Tomographic data of Trilobatus trilobus shells from central Atlantic core-top sediment samples

Understanding the controls behind the calcification and distribution of
planktonic foraminifera in the modern ocean is important when using these
organisms for paleoceanographic reconstructions. This study combines shell
geochemistry, light microscopy, and X-ray micro-computed tomography to
dissect various parameters of Trilobatus trilobus shells from surface
sediments and explore the factors influencing their biometry. The goal is
to understand which aspects of the marine environment are critical for the
calcification and vertical distribution of this species. T. trilobus is
found to produce larger, thinner and overall lighter shells in the
equatorial regions compared to the subtropical gyre regions where the
shells were up to 4% smaller, more than 60% thicker and approximately 45%
heavier. The skeletal mass percentage together with other calcification
metrics (shell weight, thickness) are found to depend primarily on ambient
seawater salinity rather than carbonate chemistry. In line with their
degree of calcification, based on geochemically reconstructed apparent
calcification depths, this group of organisms is found shallower into the
water column at the equator and the subtropical gyres, while its habitat
deepens in between these regions at the extra-equatorial sites.
Furthermore, it is demonstrated that T. trilobus, in the (central)
Atlantic, occupies a density layer slightly below the salinity maximum
isopycnal at various depths, presumably by adjusting its shell properties.