6533b870fe1ef96bd12cf6f1

RESEARCH PRODUCT

The use of very high-resolution images for mapping of Posidonia oceanica reef

subject

description

Posidonia oceanica is an endemic Mediterranean seagrass that forms wide and dense meadows from the surface up to about 40 m depth. P. oceanica can develop on matte, a typical terraced structure built up by itself, consisting of intertwined rhizomes, roots and sediment, which may allow shoots to reach the sea surface, where may form typical reefs (récif barrière) considered “natural monuments”. These structures have received increasing attention for the potential ecosystem services they provide in protecting the coasts from erosion, forming new habitats (coastal lagoons) and contributing to carbon sink. P. oceanica reefs are particularly exposed to the expected increase in temperature and to storm frequency and intensity, which represent a problem in terms of P. oceanica “natural monuments” conservation. Therefore, much more attention must be paid to the implementation of monitoring tools able to detect the early signs of seagrass regression. The main aim of this study was to investigate the distribution of the P. oceanica reefs located in front of 4 pocked beaches (PB) along both the northern and southern coasts of Sicily. A remote sensing approach was used to assess the reef extensions including their associated structures (atolls, and tiger meadows). In particular, very high-resolution drone images (~2cm of pixels size), combined with GPS field data, were used to obtain 2 and 3D-reconstruction of P. oceanica reefs. Generated orthophotos and digital elevation model were imported into geospatial analysis software to quantify their extension and volumes. The 3D-model allowed to estimate bathymetrical distribution of P. oceanica reef. This approach may enable to achieve a more detailed and complete understanding of the role of P. oceanica reefs in coastal marine dynamics and in PB in particular. This might also contribute to gain a better insight into the ecosystem services they provide.