BAD ENVIRONMENT: As carbon dioxide emissions rise, the ocean becomes more acidic making it harder for corals to grow. It could even become corrosive and dissolve reefs.
Image: NASA EARTH OBSERVATORY
SAN DIEGO -- For plants, animals and marine life whose environment changes, their options are stark and simple: Move, adapt or die.
But when the marine life in question is a coral reef cemented to the ocean floor and the threat is climate change, the outlook appears grimmer, said scientists presenting new findings here at the annual meeting of the American Association for the Advancement of Science.
Even small temperature rises of 1 to 2 degrees Celsius in the ocean can make corals more prone to bleaching, a kind of sudden death that occurs when corals expel the algae that normally live inside them, providing them with food and their bright coloration.
Scientists are also worried that, as carbon dioxide emissions rise, the ocean will absorb greater amounts of the greenhouse gas, shifting the chemistry of seawater. As the ocean becomes more acidic, it will be harder for corals to grow. Eventually, ocean water could become corrosive, dissolving reefs faster than corals can grow.
The question now is whether reef-building corals have the capacity to adapt to those changes.
"Can reefs disappear? That's the question," said Joanie Kleypas of the National Center for Atmospheric Research. "We don't have a lot of information on this."
One example comes from the Galapagos Islands, where a strong El Niño event in the early 1980s bleached more than 95 percent of corals. Then a species of sea urchin moved in and started chewing the reef, she said.
"Reefs that were there for hundreds or thousands of years disappeared in a matter of about a decade," Kleypas said. "Some people think it's a glimpse into the future ... an example of what we might expect in a high-CO2 world."
But there is some evidence to suggest all coral reefs aren't created equal, said Stephen Palumbi, a professor of marine science at Stanford University. He's studying what appear to be unusually resilient reefs off the coast of Ofu Island in American Samoa.
Samoan reefs appear resilient
Summer low tides occur at the hottest point of the day, exposing reefs in Ofu Island's shallow lagoons to temperatures normally lethal to corals -- but these reefs survive.
The secret, Palumbi said, may be that the high temperatures last for a short period of time. Temperature recorders he has placed in the lagoons experience the high temperatures for up to four hours -- and then have a chance to recover.
He has performed experiments to see whether those regular, but brief, exposures to temperature stress have "cross-trained" the corals to withstand high temperatures for even longer periods.
"Our conclusions from these experiments, ongoing now, is that corals do show temperature acclimation -- that brief excursion to high temperature in these pools hardens them in some way," he said. "This transient exposure to heat may be an exercise or conditioning program, in a sense."
The question now is whether corals in other reefs share that ability or can acquire it as climate change warms the average ocean temperature.
"We have no idea whether this is a general ability that corals have," Palumbi said. "We don't know if it's genetically hard-wired [in the Ofu corals]. It gives us the idea there may be some ways to generate more resilient populations of corals."
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Add CommentCO2 is not the big problem facing coral the problem is Carbon 6x as cabon shell cenosphere shards produced from catalytic cracking of graphite scale coated fuel cenospheres. The crystalline graphite nano-shards and nano-fragments can induce cell plasma membrane calcification with CaC6 shards which leads to cell necrosis or death by plaque.
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