AsianScientist (Jan. 29, 2016) – Pearls have adorned the necklines of women throughout history, but some evidence suggests that the gems’ future could be uncertain. Increasingly acidic seawater causes oyster shells to weaken, which doesn’t bode well for the pearls forming within.
However, as scientists report in the journal Environmental Science & Technology, the mollusks might be more resilient to changing conditions than previously thought.
Pearl aquaculture is a thriving business, particularly in Asia and Australia. In Western Australia alone, the total allowable annual catch of oysters per licensed pearl production company is 572,000 oysters, or approximately US$200 million dollars’ worth of pearls.
But much of it takes place in our oceans, which are susceptible to the increasing amounts of carbon dioxide that are released into the atmosphere by human activity. The oceans absorb carbon dioxide from the air and become more acidic as a result.
Today, the pH level of our oceans has decreased by approximately 0.1 pH units since pre-industrial times, which is equivalent to approximately 30 percent increase in acidity. According to the US Environmental Protection Agency, the surface pH level of our oceans is projected to decrease even more by the end of the century, to between 7.6-7.8. This will have adverse affects on many marine species such as plankton, shellfish, corals and mollusks.
The research team has found that these conditions weaken the shells of pearl oysters, which could affect their survival and reduce the chances of pearl formation. But in addition to acidity, rising water temperature could also play a role in oyster health. Professor Zhang Rongqing from Tsinghua University and colleagues set out to understand how combining acidity and water temperature would affect pearl oysters.
The researchers tested Pinctada fucata oysters for two months under varying water temperature and pH conditions, including those predicted for oceans in 2100. Their results confirmed previous work that had found higher water acidity led to weaker shells, but notably, this effect was reduced when the water temperature was also higher. According to the research paper, the sweet spot was 28°C.
Thus, the researchers concluded that warmer oceans could buffer these valuable marine animals from increasingly acidic seawater.
Source: American Chemical Society; Photo: SarahTz/Flickr/CC.
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