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How could Siberian Traps volcanism have changed the acidity of the oceans?

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Line graph showing the number of marine animal families from the Precambrian era to the present, with illustrations of key groups such as trilobites, ammonoids, marine reptiles, and diatoms. The graph highlights major extinction events and a rise to 1,900 living families today. — Permian extinction The diversity of marine animal families since late Precambrian time. The data for the curve comprise only those families that are reliably preserved in the fossil record; the 1,900 value for living families also includes those families rarely preserved as fossils. The several pronounced dips in the curve correspond to major mass-extinction events. The most catastrophic extinction took place at the end of the Permian Period.

The prolonged eruption of the Siberian flood basalts—known as the Siberian Traps—is widely associated with the Permian extinction through its profound impact on the global carbon cycle.12

The volcanism likely altered ocean acidity by injecting massive quantities of carbon dioxide into the [atmosphere]. This release was further intensified by the ignition of large coal seams and the burning of forests by hot [lava]. As the oceans absorbed this excess atmospheric carbon dioxide, a chemical reaction occurred: the gas dissolved in seawater to create carbonic acid, which subsequently liberated hydrogen ions.123

This increase in hydrogen ion concentration lowered the pH of the seawater, resulting in ocean acidification. This process reduced the availability of carbonate ions, making it difficult for marine calcifiers to build and maintain their shells and skeletons, ultimately threatening the stability of marine food chains during the Permian Period.34