The rising acidity of the oceans has emerged as one of the greatest threats to the continued existence of coral reefs. The acidity acts as the “osteoporosis of the sea” and threatens many things humans take for granted, ranging from food security, to tourism, to livelihoods.
The rapid change in the acidity of the oceans has caught some scientists off-guard. The problem is now widely considered to be climate change’s “equally evil twin,” said National Oceanic and Atmospheric Administration chief Jane Lubchenco.
“We’ve got sort of the perfect storm of stressors from multiple places really hammering reefs around the world,” said Lubchenco, who was in Australia to speak at the International Coral Reef Symposium in the northeast city of Cairns, near the Great Barrier Reef. “It’s a very serious situation.”
“Oceans absorb excess carbon dioxide in the atmosphere, increasing sea acidity. Scientists are worried about how that increase will affect sea life, particularly reefs, as higher acid levels make it tough for coral skeletons to form. Lubchenco likened ocean acidification to osteoporosis — a bone-thinning disease — because researchers are concerned it will lead to the deterioration of reefs.”
It was initially thought that the carbon dioxide absorbed by the oceans would “be sufficiently diluted as the oceans mixed shallow and deeper waters. But most of the carbon dioxide and the subsequent chemical changes are being concentrated in surface waters,” Lubchenco said.
“And those surface waters are changing much more rapidly than initial calculations have suggested,” she said. “It’s yet another reason to be very seriously concerned about the amount of carbon dioxide that is in the atmosphere now and the additional amount we continue to put out.”
“Higher acidity levels are especially problematic for creatures such as oysters, because acid slows the growth of their shells. Experiments have shown other animals, such as clown fish, also suffer. In a study that mimicked the level of acidity scientists expect by the end of the century, clown fish began swimming toward predators, instead of away from them, because their sense of smell had been dulled.”
“We’re just beginning to uncover many of the ways in which the changing chemistry of oceans affects lots of behaviors,” Lubchenco said. “So salmon not being able to find their natal streams because their sense of smell was impaired, that’s a very real possibility.”
These potential impacts pose a huge problem to people. Coral reefs are the primary economic driver in many tourist destinations and protect fragile coastlines from threats such as tsunamis. And probably far more importantly, seafood is the main source of protein for many people in many parts of the world. Many oyster farmers have already been experiencing drops in production from higher acidity levels.
“Some attempts to address the problem are already under way. Instruments that measure changing acid levels in the water have been installed in some areas to warn oyster growers when to stop the flow of ocean water to their hatcheries.”
Though, of course, that is only a very short-term solution. By far, the most critical and useful ‘adaption’, would be to reduce carbon emissions.
“The carbon dioxide that we have put in the atmosphere will continue to be absorbed by oceans for decades,” she said. “It is going to be a long time before we can stabilize and turn around the direction of change simply because it’s a big atmosphere and it’s a big ocean.”
In related news, NOAA announced today a major advance in the ability to predict mass coral bleaching, “providing the probability of bleaching up to four months into the future – with a newly developed global seasonal outlook system.”
“This advance in bleaching warning systems represents another milestone in our efforts to save the world’s critically important reef systems,” said Jane Lubchenco, Ph.D., under secretary of commerce for oceans and atmosphere and NOAA administrator, in the symposium’s keynote address.
“The state of reefs today should raise concerns for everyone. Reef ecosystems are globally important, and healthy reefs are the life-line for local communities. Their continued existence is a moral imperative for the global community.”
“The new system uses sea surface temperature forecasts from NOAA’s operational climate forecast system, the same system used for predicting El Niño and seasonal temperature and precipitation forecasts. Coral bleaching occurs when stress, usually high temperature, causes corals to expel their symbiotic algae (zooxanthellae) and, if prolonged or particularly severe, may result in coral death.”
“NOAA has also significantly advanced near-real time satellite monitoring of the high ocean temperatures that can cause coral bleaching. A new generation version of NOAA’s product suite now provides daily 5-km satellite monitoring of coral bleaching thermal stress for reefs around the world. This represents 100 times finer resolution, more frequent observations, and more data than the current twice-weekly 50-km global satellite coral bleaching monitoring.”