Assessing seabed carbon storage and sequestration (Blue Carbon): response to pressures and management interventions

The subtidal seabed sedimentary habitats in the UK’s English waters contain between 80 and 100 Mt of organic carbon (OC) and so have a significant climate change mitigation potential (as Blue Carbon). Although it is known that OC input (amount and rate) and composition (source and reactivity), sediment type and environmental setting (e.g., temperature, oxygen) control both amount of OC stock and OC burial rates, the regional understanding of the links between these controls, their spatial variability remains poorly understood.  

Much of the UK’s shelf seabed organic carbon stock is under pressure from physical disturbances by various human activities, significantly trawling as well as climate forcing processes and temperature increases. These pressures promote changes in OC status and climate regulation service provision (storage and burial), although the net direction of change is highly uncertain. Management of human activities, including protection or restoration of seabed areas containing OC, may therefore provide a significant Nature-based Solution (NbS) to climate change itself.

We present an exemplar case study in the North Sea which aimed to identify and explore regions of OC climate regulation service provision and draw together evidence strands to support management decisions and measures to allow optimisation of sedimentary OC (‘Blue Carbon’) to mitigate climate change.

Three key aspects and related questions are addressed:

• Organic carbon storage and burial in space across the shelf: what drives variability, and what is the role of OC composition, source and reactivity?
• Present pressures on seabed carbon: Where is OC storage under pressure? By how much? What is the potential impact?
• Policy and management: How can this evidence base inform management interventions and measures, including protection and recovery measures which promote the potential of the seabed climate change regulation service (blue carbon)?

Within each element insights into the developing underpinning datasets, future approaches needed, and remaining knowledge gaps and priorities will be presented.