Nature & Environment
Shallow Coral Reefs on Acid: Great Barrier Reef Passing Critical Damage Threshold
Catherine Griffin
First Posted: Feb 27, 2013 08:27 AM EST
Coral reefs may have something else to worry about--and it's not just bleaching this time. Australian researchers have found that coral reefs in shallow ocean waters are far more vulnerable to sea temperature rises than previously thought. If global warming continues, some areas of the Great Barrier Reef are likely to pass critical damage thresholds in only 30 years.
Warm temperatures can be devastating to corals. When ocean waters become too warm, corals often bleach. This happens when corals release the algae that help them conduct photosynthesis, called zooxanthellae, into the water. Since the zooxanthellae give corals their bright colors, this phenomenon leaves a swathe of white structures in its wake. If temperatures cool quickly enough, corals can usually reclaim enough zooxanthellae to survive. Yet if the water remains warm, corals often starve to death.
Yet on top of bleaching, coral now have to deal with ocean acidity. In the study, researchers looked at shallow corals found in tropical waters under 230 ft. in depth along the Great Barrier Reef. They found that even a tiny increase in ocean acidity in these areas could lead to extreme changes.
When the ocean waters warm and we release more CO2 into the atmosphere, more of this gas is dissolved into the ocean and the acidity of the water rises. Since acid waters can dissolve calcium carbonate, which hard corals use to make their outer structures, it puts their survival at risk. It can cause corals to grow more slowly, and make them less able to make a comeback after storms. In fact, studies last year found that coral reef growth in areas of the Caribbean had dropped by as much as 70 percent, according to Reuters.
In addition to their dire predictions, the researchers found that organisms living in shallow coral reefs and marine ecosystems would be exposed to more acidity than those found at deeper depths. Why? The scientists noted that on shallow reefs, natural acidity levels varied more during tidal changes and as chemical activity among zooxanthellae shifted between daytime and nighttime. This means that if acidity rises, shallower reefs will be more exposed to constant shifts than deeper waters that might not be as affected.
Emily Shaw, the study's lead author, said in an interview with Reuters, "Honestly, we thought damaging thresholds would not be crossed in coral reefs this century. Now we know that for parts of the day, at least on our reef, it will be passed by 2040."
The findings show that corals are likely to face a fight for their survival in the coming years. Even so, there are those that are attempting to help keep these reefs alive. In the Caribbean, conservationists are planting fast-growing coral species as they "seed" reefs. Yet with the persistence of global warming and CO2 emissions, it's unlikely that corals will receive any real relief any time soon.
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First Posted: Feb 27, 2013 08:27 AM EST
Coral reefs may have something else to worry about--and it's not just bleaching this time. Australian researchers have found that coral reefs in shallow ocean waters are far more vulnerable to sea temperature rises than previously thought. If global warming continues, some areas of the Great Barrier Reef are likely to pass critical damage thresholds in only 30 years.
Warm temperatures can be devastating to corals. When ocean waters become too warm, corals often bleach. This happens when corals release the algae that help them conduct photosynthesis, called zooxanthellae, into the water. Since the zooxanthellae give corals their bright colors, this phenomenon leaves a swathe of white structures in its wake. If temperatures cool quickly enough, corals can usually reclaim enough zooxanthellae to survive. Yet if the water remains warm, corals often starve to death.
Yet on top of bleaching, coral now have to deal with ocean acidity. In the study, researchers looked at shallow corals found in tropical waters under 230 ft. in depth along the Great Barrier Reef. They found that even a tiny increase in ocean acidity in these areas could lead to extreme changes.
When the ocean waters warm and we release more CO2 into the atmosphere, more of this gas is dissolved into the ocean and the acidity of the water rises. Since acid waters can dissolve calcium carbonate, which hard corals use to make their outer structures, it puts their survival at risk. It can cause corals to grow more slowly, and make them less able to make a comeback after storms. In fact, studies last year found that coral reef growth in areas of the Caribbean had dropped by as much as 70 percent, according to Reuters.
In addition to their dire predictions, the researchers found that organisms living in shallow coral reefs and marine ecosystems would be exposed to more acidity than those found at deeper depths. Why? The scientists noted that on shallow reefs, natural acidity levels varied more during tidal changes and as chemical activity among zooxanthellae shifted between daytime and nighttime. This means that if acidity rises, shallower reefs will be more exposed to constant shifts than deeper waters that might not be as affected.
Emily Shaw, the study's lead author, said in an interview with Reuters, "Honestly, we thought damaging thresholds would not be crossed in coral reefs this century. Now we know that for parts of the day, at least on our reef, it will be passed by 2040."
The findings show that corals are likely to face a fight for their survival in the coming years. Even so, there are those that are attempting to help keep these reefs alive. In the Caribbean, conservationists are planting fast-growing coral species as they "seed" reefs. Yet with the persistence of global warming and CO2 emissions, it's unlikely that corals will receive any real relief any time soon.
See Now: NASA's Juno Spacecraft's Rendezvous With Jupiter's Mammoth Cyclone