Hyperspectral imaging as a tool for assessing coral health utilising natural fluorescence

Jonathan Teague,John Day,Michael Allen,Jack Willans,Thomas Scott

doi:10.1255/jsi.2019.a7

Abstract

Fluorescent proteins are a crucial visualisation tool in a myriad of research fields including cell biology, microbiology and medicine. Fluorescence is a result of the absorption of electromagnetic radiation at one wavelength and its reemission at a longer wavelength. Coral communities exhibit a natural fluorescence which can be used to distinguish between diseased and healthy specimens, however, current methods, such as the underwater visual census, are expensive and time-consuming constituting many manned dive hours. We propose the use of a remotely operated vehicle mounted with a novel hyperspectral fluorescence imaging (HyFI) “payload” for more rapid surveying and data collection. We have tested our system in a laboratory environment on common coral species including Seriatopora spp., Montipora verrucosa, Montipora spp., Montipora capricornis, Echinopora lamellose, Euphyllia ancora, Pocillopora damicornis and Montipora confusa. With the aid of hyperspectral imaging, the coral specimens’ emission wavelengths can be accurately assessed by capturing the emission spectra of the corals when excited with light emitting diodes (395–405 and 440 nm). Fluorescence can also provide an indicator of coral bleaching as shown in our bleaching experiment where we observe fluorescence reduction alongside coral bleaching.

Highlights

Corals are marine invertebrates in the class Anthozoa of the phylum Cnidaria, they often live in sessile colonies of many individual polyps
Some of the corals did not produce any fluorescence such as C5, C7, C12, C13, C20 and C22. These make a suitable control as nonfluorescence coral spectra vs fluorescence coral spectra
Some of the coral samples exhibited other weaker emission peaks displaying the presence of dual colour fluorescence, such as C2, which displays a main peak at 445 nm and weaker one at 510 nm

Summary

Introduction

Corals are marine invertebrates in the class Anthozoa of the phylum Cnidaria, they often live in sessile colonies of many individual polyps. Reef-building corals are geographically distributed in tropical and subtropical waters, typically occurring between the 300° north and 300° south latitudes.[1] Corals primarily responsible for building modern reefs are Hermatypic corals, belonging to the “Stoney corals” group or Scleractinia. Hermatypic corals contain photosynthetic algae, dinoflagellates belonging to the genus Symbiodinium often referred to as Zooxanthellae, that live symbiotically within its cells. The algae provide the coral with energy synthesised through photosynthesis and in exchange receive protection and nutrients required to conduct. Spectral Imaging 8, a7 (2019). https://doi.org/10.1255/ jsi.2019.a7

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