er million-year timescales, weathering of silicate and carbonate rocks draws down atmospheric carbon dioxide to be stored within the oceans. This acts as a negative feedback on carbon emissions within the carbon cycle, and prevents "runaway" greenhouse climate effects.

This DPhil project has been funded as part of the NERC-led Greenhouse Gas Removal
Programme. The aim of the NERC-led programme is to establish whether natural weathering rates could be artificially accelerated to draw down atmospheric carbon dioxide on a timescale which could achieve negative emissions i.e. the intentional removal of carbon dioxide from the atmosphere. This could help mitigate the current and future impact of global warming.

However, assuming weathering rates could be artificially accelerated, storing carbon dioxide in the ocean may have significant as yet unconstrained and unquantified ramifications. Increased weathering would raise the alkalinity of the ocean. There are three main aims of this DPhil project:

1) Determine the calcification response of the main marine calcifiers (foraminifera and corals) through laboratory and field experiments. If calcification rates can keep pace with alkalinity addition, then the draw-down of atmospheric carbon dioxide could be reversed, rendering accelerated weathering an inadequate method to achieve negative emissions. Calcein and 135Ba will be used as novel tracers of new growth in calcification rate determination experiments. The results of these experiments will then be integrated into ocean circulation models.
2) Establish the response of phytoplankton groups e.g. diatoms, dinoflagellates, cyanobacteria, coccolithophores to alkalinity addition, again through laboratory and field experiments. This addresses how marine ecosystems may be altered because of raised ocean alkalinity.
3) Investigate how phytoplankton groups respond to contaminants associated with weathering of mine waste, again through laboratory and field experiments. Mining waste is a potential material which could be artificially weathered to achieve negative emissions due to its ready availability and large surface area. This material will inevitably contain heavy metals which could stimulate growth and carbon fixation in ocean biota, or act as a toxin.

The aim is to perform field experiments in controlled reef environments in both the Gulf of Eilat and the Great Barrier Reef, in collaboration with Professor Jonathan Erez at the Hebrew University of Jerusalem and Professor Ove Hoegh-Guldberg at the University of Queensland respectively.