Quantifying the macroalgae-based carbon storage capacity of an intertidal eco-engineered seawallMacroalgae and Ecosystem Services (sponsored by Annals of Botany)

Franz Bauer¹, Mick Hanley¹, Antony Knights², John Griffin³, Andy Foggo¹, Austin Brown⁴, Louise Firth²

¹University of Plymouth, UK, ²University College Cork, Ireland, ³Swansea University, UK, ⁴Arup, UK

Modern coastal infrastructure is typically poor in species diversity and abundance, consequently also lacking biogenic habitat provisioning and ecosystem services. Ecology-based alteration of surface topography on urbanized shorelines (marine eco-engineering) has the potential to restore ecological communities and associated ecosystem services. Here, we non-destructively quantified macroalgal habitat formation (cover area, thickness, frond length) and associated carbon storage on an intertidal eco-engineering installation (“Living Seawalls in Plymouth”), composed of 72 biomimetic panels with six designs. Topographically complex panels supported approximately 10x higher macroalgal cover, 3x greater canopy thickness, and 2x longer algal fronds. Based on these biogenic habitat metrics, we present estimates of carbon storage capacity per square meter of eco-engineered seawall topography. These estimates may provide early insights into the blue carbon potential of eco-engineered urbanized shorelines, combining ecological benefits (habitat provisioning) with societal benefits (climate change mitigation).