Impacts of ocean acidification and warming on planktic foraminifera in the Catalan Sea (Western Mediterranean) during the last centuries

Abstract

This final degree project is part of the practice's realized at research institute ICTA-UAB (Institut de Ciència i Tecnologia Ambientals), which consisted in the analysis of an oceanic sedimentological register. Core 1 was obtained in May 2013, adjacent to Barcelona’s coast, latitude 41.1121 N and longitude 2.382 E, at 1156 m water depth at the end of the MedSeA Cruise, in order to collect further data for the project. Once collected, the core was transported to ICTA where during 2016 the upper half part of Core 1 was analyzed by Griselda Anglada as a part of her Master’s Thesis. Following the same procedures, planktic foraminifera of the bottom part of core 1 were extracted from the remaining lower samples and separated by fractions, whereby the most common foraminiferal species in the size fraction between 250 to 315 µm were picked from each half centimetre of the sediment core, determining its absolute and relative abundance. Then specimens of the five most abundant species were selected, weighed and image analyzed to determinate its Size-Normalized weight (SNW). The main aim is to reconstruct the dynamics of planktonic calcifiers in the Catalan Sea (Western Mediterranean) during the last ˜400 years, through the characterization of the species absolute abundance, relative abundance and SNW. This study will contribute to the understanding of the natural variability and the recent impacts of elevated atmospheric CO2, determining ocean warming and acidification effects in the region. For this reason the results obtained by Griselda were coupled with those of the bottom part in order to get core 1 completed and later analyze the obtained results. The sediments have been dated with the aim of relating the obtained results with the following reconstructed physical parameters: atmospheric CO2 concentration, Sea Surface Temperature (SST), North Atlantic Oscillation and Total Solar Irradiation. Through statistical correlation by Pearson’s coefficient, I determined the possible effects on the dynamics of the foraminiferal analyzed species. The results indicate changes in ecological conditions all over the studied period, but especially from approximately year CE 1840 until today due to the considerable increase of atmospheric CO2 that penetrates to the superficial sea waters and has modified the water column conditions and also altered species absolute abundance, relative abundance and SNW. The statistical results of Pearson’s correlation coefficient show that an abundance decrease and a calcification increase has happened during the studied period. Acidification, through the increase of CO2, is the principal cause of the reduction in foraminiferal abundance, while the increase on solar irradiation is the main cause of calcification increase. Warming is harmful for foraminifera due to SST increase reducing both abundance and calcification.