Underwater Hyperspectral Imaging of Arctic Macroalgal Habitats during the Polar Night Using a Novel Mini-ROV-UHI Portable System

Natalie Summers,Geir Johnsen,Glaucia Fragoso,Håvard Løvås,Aksel Mogstad,Jørgen Berge

doi:10.3390/rs14061325

Abstract

We describe an Underwater Hyperspectral Imager (UHI) deployed on an instrument-carrying platform consisting of two interconnected mini-ROVs (Remotely Operated Vehicle) for the mapping and monitoring of Arctic macroalgal habitats in Kongsfjorden (Svalbard) during the Polar Night. The mini-ROV-UHI system is easy to transport, assemble and deploy from shore, even under the dark, icy and cold conditions of the Arctic Polar Night. The system can be operated by two persons, keeping the operational costs low. In vivo hyperspectral reflectance of collected specimens of brown, red and green macroalgae was measured with a spectrometer in the lab to provide a spectral library for supervised pigment group classification based on UHI photomosaics. The in situ UHI-photomosaics provided detailed information of the areal coverage of the seafloor substrate (16%), as well as brown (51% habitat cover), red (18%), and green (14%) macroalgae, with spatial resolution in the range of cm and spectral resolution of 2 nm. The collected specimens from the mapped area were also used for species identification and health state evaluation. This innovative UHI sampling method provides significant information about macroalgal distribution and physiology, and due to its flexibility in terms of deployment, it is applicable to a variety of environments.

Highlights

Introduction iationsThe use of underwater hyperspectral imaging (UHI) was first published in 2013 [1,2]and first reviewed by [3,4], covering the use of Underwater Hyperspectral Imager (UHI) for the identification and mapping of different bio-geo-chemical Objects of Interest (OOI)
UHI has been conducted from different instrument-carrying platforms, such as SCUBA diving [2,5] landers [6], underwater slides [1], remotely operated vehicles (ROV) operating from the surface and down to 4200 m [5,7–10], autonomous underwater vehicles (AUV) [11] and unmanned surface vehicles (USV), [12]
We here report a novel ROV-UHI-survey indicating that the majority of brown, green and red macroalgal species were healthy during the Polar Night

Summary

Introduction

The use of underwater hyperspectral imaging (UHI) was first published in 2013 [1,2]. First reviewed by [3,4], covering the use of UHI for the identification and mapping of different bio-geo-chemical Objects of Interest (OOI). UHI has been conducted from different instrument-carrying platforms, such as SCUBA diving [2,5] landers [6], underwater slides [1], remotely operated vehicles (ROV) operating from the surface and down to 4200 m [5,7–10], autonomous underwater vehicles (AUV) [11] and unmanned surface vehicles (USV), [12]. Aerial hyperspectral imaging of kelp forests in the Arctic was performed for the first time by using a two engine Dornier airplane carrying a prototype hyperspectral imager (HI) [13]. The airborne campaign was conducted in concert with kelp forest measurements (in situ spectral reflectance) in Kongsfjorden, May 2004 [13].

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Conclusion