REMOTELY PILOTED AIRCRAFT SYSTEMS (RPAS) APPLICATION FOR STRUCTURE DESCRIPTION OF MEDITERRANEAN VERMETID REEFS

Abstract

Vermetid gastropods are coastal habitat engineers which build biogenic platforms typical of intertidal rocky shores of central and south -east of the Mediterranean. These bioconstructions create a secondary habitat which increases resource availability and space for organisms, locally transforming the environment and modifying coastal geomorphology. Biological characteristics and physical structure of these bioconstructions are commonly studied by field-based sampling. Nevertheless, a lot of time is required to collect data over large areas of reef, field conditions can impair data collection and direct reef image interpretation may be a challenge due to their intertidal position. In this study, a small RPAS is used to describe the macrostructure of two vermetid reefs in different areas: Capo Gallo (NW Sicily) and Favignana Island (W Sicily). 800 m of each reef have been surveyed by using high-resolution aerial orthophotomosaics (2cm/px). Detailed 3D maps have been realized for both reefs and the following measures of ecological relevance have been estimated: external rim length, internal rim length, surface of external rim (mq), cuvette surface (mq) and reef surface (mq). Index of external rim development and Index of internal rim development have been calculated as a relationship between a standardized linear length and the length of the external and internal rim respectively. Total area for Capo Gallo reef is 2563,26 mq; indexes of external and internal rim development are respectively 3,40 and 1,90. For Favignana, reef area is 1263,15 mq and indexes of external and internal rim development are respectively 2,56 and 1,80. These results reveal RPAS as a powerful tool for physical description of vermetid reefs and to calculate how this biogenic habitat shapes the coast and increases habitat complexity on rocky shores. This study, moreover, shows the high potential for RPAS technique to be applied for mapping vermetid reefs and to aid the management and conservation of natural systems, as required by the EU Strategy on Biodiversity which declares the necessity of mapping habitats and the ecosystem services they provide.