Coastal benthic habitat mapping and monitoring by integrating aerial and water surface low-cost drones

Abstract

Accurate data on community structure is a priority issue in studying coastal habitats facing human pressures. The recent development of remote sensing tools has offered a ground-breaking way to collect ecological information at a very fine scale, especially using low-cost aerial photogrammetry. Although coastal mapping is carried out using Unmanned Aerial Vehicles (UAVs or drones), they can provide limited information regarding underwater benthic habitats. To achieve a precise characterisation of underwater habitat types and species assemblages, new imagery acquisition instruments become necessary to support accurate mapping programmes. Therefore, this study aims to evaluate an integrated approach based on Structure from Motion (SfM) photogrammetric acquisition using low-cost Unmanned Aerial (UAV) and Surface (USV) Vehicles to finely map shallow benthic communities, which determine the high complexity of coastal environments. The photogrammetric outputs, including both UAV-based high (sub-meter) and USV-based ultra-high (sub-centimetre) raster products such as orthophoto mosaics and Digital Surface Models (DSMs), were classified using Object-Based Image Analysis (OBIA) approach. The application of a supervised learning method based on Support Vector Machines (SVM) classification resulted in good overall classification accuracies > 70%, proving to be a practical and feasible tool for analysing both aerial and underwater ultra-high spatial resolution imagery. The detected seabed cover classes included above and below-water key coastal features of ecological interest such as seagrass beds, “banquettes” deposits and hard bottoms. Using USV-based imagery can considerably improve the identification of specific organisms with a critical role in benthic communities, such as photophilous macroalgal beds. We conclude that the integrated use of low-cost unmanned aerial and surface vehicles and GIS processing is an effective strategy for allowing fully remote detailed data on shallow water benthic communities.

An integrated approach for the benthic habitat mapping based on innovative surveying technologies and ecosystem functioning measurements

“…However, sampling activities and traditional marine monitoring with fuelled vessels increase survey costs and pollution risks. In this context, the development of new monitoring methodologies involving the use of innovative autonomous platforms is of particular help, contributing to the reduction of work costs, while enabling rapid data collection and facilitating measurements in hard-to-reach sites (e.g., Marine Protected Areas—MPAs, extremely shallow waters, areas forbidden to ordinary navigation) [e.g., 25 – 28 ]. Effective new approaches involve the use of Unmanned Surface Vehicles (USVs) equipped with specific sensors for mapping purposes 29 , Uncrewed Aerial Systems (UAS) equipped with light weight sensors (e.g., multispectral, hyperspectral, and LiDAR systems) [e.g., 30 , 31 ], and technologies to support divers' scientific activities (for example, Diver Propulsion Vehicles—DPVs) [e.g., 32 ].…”

Aquaculture of emerging species in North-Eastern Atlantic and Mediterranean Sea: a systematic review on sea cucumber farming and potential development

“…The increase in harvesting pressure has led to a rapid decline in natural stocks of marketable species, resulting in reduction of abundance, size and genetic diversity, with detrimental effects on benthic communities and ecosystems (Gonzaĺez-Wangüemert et al, 2014Maggi and Gonzaĺez-Wangüemert, 2015;Ventura et al, 2023). Indeed, in addition to being an important economic resource, sea cucumbers play a key ecological role as ecosystem engineers, and their decline may affect the entire ecosystem.…”

UAV-Based Subsurface Data Collection Using a Low-Tech Ground-Truthing Payload System Enhances Shallow-Water Monitoring

“…Especially, lightweight multirotor platforms have gained popularity among researchers due to their low acquisition cost, vertical take-off and landing capability, easy handling, flexible payload arrangements and their ability to hover in a fixed position over a point of interest. Examples of research conducted in shallow-water habitats using UAVs include mapping and monitoring coral reefs [11][12][13], submerged vegetation in marine [3,4,[14][15][16] and freshwater [17][18][19][20] environments, as well as of submerged habitats as a whole [21][22][23].…”