Protect and restore marine sediments
Halt impacts on existing marine carbon stores by establishing appropriate spatial management.
The Scottish Government should designate as Marine Protected Areas marine sediments with significant carbon sequestration value and implement spatial management measures to ensure they are protected from adverse pressures.
Scotland’s sea-loch sediments are important stores of carbon. It is estimated that 115-150ktCO2e is buried in the sediment of Scotland’s 111 sea-lochs annually. This annual burial of carbon which, although efforts to confidently quantify this service are incomplete, may provide a climate regulating service on top of the sea-lochs’ existing service of storing carbon.293
It is important to recognise the distinction between carbon sequestered in the top 10 cm of sealoch sediment (‘surficial sediment’) and the more stable stores of carbon deeper in the sediment basins (which may be 100s of metres deep), which may be 100 times greater.
Surface sediments are vulnerable to disturbance and may currently be regularly impacted by fishing activity, particularly trawling (which focuses on muddy habitats such as those in sea lochs) and dredging (which focuses on sandier seabeds with lower carbon concentrations). These fisheries disturb and then re-suspend carbon stores into the water column, from where it may be re-released into the atmosphere, which is why appropriate spatial management should be used to remove or restrict the impact of these activities such that the carbon stores remain intact.294 In selecting marine sediments for protection, account must be taken not only of the quantity of carbon that is stored in certain areas, but also of its reactivity (and hence the likelihood of it being remineralised back into the water column) and the rate at which it is continuing to be deposited.
This policy would need some co-operation with the UK Government, especially beyond 12 nautical miles.
For further information:
- Assessing the potential vulnerability of sedimentary carbon stores to bottom trawling disturbance within the UK EEZ, Kirsty E. Black, Craig Smeaton, William R. Turrell and William E. N. Austin, Frontiers in Marine Scotland, August, 2022, https://www.frontiersin.org/articles/10.3389/fmars.2022.892892/full
High rates of organic carbon burial in fjord sediments globally Richard W. Smith, Thomas S. Bianchi, Mead Allison, Candida Savage & Valier Galy Nature Geoscience volume 8, pages 450–453(2015)
From SCCS document ‘CCP revision – SCCS proposals – single doc – FINAL 250320’