The bottom of the Gulf of Mexico around Texas and Louisiana was recently surveyed by scientists. They discovered a larger-than-average area of oxygen-depleted water – a “dead zone” where nothing can live.
Dead Zones are low in oxygen areas in the world’s large lakes and oceans. This occurs when dissolved oxygen concentration falls to or below 2ml of O2/liter. When a body of water experiences this condition, fauna, and aquatic flora begin to change behavior so that they can section of water with higher oxygen levels can be reached. Mass mortality occurred when dissolved oxygen declines below 0.5 ml O2/liter in a body of water, and these water bodies failed to support aquatic life. In the 1970s, oceanographers began noticing the increasing number of dead zones. These mostly occur in inhabitant coastline where aquatic life is more concentrated.
Dead Zones occur when nutrients and fertilizers from farmland drain into lakes or oceans, creating an algae bonanza that eventually dies and decomposes. With more available nutrients, algae have the resources necessary to exceed their previous growth limit and begin to multiply at an increasing rate. Increasing growth leads to rapid increases in the density of certain types of algae, and this phenomenon is known as an algal bloom.
As the algae decompose, it reduces the oxygen level of water. Studies have shown that fish in dead zones change what they eat, affecting what people can catch. These zones also make commercially important species like shrimp less available in the Gulf and kill crabs and fish off the pacific northwest coast. To the marine habitat and fisheries, fertilizer pollution has caused an estimated $2.4bn in damage every year since 1980, according to the Union of Concerned Scientists.
Anthropogenic and natural factors can cause dead zones. Natural causes include water circulation patterns, changes in wind, coastal upwelling. Other environmental factors include high levels of sunlight penetration, high temperatures, and long water residence times through the water column. Natural oceanographic phenomena can also cause oxygen levels to reduce in water. Changes in ocean circulation because of climate change could cause the oxygen levels to reduce in water. Anthropogenic causes include the use of chemical fertilizers, direct sewage discharge, nutrient discharge.
In March 2004, the UN Environment Program reported 146 dead zones in the world’s oceans where there was no marine life because of a lack of oxygen. As a square kilometer, some were as small, and the largest dead zone covered 70,000 square kilometers. Four hundred five dead zones worldwide were counted by a study in 2008.
Research in details –
Scientists National Oceanographic and Atmospheric Administration (NOAA) this week shared their finding. In the Gulf, about 4m acres of habitat are unusable for bottom-dwelling species and fish. This year researchers have predicted a smaller dead zone, predicting an average-sized area.
According to Nancy Rabalais, the professor at Louisiana State University who led the study, “The distribution of the low dissolved oxygen was unusual this summer. The low oxygen conditions were very close to shore with many observations showing an almost complete lack of oxygen.”
But the Gulf is not alone in terms of the coastal region experiencing dead zones this summer. Every year since 2002, the waters off Oregon had a low oxygen area. But this year was different than other years for Oregon because, as compared to the last 35 years, the dead zone emerged earlier this year.
The global climate crisis in Oregon is making the problem worse. Warmer summer holds less oxygen than cold waters, which leads to the growth of dead zones. As the ocean absorbs more carbon, the waters become more acidic, and shellfish and crabs find it difficult to grow their cells. According to NOAA researcher Richard Feely, all this amounts to “a double whammy from the atmosphere and the ocean,” according to NOAA researcher Richard Feely.
This year along the shores of Oregon and Washington, crab fishers have described finding the carcasses of hundreds of Dungeness crabs. A task force of federal agencies and states had kept a target of keeping the dead zone’s five-year average to no greater than 1,900 sq miles. But this summer dead zone is three times larger than that. A tool has been created by NOAA, the runoff risk forecast, to help farmers apply fertilizer at optimum times so that it stays on the field, with the hopes of reducing nutrient runoff to the Gulf.
According to Rebecca Boehm, an economist with the Union of Concerned Scientists food and environment program said, “Without a significant, concentrated effort to reduce nitrogen runoff from farms and livestock operations, Gulf Coast communities will continue to bear the costs of the dead zone. The dead zone has not meaningfully shrunk in the last 30 years, and we are no closer to the goals set by the Hypoxia Task Force. Policymakers need to rethink their strategy, or we will find ourselves back here next year with the same bad news.”
The dead zone in the Gulf of Mexico –
The Gulf of Mexico is an ocean basin of the Atlantic ocean and a marginal sea, largely surrounded by the North American continent. It is bounded on the northwest, northeast, north by the Gulf Coast of the U.S and on the south and southwest by the Mexican States of Quintana Roo, Yucatan, Campeche, Tabasco, Veracruz, Tamaulipas, and on the southeast by Cuba. About 300 million years ago, it took shape as a result of plate tectonics.
Melting snow and heavy rains washed huge amounts of nutrients, particularly phosphorus and nitrogen, from sewage treatment plants, lawns, farmland, and other sources along the Mississippi River into the Gulf of Mexico. Once in the Gulf, these nutrients help crop and plant growth, help algae to bloom that reduces oxygen levels in the water, and make marine life impossible to survive.
According to NOAA, the dead zone costs the U.S. tourism and seafood industries $82 million a year. The impact could be highly damaging to the Gulf’s seafood industry. This seafood industry accounts for 40% of the nation’s seafood. Commercial species and fish usually move out to sea to avoid the dead zone, and because of this, fishers are forced to travel farther from land. They have to spend more money and time getting their catches, which adds stress to the industry, which is already affected by oil spills and hurricanes. The species that cannot move or move fast die out, giving the area the dead zone.
The dead zone in the Oregon Coast –
U.S. Route 101 is a major north-south U.S. Highway in Oregon that is along the coastline near the pacific ocean runs through the state. It runs from the south of Brooking from the California border on the Columbia River to the Washington State Line between Washington, Megler, Oregon, Astoria. US 101 is appointed as the Oregon Coast Highway No. 9 as it serves the Oregon Coast.
According to the research done in 2009, scientists say a fundamentally new trend in the ocean and atmospheric circulation patterns in the Pacific Northwest has begun and is expanding its scope beyond Oregon waters. On the Oregon Coast, there have been reported dead crabs. At 180 feet, some dissolved oxygen levels had been measured was as low as 0.55 milliliters per liter, and areas as shallow as 45 feet had been measured at 1 milliliter per liter. These oxygen levels were many times lower than normal. There was a huge pool of low-oxygen water with values as low as 0.46 milliliters per liter off the central Oregon coasts.