Quantifying intertidal canopy-forming macroalgal production, extent, degradation, and blue carbon potential

Abstract

Carbon dioxide is the most abundant greenhouse gas (GHG), contributing 80% to the total GHG’s released in the atmosphere. As a result, it is often the emission targeted to reduce the impacts of climate change. Nature-based solutions are increasingly being used to mitigate the effects of climate change. Terrestrial and marine systems act as carbon sinks due to their ability to sequester carbon within their biomass and sediments. Macroalgae remove CO2 from the
atmosphere through the process of photosynthesis and are considered to be one of the most productive ecosystems worldwide. However, unlike traditional carbon sinks, macroalgae beds occur on rocky substrate preventing the burial of detrital matter in situ. These habitats may, however, still contribute towards carbon sequestration by acting as important ‘carbon donors’, transporting their detrital material to offshore and deep sea sediments where long-term storage
of carbon is possible. Of all macroalgae, Laminariales have received the most attention in their potential to act as blue carbon donors, while intertidal fucoid species have been overlooked. This thesis concentrates on three common intertidal fucoid species from the NE Atlantic, Ascophyllum nodosum, Fucus vesiculosus and Fucus serratus and assesses their potential for carbon sequestration through carbon donation. To determine whether these fucoids species of interest were significant carbon donors, this thesis investigated rates of carbon accumulation and release, degradation of tissue, and the national spatial extent of fucoids in Wales, UK. Finally, an estimate of the carbon stored within standing biomass and amount sequestered was calculated for Wales. Results found that carbon accumulation and release, for some species was equal to that of kelp species if not in some instances greater. Degradation estimates of tissues were also promising, with the presence of refractory elements, specifically in holdfast and receptacle tissues, in kelps and fucoids. At a national scale, fucoids within Wales are unlikely to be of high importance in carbon sequestration due to their low spatial distribution. However, per area 0.04 kg C m-2 yr-1 of carbon was found to be sequestered by Ascophyllum nodosum, Fucus vesiculosus and Fucus serratus combined, a rate similar to other terrestrial and marine carbon sinks within Wales. As a result, intertidal fucoids should be included in estimates determining the contribution of macroalgae to blue carbon

Date of Award	2020
Original language	English
Awarding Institution	Aberystwyth University
Sponsors	Knowledge Economy Skills Scholarships
Supervisor	Pippa Moore (Supervisor)