Assessing the Potential Vulnerability of Sedimentary Carbon Stores to Benthic Trawling within the UK EEZ

Shelf and coastal seas hold vast quantities of sedimentary carbon, which if left undisturbed, will contribute towards long-term carbon and underpin natural ocean climate services. It is estimated that within the UK exclusive economic zone, 524 Mt of organic carbon is stored within sediments (Smeaton et al., 2021). However, the stability and potential vulnerability of this key component of global natural capital remains poorly quantified, particularly under anthropogenic stressors, such as benthic fishing activity. Benthic trawling activity is the most significant cause of anthropogenic disturbance to the seabed, leading to massive sediment resuspension events and wide scale impact to benthic communities. The impacts of trawling on benthic ecosystems and communities are well reported within the literature (e.g. Hughes et al., 2014); however, a knowledge gap remains regarding the impact of trawl-induced disturbance events on sedimentary carbon stores.

In order to improve our understanding of the areas where sedimentary carbon is potentially at greatest risk from trawling events, we have developed a carbon vulnerability ranking to signify the areas of the seabed where preventative protection would be most beneficial to help maintain our current carbon stocks while further research continues to shed light on the fate of carbon after trawling (e.g. carbon remineralization, transport, and consumption etc.). These maps have been modelled within GIS via fuzzy set theory by making use of currently available fishing intensity, carbon and sediment distribution, and sediment lability datasets (ICES, 2014; Smeaton et al., 2021).

Our results show that the fjordic west coast of Scotland represents one of the key areas where sedimentary carbon is highlighted as being potentially at risk from bottom trawling. This is largely due to the high lability of the sediments as a function of both sediment type and the elevated organic carbon content present within these sediments. In addition, higher occurrences of repetitive trawling activity within inshore waters may add to these pressures. Our research shows that these organic carbon hotspots are potentially at risk of disturbance from benthic trawling activity and should be prioritized for future safeguarding measures to ensure avoided emissions are minimized and to protect this natural carbon capital resource.

References

Hughes, K.M., Kaiser, M.J., Jennings, S., McConnaughey, R.A., Pitcher, R., Hilborn, R., Amoroso, R.O., Collie, J., Hiddink, J.G., Parma, A.M., Rijnsdorp, A., 2014. Investigating the effects of mobile bottom fishing on benthic biota: A systematic review protocol. Environ. Evid. 3. https://doi.org/10.1186/2047-2382-3-23

ICES, 2014. OSPAR request on mapping of bottom fishing intensity using VMS data, Special request, Advice September 2014.

Smeaton, C., Hunt, C.A., Turrell, W.R., Austin, W.E.N., 2021. Marine Sedimentary Carbon Stocks of the United Kingdom’s Exclusive Economic Zone. Front. Earth Sci. 9, 1–21. https://doi.org/10.3389/feart.2021.593324