Researchers from both the University of Southampton and Leibniz Center for Tropical Marine Ecology (Germany) believe that the impact of an asteroid sixty-six millions years ago on the Yucatan peninsula could be mistaken. Asteroid that crashed into Yucatan Peninsula also led to the death of several species and the extermination of dinosaurs. Researchers published their most recent study in Proceedings of the National Academy of Sciences. (citation below). What caused the ammonite extinction? Extended darkness? Image: Wikimedia. Ammonites, an extinct marine invertebrate group – free-swimming Mollusks – are closely related to the living coleoids like squids, cuttlefish and octopuses. The end-Cretaceous impact of an asteroid made ammonites extinct. This was also true for many other species of calcium carbonate shelled plankton, such as coccolithophores and foraminifera. Initial scientists believed sea acidification to be the reason. However, other marine species with calcium carbonate shells weren’t so affected. This led scientists believe ocean acidification as a result of the collision of asteroid sandstones may also have contributed to the apparent selective extinctions. The previous increases in carbon dioxide on Earth were so gradual that acidification did not occur. Ammonites, along with other planktonic calciumifiers, survived the changes in ocean chemistry. However, the asteroid collision caused drastic changes. The first modeling study on ocean acidification after an asteroid collision is this. Toby Tyrrell (Ocean and Earth Science Centre Southampton), co-author of this study, and his colleagues, simulated several acidifying mechanisms including wildfires emitting carbon dioxide and the vaporisation gypsum rock causing sulphuric acid (US: sulfuric), acid, or ‘acid rain, to be deposited on ocean surface. Scientists conclude that acidification was not enough to kill off calcifying organisms. Professor Tyrrell stated that although the impact mechanism could have caused the ocean to become more acidic, the scientists concluded that the acidification levels produced by the asteroid impact were not sufficient to kill the calcifying organisms. These alternatives, Prof. Tyrrell believes, should be explored further. This study was supported by the UK Ocean Acidification program, the European Project on Ocean Acidification and NERC. Citation: Toby Tyrrell and Agostino Merico cited “Severity ocean acidification after the end-Cretaceous Asteroid Impact.” Proceedings of the National Academy of Sciences. 11 May. 2015. DOI: 10.1073/pnas. 1418604112.
