Decadal increase in the ecological status of a North-Atlantic intertidal seagrass meadow observed with multi-mission satellite time-series

Seagrass meadows are monitored in the frame of several environmental programs worldwide, including Water Framework Directive (WFD), to evaluate ecological status European coastal and transitional water bodies. The large size, spatial complexity, interannual variability seagrass ecosystems significantly challenge field monitoring. In this study, a multi-mission satellite time-series was used estimate long-term changes macrotidal system dominated by Zostera noltei, at Bourgneuf Bay (French Atlantic coast). Metrics extent density were obtained from Earth Observation (EO) using validated inter-calibrated Landsat, SPOT Sentinel2 data 1985 2020. information provided made it possible compute compare indicators currently use countries (France, Portugal UK) within WFD. Both meadow-averaged displayed increasing trends since 1985. A merged observations various satellites revealed high degree extent, with abrupt losses (up 50% one year) alternating periods slow recovery (typically 4–6 years). meadow which moderate (sensu WFD) 1980s, achieved an overall recurrent good or mid-1990s. Altogether, methods results presented here demonstrated that EO is reliable source for mapping assessing intertidal seagrass, complementing situ measurements providing long-term, view standardized observation framework. We recommend systematic complement traditional monitoring such as