The Earth's oceans are in worse shape than scientists thought, with acidity levels so high that our seas may have entered a "danger zone" as early as 2020, according to a new study.
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Humans are unwittingly making the oceans more acidic by releasing carbon dioxide (CO₂) through industrial activities such as burning fossil fuels. This ocean acidification is destroying marine ecosystems and threatening coastal human communities that depend on healthy waters for their survival.
Previous research had shown that the oceans were approaching a planetary threshold or "danger zone" in terms of acidity levels. However, in a new study published Monday, June 9 in the journal Global Change Biology, scientists found that acidification is more advanced than previously thought and that our oceans may have crossed that threshold as early as 2020.
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The researchers concluded that by 2020, the average state of the world's oceans was within a range of uncertainty about the ocean acidity threshold, meaning the safe limit may already have been exceeded. According to the study, conditions also appear to be deteriorating faster in deeper waters compared to the surface.
Ocean acidification is mainly caused by the absorption of carbon dioxide (CO₂) by the sea. The oceans absorb about 30% of the CO₂ in the atmosphere, so as human activities release more CO₂, the amount absorbed by the oceans increases. CO₂ dissolves in seawater, forming carbonic acid and releasing hydrogen ions. Acidity levels depend on the number of dissolved hydrogen ions in the water; so the more CO₂ is absorbed by the ocean, the more acidic it becomes.
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Not all oceans are acidifying at the same rate. For example, researchers found that about 40% of surface waters have exceeded the threshold, but that percentage increases to 60% for deeper waters, up to 200 meters deep.
Source: livescience
