Morphological variations of calcite microfossils synchrotron-based μCT reveal the last 200 years of environmental changes at the Baltic Sea entrance

Summary, in English

Human activities in coastal areas have accelerated during the last 200 years. Environmental changes resulting in a combination of three threats, i.e., deoxygenation, warming, and ocean acidification, impact particularly sub-polar regions. To better understand these environmental challenges, we need to develop tools to compare our present situation with previous periods less impacted by anthropogenic activities. Foraminifera are marine microorganisms often with a CaCO3 shell (test), which readily fossilize in marine sediments. Morphometric changes of the test are increasingly used thanks to the high-resolution 3D development imagery acquired with microcomputed tomography (μCT). In this project, we analyzed a set of 124 specimens recording the period from pre-industrial into present-day conditions at the entrance of the Baltic Sea/Öresund. In this area, widespread hypoxia events have been recorded due to combined natural climatic variability and anthropogenic pressures, and foraminiferal fauna has changed profoundly in the last 200 years. We hypothesize that the foraminifera will respond to the environmental variations by having changed test morphology. Here, we describe an easily reproducible and efficient post-data routine with free software to analyze the morphometrics of the whole test (thickness, calcite volume, calcite surface, number of pores). We illustrate the efficiency of this post-data routine with a study case, using 4D time series. Especially, the changes in test morphometrics indicated a decreasing trend in test thickness, by 36% in the early 2000s. Moreover, the calcite surface and the number of pores indicated increasing trends, by 63% and 151% respectively. These outstanding results corroborate the accumulation of multiple stressors occurring in this area. Finally, our project demonstrates that the synchrotron-based μCT is a high-resolution, non-destructive, and time-efficient method to reveal past environmental evolution.

• Author: Constance Choquel; Dirk Müter; Sha Ni; Laurie Charrieau; Behnaz Pirzamanbein; Gerhard Schmiedl; Helena L. Filipsson
• Department/s: Department of Geology; Department of Statistics
• Publishing year: 2022
• Language: English
• Document type: Poster
• Topic: Climate Science
• Conference name: 14th International Conference on Paleoceanography
• Conference date: 2022-08-28 - 2022-09-02
• Conference place: Bergen, Norway
• Status: Published