REPORT Mass extinctions and ocean acidification: biological constraints on

• Main Authors: Geological Dilemmas, J. E. N. Veron
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Ocean acidification
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.574.4305; http://iod.ucsd.edu/courses/sio278/documents/veron_08_coral_reefs.pdf

Abstract The five mass extinction events that the earth has so far experienced have impacted coral reefs as much or more than any other major ecosystem. Each has left the Earth without living reefs for at least four million years, intervals so great that they are commonly referred to as ‘reef gaps ’ (geological intervals where there are no rem-nants of what might have been living reefs). The causes attributed to each mass extinction are reviewed and sum-marised. When these causes and the reef gaps that follow them are examined in the light of the biology of extant corals and their Pleistocene history, most can be discarded. Causes are divided into (1) those which are independent of the carbon cycle: direct physical destruction from bolides, ‘nuclear winters ’ induced by dust clouds, sea-level chan-ges, loss of area during sea-level regressions, loss of biodiversity, low and high temperatures, salinity, diseases and toxins and extraterrestrial events and (2) those linked to the carbon cycle: acid rain, hydrogen sulphide, oxygen and anoxia, methane, carbon dioxide, changes in ocean chemistry and pH. By process of elimination, primary causes of mass extinctions are linked in various ways to the carbon cycle in general and ocean chemistry in particular with clear association with atmospheric carbon dioxide levels. The prospect of ocean acidification is potentially the most serious of all predicted outcomes of anthropogenic carbon dioxide increase. This study concludes that acidi-fication has the potential to trigger a sixth mass extinction event and to do so independently of anthropogenic extinctions that are currently taking place.