On the 6th of December Griselda Anglada-Oritz successfully defended her PhD entitled “Planktonic foraminifers and shelled pteropods in the Barents Sea: seasonal distribution and contribution to the carbon pump of the living fauna, and foraminiferal development during the last three millennia”.
To the left: Griselda defending her PhD in December at UiT in Tromsø. Photo: Pauke Schots, UiT
In her PhD, Griselda found that pteropods play an important role in carbon dynamics in all seasons of the year in both the northern Barens Sea and the northern Svalbard margin, while foraminifers appear to have a higher productivity in the southern Barents Sea compared to the northern Barents Sea. Her research suggests that calcium carbonate (CaCO3), which forms the shells of these zooplankton species, dissolves in the sediment. This is an important implication for paleoceanographers, who reconstruct the physical, chemical, and biological characteristics of the oceans from the past.
The Barents Sea is affected by increasing temperatures and emissions of carbon dioxide (CO2) due to human activities. The Barents Sea has also been described as a hotspot for ocean acidification. Ocean acidification is referred to as a decreased pH over an extend period of time combined with a decreased calcium carbonate (CaCO3) saturation state and carbonate ion concentration (CO32-), and it is the result of an increased CO2 uptake by the ocean from the atmosphere. Ocean acidification can thus alter the carbonate chemistry in the water column, thereby affecting marine organisms. Planktonic marine calcifiers, such as foraminifers and pteropods, are especially susceptible for ocean acidification since these organisms have a shell made of CaCO3. During their lifecycle they live in the water column but sink to the sea floor when they die, thereby contributing to the carbon cycle by exporting not only organic carbon, but also CaCO3.
Infographic of the ocean acidification process (Figuerola, Blanca, et al. “A review and meta-analysis of potential impacts of ocean acidification on marine calcifiers from the Southern Ocean.” Frontiers in Marine Science 8 (2021): 584445.)
The aim of Griselda’s PhD was to study the distribution of planktonic foraminifers and shelled pteropods in the Barents Sea and the adjacent Arctic Basin. She investigated their distribution patterns and contribution to carbon dynamics in the northern Svalbard margin in the Arctic Ocean, and reconstructed production and preservation patterns of planktonic foraminifera in sediment cores from the northern and southern Barents Sea from the last three millennia.
The main findings of Griselda’s PhD are that throughout the year pteropods contribute significantly to the carbon dynamics in the northern Barents Sea and northern Svalbard region, and these organisms are more likely to be affected by ocean acidification compared to foraminifers, due to their more sensitive shells. Abundance estimates of foraminifers from sediment samples suggest that there is a higher planktonic foraminifer productivity in the southern Barents Sea compared to the northern Barents Sea. The observed scarce abundance of foraminifers in the northern Barents Sea sediment core, combined with observations on the seasonality of marine calcifiers and other parameters suggest that CaCO3 dissolves in the sediment.
The suggestion that CaCO3 dissolves in the sediment combined with the fact that the shells of marine organisms are used in paleoceanography as a proxy to reconstruct the paleoenvironmental and paleoclimatic conditions in the Barents Sea, supports the need for further investigation of CaCO3 dissolution and its use in paleoceanography.
Griselda Anglada-Oritz was supervised by Professor Tine Rasmussen (UiT), Researcher Katarzyna Zamelczyk (UiT), Researcher Melissa Chierici (IMR), Researcher Agneta Fransson (NPI) and Professor Patrizia Ziveri (Universitat Autònoma de Barcelona, Spania). Her evaluation committee consisted of Prof. Dr. Marit-Solveig Seidenkrantz (Aarhus University, Denmark), Prof. Andrés Rigual-Hernandez (University of Salamanca, Spain), and Professor Jan Sverre Laberg (UiT).
Length measurements of foraminifera (minimum size, panel A) and pteropods (diameter, panel B). from: Anglada-Ortiz, Griselda, et al. “Seasonality of marine calcifiers in the northern Barents Sea: Spatiotemporal distribution of planktonic foraminifers and shelled pteropods and their contribution to carbon dynamics.” Progress in Oceanography218 (2023): 103121.