Fast and easy method for seagrass monitoring: Application of acoustic telemetry to precision mapping of Posidonia oceanica beds

► Acoustic telemetry is an efficient method for precision underwater mapping. ► Seagrass beds with various meadow/limit types were monitored by acoustic telemetry. ► Maps obtained on eight sites provide baseline documents for further monitoring. ► A four-year temporal survey shows a weak global progression of 4m2. Posidonia oceanica is an endemic seagrass from the Mediterranean Sea. It is an indicator of water quality and of the ecological state of coastal ecosystems. The aim of this paper is to test acoustic telemetry for monitoring the position of P. oceanica meadow limits with varied types. After evaluating the accuracy of the system, we present results from a spatiotemporal survey of P. oceanica meadows on nine sites located on the French coast. The method has been demonstrated to be highly efficient for high precision underwater mapping regardless of meadow type, with 1cm accuracy for a distance of 40m between the base and the pointer. A temporal survey led at Cerbere–Banyuls shows a weak global progression of 4m2 (progression of 26m2 - regression of 22m2) between 2006 and 2010. Finally, we discuss the cost and efficiency of this method, and wether it should be generalized for further studies.