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The Ocean Is Running Out of Oxygen, Largest Study of Its Kind Finds
The International Union for Conservation of Nature (IUCN) report combined the work of 67 scientists from 17 countries to conclude that oxygen levels in the ocean had declined around two percent since the mid-20th century, and the volume of waters entirely deprived of oxygen had increased four-fold since the 1960s. The report was released Saturday at the COP25 UN Climate Change Conference in Madrid, CBS News reported, in hopes of persuading world leaders to protect the oceans from future oxygen loss.
"Urgent global action to overcome and reverse the effects of ocean deoxygenation is needed," IUCN Global Marine and Polar Programme director Minna Epps said, as CBS News reported. "Decisions taken at the ongoing climate conference will determine whether our ocean continues to sustain a rich variety of life, or whether habitable, oxygen-rich marine areas are increasingly, progressively and irrevocably lost."
Ocean deoxygenation comes from two major causes: nutrient pollution and the climate crisis.
Nutrient pollution has long been understood as a threat to ocean oxygen levels. Run-off from sewage and agriculture, as well as nitrogen from fossil fuel emissions, encourages the excessive growth of algae, which depletes oxygen. This process is relatively fast and easy to fix.
But in recent years scientists have come to understand how rising ocean temperatures are also lowering oxygen levels. Warmer water can't hold as much oxygen, and it is also more buoyant, which means it mixes less with deeper, less-oxygenated water, reducing oxygen circulation overall. Rising temperatures are likely responsible for around 50 percent of the oxygen loss in the top 1,000 meters (approximately 3,281 feet) of the ocean, which are also the most abundant in biodiversity. Climate-change-related oxygen loss is difficult or impossible to reverse.
"This is one of the newer classes of impacts to rise into the public awareness," Kim Cobb, a Georgia Tech climate scientist who was not involved with the study, told The New York Times.
While a two percent decrease in overall oxygen levels might not sound like a lot, there are environments where a small change in oxygen can make a huge difference, report editor Dan Laffoley explained to The New York Times.
"[I]f we were to try and go up Mount Everest without oxygen, there would come a point where a 2 percent loss of oxygen in our surroundings would become very significant," he said.
He also said the oxygen loss was not evenly distributed. Some waters in the tropics had seen a 40 to 50 percent decrease in oxygen. The number of oxygen-deprived areas has also increased, from 45 before the 1960s to 700 in 2011, according to the report.
This oxygen loss is especially threatening to larger fish species like marlin, tuna and sharks, who require more energy, BBC News reported. These species are already moving closer to the surface for oxygen, which puts them at greater risk from overfishing. Cobb also pointed to the mass die-offs of fish along the coast of California as another symptom of falling oxygen levels.
Loss of oxygen could also impact Earth systems that extend beyond the ocean, such as the nitrogen and phosphorus cycles.
"If we run out of oxygen it will mean habitat loss and biodiversity loss and a slippery slope down to slime and more jellyfish," Epps said, according to CBS and BBC News. "It will also change the energy and the biochemical cycling in the oceans and we don't know what these biological and chemical shifts in the oceans can actually do."
The report warned that if nations continue to emit greenhouse gases at business-as-usual levels, the ocean will lose three to four percent of its oxygen by century's end.
"To stop the worrying expansion of oxygen-poor areas, we need to decisively curb greenhouse gas emissions as well as nutrient pollution from agriculture and other sources," Laffoley said, according to BBC News.
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In a pilot study at the University of Helsinki, dogs trained as medical diagnostic assistants were taught to recognize the previously unknown odor signature of the COVID-19 disease caused by the novel coronavirus. And they learned with astonishing success: After only a few weeks, the first dogs were able to accurately distinguish urine samples from COVID-19 patients from urine samples of healthy individuals.
Important Findings for Other Teams<p>The very rapid and promising findings from Finland are also important for other research teams, such as those in Great Britain and France, who are training sniffer dogs to detect COVID-19.</p><p>Fellow researchers from the <a href="http://assistenzhunde-zentrum.de/index.php/news/covid-19-hunde" target="_blank">German Assistance Dog Center (TARSQ)</a> have also benefited from the Finnish results.</p><p>"No one could tell us with certainty whether training with the aggressive virus is <a href="https://www.dw.com/en/dutch-house-pets-test-positive-for-coronavirus/a-53460111" target="_blank">dangerous or not for humans and dogs</a>. We wanted to gather more information first before we started training because the German virologists advised us against it — after all, so little is known about the virus so far," explains Luca Barrett from TARSQ.</p>
Where Does the Characteristic Smell Come From?<p>It is still unclear which substances in urine produce the apparently characteristic COVID-19 odor. Since SARS-CoV-2 not only attacks the lungs, but also causes damage to blood vessels, kidneys and other organs, it is assumed that the patients' urine odor also changes. This is something which the dogs, with their highly sensitive olfactory organs, notice immediately.</p><p>Certain diseases appear to have a specific olfactory signature that trained dogs can sniff out with amazing accuracy, Barrett says.</p><p>"According to one study, dogs can detect breast cancer with a 93% probability, for example. And lung cancer with a 97% probability," she says.</p><p>But dogs can also identify skin cancer, colon cancer, ovarian cancer or prostate cancer very reliably, according to Barrett. "The hit rate, which was not so good in the early days of training, has risen enormously in recent years," she says.</p>
Hit Rate Decisive<p>Besides cancer, the <a href="https://www.dw.com/en/german-sniffer-dog-makes-1-million-drug-bust/a-53433307" target="_blank">dogs</a> can also detect Parkinson's disease. Parkinson's sufferers smell different even years before they have the disease. "That's how we came up with the idea of training dogs as an early warning system for Parkinson's," Barrett says.</p><p>Dogs are also trained to detect malaria, but the hit rate is not yet satisfactory, she says. So far, the dogs recognize seven out of 10 infected persons, which is not enough.</p><p>A high hit rate is, of course, also absolutely necessary when training for the aggressive SARS-CoV-2 pathogen, according to Barret. "We hope that the hit rate for the coronavirus is significantly higher in the fully trained dogs; after all, it would be very dangerous if COVID-19 were not detected," she says</p>
Trained Tracking Dogs<p>Dogs' ability to smell is about a million times better than that of humans. Humans have about 5 million olfactory cells, compared with 125 million for dachshunds and 220 million for sheepdogs.</p><p>Dogs also inhale up to 300 times per minute in short breaths, meaning that their olfactory cells are constantly supplied with new odor particles. In addition, dogs' noses differentiate between right and left. This spatial sense of smell allows the animals to follow a trail more easily.</p><p>During the training sessions, the dogs — mostly Labrador retrievers or retrievers in general, but also cocker spaniels or sheepdog breeds — are each trained for one scent. That can be the smell of a drug or an explosive, or, as here, the olfactory signature of a specific disease.This means that one dog cannot recognize several types of cancer.</p><p>The animals are trained with containers holding samples of breath or sweat, for example. As soon as they have identified the smell they are looking for, the dogs hear a click and get a treat. They are reliably trained for the one smell on this reward principle.</p>
Great Potential, Great Skepticism<p>Drug and explosive detection dogs have been used for some time. But trained medical scent detection dogs are also now working in hospitals. For example, they sniff the bodies of patients with suspected skin cancer to try and detect the disease — only with the patients' consent, of course. So these skilled snufflers are helping doctors in diagnosing diseases and detecting them early on.</p><p>However, so far there are only very few medical detection dogs. The dog owners almost always work voluntarily and the trained sniffer dogs live in normal households. There is great skepticism, especially among traditional doctors and health insurance companies, even though the first indications given by the dog have to be followed by further medical tests anyway and a lot of time and costs could be saved by early cancer detection.</p>
Possible Coronavirus Applications<p>If the findings from Finland are confirmed, the sniffer dogs with their extremely sensitive sense of smell could prove to be a great help in the fight against the new coronavirus.</p><p>Luca Barrett from TARSQ can easily picture coronavirus sniffer dogs being used in situations where there is a high risk of infection. For example, people attending football matches and other major events could be checked before they are admitted.</p><p>The dogs could also be employed at airports to scan people entering a country. "When the dogs go down the queue, they can detect if someone is healthy and can enter the country. But if a person smells of COVID-19, the handler could send that person to a coronavirus testing center instead," Barrett says. That is because a second test is still needed to confirm the dog's initial sniff detection.</p><p><span></span>Barrett says dogs could also be used to search for the virus on surfaces. For example, before passengers board an aircraft, a four-legged friend could first check whether the machine is free from SARS-CoV-2. Similar measures are planned for doctors' surgeries, aged care homes or nursing homes that have had to be evacuated because of COVID-19 cases. Before these are used again, a sniffer dog could check whether the environment is "clean."</p>
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