by Rachael Shuttleworth
Geochemists and palaeoceanographers use the chemical and isotopic composition of preserved foraminifera (carbonate microfossils) in deep sea sediments to reconstruct the environment of the past. There are a vast range of things we can reconstruct based on the chemistry of these fossils from temperature to nutrient utilisation. The research I do focuses on the boron isotopic composition of foraminifera, and how this can be used to calculate the pH that the carbonate shell precipitated in.
Palaeoclimate and palaeoceanography is a very necessary branch of geochemistry in today’s world as we head towards a higher CO2 world. By looking back in Earth’s history to a time when CO2 was equal to that or higher than observed today we can make better predictions as to how environments will change in our future. However, to do this effectively we need to better understand how different the chemical composition the forams (foraminifera) record is to the ambient environment, it is this question that led to my venture into modern biology and hitting the fieldwork jackpot of 3 months in Bermuda…
The idea here is that respiration, calcification (& photosynthesis if the foram hosts symbionts) work to alter that chemistry of the environment immediately surrounding the foram where based on the viscosity of water diffusion dominates over turbulence. In order to investigate this we aim to initially define what this offset is by measuring the isotopic composition of the water and forams of a range of species and size fractions. We then want to look at how much each process (eg. Respirartion) contributes to altering the isotopic composition of the microenvironment. This work was a massive learning curve for me, swapping a clean lab for boat trips, and Teflon cleaning for shackling up plankton nets!
This work is still ongoing and is part of the SWEET (http://www.thefosterlab.org/sweet/) project and will (hopefully) form part of my thesis.