Coastal benthic habitat monitoring using Copernicus and contributing missions

Monitoring of seagrasses and macroalgae is important both for surveillance of habitat conservation and for quantifying the effects of anthropogenic pressure on marine ecosystems. Satellite remote sensing, allows for global and local scale environmental monitoring with low cost and high revisit time. The availability of agency satellites, such as Sentinel-2, and commercial satellites, such as the Planetscope constellation, makes continuous and long-term monitoring of the underwater vegetation possible. However, the interposition between the underwater vegetation and the marine surface of the water column significantly limits the possibility of carrying out satellite monitoring, which is therefore suitable for shallow coastal areas but not for the open sea.  Furthermore, in order to properly and detailly interpret the nature of the monitored vegetation, for example in terms of species, it is necessary to compare satellite data with sea truth.

In this work, some strategies are proposed to delimit areas of marine vegetation and to compare them with the sea truth in order to monitor ecosystems continuously and in the long term, possibly starting from an initial accurate on field assessment. The use of free agency data (with lower spatial resolution) and commercial data (with higher resolution) is combined in such a way as to contain the costs of data acquisition. Furthermore, data obtained from the Copernicus Marine Service are used, together with bathymetry data, to estimate the effects of the water column on the reflectance of underwater vegetation. Multi-temporal analysis approaches are proposed to identify possible changes in vegetation covers that can trigger acquisition campaigns at sea, to directly verify the detected anomalies. The proposed approaches, as mentioned, exploit the availability and large geographical coverage of satellite data, without renouncing the use of (more expensive) resources on field when strictly necessary.