Angélique Meyer: Explaining Zostera noltii seed distribution in Arcachon Bay

Rijksuniversiteit Groningen

Seagrass meadows, found in shallow coastal waters, provide valuable ecosystem services such as nutrient filtering, carbon storage, and supporting biodiversity. However, human pressure has led to rapid losses of these ecosystems on a global scale. Traditional methods of restoring seagrass meadows through transplanting shoots and rhizomes have limitations, leading to an increased interest in seed-based restoration as a cost-effective and feasible method for larger-scale restoration. In France’s Arcachon Bay, which hosts the largest Zostera noltii beds in Europe, there has been a 33% loss in the total area of Z. noltii beds. The Marine Natural Park of the Bay is working to restore the seagrass meadows to their early 2000s level. As part of this restoration effort, I investigated the environmental factors that affect the presence of a Zostera noltii seed bank at both a large and small scale. Results showed that seagrass cover, bottom flow speed, shear stress, immersion time, salinity, and sediment grain size were the main variables influencing seed presence and density. However, seed density varied greatly on a local scale, and no predictive model of seed presence could be constructed. Despite this, understanding seed bank presence can still guide seed-based seagrass restoration efforts, with the potential to contribute to seagrass recovery and the colonization or recolonization of zones globally.