Living in a crazy ocean: calcareous nannoplankton response to Oceanic Anoxic Event 2 and comparison with living coccolithophores algae

• Main Authors: G. Faucher, E. Erba
• Other Authors: G, ., F, a, u, c, h, e, r, ; E, E, b
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2014
• Subjects: nannofossil; dwarfism; OAE2; Settore GEO/01 - Paleontologia e Paleoecologia; Ocean acidification
• Online Access: http://hdl.handle.net/2434/250208; https://rendiconti.socgeol.it/296/issue-10/issue.html

Coccolithophores algae are phytoplanktonic organisms that play a fundamental role in the ocean food web and in the global carbon cycle. They produced some tiny calcium carbonate plate, coccoliths, that surround the cell and therefore they actively contribute to the marine carbonate cycling. Nowadays the ocean is facing an alteration of seawater carbonate chemistry due to anthropogenic release of carbon dioxide. Laboratory experiments suggest that coccolithophores are very sensitive to seawater pH, dissolved CO2, temperature and nutrient concentration all of which are impacted by human CO2 emissions. Some species might have the ability to adapt but coccolithophores responses to environmental stress in culture experiments are not straightforward. Furthermore studies on large volcanic eruptions, demonstrate that metals contained in volcanic ashes, such as Cd, Cu, Pb and Zn, can have both fertilizing and toxic effects on marine phytoplankton species (diatoms and coccolithophores algae) which will ultimately lead to changes in species composition with implications for community productivity. The geological record is imprinted with numerous examples of natural global perturbations of the global carbon cycle and climate changes some of which are characterized by large-scale release of natural CO2 and ocean acidification. The selected case history we analyzed is the Cenomanian-Turonian Oceanic Anoxic Event (OAE2), during which the formation of the Carribean Plateau Large Igneous Provinces (LIP), induced the degassing of large amounts of CO2 and associated environmental consequences of warming, lower oxygen minimum zone and possibly ocean acidification. Here we present biometric data of 4 coccolith species mostly dominant in the Cenomanian and Turonian. The morphometric analyses showed a species-specific response to the perturbation: W. barnesiae, the most cosmopolitan species, doesn’t show any significant variation in size through all the event. On the contrary the other eutrophic species, respectively B. constans, D. ...