some mixing in the studied region.

A smaller-than-expected dead zone in 2020 was ascribed to substantial mixing produced by Hurricane Hanna, which passed across the Gulf ahead of the study, rather than a reduction in nutrients carried downstream.

Combatting Hypoxia

According to the Hypoxia Task Force, the hypoxic zone in 2020 was 2,116 square miles, the third smallest in the 34 years of data. The dead zone was initially estimated to cover 6,700 square miles.

Spreading Dead Zone

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In contrast, the biggest dead zone measured in 2017 was 8,776 square miles.

According to NOAA, the average hypoxic zone over the last five years was 5,380 square miles, about three times bigger than the Hypoxia Task Force's 2035 objective of 1,930 square miles. To put things in perspective, the region is now larger than Connecticut, with the aim of shrinking it to the size of Rhode Island.

While Louisiana has been hit the worst, it isn't the only state that has contributed to the development of the dead zone.

Possible Causes

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According to the US Environmental Protection Agency, water from 31 states in the United States and two Canadian provinces drains into the Mississippi River, forming a drainage basin of over 1,245,000 square feet. These extra nutrients are carried to the Mississippi River via tributaries and rivers from these states, notably the Ohio and Missouri rivers. In addition, farms provide a significant amount of nitrogen.

Agriculture is the primary source of nitrogen, according to Rabalais. "It's roughly 70% row crops," says the farmer.

Rabalais went on to say that local water boards might enhance their sewage treatment and that the more fossil fuels are used, the more nitrogen is released into the river.

Rabalais remarked, "We're all in this together."

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