Toolset scale-up and development to evaluate and optimize carbon sequestration in New Brunswick tidal flats

Tidal flats are expansive intertidal sandy-muddy areas, and globally prevalent. They are vulnerable to degradation and fragmentation from coastal development, sea-level rise, and reduced fluvial deposition. Their sediment, many metres deep, is a large carbon pool which was overlooked in the past but is now being recognized as globally significant. This carbon burial potential is related to high primary production (uptake of CO2) by the photosynthetic microalgal biofilm responding to sunlight and nutrient availability, and to the long shallow slope that slows water movement, trapping sediment and carbon matter coming from surrounding ecosystems. New Brunswick is notable in that its coastline (Bay of Fundy, Gulf of St. Lawrence) is mostly sedimentary, suggesting high carbon sequestering potential. In a first NZA project, our team developed tools to assess carbon capture and burial potential for two inner Bay mudflats; in the process, we identified knowledge gaps. Our present NZA proposal will develop additional tools to address these gaps, and scale up coverage of the diversity of tidal flats along the New Brunswick coastline. These tools will (i) Delineate tidal flat areas, measure stored carbon, and identify hotspots of high carbon burial to prioritize for conservation; (ii) Predict CO2 flux and carbon dynamics in tidal flats, using machine learning based upon remote sensing of microalgal biomass, climate, and geographical data; (iii) Address cross-ecosystem movements of dissolved carbon between tidal flats and surrounding ecosystems to enable an inclusive accounting of carbon inputs and outputs; and (iv) Use environmental DNA and RNA to identify microbial biota and gene activity associated with carbon metabolism, to identify steps between carbon capture and burial. This comprehensive toolset will be invaluable to assess the role of one of New Brunswick’s most common coastal ecosystems as a nature-based climate solution and inform coastal management practices to optimize carbon storage.