UBC Theses and Dissertations
The effect of temperature and pH on the growth and biomechanics of coralline algae Guenther, Rebecca
Climate change is progressing rapidly and is causing shifts in ecosystem function, species distributions, biodiversity, and abundances worldwide. In this thesis, I explore the physiological and biomechanical responses of red algae in multiple life history stages to climate change. In Chapter 1, I introduce the looming threat of climate change, and some of the forces driving ocean acidification. I introduce my study system and my study species: rocky intertidal ecosystems and articulated coralline algae. I also describe potential differences in responses to ocean acidification based on life history stage. Finally, I give an overview of my dissertation and objectives. In Chapter 2, I investigate the effect that ocean acidification may have on spore stages of red algae. Under reduced pH, I document a reduction in spore settlement of both Pterosiphonia bipinnata and Corallina vancouveriensis, and weakened spore attachment in C. vancouveriensis. Results demonstrate that ocean acidification can negatively impact macroalgal spore adhesion in both calcified and non-calcified algae, but in different phases of their spore adhesion process. In Chapter 3, I explore the effect of elevated pCO₂ and temperature on the growth, calcification, and material properties of two species of articulated coralline algae. I found that increased temperatures and reduced pH were found to negatively affect growth rates of these two species of coralline algae. On the other hand, increased temperature and reduced pH had little influence on the amount of calcium carbonate in the intergenicula, and also had minimal effects on the biomechanical properties. In Chapter 4, I explore the amount of natural variability of chemistry in tidepools and attempted to relate chemical differences to differences in Corallina vancouveriensis growth, calcification, and biomechanics. In general, I found that organisms within tidepools greatly alter the chemistry of the surrounding water, and these changes are larger in magnitude than what is predicted for global climate change. I also found that, despite extreme changes in chemistry during low tides, C. vancouveriensis was still able to grow all year long.
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