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Dryad

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

Abstract

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.