The impact of ocean acidification on calcareous nannoplankton has been debated among researchers. This study focused to enrich the available data on coccolith size and calcification for the cosmopolitan species Emiliania huxleyi and assess their connection to natural and anthropogenic environmental changes. The analysis was based on the M2 core from Athos basin (North Aegean Sea, Greece). In total, 80 samples were selected and processed in laboratory to prepare for Scanning Electron Microscope (SEM) imaging. About 4000 E. huxleyi coccoliths were inspected under the SEM and their morphometric values were calculated. Morphometric values displayed fluctuations across the core depths, which were compared to the age model and multiproxy analyses of previous studies in the same area (Gogou et al., 2016; Skampa et al., 2019; Dimiza et al., 2020). Evident changes were based mainly to the Relative Tube Width (RTW), with a tendency towards slightly increased calcified coccoliths within the Little Ice Age (c. 1200-1850 AD). Afterwards, during the Instrumental Period (c. 1850-present) values show a decreasing pattern. It is possible that human activities, especially in the last century, have affected the marine equilibrium with higher atmospheric CO2 absorption, environmental parameters changes and depletion of bioavailable carbonate ions. Although naturally induced environmental changes in the Northern Aegean could mask the clear effect of ocean acidification on E. huxleyi, these data may contribute to a potential tool for environmental monitoring in the context of tackling future climate change.
Efstathiou A. S., 2022. Investigating the effect of ocean acidification (natural and anthropogenic) on the size of Emiliania huxleyi from late Holocene sediments of the north Aegean sea (NE Mediterranean). MSc thesis, Aristotle University of Thessaloniki. Thesis (restricted access).
