Current acidification could be worse than during the four largest mass extinctions in history, when a natural rise in carbon from asteroids and volcanic eruptions increased global temperatures, said the Science study, led by British, American and French experts.
Anthropogenic (human-generated) CO2 emissions, apart from contributing to global warming, also alter the chemistry of the seas and oceans, progressively acidifying them, which has significant repercussions for marine organisms and ecosystems. An international study published in the latest issue of the journal Science concludes that, over the last 300 million years, ocean chemistry has undergone profound changes, although none of them seems to have been as rapid, as large-scale and as global as what is happening today.
Marine acidification occurs as CO2 emitted by human activities, mainly from the burning of fossil fuels, dissolves into the oceans. More than 30% of anthropogenic CO2 emissions pass directly into the oceans, which become progressively more acidic.
Acidification is detrimental to many forms of marine life, for example by interfering with the development of species that build shells or skeletons of calcium carbonate, such as corals and molluscs. It can also affect species of phytoplankton, which are an essential link in marine food webs on which fish, crustaceans and other species depend.
Much of the research on this issue has been based on observations, simulating future acidification scenarios and assessing the response of organisms. However, in this study, the analysis was based on paleontological and geochemical records, looking for past marine acidification events to detect possible effects on marine biota.
Acidification and the great extinctions
The study found historical coincidences in Earth's history associated with profound acidification, such as the Paleocene-Eocene thermal maximum, 56 million years ago, when global temperatures rose 6 degrees and between 5 and 10% of marine species disappeared.
“Volatile emissions and the destabilization of frozen methane hydrates on the seabed released large amounts of carbon into the atmosphere, on a scale similar to what humans could emit in the future. During this event, there were large extinctions, especially of benthic fauna. However, the injection of CO2 was at least 10 times slower than at present, which predicts more catastrophic consequences for current anthropogenic change,” concludes Carles Pelejero, researcher at the Institute of Marine Sciences of the CSIC and ICREA.
The geological record provides details of biological changes associated with other major global disturbances, such as the great extinction that occurred after the asteroid impact that marked the end of the Cretaceous 65 million years ago, an event that is also believed to have acidified the oceans.
Other extinctions, such as the one at the end of the Triassic, 200 million years ago, and the one at the end of the Permian, 252 million years ago, may also have involved a significant acidification process. However, all of these extinctions were also associated with decreases in the oxygen content of the oceans and with significant warming. In fact, these three environmental pressures are the ones that are most globally affecting the current oceans: warming, acidification and deoxygenation.
“In view of the impacts we have detected in the fossil record, there is no doubt that we should tackle the problem at its root as soon as possible, by adopting measures to immediately reduce our CO2 emissions into the atmosphere,” concludes Patrizia Ziveri, researcher at ICTA.
Sources: Tendencias21.net ; America.InfoBae.com
Sources: Tendencias21.net ; America.InfoBae.com
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