Can eDNA Analysis Provide Insights into the Blue Carbon Contributions of Invasive Macroalgae in Jersey’s Marine Environment?

Environmental DNA (eDNA) is a promising tool for investigating the role of macroalgae inblue carbon sequestration. This dissertation uses a newly designed rbcL primer to examine whether eDNA can provide insights into the organic carbon contributions of macroalgae in
Jersey’s marine sediments, with a particular focus on invasive species. eDNA analysis was conducted on samples from 26 sedimentary cores collected within Jersey’s marine territory. Results show that macroalgae eDNA is both abundant and taxonomically representative in
these sediments. However, limitations in species-level classifications prevented the study of invasive species. Rhodophyta exhibited the highest sequence abundance and order richness, consistent with its high species diversity and past amplification success. Little variation in
eDNA composition variables were observed between the two blue carbon classes. Yet, both sequence abundance and order richness were higher in seagrass habitats compared to non seagrass habitats, highlighting the key role of seagrass for carbon sequestration in Jersey. Depth effects contrasted between the two variables, possibly reflecting different influencing factors for order richness, such as seasonal fluctuations in biomass export. In addition, further research is needed to assess the impact of the sediment mixing layer on macroalgae carbon in sediments. Finally, the significant relationship between total organic carbon and eDNA composition variables supports the use of eDNA as a tracer for macroalgae carbon. This study emphasises the importance of understanding macroalgae’s contributions to carbon stocks for evaluating blue carbon resources and informing environmental management strategies that involve enhancing sequestration and offsetting. Future research should focus on improving species level classifications to better explore the blue carbon potential of invasive macroalgae.