THROUGH THE WALLS: BIOTIC AND ABIOTIC DETERMINANTS OF PLANKTONIC FORAMINIFERAL POROSITY IN CORE TOP ASSEMBLAGES

To varying degrees, the morphology of taxa reflects--and affects--how they interact with their biotic and abiotic surroundings. For planktonic foraminifera, single celled protists with calcium carbonates tests (i.e., ‘shells’), the key morphologies preserved in fossils are test shape and wall structures like porosity and ornamentation. Porosity is particularly interesting as it likely reflects a combination of physiological and abiotic factors. Pores in the test walls vary in size, shape, and density and are believed to be instrumental in the processes of metabolic gas exchange. Because of this metabolic link, planktonic foraminiferal porosity may reflect some combination of basal metabolic rates and environmental conditions. To better understand factors influencing this aspect of foraminiferal morphology we conducted an in-depth study of planktonic foraminifera communities in four core top samples from the Atlantic Ocean. Test surface area, volume, thickness, and porosity were measured using images from both light microscope and scanning electron microscope images from approximately 2000 individual foraminifers. The resulting data provides an detailed documentation of the porosity variation within and among species of planktonic foraminifera as well as between communities in different abiotic contexts, specifically relating to temperature and oxygenation of the water column. This work provides a detailed baseline for assessing the potential of planktonic foraminiferal porosity to be used, in conjunction with other proxies, to monitor foraminiferal population response to past oceanic environmental change.