Experimental determination of reflectance spectra of Antarctic krill (Euphausia superba) in the Scotia Sea

Belcher, Anna ORCID: https://orcid.org/0000-0002-9583-5910; Fielding, Sophie ORCID: https://orcid.org/0000-0002-3152-4742; Gray, Andrew; Biermann, Lauren; Stowasser, Gabriele ORCID: https://orcid.org/0000-0002-0595-0772; Fretwell, Peter ORCID: https://orcid.org/0000-0002-1988-5844; Ireland, Louise ORCID: https://orcid.org/0000-0003-0960-0486; Tarling, Geraint A. ORCID: https://orcid.org/0000-0002-3753-5899. 2021 Experimental determination of reflectance spectra of Antarctic krill (Euphausia superba) in the Scotia Sea. Antarctic Science, 33 (4). 402 -414. https://doi.org/10.1017/S0954102021000262

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Abstract/Summary

Antarctic krill are the dominant metazoan in the Southern Ocean in terms of biomass; however, their wide and patchy distribution means that estimates of their biomass are still uncertain. Most currently employed methods do not sample the upper surface layers, yet historical records indicate that large surface swarms can change the water colour. Ocean colour satellites are able to measure the surface ocean synoptically and should theoretically provide a means for detecting and measuring surface krill swarms. Before we can assess the feasibility of remote detection, more must be known about the reflectance spectra of krill. Here, we measure the reflectance spectral signature of Antarctic krill collected in situ from the Scotia Sea and compare it to that of in situ water. Using a spectroradiometer, we measure a strong absorption feature between 500 and 550 nm, which corresponds to the pigment astaxanthin, and high reflectance in the 600–700 nm range due to the krill's red colouration. We find that the spectra of seawater containing krill is significantly different from seawater only. We conclude that it is tractable to detect high-density swarms of krill remotely using platforms such as optical satellites and unmanned aerial vehicles, and further steps to carry out ground-truthing campaigns are now warranted.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	https://doi.org/10.1017/S0954102021000262
ISSN:	0954-1020
Additional Keywords:	Antarctic krill; Euphausia superba, reflectance, remote sensing; South Georgia, South Orkney Islands
Date made live:	12 Jul 2021 14:27 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/530363

Item Type:

Publication - Article

Digital Object Identifier (DOI):

https://doi.org/10.1017/S0954102021000262

ISSN:

0954-1020

Additional Keywords:

Antarctic krill; Euphausia superba, reflectance, remote sensing; South Georgia, South Orkney Islands

Date made live:

12 Jul 2021 14:27 +0 (UTC)

URI:

https://nora.nerc.ac.uk/id/eprint/530363