Scottish rhodolith bed blue carbon in a changing world

James, Kelly Margaret (2023) Scottish rhodolith bed blue carbon in a changing world. PhD thesis, University of Glasgow.

Abstract

The current climate crisis, caused by elevated atmospheric CO2 and Greenhouse Gases, has the potential to cause ecological, social and economic impacts. Marine systems can act as a natural-based solution to help mitigate climate change, with systems drawing down CO2 by sequestering and storing carbon (termed blue carbon (BC)).
Rhodolith beds are globally ubiquitous systems and are formed from non-geniculate red coralline algae. There is recent evidence that their 3D structure facilitates the burial of allochthonous and autochthonous organic carbon (OC), thus rhodolith beds can act as BC repositories. Currently, little is known about how rhodolith bed blue carbon varies with structure and health status, with beds existing in a variety of sheltered and exposed environments, ranging from 100% live to 100% dead coralline algae on the surface of the beds. Furthermore, with increasing evidence that climate change (such as warming and ocean acidification (OA)) can reduce the capacity of BC systems to sequester and store carbon, research is needed to determine if rhodolith beds will continue to operate as BC repositories under future climate scenarios.
Using Scotland as a model system, this thesis aimed to contribute to these knowledge gaps by investigating 1) spatial and temporal trends in rhodolith bed blue carbon, 2) how autochthonous carbon production is affected by elevated temperature and OA, and 3) how carbon burial and the current sedimentary OC (SOC) stock is affected by elevated temperature and OA.
Rhodolith beds were characterised by having low decomposition rates which facilitated the burial of SOC. The rhodolith bed SOC stock was found to vary 10-fold between sheltered and exposed sites, with sheltered fjordic sites storing a higher amount of BC. There was also evidence that the SOC was “locked away” after a certain depth, meaning that BC may be preserved in rhodolith beds for centuries. Dead rhodolith beds continued to store SOC, with OC preserved when the dead bed was undisturbed. Under future conditions, rhodolith bed communities experienced increased carbonate dissolution, suggesting that both live and dead rhodolith bed distribution may decrease over the coming century. The effects of climate change on OC burial and storage depended on carbon type, with labile carbon (more biodegradable) vulnerable to warming and ocean acidification. On the other hand, refractory carbon (less biodegradable) was not affected by future conditions, suggesting that the current SOC stock will remain preserved if undisturbed.
This thesis provided evidence that rhodolith beds can act as BC repositories, with their global distribution meaning that they may contribute to both national and global carbon inventories. Not acknowledging the ability of both live and dead beds to store carbon could result in beds being damaged. This could result in carbon that has accumulated over thousands of years being exposed to O2 and released back into the environment further exasperating the climate crisis.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Subjects: G Geography. Anthropology. Recreation > G Geography (General); G Geography. Anthropology. Recreation > GE Environmental Sciences
• Colleges/Schools: College of Science and Engineering > School of Geographical and Earth Sciences
• Supervisor's Name: Kamenos, Prof. Nick, Burdett, Prof. Heidi, Cameron, Dr. Karen, MacDonald, Dr. John, Davies, Dr. Ian and Baxter, Prof. John
• Date of Award: 2023
• Depositing User: Theses Team
• Unique ID: glathesis:2023-83600
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 23 May 2023 06:41
• Last Modified: 21 May 2026 13:37
• Thesis DOI: 10.5525/gla.thesis.83600
• URI: https://theses.gla.ac.uk/id/eprint/83600

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