Seagrass restoration monitoring and shallow-water benthic habitat mapping through a photogrammetry-based protocol. (15th February 2022)

• Record Type: Journal Article
• Authors: Ventura, Daniele; Mancini, Gianluca; Casoli, Edoardo; Pace, Daniela Silvia; Lasinio, Giovanna Jona; Belluscio, Andrea; Ardizzone, Giandomenico
• Is Part Of: Journal of environmental management. Volume 304(2022)
• Publication Date: 2022-02-15
• Subjects: Structure-from-Motion (SfM) -- Posidonia oceanica -- 3D points clouds -- Restoration ecology -- Remote sensing; Environmental policy -- Periodicals; Environmental management -- Periodicals; Environment -- Periodicals; Ecology -- Periodicals; 363.705
• DOI: 10.1016/j.jenvman.2021.114262
• Languages: English
• ISSNs: 0301-4797

Abstract

Abstract: Seagrasses rank among the most productive yet highly threatened ecosystems on Earth. Loss of seagrass habitat because of anthropogenic disturbances and evidence of their limited resilience have provided the impetus for investigating and monitoring habitat restoration through transplantation programmes. Although Structure from Motion (SfM) photogrammetry is becoming a more and more relevant technique for mapping underwater environments, no standardised methods currently exist to provide 3-dimensional high spatial resolution and accuracy cartographic products for monitoring seagrass transplantation areas. By synthesizing various remote sensing applications, we provide an underwater SfM-based protocol for monitoring large seagrass restoration areas. The data obtained from consumer-grade red-green-blue (RGB) imagery allowed the fine characterization of the seabed by using 3D dense point clouds and raster layers, including orthophoto mosaics and Digital Surface Models (DSM). The integration of high spatial resolution underwater imagery with object-based image classification (OBIA) technique provided a new tool to count transplanted Posidonia oceanica fragments and estimate the bottom coverage expressed as a percentage of seabed covered by such fragments. Finally, the resulting digital maps were integrated into Geographic Information Systems (GIS) to run topographic change detection analysis and evaluate the mean height of transplanted fragments and detect fine-scale changes in seabed vector ruggedness measure (VRM). Our study provides a guide for creating large-scale, replicable and ready-to-use products for a broad range of applications aimed at standardizing monitoring protocols in future seagrass restoration actions. Highlights: Seagrass species are essential for marine ecosystems' functioning and services. Habitat restoration through transplantation is becoming a relevant technique. We propose for the first time an accurate mapping protocol to remotely monitor seagrass transplantation areas. High spatial resolution orthomosaics allowed image classification aimed at detecting transplanted seagrass fragments. 3D point cloud comparison allowed multi-temporal geomorphological change detection analysis of the transplantation area.