Novel approach to enhance coastal habitat and biotope mapping with drone aerial imagery analysis

João Gama Monteiro,Ricardo S Santos,Jonathan S Lefcheck,Jesús L Jiménez,Petr Přikryl,João Canning-Clode,Francesca Gizzi

doi:10.1038/s41598-020-80612-7

Abstract

Understanding the complex factors and mechanisms driving the functioning of coastal ecosystems is vital towards assessing how organisms, ecosystems, and ultimately human populations will cope with the ecological consequences of natural and anthropogenic impacts. Towards this goal, coastal monitoring programs and studies must deliver information on a range of variables and factors, from taxonomic/functional diversity and spatial distribution of habitats, to anthropogenic stress indicators such as land use, fisheries use, and pollution. Effective monitoring programs must therefore integrate observations from different sources and spatial scales to provide a comprehensive view to managers. Here we explore integrating aerial surveys from a low-cost Remotely Piloted Aircraft System (RPAS) with concurrent underwater surveys to deliver a novel approach to coastal monitoring. We: (i) map depth and substrate of shallow rocky habitats, and; (ii) classify the major biotopes associated with these environmental axes; and (iii) combine data from i and ii to assess the likely distribution of common sessile organismal assemblages over the survey area. Finally, we propose a general workflow that can be adapted to different needs and aerial platforms, which can be used as blueprints for further integration of remote-sensing with in situ surveys to produce spatially-explicit biotope maps.

Highlights

Understanding the complex factors and mechanisms driving the functioning of coastal ecosystems is vital towards assessing how organisms, ecosystems, and human populations will cope with the ecological consequences of natural and anthropogenic impacts
The present study explores the integration of scientific diving and underwater surveys with aerial surveys using a low-cost recreational Remotely Piloted Aircraft System (RPAS) to map and provide information on the distribution of sessile biotopes: distinct assemblages of sessile organisms occurring under specific environmental conditions
Based on the Digital Surface Model (DSM), on the reflectance index maps (Fig. 2a, b) and on the photomosaic generated with Pix4D Mapper[33], we produced a baseline bathymetry map (Fig. 2c) and an optically derived bathymetry over rocky substrate, with 11 discrete depth classes from the surface to 14 m depth (Figs. 1, 2c)

Summary

Introduction

Understanding the complex factors and mechanisms driving the functioning of coastal ecosystems is vital towards assessing how organisms, ecosystems, and human populations will cope with the ecological consequences of natural and anthropogenic impacts Towards this goal, coastal monitoring programs and studies must deliver information on a range of variables and factors, from taxonomic/functional diversity and spatial distribution of habitats, to anthropogenic stress indicators such as land use, fisheries use, and pollution. Developments in scientific diving and underwater photography and video have increasingly enhanced the speed and accuracy of underwater data acquisition, annotation and a nalysis[7,9,10,11,12,13,14] Despite such advances, there are still several constraints and limitations associated with underwater surveys by scuba divers: in addition to requiring high-level of expertise, SCUBA diving and UVC have limited bottom times and sampling areas, producing (geographically) discrete spatial data points. Outputs from these approaches typically provide physiographic information and general traits to classify different habitat types (e.g. rocky reef, sand, fore- and back-reef), but usually do not integrate information on how different biological assemblages are distributed over the mapped physiographic habitats[17,21,22,23]

Methods

Results

Conclusion