|TITLE||EMILIANIA HUXLEYI CALCITE MASS VARIABILITY DURING PERIODS OF RISING ATMOSPHERIC CO2 IN THE MEDITERRANEAN SEA|
|AUTHORS||Michaël Grelaud (1), Barbara D’Amario (1), Patrizia Ziveri (1,2)|
- Institute of Environmental Science and Technology (ICTA), Universitat Autònoma de Barcelona (UAB), Bellatera (Barcelona), Spain
- Catalan Institution for Research and Advanced Studies (ICREA), Pg. Lluís Companys 23, 08010 Barcelona, Spai
|ABSTRACT||Coccolithophores are marine phytoplanktonic organisms that play a significant role in both the marine food web and the carbon cycle. They are responsible for the photosynthetic fixation of inorganic carbon, regulating the particulate inorganic-organic carbon (PIC : POC) ratio and a large portion of the calcium carbonate (CaCO3) production. It is challenging to understand how the current rising of atmospheric CO2 concentration and the subsequent change in carbonate chemistry (i.e. ocean acidification) and temperature will impact the marine calcifying organisms. Most of the experiments conducted in vitro on the cosmopolitan species Emiliania huxleyi show in general a decrease of PIC production and PIC : POC ratio when grown in high pCO2 conditions, pointing to the adverse effect of ocean acidification on these organisms. However, a recent study shed a new light on the factors controlling the average mass of E. huxleyi coccoliths in natural assemblages of the Mediterranean Sea (D’Amario et al., subm.). In this semi-enclosed sea, E. huxleyi is mainly represented by the morphotype A, which can be categorized into four calcification varieties going from low- to high-calcified coccoliths. As a result, the average mass of E. huxleyi is modulated by the relative abundances of the Type A calcification varieties, which in turn see their geographical distribution related to the sea water carbonate system.
Here we present data of E. huxleyi calcite mass from Mediterranean surface sediments and sedimentary cores that cover the industrial era, the Holocene, the last glacial-interglacial transition and the marine isotopic stage (MIS) 5e. The relative abundances of the four calcification varieties and the average E. huxleyi calcite mass are investigated during periods of low and high atmospheric CO2 concentrations. The calcite mass of E. huxleyi is anticorrelated with the atmospheric CO2 concentrations both during the warm MIS 5e and the last deglaciation, Remarkably, the calcite mass variation of E. huxleyi observed over the last five centuries and in the surface sediment is of the same magnitude as for the last glacial-interglacial transition or the MIS 5e. This highlights the vulnerability and complexity of coccolithophore responses to the rapid rise of atmospheric CO2 and environmental changes since the beginning of the industrial age.|