Not global warming. Not ocean acidification.
Key quotes:
… they suspected it was caused by a dead zone–a low-oxygen area that snuffs out marine life–rather than by ocean warming or acidification…
The team thinks that such dead zones may be common in the tropics but have gone largely unreported, simply because scientists never looked…
Based on our analyses, we think dead zones may be underreported by an order of magnitude…
The media release is below.
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Dead zones may threaten coral reefs worldwide
SMITHSONIAN TROPICAL RESEARCH INSTITUTE
Dead zones affect dozens of coral reefs around the world and threaten hundreds more according to a new study by Smithsonian scientists published in Proceedings of the National Academy of Sciences. Watching a massive coral reef die-off on the Caribbean coast of Panama, they suspected it was caused by a dead zone–a low-oxygen area that snuffs out marine life–rather than by ocean warming or acidification.
“Ocean warming and acidification are recognized global threats to reefs and require large-scale solutions, whereas the newly recognized threats to coral reefs caused by dead zones are more localized, said Andrew Altieri, staff scientist at the Smithsonian Tropical Research Institute and first author of the study. Fortunately dead zones can be reduced by controlling sewage and agricultural runoff into the ocean.”
In September, 2010, coral reefs in Almirante Bay, Bocas del Toro Province, showed severe signs of stress. In addition to corals turning white and dying, which is typical during coral bleaching associated with warming events, there were other clues suggesting that more was involved than high temperatures. Many unusual observations pointed to something else as the culprit. There were thick mats of bacterial slime, and the dead bodies of crabs, sea urchins and sponges lay scattered on the ocean floor. Even more odd, there was a clear depth line above which the reefs looked OK, and below which, something had gone terribly wrong. Even single colonies of corals that straddled the line were fine above and dying below.
Scientists went to work, measuring several aspects of water quality. One set of measurements came back as a shock. Extremely low oxygen levels in deeper waters contrasted with high oxygen levels in shallow waters where corals were still healthy. This is the hallmark of a dead zone.
The team thinks that such dead zones may be common in the tropics but have gone largely unreported, simply because scientists never looked. “The number of dead zones currently on our map of the world is 10 times higher in temperate areas than it is in the tropics, but many marine biologists work out of universities in Europe and North America and are more likely to find dead zones close to home,” Altieri said.
“We were lucky that there was already a reef monitoring program in place at STRI’s Bocas del Toro Research Station as part of the Smithsonian’s Marine Global Earth Observatory Network,” said Rachel Collin, station director.
“Based on our analyses, we think dead zones may be underreported by an order of magnitude.” said Nancy Knowlton, coauthor and Sant Chair for Marine Science at the Smithsonian’s National Museum of Natural History. “For every one dead zone in the tropics, there are probably 10–nine of which have yet to be identified.”
The researchers found 20 instances when dead zones were implicated in the mass mortality of coral reefs worldwide. “Hypoxia (low oxygen) isn’t even mentioned in several of the most important academic reviews of threats to coral reefs and is rarely discussed at scientific meetings,” Altieri said, “Even worse, many coral-reef monitoring efforts do not include measurement of oxygen levels, making it nearly impossible to identify low oxygen as the cause of mass coral mortality after the fact.” For example, the cause of a 2016 mass mortality at the Flower Garden Reefs in the Gulf of Mexico remains unclear, but some of the photographs look strikingly similar to what was observed in Panama.
The authors argue that building capacity to monitor oxygen on reefs will help people to improve coral reef health and understand how dead zones might interact with other forces such as global warming in a one-two punch, which put reefs in even greater danger.
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The Smithsonian Tropical Research Institute, headquartered in Panama City, Panama, is a part of the Smithsonian Institution. The Institute furthers the understanding of tropical nature and its importance to human welfare, trains students to conduct research in the tropics and promotes conservation by increasing public awareness of the beauty and importance of tropical ecosystems. Website. Promo video.
Andrew H. Altieri, Seamus Harrison, Janina Seeman, Rachel Collin, Robert J. Diaz, Nancy Knowlton . 2017. Tropical dead zones and mass mortalities on coral reefs. PNAS http://www.pnas.org/cgi/doi/10.1073/pnas.1621517114
Much more is known about dead zones than shown by these surprised scientists. At least they didn’t blame them on CO2 as others have done.
ince 1994, he and the World Resources Institute (report here) in Washington,D.C., have identified and mapped 479 dead zones around the world. That’s more than nine times as many as scientists knew about 50 years ago.
What triggers the loss of oxygen in ocean water is the explosive growth of sea life fueled by the release of too many nutrients. As they grow, these crowds can simply use up too much of the available oxygen.
Many nutrients entering the water — such as nitrogen and phosphorus — come from meeting the daily needs of some seven billion people around the world, Diaz says. Crop fertilizers, manure, sewage and exhaust spewed by cars and power plants all end up in waterways that flow into the ocean. Each can contribute to the creation of dead zones.
Ordinarily, when bacteria steal oxygen from one patch of water, more will arrive as waves and ocean currents bring new water in. Waves also can grab oxygen from the atmosphere.
https://rclutz.wordpress.com/2017/02/19/ocean-oxygen-misdirection/
A revealing media release that up until the last paragraph pretty much stayed away from conjecture, but finally had to include a “might” to be politically correct and not over look implicating the universal bug-a-boo, Global Warming. No matter what other evidence may suggest, or even prove, GW, if not obviously dominant, always has to be at least a co-cause of whatever the problem may be.
Any cause that can’t be somehow linked to AGW, “Ignore it!”
Solution, giant Whisper aquarium pumps attached to bubblers, to bring O2 to the ocean depths!
“Ocean warming and acidification are recognized global threats to reefs and require large-scale solutions, …”
Total BS of course, just more amping the rhetoric to ensure a steady stream of grant money.
Corals have been with us for some 500 million years or so. In that time they’ve been through numerous ice ages and interglacials. Several of the more recent interglacials were warmer than today. In addition several warm periods since the last glacial melt down some 12,000 years ago were quite a bit warmer than today. Corals are still with us. Duh.
First of all, this article is misleading. Yes in this case low oxygen was a cause of coral mortality, and in areas where hypoxia is an issue, monitoring O2 levels is extremely relevant piece of information to have to assess the health of the ecosystem. However the mass bleaching that occurred throughout the South Pacific last year (also in 1998 and 2010) had nothing to do with low oxygen dead zones. When you have pristine reefs far removed from terrestrial runoff (the primary cause of eutrophication and low O2 deadzones) it’s misleading to suggest that increased temperatures still aren’t the primary cause of mass coral bleaching.
In regards to the comment by Stpaulchuck,
“Corals have been with us for some 500 million years or so. In that time they’ve been through numerous ice ages and interglacials. Several of the more recent interglacials were warmer than today. In addition several warm periods since the last glacial melt down some 12,000 years ago were quite a bit warmer than today. Corals are still with us. Duh.”,
this statement is utterly false. Scleractinian corals have been around for about half of that time (240 million years). From that time to the present there have been significant “reef gaps” where coral reefs have largely ceased to exist or deposit calcium carbonate skeletons which is what is fossilized. These also coincide with the major mass extinction events the earth has had. Since the earth has been in the glacial/interglacial cycle coral reefs have done quite well. As all scientists who are knowledgeable on the effects of climate change on the biology of corals would say, it’s the rate of temperature change that’s the problem. Put it another way the rate of temperature change is outpacing the capacity of corals to adapt to those changes. This is not politicized information, this is the best science the collective wisdom of the world’s coral reef scientists has to offer.
So nobody disagrees that we are poisoning the water and killing corals? Maybe we should be concerned about the pact our lifestyles are having on the planet?