Molly Crowe1, Gemma Beatty2, Jim Provan2, William Hunter3, Louise Kregting1
1 School of Natural and Built Environment, Queen’s University Belfast, Belfast, BT9 5AG, UK
2 Institute of Biological, Environmental and Rural Sciences, Aberystwyth University, Aberystwyth, SY23 3DA, UK
3 Agri-Food and Biosciences Institute Northern Ireland, Fisheries and Aquatic Ecosystems Branch, Belfast, BT9 5PX, UK
Knowledge of the fate of kelp biomass to shelf and deep seas is important for our understanding of carbon sequestration potential. Kelp forests have high annual turnover of biomass, from 460 g C m-2 yr-1 to 3000 g C m-2 yr-1 globally, with an estimated 80% exported to shelf and deep-sea environments. Laminaria hyperborea could make a significant contribution to exported material each year through the May Cast, where the entire prior year’s blade growth is released into the water column. Current methods for identifying detrital material include carbon isotope analysis or eDNA, which have their limitations in differentiating to species level. As input from different macroalgal species can vary so widely, it is important to develop targeted means of identifying kelp sink locations, so that carbon flow dynamics can be better understood. This study tested the feasibility of using species-specific DNA markers to detect degraded seaweed material in Irish Sea sediment and water samples. This was used in combination with a hydrodynamic model to contextualise how seaweed material moves around the Irish Sea and what this may mean for carbon sequestration in offshore marine environments. Organic material reaching offshore sediment is expected to be degraded, which is why the success of this feasibility study is so exciting.