ADILAH EBRAHIM PONNURANGAM

• Rising atmospheric CO2 from anthropogenic sources has led to many changes in the earth ecosystem. To better understand this phenomenon, proxies are being developed to simulate past conditions. The models can be used to accurately predict the future based on the understanding of the climate conditions and changes of the past. Mussels incorporate trace metals into their shells and chemical analysis of the growth bands is then possible due to the fact that shells are composed of sequentially deposited layers of mineralized material, which are laid down according to the growth of the organism. Intra-species variability in trace elements, specifically the Rare earths and Yttrium (REY) was investigated using Mytilus edulis shells. Findings through a comparison of the partitioning coefficient patterns to the REY speciation in seawater suggests that the free REY3+ are the likely species incorporated into the shells Additionally, absolute REY concentrations in M. edulis shells may have the potential to be used as a pH proxy, whereas REYSN distribution patterns of the shells may rather be used as a temperature proxy. Furthermore, trace metal concentrations in shells of Mytilus edulis, Arctica islandica and Serripes groenlandicus, were compared. This thesis highlights the fact that REY and other trace metal accumulations in the shells of mussels from different species is not the same and that there are indeed significant differences in the accumulation of most of the elements between the different species. Lastly, the possibilities of analyzing trace metals along the growth lines of the M. edulis shells that were grown in a culturing experiment with four different pCO2 conditions are explored. The behavior of the different metal/Ca ratios across the different pCO2 conditions revealed some possible trends that could possibly allow the elements to be used as proxies by responding to changes in pCO2 conditions.