Ocean Acidification

Recently, it has been proposed that anthropogenic CO2 emissions may affect marine ecosystems by causing ocean acidification. In particular, it is suggested that within acidified surface waters, calcifying organisms would be subject to malformation and enhanced dissolution. Here, we present evidence of this process occurring naturally where explosive volcanism leads to the deposition of volcanic ash into ocean surface waters. Sediment cores from around the island of Montserrat, Lesser Antilles, contain distinct horizons of planktic fauna associated with recently deposited volcanic ash layers from the Soufrière Hills volcano. Within these layers are abundant pteropod shells that display evidence of partial dissolution and etching of their aragonitic shells, and appear to have suffered mass mortality in response to ash deposition during an eruption. Laboratory studies show that the ~3 cm of ash resulting from the 2006 volcanic dome collapse eventcould have caused the upper 5 m of the water column to become undersaturated with respect to aragonite. Volcanogenic ocean acidification is proposed to be the most likely trigger of the observed pteropod mass mortality events associated with recent Montserrat volcanism. The difficulty of documenting pteropod mortality may have led to this process being overlooked as a by product of large explosive volcanic events, but the importance of pteropods in the marine food chain suggests that further investigation is warranted.



Jones M, Fisher J & Palmer M, 2009. Ocean acidification from explosive volcanism as a cause for mass mortality of Pteropods. Awards Ceremony Speeches and Abstracts of the 19th Annual V.M. Goldschmidt Conference, V.M. Goldschmidt Conference. Geochimica et Cosmochimica Acta 73(13)-1:A604. Supplement.