Gulf of Mexico 'dead zone' has grown larger than Connecticut
By
Adriana Navarro, AccuWeather staff writer
Updated Aug 9, 2021 2:50 PM EDT
Scientists prepare to collect near-bottom water aboard the R/V Pelican to verify oxygen measurements used to determine the size of the Gulf of Mexico hypoxic zone. (NOAA/LUMCON/LSU)
(NOAA/LUMCON/LSU)
A “dead zone,” or an area of low to no oxygen, in the Gulf of Mexico has grown larger than Connecticut, creating an uninhabitable environment for some commercial marine life, and scientists are saying the sparse amount of tropical activity has played a role.
An hypoxic zone, also referred to as a dead zone, is formed when excess nutrients such as nitrogen and phosphorus from agriculture and sewage from cities and farms upstream wash into the Gulf. Algae then feeds on these nutrients during the warmer months, and when that algae dies and sinks to the Gulf's floor, the bacteria that then eats away at the large tangled masses depletes the oxygen in the surrounding water.
The resulting area of low oxygen is called a hypoxic zone, or a dead zone as it becomes unable to support marine life, and it forms in the Gulf every year. Not only can it harm local wildlife, but it can also financially impact fisheries.
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Hypoxic waters have been found to alter fish diets, growth rates, reproduction, habitat use and availability of commercially harvested species such as shrimp, according to the National Oceanic and Atmospheric Administration (NOAA).
Now, fisheries along the coast of Louisiana will have to deal with a larger-than-average dead zone.
"Basically half of the Louisiana coast for several miles, many miles off shore, the oxygen was too low to support the occurrence of penaeid shrimp, which is one of our biggest economic fisheries in that area," Dr. Nancy Rabalais, professor at Louisiana State University and LUMCON, and also the principal investigator, told AccuWeather. "So that area was basically lost as available and suitable habitat to those shrimp. How that's going to convert to catches in money in the next month or so, I can't really say."
Map of measured Gulf hypoxia zone, July 25-31, 2021. (LUMCON/NOAA)
(LUMCON/NOAA)
The hypoxic area had previously been forecast to reach 4,880 square miles, but when scientists at Louisiana State University and at the Louisiana Universities Marine Consortium had conducted the annual survey from July 25 to Aug. 1, they found a few anomalies.
For one, the dead zone ended up measuring 6,334 square miles -- and while that doesn't appear much larger, the difference in square miles is roughly the size of Rhode Island.
The scientists attributed the above-forecast size to a larger-than-average summer output of water from the Mississippi River, which meant more of the algae-feeding nutrients as well as more fresh water pumped into the basin.
"[More fresh water] strengthened the difference between the upper layer and the bottom layer, and that prevents oxygen from getting from the surface to the bottom," Rabalais explained.
The R/V Pelican at dock before heading out to sample the Gulf of Mexico hypoxic zone. The annual survey cruise has been performed since 1985, creating an important long-term data set for scientists. (LUMCON/LSU)
The distribution of the low oxygen was also different from past years, with the area west of the Atchafalaya River larger than it had been in the past. Rabalais attributed this to southerly winds and the resulting currents, which would have pushed the outflow of fresh water back toward the shore and west of the Atchafalaya Delta.
This Atlantic hurricane season's sparse amount of tropical activity in the area may have also had a role. Over the past three years, wind directions, hurricane conditions or both have disrupted hypoxia formation and maintenance. This year, however, the Atlantic basin has been quiet for nearly a month following the dissipation of Elsa.
The last tropical system in the Gulf had been Hurricane Elsa in early July, but that storm had closely hugged Florida's west coast. Tropical Storm Claudette was the only storm to come close to the surveyed area to offer some mixing during late June.
During 2020, a smaller-than-forecast dead zone was attributed, not to a reduction in nutrients that were washed downstream, but to extensive mixing caused by Hurricane Hanna, which passed through the Gulf ahead of the survey.
Long-term measured size of the hypoxic zone (green bars) measured during the ship surveys since 1985, including the target goal established by the Mississippi River/Gulf of Mexico Watershed Nutrient Task Force and the 5-year average measured size (black dashed lines). (LUMCON/NOAA)
The hypoxic zone measured 2,116 square miles in 2020 -- the third smallest year in the 34 years of records, according to the Hypoxia Task Force. The original forecast for the dead zone was at 6,700 square miles.
Conversely, the largest dead zone measured was 8,776 square miles during 2017.
The average hypoxic zone over the past five years has been 5,380 square miles, nearly three times larger than the 2035 target of a five-year average of 1,930 square miles set by the Hypoxia Task Force, NOAA noted. For context, the area is currently larger than Connecticut, and the goal has been to shrink it to the size of Rhode Island.
While Louisiana is the state that's the most impacted, it's not the only state that contributes to the formation of the dead zone.
Water from 31 states across the U.S., plus two Canadian provinces, drain into the Mississippi River, creating a drainage basin over 1,245,000 square feet, according to the U.S. Environmental Protection Agency. As tributaries and rivers from these states, including the Ohio and Missouri rivers, join the Mississippi River, they bring along these excess nutrients that are eventually dumped in the Gulf. A large chunk of the nitrogen comes from farms.
"The main source of the nitrogen is agriculture," Rabalais said. "It's about 70% row crops."
Rabalais added that there were also municipal water boards that could improve their sewage treatment, and the more that fossil fuels are used, the more the resulting nitrogen will find its way down the river.
"We're all in this together," Rabalais said.
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News / Weather News
Gulf of Mexico 'dead zone' has grown larger than Connecticut
By Adriana Navarro, AccuWeather staff writer
Updated Aug 9, 2021 2:50 PM EDT
Scientists prepare to collect near-bottom water aboard the R/V Pelican to verify oxygen measurements used to determine the size of the Gulf of Mexico hypoxic zone. (NOAA/LUMCON/LSU)
A “dead zone,” or an area of low to no oxygen, in the Gulf of Mexico has grown larger than Connecticut, creating an uninhabitable environment for some commercial marine life, and scientists are saying the sparse amount of tropical activity has played a role.
An hypoxic zone, also referred to as a dead zone, is formed when excess nutrients such as nitrogen and phosphorus from agriculture and sewage from cities and farms upstream wash into the Gulf. Algae then feeds on these nutrients during the warmer months, and when that algae dies and sinks to the Gulf's floor, the bacteria that then eats away at the large tangled masses depletes the oxygen in the surrounding water.
The resulting area of low oxygen is called a hypoxic zone, or a dead zone as it becomes unable to support marine life, and it forms in the Gulf every year. Not only can it harm local wildlife, but it can also financially impact fisheries.
CLICK HERE FOR THE FREE ACCUWEATHER APP
Hypoxic waters have been found to alter fish diets, growth rates, reproduction, habitat use and availability of commercially harvested species such as shrimp, according to the National Oceanic and Atmospheric Administration (NOAA).
Now, fisheries along the coast of Louisiana will have to deal with a larger-than-average dead zone.
"Basically half of the Louisiana coast for several miles, many miles off shore, the oxygen was too low to support the occurrence of penaeid shrimp, which is one of our biggest economic fisheries in that area," Dr. Nancy Rabalais, professor at Louisiana State University and LUMCON, and also the principal investigator, told AccuWeather. "So that area was basically lost as available and suitable habitat to those shrimp. How that's going to convert to catches in money in the next month or so, I can't really say."
Map of measured Gulf hypoxia zone, July 25-31, 2021. (LUMCON/NOAA)
The hypoxic area had previously been forecast to reach 4,880 square miles, but when scientists at Louisiana State University and at the Louisiana Universities Marine Consortium had conducted the annual survey from July 25 to Aug. 1, they found a few anomalies.
For one, the dead zone ended up measuring 6,334 square miles -- and while that doesn't appear much larger, the difference in square miles is roughly the size of Rhode Island.
The scientists attributed the above-forecast size to a larger-than-average summer output of water from the Mississippi River, which meant more of the algae-feeding nutrients as well as more fresh water pumped into the basin.
"[More fresh water] strengthened the difference between the upper layer and the bottom layer, and that prevents oxygen from getting from the surface to the bottom," Rabalais explained.
The R/V Pelican at dock before heading out to sample the Gulf of Mexico hypoxic zone. The annual survey cruise has been performed since 1985, creating an important long-term data set for scientists. (LUMCON/LSU)
The distribution of the low oxygen was also different from past years, with the area west of the Atchafalaya River larger than it had been in the past. Rabalais attributed this to southerly winds and the resulting currents, which would have pushed the outflow of fresh water back toward the shore and west of the Atchafalaya Delta.
This Atlantic hurricane season's sparse amount of tropical activity in the area may have also had a role. Over the past three years, wind directions, hurricane conditions or both have disrupted hypoxia formation and maintenance. This year, however, the Atlantic basin has been quiet for nearly a month following the dissipation of Elsa.
The last tropical system in the Gulf had been Hurricane Elsa in early July, but that storm had closely hugged Florida's west coast. Tropical Storm Claudette was the only storm to come close to the surveyed area to offer some mixing during late June.
During 2020, a smaller-than-forecast dead zone was attributed, not to a reduction in nutrients that were washed downstream, but to extensive mixing caused by Hurricane Hanna, which passed through the Gulf ahead of the survey.
Long-term measured size of the hypoxic zone (green bars) measured during the ship surveys since 1985, including the target goal established by the Mississippi River/Gulf of Mexico Watershed Nutrient Task Force and the 5-year average measured size (black dashed lines). (LUMCON/NOAA)
The hypoxic zone measured 2,116 square miles in 2020 -- the third smallest year in the 34 years of records, according to the Hypoxia Task Force. The original forecast for the dead zone was at 6,700 square miles.
Conversely, the largest dead zone measured was 8,776 square miles during 2017.
The average hypoxic zone over the past five years has been 5,380 square miles, nearly three times larger than the 2035 target of a five-year average of 1,930 square miles set by the Hypoxia Task Force, NOAA noted. For context, the area is currently larger than Connecticut, and the goal has been to shrink it to the size of Rhode Island.
While Louisiana is the state that's the most impacted, it's not the only state that contributes to the formation of the dead zone.
Water from 31 states across the U.S., plus two Canadian provinces, drain into the Mississippi River, creating a drainage basin over 1,245,000 square feet, according to the U.S. Environmental Protection Agency. As tributaries and rivers from these states, including the Ohio and Missouri rivers, join the Mississippi River, they bring along these excess nutrients that are eventually dumped in the Gulf. A large chunk of the nitrogen comes from farms.
"The main source of the nitrogen is agriculture," Rabalais said. "It's about 70% row crops."
Rabalais added that there were also municipal water boards that could improve their sewage treatment, and the more that fossil fuels are used, the more the resulting nitrogen will find its way down the river.
"We're all in this together," Rabalais said.
Related:
Keep checking back on AccuWeather.com and stay tuned to the AccuWeather Network on DirecTV, Frontier, Spectrum, FuboTV, Philo, and Verizon Fios.
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