Discriminating between Posidonia oceanica meadows and sand substratum using multibeam sonar

Abstract

Abstract Di Maida, G., Tomasello, A., Luzzu, F., Scannavino, A., Pirrotta, M., Orestano, C., and Calvo, S. 2011. Discriminating between Posidonia oceanica meadows and sand substratum using multibeam sonar. – ICES Journal of Marine Science, 68: 12–19. High-resolution, multibeam sonar (MBS) (455 kHz) was used to identify two typologies of seabed 8 m deep: Posidonia oceanica meadow and sandy substratum. The results showed that the heterogeneity of the architecture of the P. oceanica canopy and the relatively simple morphology of a sandy substratum can be detected easily by statistical indices such as standard deviation or range-of-beam depth. Based on these indices, an automated classification was performed for seabed mapping. The overall classification accuracy was as high as 99 and 98% in October and January, respectively. The probability that P. oceanica in situ was omitted on the map was <7%, whereas the probability that an area classified as P. oceanica on the map did not correspond to the seagrass in situ was consistently negligible. Based on these results, high-resolution MBS can be considered to be an accurate tool for mapping P. oceanica and sand substrata, and its discriminating power seems to be independent of season (autumn or winter).