CAN SHARED EVOLUTIONARY HISTORY HELP PALEOCEANOGRAPHERS TO UNLOCK THE "BLACK-BOX" OF PLANKTONIC FORAMINIFERAL VITAL-EFFECTS? (Invited Presentation)

The carbon and oxygen stable isotope ratios (δ¹³C and δ¹⁸O) of planktic foraminiferal tests are one of the major tools in palaeoceanography. However, foraminiferal physiology and life history (e.g., symbioses, metabolism, diet, reproduction etc.) can offset their test chemistry from isotopic equilibrium with ambient seawater. These factors are commonly referred to as “vital-effects” which, along with calcite preservation, can significantly complicate the interpretation of chemical proxies preserved in foraminiferal calcite particularly in extinct taxa. Despite recent advances in our understanding of biological controls on geochemical proxies many factors such as the influence of metabolism have remained a poorly constrained “black-box”.

Phylogenetic approaches offer a tantalising opportunity to help unlock the vital effect black-box because the biology and ecology of related species depends, in part, on their shared evolutionary history. Closely related species are expected to share more biological and ecological characteristics (e.g., vital effects) then more distantly related species. Thus, if evolutionary relationships are known, it is possible to infer the effect of unmeasured ‘black box’ variables, like metabolism, on δ¹³C and δ¹⁸O values. Here we present new and published size-specific δ¹³C and δ¹⁸O records from planktic foraminifera spanning the last 65 million years of Earth history to quantitatively test whether the difference in vital effects (particularly metabolism and symbiosis) amongst species can be accounted for by their phylogenetic relatedness.