Missing the Forest and the Trees: Utility, Limits and Caveats for Drone Imaging of Coastal Marine Ecosystems

Coastal marine ecosystems are under stress, yet actionable information about the cumulative effects of human impacts has eluded ecologists. Habitat-forming seaweeds in temperate regions provide myriad irreplaceable ecosystem services, but they are increasingly at risk of local and regional extinction from extreme climatic events and the cumulative impacts of land-use change and extractive activities. Informing appropriate management strategies to reduce the impacts of stressors requires comprehensive knowledge of species diversity, abundance and distributions. Remote sensing undoubtedly provides answers, but collecting imagery at appropriate resolution and spatial extent, and then accurately and precisely validating these datasets is not straightforward. Comprehensive and long-running monitoring of rocky reefs exist globally but are often limited to a small subset of reef platforms readily accessible to in-situ studies. Key vulnerable habitat-forming seaweeds are often not well-assessed by traditional in-situ methods, nor are they well-captured by passive remote sensing by satellites. Here we describe the utility of drone-based methods for monitoring and detecting key rocky intertidal habitat types, the limitations and caveats of these methods, and suggest a standardised workflow for achieving consistent results that will fulfil the needs of managers for conservation efforts.

Download Full-text

How Far Can We Classify Macroalgae Remotely? An Example Using a New Spectral Library of Species from the South West Atlantic (Argentine Patagonia)

Remote Sensing ◽

10.3390/rs12233870 ◽

2020 ◽

Vol 12 (23) ◽

pp. 3870

Author(s):

O. Magalí Olmedo-Masat ◽

M. Paula Raffo ◽

Daniel Rodríguez-Pérez ◽

Marianela Arijón ◽

Noela Sánchez-Carnero

Keyword(s):

Remote Sensing ◽

Marine Ecosystems ◽

Spectral Features ◽

Depth Range ◽

Spectral Library ◽

The South ◽

Argentine Patagonia ◽

South West ◽

Coastal Marine ◽

Coastal Marine Ecosystems

Macroalgae have attracted the interest of remote sensing as targets to study coastal marine ecosystems because of their key ecological role. The goal of this paper is to analyze a new spectral library, including 28 macroalgae from the South-West Atlantic coast, in order to assess its use in hyperspectral remote sensing. The library includes species collected in the Atlantic Patagonian coast (Argentina) with representatives of brown, red, and green algae, being 22 of the species included in a spectral library for the first time. The spectra of these main groups are described, and the intraspecific variability is also assessed, considering kelp differentiated tissues and depth range, discussing them from the point of view of their effects on spectral features. A classification and an independent component analysis using the spectral range and simulated bands of two state-of-the-art drone-borne hyperspectral sensors were performed. The results show spectral features and clusters identifying further algae taxonomic groups, showing the potential applications of this spectral library for drone-based mapping of this ecological and economical asset of our coastal marine ecosystems.

Download Full-text

A novel approach to model exposure of coastal-marine ecosystems to riverine flood plumes based on remote sensing techniques

10.31230/osf.io/kh7aw ◽

2018 ◽

Author(s):

Jorge Gabriel Álvarez-Romero ◽

Michelle Devlin ◽

Eduardo Teixeira da Silva ◽

Caroline Petus ◽

Natalie Ban ◽

...

Keyword(s):

Remote Sensing ◽

Marine Ecosystems ◽

Marine Conservation ◽

Ecological Impacts ◽

Catchment Management ◽

Coastal Marine ◽

Novel Approach ◽

Coastal Marine Ecosystems ◽

True Color

Increased loads of land-based pollutants are a major threat to coastal-marine ecosystems. Identifying the affected marine areas and the scale of influence on marine ecosystems is critical to assess the ecological impacts of degraded water quality and to inform planning for catchment management and marine conservation. Studies using remotely sensed data have contributed to our understanding of the occurrence and influence of river plumes, and to our ability to assess exposure of marine ecosystems to land-based pollutants. However, refinement of plume modeling techniques is required to improve risk assessments. We developed a novel approach to model exposure of coastal-marine ecosystems to land-based pollutants. We used supervised classification of MODIS-Aqua true-color satellite imagery to map the extent of plumes and to qualitatively assess the dispersal of pollutants in plumes. We used the Great Barrier Reef (GBR), the world's largest coral reef system, to test our approach. We combined frequency of plume occurrence with spatially distributed loads (based on a cost-distance function) to create maps of exposure to suspended sediment and dissolved inorganic nitrogen. We then compared annual exposure maps (2007-2011) to assess inter-annual variability in the exposure of coral reefs and seagrass beds to these pollutants. Our findings indicate that classification of true-color satellite images is useful to map plumes and to qualitatively assess exposure to land-based pollutants. This approach should be considered complementary to remote sensing methods based on ocean color products used to characterize surface water in plumes. Observed inter-annual variation in exposure of ecosystems to pollutants stresses the need to incorporate this temporal component into plume exposure/risk models. Our study contributes to our understanding of plume spatial-temporal dynamics of the GBR and offers a method that can improve plume exposure models. Our method can also be applied to monitor exposure of coastal-marine ecosystems to plumes and explore their ecological influences.

Download Full-text