Underwater robots have recently made a discomforting discovery: the Gulf of Oman harbors a “dead zone” nearly the size of Florida. 
 
 Remote-controlled submarines — sent forth by researchers from the University of East Anglia — have identified the world’s largest dead zone. This mass of water, spanning a chilling 63,700-square-mile (roughly 165.000 km²) area in the Gulf of Oman, is nearly devoid of oxygen. That’s an area comparable to the surface of Florida (170,305 km²), and over two times larger than Scotland (80,077 km²). 
 
 Although the technical term for such a place is an “oxygen minimum area”, their colloquial name of “dead zones” is quite apt. Marine flora and fauna are completely dependent on oxygen dissolved in the water for their survival. The absence of this element also alters the local nitrogen cycle, causing nitrous oxide emissions — which is a greenhouse gas 300 times more powerful than carbon dioxide. 
 
 Dead zones are generally the product of climate change-induced ecological shifts and/or chemical run-off from land — for example, from sewage or chemical fertilizers. One particularly worrying prospect is that as climate change makes ocean water warmer, it will be less able to hold oxygen — meaning more frequent and more intense dead zones. 
 
 “Our research shows that the situation is actually worse than feared – and that the area of dead zone is vast and growing,” said Dr Bastien Queste, who led the research. “The ocean is suffocating.” 
 
 Dead zones are “a disaster waiting to happen,” he adds. 
 
 The Gulf of Oman dead zone sits between a depth of 200 and 800 meters. The team report that it is made up of entirely anoxic or suboxic conditions — meaning there’s no oxygen or very low oxygen present, respectively. 
 
 Computer simulations, based on data the team recovered on site, revealed that the dead zone has increased both in size and severity since the 1990s and is still growing, the team reports. Unless addressed it could have drastic consequences for life both in and out of the sea. 
 
 “Another interesting question is now that the Gulf of Oman is clearly consuming oxygen faster than it is replenished, how much of that is exported to the Arabian Sea and making the wider Arabian Sea OMZ extend and grow even more?” Queste asks. 
 
 The next step for the team is to figure out whether this is due to the overall supply of oxygen decreasing, or an increased consumption of oxygen in the region. 
 
 The “Seaglider” robots that made the discovery possible are roughly the size of a person, but can spend several months at depths of 1,000 meters. In an article recently published in Geophysical Research Letters, the researchers note that access to these waters had previously been limited by “piracy and geopolitical tensions.” 
 
 The paper “Physical controls on oxygen distribution and denitrification potential in the north west Arabian Sea” has been published in the journal Geophysical Review Letters. 
 
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 Friday, May 4, 2018, 3:21 PM - Scientists have identified a dead zone as large as Florida in the Gulf of Oman, which connects the Arabian Sea to the Persian Gulf. Around the world there are more than 400 current dead zones in oceans and lakes, where water contains so little oxygen that aquatic life can’t survive. 
 
 Dead zones form when aquatic organisms consume dissolved oxygen faster than it can be supplied. This typically happens when warmer water sits on top of colder water, or freshwater sits on top of saltier water - for example, where a river meets the sea. In either case the water on top is less dense and floats. The layers don’t mix much, so very little oxygen from the atmosphere reaches the lower layers. 
 
 The next ingredient is organic matter in the water. It can come from untreated sewage, or from blooms of algae, along with dead plankton and fish. This material eventually sinks into the bottom layer, where bacteria decompose it, using oxygen as fuel. This process can consume most or all of the oxygen from the water. 
 
 
 
 
 
 Temperature is also a factor. Higher temperatures promote faster algae growth, enhance formation of layers in the water, and reduce the amount of dissolved oxygen that the water can hold. Climate change is tending to increase temperatures and make dead zones worse. 
 
 But the biggest driver is nutrient pollution – excess inputs of nitrogen and phosphorus. These nutrients stimulate algae growth. They come from municipal and industrial wastewater treatment plants, and increasingly from fertilizer runoff from industrial-scale agriculture. 
 
 A recent global-scale analysis shows that oxygen-depleted zones in the open ocean have expanded by several million square kilometers since the mid-20th century, and oxygen concentrations at hundreds of coastal sites like the Gulf of Mexico are now low enough to limit the distribution and abundance of fish. These impacts are also being felt in estuaries and the Great Lakes. 
 
 As my research has shown, large-scale dead zones are resistant to change. But nutrient reductions in the Chesapeake Bay are starting to improve conditions there. Communities around Lake Erie dramatically reduced its dead zone and toxic algae blooms in the 1970s by reducing phosphorus inputs. Now, however, these issues are resurfacing there – evidence that this problem is an ongoing challenge. 
 
 Blooms of algae, like this growth in 2015 in Lake St. Clair between Michigan and Ontario, promote the formation of dead zones. NASA Earth Observatory, CC BY 
 
 
 
 
 
 Donald Scavia, Professor Emeritus of Environment and Sustainability, University of Michigan 
 
 This article was originally published on The Conversation. Read the original article. 
 
 WATCH BELOW: Tasmania beach glows bright blue due to bioluminescent algae ||||| New research from the University of East Anglia (UEA) has confirmed a dramatic decrease in oxygen in the Gulf of Oman part of the Arabian Sea. But the environmental disaster is worse than expected. 
 
 The ‘dead zone’ was confirmed by underwater robots called Seagliders – which were able to collect data in areas of water previously inaccessible due to the piracy and geopolitical tensions. 
 
 The robots are about the same size as a small human diver, but can reach depths of 1000 metres and travel the ocean for months, covering thousands of kilometres. 
 
 Two gliders were deployed in the Gulf of Oman for eight months. They communicated by satellite to build an underwater picture of oxygen levels, and the ocean mechanics that transport oxygen from one area to another. 
 
 Where they expected some oxygen, they found an area larger than Scotland with almost no oxygen left. 
 
 The research was led by Dr Bastien Queste from UEA’s School of Environmental Sciences, in collaboration with Oman’s Sultan Qaboos University. 
 
 Dr Queste said: “Dead zones are areas devoid of oxygen. In the ocean, these are also known as ‘oxygen minimum zones’ and they are naturally occurring between 200 and 800 meters deep in some parts of the world. 
 
 “They are a disaster waiting to happen – made worse by climate change, as warmer waters hold less oxygen, and by fertiliser and sewage running off the land into the seas. 
 
 “The Arabian Sea is the largest and thickest dead zone in the world. But until now, no-one really knew how bad the situation was because piracy and conflicts in the area have made it too dangerous to collect data. 
 
 “We barely have any data collected for almost half a century because of how difficult it is to send ships there. 
 
 “Our research shows that the situation is actually worse than feared – and that the area of dead zone is vast and growing. The ocean is suffocating. 
 
 “Of course all fish, marine plants and other animals need oxygen, so they can’t survive there. It’s a real environmental problem, with dire consequences for humans too who rely on the oceans for food and employment. 
 
 “Another problem is that when oxygen is absent, the chemical cycling of nitrogen - a key nutrient for plant growth - changes dramatically. Nitrous oxide, a greenhouse gas 300 times more potent than CO2 is produced,” he added. 
 
 Computer simulations of ocean oxygen show a decrease in oxygen over the next century and growing oxygen minimum zones. 
 
 However these simulations have a difficult time representing small but very important features such as eddies which impact how oxygen is transported. 
 
 The team combined their Seaglider data with a very high-resolution computer simulation to determine how oxygen is spread around the north-western Arabian Sea throughout different seasons and the monsoons. 
 
 They found that the deadzone moves up and down between seasons, causing fish to be squeezed in a thin layer near the surface. 
 
 “Management of the fisheries and ecosystems of the western Indian Ocean over coming decades will depend on better understanding and forecasting of oxygen levels in key areas such as the Gulf of Oman,” added Dr Queste. 
 
 ‘Physical controls on oxygen distribution and denitrification potential in the north west Arabian Sea’ is published in Geophysical Research Letters on Tuesday, April 27, 2018. 
 
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– Robots have found the world's biggest underwater "dead zone" in the Gulf of Oman—yet another sign that such oxygen-depleted regions are only increasing worldwide, ZME Science reports. Scientists sent the remote-controlled submarines underwater for eight months and uncovered roughly 63,000 square miles with little to no oxygen in waters that link the Persian Gulf to the Arabian Sea. "Our research shows that the situation is actually worse than feared—and that the area of dead zone is vast and growing," research leader Bastien Queste says in a statement. "The ocean is suffocating. Of course all fish, marine plants and other animals need oxygen, so they can’t survive there." Such dead zones can happen naturally, the CBC notes, but they're becoming bigger and more common, mostly due to wastewater and chemical fertilizers. The run-off feeds algae blooms that suck up much-needed underwater oxygen. They also clog the gills of fish, which drain more oxygen when the fish decay and die. Climate change plays a role too, Queste says, because "warmer waters hold less oxygen." The Weather Network explains that warmer water floats on top of colder water, so the layers can't mix and allow oxygen from the air to reach down below. The latest find only adds to alarming data that the number of coastline dead zones has gone from 50 to 500 since 1950. Large dead zones are also hard to fix, and Queste doesn't sound too optimistic. "It's a real environmental problem, with dire consequences for humans too who rely on the oceans for food and employment," he says. (Meanwhile, the dying Gulf Stream could trigger a global nightmare.)