Coastal ecosystems (saltmarsh, seagrass and some kelp) can sequester up to 20 times more carbon per acre than land forests. However, unlike saltmarsh and seagrass habitats which have a buried root structure, kelp’s holdfast sits on top of firm substrate. This means the carbon fixed into kelp tissues cannot be sequestered in the immediate vicinity.
When kelp die and, unless they are buried, any kelp exposed to the elements will decompose and will ultimately return captured carbon to the atmosphere. Burial can occur naturally under certain conditions, for example when kelp matter is carried out to the deep-sea and sinks into sediment on the seafloor. However, it is very difficult to measure the amount of kelp being buried and it is likely to be highly variable due to local currents and seabed topography.
The Sussex Kelp Recovery Project aims to provide some answers to questions around kelp carbon cycles at a local level and may even inform the development of a quantifiable kelp carbon sequestration rate, though this is still some years away.
Ultimately, kelp is a key species in a broader ecosystem and the presence of kelp will stimulate other parts of the trophic levels in Sussex seas, with all marine life being carbon based. This is referred to as ‘animating the carbon cycle’ and reminds us that healthy marine ecosystems are better at capturing and storing carbon than those that are depleted or damaged.
Assessing kelp’s carbon storage and sequestration potential
To inform our understanding of the value of kelp as a blue carbon store, the rate of carbon draw-down and storage in sediments will be assessed within the Sussex Nearshore Trawling Byelaw area and also within the wider, deeper, Sussex waters where trawling continues.
This is done by collecting sediment samples to identify sources of carbon and how these have changed over time. Seabed samples will be analysed using radionuclide dating techniques and stable isotope analysis to provide a geochronology and establish the provenance of carbon origin. Novel technology using eDNA barcode and primer sequences will pinpoint the carbon patronage.