Mapping the small-scale extent of Posidonia meadows in Ċumnija and Anchor bay

Abstract

Seagrass meadows are vital components of marine ecosystems, providing numerous ecological services, acting as a foundation for a healthy marine habitat. This study aimed to map out seagrass meadow coverage in Ċumnija and Anchor Bay whilst also acting as a proof of concept for future studies attempting to map out seagrass across the Maltese coast. The study employed remote sensing techniques, including satellite imagery, geographic information systems (GIS) and classification algorithms, to identify and delineate seagrass meadows in the target bays. Field validation was also conducted through underwater surveys and drone surveys to confirm the presence of seagrass and assess the accuracy of the remote sensing results. The results demonstrated the feasibility of utilizing remote sensing techniques to map seagrass coverage, achieving an accuracy of 65-70% based on ground-truthed data from 2022. The results indicated that out of a total area of 435,400 m² in both bays, 65% consisted of bare sand and 35% was seagrass coverage. Temporal analysis for seagrass coverage, although less successful due to the absence of ground-truthing data, provided insights on seagrass populations achieving an accuracy ranging from 55-60%. The results showed that there was no major change in seagrass populations across the 7-year period analysed. There were various limitations encountered throughout the study which will need to be tackled in future bathymetric classification attempts. With the aims achieved, this study can serve as a foundational reference and methodology for mapping seagrass along the Maltese coast, while future research can address the encountered limitations.