New Insights in Seagrass Mortality Patches at the Arguin Bank in the Perspectives of Climate Change

All over the world, seagrass beds are key natural habitats for their ecosystem services. Those in the Gulf of Arguin, in Mauritania, have been monitored for more than twenty years; their conservation status is considered good despite very variable climatic conditions. In the absence of anthropogenic stress, the abiotic conditions have given rise to a number of hypotheses explaining temporary patches of mortality. These observations and hypotheses were revisited during the analysis of the evolution over 20 years of the total vegetation cover in Arguin Bay, evaluated by the NDVI index. This change over the medium term is consistent with wind conditions, drivers of sediment transport and hydrodynamics. The chronological contextualization of field observations by climatic conditions provides a new understanding of short-term variations. The importance of ongoing monitoring of this ecosystem is demonstrated; additional guidance is suggested to assess the specific resilience of each of the species that make up this seagrass beds.