Abstract

The investigation of intertidal coralline algae capability as a paleo archive for temperature and pH reconstruction was the main topic of this study. In order to achieve this, a two different culturing experiments were carried out: a three-month temperature experiment with set temperatures at 7.5°C and 12°C and a three-month pH experiment with set pCO2 at 380 μatm and 1000 μatm. Both experiments were then used to create species-specific temperature equation using magnesium Calcium (Mg/Ca) ratio and strontium calcium (Sr/Ca) ratio as proxies for temperature, and pCO₂ calibrations using magnesium oxygen (Mg-O) bonding as pH proxy. The temperature calibration was then used on coralline algae collected at Ilfracombe beach in August at 2017 and 1889. Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) and Electron probe microanalysis (EPMA) were used to measure Mg/Ca and Sr/Ca while Raman spectroscopy was used to analyse the Mg-O bonding. The temperature calibration showed an increase in temperature of 2.75±0.3081oC from 1889 to 2017. The Mg-O bond strength provided to be a very good pH recorder, giving an accuracy of 98.7% with SD±0.22417 between the reconstructed pH from the algae thallus and the field measurement. C. officinalis cell walls thickness decreased at high CO₂ as a result of the decrease in pH. C. officinalis showed to be a good archive for temperature using Mg/Ca and Mg-O as pH proxies.

Course: Master of Philosophy - MPhil

Date Deposited: 2020-01-23

URI/permalink: https://library.port.ac.uk/dissert/dis13521.html