Flickr | Gulf of Oman | by Francisco Anzola[/caption] It seems like every day we’re learning something new about the oceans. Sometimes we discover new sea life or new ways that animals communicate with each other under water, other times, however, we come across disturbing features like this one… Recently, robots exploring the depths of the Gulf of Oman have discovered a “dead zone” the size of Scotland! From IFLScience: “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 published this week in Geophysical Research Letter. “The ocean is suffocating.”

Wikimedia Commons[/caption] “Of course all fish, marine plants and other animals need oxygen, so they can’t survive there,” Dr Queste continued. “It’s a real environmental problem, with dire consequences for humans too who rely on the oceans for food and employment.” Researchers have known about the dead zone in the Gulf of Oman for a while but, until now, have been unable to fully investigate it. Between the geopolitical instability of the region and the frequency of pirate attacks, research ships have been unable to do any investigations for the last 50 years.

Wikimedia Commons[/caption] So, as a solution, scientists form the University of East Anglia along with researchers from Oman’s Sulta Qaboos University decided to make the use of Seagliders to carry out the investigation. Seagliders are underwater robots that can collect data autonomously and send it back via satellites. The robots surveyed the region in the gulf down to 1,000 meters for eight months, measuring oxygen levels and the underwater currents that move oxygen around at these deep levels. After all the data had been collected, scientists were stunned at the results. Yes, they knew there was a dead zone in the Gulf of Oman, but thanks to the Seaglider, they were able to see just how big it was. See the results after the jump!

Gulf of Oman from International Space Station - Wikimedia Commons From IFLScience: It revealed that the dead zone that sits between 200 and 800 meters (650 to 2,620 feet) beneath the surface is enormous, much larger than they thought it would be. It is currently comparable to the size of Scotland, making it the largest and thickest ocean dead zone in the world. And it’s growing. This is not only an issue for any animals that want to live there, but has a knock-on effect on how other vital nutrients cycle through the oceans. For example, the researchers note how when oxygen is absent, it impacts how nitrogen moves through the water, too. This has a negative effect on plants, but can also lead to the production of nitrous oxide, which is roughly 300 times more potent than carbon dioxide.

Pixabay Predictions show that over the next century, this zone is expected to grow. This means that the fishing industry needs to pay serious attention and change their management practices to maintain sustainability in the region now. Poorly oxygenated water can lead to huge fish kills like the one that took place in the Gulf in the summer of 2,000. At that time, Omani officials were worried that a toxic algae was responsible for the deaths, but satellite imagery helped them determine that it was due to poorly oxygenated water. The Seaglider expedition has confirmed that to be true.

Pexel The original source for this story is the Geophysical Research Letter, and if you go over there you can read the full scientific report, but here’s the plain language summary drawn directly from that report and written by the researchers: _“Oxygen is present in the ocean and is required by all marine plants and animals to breathe. In certain regions around the world, oxygen concentrations reach very low levels. These are known as “oxygen minimum zones”. When oxygen is absent, chemical cycling of nitrogen, a key nutrient for plant growth, changes dramatically.

Wikimedia Commons 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. It is difficult to predict what will happen in the biggest of the world’s oxygen minimum zones, the Arabian Sea, as piracy and geopolitical tensions have limited past opportunities for observing these processes. How ever there was a workaround… To remedy this, we deployed two remote‐controlled submarines, known as a Seagliders, in the Gulf of Oman. These instruments measured a strong decrease of oxygen in the oxygen minimum zone compared to pre‐1990 values.

Wikimedia Commons We then combined the Seaglider data with a very high resolution computer simulation to determine how oxygen is spread around the northwestern Arabian Sea throughout different seasons and the monsoons.” The Gulf of Oman isn’t the only dead zone area. In fact, a study done in 2008 found 405 dead zones spread around the globe. Wikipedia offers more insight onto the dead zone problem: _Dead zones are hypoxic (low-oxygen) areas in the world’s oceans and large lakes, caused by “excessive nutrient pollution from human activities coupled with other factors that deplete the oxygen required to support most marine life in bottom and near-bottom water. (NOAA)”.

By Robert Simmon & Jesse Allen - NASA Earth Observatory In the 1970s oceanographers began noting increased instances of dead zones. These occur near inhabited coastlines, where aquatic life is most concentrated. (The vast middle portions of the oceans, which naturally have little life, are not considered “dead zones”.) In March 2004, when the recently established UN Environment Programme published its first Global Environment Outlook Year Book (GEO Year Book 2003), it reported 146 dead zones in the world’s oceans where marine life could not be supported due to depleted oxygen levels.

Algal Blooms - La Jolla, CA - Wikipedia Some of these were as small as a square kilometre (0.4 mi²), but the largest dead zone covered 70,000 square kilometres (27,000 mi²). A 2008 study counted 405 dead zones worldwide. North America is home to several dead zones, including many in the Great Lakes and a huge one in the Gulf of Mexico. North American Dead Zones The Elizabeth River estuary is important to many areas in Virginia, including Norfolk, Chesapeake, Virginia Beach, and Portsmouth, but thanks to pollution, it’s been a dead zone that’s seen no fish since the 1920’s. The main culprits here are the refineries, loading docks, shipbuilders, container repair facilities, coal exporters, and others that have contaminated the river with toxic deposits.

By Patrick Bloodgood - US Army Since the early 1990’s, efforts have been made to clean up the river, and in 2006 Money Point, a 35-acre dead zone, was dredged out and showed positive results as fish returned and the wetlands began to recover. The Great Lakes In the 1960’s and 70’s dead zones caused by algal blooms plagued the Great Lakes and are still an issue according to Limnologist Dr. David Schindler: “The fish-killing blooms that devastated the Great Lakes in the 1960s and 1970s haven’t gone away; they’ve moved west into an arid world in which people, industry, and agriculture are increasingly taxing the quality of what little freshwater there is to be had here….This isn’t just a prairie problem. Global expansion of dead zones caused by algal blooms is rising rapidly.” (Wikipedia) Today, however, the dead zone crisis in the Great Lakes is focused on the center part of Lake Eerie from East of Point Pelee to Long Point and stretching to shores in Canada and the United States.

University of Michigan Gulf of Mexico The largest occuring hpoxic zone in the US in the Gulf of Mexico off the coast of Louisiana where the Mississippi River delivers 1.7 million tons of phosphorous and nitrogen into the Gulf of Mexico every single year. This is the result of runoff from the agricultural industry and the discharge of treated sewage from urban areas into the river. One of the biggest contributors to this runoff is the state of Iowa. It only makes up less than 5% o the Mississippi River drainage basin, but it’s responsible for 25% of the nitrate that makes it down the Mississippi and into the Gulf of Mexico.

By NASA NOAA - Wikimedia The size of the Gulf of Mexico has been measured most years from 1985 through 2017. Its lowest point was in 1988 when it only covered 15 square miles to its record high last year (2017) when it encompassed more than 8,776 square miles! The 1988 number is a bit of an anomally as the there was a huge drought that year and the flow down the Mississippi to the Gulf was the lowest that it had been since 1933. Shrimp trawlers first noticed the dead zone in the 1950’s and as things continued to get worse, scientists began taking a serious look at the problem during the 70’s. The conversion of forests and wetlands to agricultural and urban developments along the Missouri River basin and the Lower Mississippi are believed to be responsible for the increase in size of the dead zone.

NOAA - Wikimedia Commons The good news about dead zones is that they seemingly can be reversed. Again from Wikipedia: The Black Sea dead zone, previously the largest in the world, largely disappeared between 1991 and 2001 after fertilizers became too costly to use following the collapse of the Soviet Union and the demise of centrally planned economies in Eastern and Central Europe. Fishing has again become a major economic activity in the region. While the Black Sea “cleanup” was largely unintentional and involved a drop in hard-to-control fertilizer usage, the U.N. has advocated other cleanups by reducing large industrial emissions. From 1985 to 2000, the North Sea dead zone had nitrogen reduced by 37% when policy efforts by countries on the Rhine River reduced sewage and industrial emissions of nitrogen into the water. Other cleanups have taken place along the Hudson River and San Francisco Bay.

Black Sea - NASA - Wikimedia Commons The chemical aluminium sulfate can be used to reduce phosphates in water. The downside, of course, is that the plant and sea life that goes extinct because of these zones can not be brought back to life. The problem with the dead zone in the Gulf of Oman is that it encompasses nearly the entire gulf, all 63,700 square miles of it. Because of all of the geopolitical unrest in the region, scientists have been unable to study it. That’s why advances in technology like the Seaglider are so important. With these underwater robots scanning the depths and sending back data, scientists will be better able to put together a plan to stop the dead zones from getting a foothold in the first place.

University of Washington The underwater robots, the Seagliders, are a remarkable story in and of themselves. Here’s more on them from the University of Washington’s Seaglider page: “Seagliders fly through the water with extremely modest energy requirements using changes in buoyancy for thrust coupled with a stable, low-drag, hydrodynamic shape. Designed to operate at depths up to 1000 meters, the hull compresses as it sinks, matching the compressibility of seawater. The AUV Seaglider is the result of a collaborative effort between APL-UW and the UW School of Oceanography. These small, free-swimming vehicles can gather conductivity-temperature-depth (CTD) data from the ocean for months at a time and transmit it to shore in near-real time via satellite data telemetry.”

University of Washington And… Its low drag body, horizontal wings, and fixed rudder allows it to fly up and down through the water column. As Seaglider dives and ascends its wings cause it to glide, allowing horizontal movement. Internal sensor monitor the depth, heading and attitude of the AUV. External sensors are constantly scanning the ocean to determine water properties. As well as scanning the Gulf of Oman, the University of Washington’s underwater robots have also made news for undertaking the mission of exploring the oceans around Antarctica:

Pixabay The water circling Antarctica has some of the roughest, most dangerous conditions on the planet. This water also is crucially important to Earth’s climate: It stores a massive amount of carbon dioxide, supports vast communities of marine life and connects to all the major ocean basins. To learn how these waters work, University of Washington oceanographers are sending robots to monitor conditions too dangerous or expensive for research ships to visit regularly.

Wikimedia Commons The Southern Ocean is taking up a sizable fraction of all the atmospheric CO2 that goes into the ocean. But we know very little about the Southern Ocean, especially under the ice," said Stephen Riser, a UW professor of oceanography. His group has built Argo ocean-monitoring floats since 1999, and still builds about 120 per year for several international efforts. The hardy, low-power robots cruise through the world’s oceans collecting observations, what The New York Times a few years ago called “one of the scientific triumphs of the age.” Indeed they are.