Towards carbon neutrality by 2040 in La Rochelle metropolitan area (France): quantifying the role of wetlands and littoral zone in the capture and sequestration of blue carbon

Rising greenhouse gas emissions are causing increasing worldwide impacts and changes on climate patterns, sea level, food production, human lives and livelihoods. Maintaining or improving the ability of coastal aquatic ecosystems and oceans to remove CO2 from the atmosphere is a crucial aspect for climate mitigation. The vegetated coastal ecosystems are able to catch and to sequestrate carbon, the so-called Blue Carbon. These ecosystems are key exchange zones that mediate the biogeochemical cycles across the continent, the ocean and the atmosphere. Given the importance of these ecosystems in biogeochemical cycles and their sensitivity to natural and anthropogenic pressures, the carbon cycle within and between compartments (e.g. pelagos, benthos…) and across the interfaces (e.g. atmosphere, ocean…) need to be addressed. On a regional scale, in the extended urban area of La Rochelle located on the French Atlantic coast (La Rochelle metropolitan area), lack in situ measurements within the wetlands and littoral zone make very uncertain their role as a sink or a source of CO2 to the atmosphere. We will first present a vast research project "La Rochelle Territoire Zéro Carbone" project (https://www.agglo-larochelle.fr/projet-de-territoire/territoire-zero-carbone), that target the ambition of carbon neutrality in La Rochelle metropolitan area by 2040 through a holistic approach (from measuring CO2 to raising people's awareness and assessing the impact of exogenous natural factors). Second, we will present some first results on the Blue Carbon dynamics within the freshwater and salt marshes, and seagrasses.