Sophie M. Alexander *1, Philip Sexton 1, Pallavi An and 1 & Steven Bohaty 2
1 School of Environment, Earth and Ecosystem Sciences, The Open University, Walton Hall, Milton Keynes, MK7 6AA; Sophie.alexander@open.ac.uk 2 Ocean and Earth Science, National Oceanography Centre Southampton, University of Southampton Waterfront Campus, European Way, Southampton, SO14 3ZH
The biological pump draws atmospheric carbon into the ocean, where it is used to create living matter, before sequestering it into sediments. The early-to-middle Eocene interval (~42 to 50 Ma) witnessed elevated atmospheric CO2 levels and greenhouse warmth, so is a valuable interval with which to better understand changes in biological pump operation under future anthropogenic warming. In this study, we utilise accumulation rates of fish teeth (IAR) and benthic foraminifera (BFAR) within sediments, combined with morphometric analysis of fish teeth at sites across the Southern Ocean. Comparison of sites in both the Antarctic (>60 oS) and Sub-Antarctic Zones (45-60 oS), seeks to conclude if the biological pump operated differently in each zone, as it does today. It is well established that BFAR reflects organic carbon delivery to the seafloor. At all sites, we find a positive correlation between IAR and BFAR, suggesting the two are similarly recording organic carbon transfer through the water column, and as such are representative of biological productivity. Timing of productivity pulses within each zone were offset, suggesting the biological pump operated differently within each. Analysis of fish tooth morphometry suggests differences in fish populations in each zone. It remains uncertain whether spatial fish population variations were a cause or effect of the differing productivity and biological pump responses. Further morphometric analysis may allow comparison to the existing fossil record, allowing semi-quantitative comparison of the volume of organic carbon flux that each morphotype represents.