| Summary: | It is apparent that in order to reach international climate goals, it will not be sufficient to simply reduce greenhouse gas emissions. There must also be a degree of removal of legacy emissions from our atmosphere to remain within 1.5-2 oC of warming relative to pre-industrial values. Several carbon removal schemes have been proposed which use the ocean as the site of removal, termed marine Carbon Dioxide Removal (mCDR). Meta-analysis of mCDR literature conducted as part of this thesis has revealed that there are six key “elimination” criteria that must be satisfied in order for any mCDR scheme to be viable. There are three main “elimination” criteria which are currently lacking from peer-reviewed mCDR publications: (i) completion of field trials, pilot studies and demonstration projects, (ii) assessment of governance/finance/social aspects of mCDR, and (iii) accurate quantification of CO2 drawdown/CDR potential. The mCDR scheme of Ocean Alkalinity Enhancement (OAE), which involves raising surface ocean Total Alkalinity (TA) to shift the carbonate buffer system such that it absorbs more atmospheric CO2, has great potential as an mCDR technique due to its co-benefits and relative advancement compared to other mCDR methods. However, the growth and calcification response of major pelagic calcifiers to OAE (the coccolithophores and the foraminifera) are as yet unquantified. This thesis has constrained these responses for two key “endmember” species of coccolithophore (E. huxleyi and C. braarudii) and five key species of planktonic foraminifera (G. ruber, G. siphonifera, G. bulloides, G. sacculifer and O. universa) using in-vitro experiments. Growth and calcification response to OAE has been found to be species- and taxa-specific, similar to responses to ocean acidification studies. There is evidence that G. siphonifera, G. ruber and O. universa may have an optimum reproductive success at TA ~ 3000 μmol kg-1, but calcification responses of planktonic foraminifera in enhanced TA did not change, although these were ...
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