Ocean acidification could impact Atlantic cod populations more severely than previously thought

The new study, which was published in the journal Global Change Biology last month, found that surviving cod larvae suffer significant organ damage and developmental delays that could cause problems throughout their lifetimes.

Research over the past few years has shown that ocean acidification impacts Atlantic cod at the earliest stages of their lives, while they are still eggs and larvae. Scientists hoped that those cod who managed to reach maturity might be helping the species adapt to the conditions brought on by global climate change. But new research appears to have dashed those hopes.

Earth’s oceans absorb as much as one-third of the excess carbon dioxide pumped into the atmosphere by human activities. When that CO2 reacts with water, it forms carbonic acid, lowers the pH level of marine waters, and thus makes the oceans more acidic. While marine species can shift their ranges to avoid the warmer water temperatures driven by climate change, there is no way for them to escape ocean acidification.

For a 2016 study, Martina Stiasny of the GEOMAR Helmholtz Centre for Ocean Research, a research institute in Kiel, Germany, led a research team that conducted experiments with Atlantic cod (Gadus morhua) caught from two wild populations in the Western Baltic and the Barents Sea. The researchers determined that, at the ocean acidification levels expected by the end of the century if we do nothing to draw down C02 emissions, twice as many cod larvae will die within their first 25 days, causing the number of cod who reach maturity and reproduce to drop by 8 and 24 percent for the Western Baltic and Barents Sea populations, respectively.

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