The QUANTIFICATION, CHARACTERISATION, SOURCE AND FATE OF PAST AND PRESENT CARBON STORAGE IN COASTAL AND OFFSHORE SEDIMENTS FOR EFFECTIVE MARINE MANAGEMENT (QUEST)

Globally, continental shelf environments, and the marine sediments therein, have been recognised as having significant roles to play in the sequestration, cycling and storage of. Recently, shelf sediments have been identified as the largest, but most uncertain, stock of carbon stored on the continental shelf, citing a lack of empirical data. Moreover, seabeds are coming under increased pressure through anthropogenic impacts, such as offshore renewable energy development, trawling and dredging, and climate change effects. To fully understand, and effectively manage the seabed in terms of maximising this Blue Carbon potential requires a thorough understanding of carbon cycling in the marine environment over time, physical processes at the seafloor and high-quality spatial mapping. The QUEST project scope aims to conduct a multidisciplinary research programme to qualify, quantify and elucidate the provenance of carbon stocks in offshore marine sediments in Irelands EEZ. Furthermore, the research will examine and characterise threats to the stability of Blue Carbon in these settings and support the development of long-term management strategies. This programme will comprise spatial predictive modelling along with offshore surveying and sampling, laboratory analysis and hydrodynamic modelling, with past and new data to deliver comprehensive geochemical, geological, geotechnical, environmental and morphodynamical assessments of Blue Carbon ‘hotspots’ in the Irish offshore, as identified in the National Marine Planning Framework.

To date, this programme has worked with a variety of stakeholders to collate historical data relevant as predictors for sediment OC and generated new geochemical data sets through analysis of legacy sediment samples. The combined data sets have been used to produce spatial predictive modelling maps providing preliminary baselines for sediment OC stocks in Ireland’s EEZ.

Spatial mapping has identified knowledge gaps in the spatial extent and resolution of available sediment data. Additionally, the data collation and mapping exercise has highlighted a sparsity of physio-geochemical data essential for the accurate estimation and upscaling of OC stocks including OC content, Bulk density, and grain size analysis. Likewise, the paucity of available data extends to deeper sediments, consequently inhibiting the determination of OC stocks to the desired standard of 1 meter depth in assessment of BC ecosystems.  The first off-shore sampling survey for QUEST was completed in October 2023 providing a selection of grab (surface ~10cm depth), gravity (1-2m depth ), Vibro- ( 2-5m) and box core ( 10-25cm) samples from a series of near to off-shore transects from Ireland’s East coast encompassing the high sedimentary region of the Western Irish Sea Mudbelt (WISMB). Initial work carried out on cores has generated data describing updated OC stocks for Irish Sea sediments up to a 1m depth. Furthermore, data sets have been used to produce a region-specific conversion equation to calculate OC content using values attained from Loss on ignition analysis (LOI). This conversion factor has been applied to convert historical data LOI data for spatial predictive modelling.