Evidence of Stable Foraminifera Biomineralization during the Last Two Climate Cycles in the Tropical Atlantic Ocean

• Main Authors: Stergios D. Zarkogiannis, Assimina Antonarakou, Vincent Fernandez, P. Graham Mortyn, George Kontakiotis, Hara Drinia, Mervyn Greaves
• Format: Article
• Language: English
• Published: MDPI AG 2020-09-01
• Series: Journal of Marine Science and Engineering
• Subjects: planktonic foraminifera; shell weight; climate variability; sea surface density; carbonate production; X-ray microscopy (μCT)
• Online Access: https://www.mdpi.com/2077-1312/8/10/737

Planktonic foraminiferal biomineralization intensity, reflected by the weight of their shell calcite mass, affects global carbonate deposition and is known to follow climatic cycles by being increased during glacial stages and decreased during interglacial stages. Here, we measure the dissolution state and the mass of the shells of the planktonic foraminifera species <i>Globigerina bulloides</i> from a Tropical Eastern North Atlantic site over the last two glacial–interglacial climatic transitions, and we report no major changes in plankton calcite production with the atmospheric <i>p</i>CO₂ variations. We attribute this consistency in foraminifera calcification to the climatic and hydrological stability of the tropical regions. However, we recorded increased shell masses midway through the penultimate deglaciation (Termination II). In order to elucidate the cause of the increased shell weights, we performed <i>δ</i>¹⁸O, Mg/Ca, and μCT measurements on the same shells from a number of samples surrounding this event. Compared with the lighter ones, we find that the foraminifera of increased weight are internally contaminated by sediment infilling and that their shell masses respond to local surface seawater density changes.