The asteroid that landed on earth which killed the dinosaurs was also the reason for making the ocean acidic. This may have led to the extinction of ammonites 66 million years ago.
According to a study by the University of Southampton, ammonites, which were also known as free-swimming mollusks of the prehistoric oceans, are common fossils found today. Their annihilation was also caused by the asteroid impact. More than 90% of species of calcium carbonate-shelled plankton also were exterminated.
Similar groups without calcium carbonate shells were not seriously affected, increasing the probability that ocean acidification as an unexpected result of impact, might have probably caused the extinction.
Professor Toby Tyrrell, from Ocean and Earth Science at the University of Southampton, said: “While the consequences of the various impact mechanisms could have made the surface ocean more acidic, our results do not point to enough ocean acidification to cause global extinctions.
“Out of several factors we considered in our model simulation, only one (sulphuric acid) could have made the surface ocean severely corrosive to calcite, but even then the amounts of sulphur required isn’t large.
“It throws up the question, if it wasn’t ocean acidification what was it?
“Possible alternative extinction mechanisms, such as intense and prolonged darkness from soot and aerosols injected into the atmosphere, should continue to be investigated.”
Professor Tyrrell clarified that earlier increases of CO2 on Earth occurred very slowly that the ocean acidification was comparatively slight. Ammonites and other planktonic calcifiers were able to deal with the transforming ocean chemistry.
The study is distributed in the Proceedings of the National Academy of Sciences (PNAS).