Oral Session 1

Light in dark places: the impact of ship lights on animal behavior during polar night

During the long period of polar night, animals in the Arctic Ocean spend extended periods in relatively dark conditions where moonlight, starlight and aurora provide limited amounts of light input to the ecosystem. Ships entering this environment inevitably disrupt an otherwise pristine lightscape, with our study demonstrating observable animal responses down to as much as 300m. Here we investigate if this response can be attributed to direct animal detection of light from the ship as opposed to some other cascading effect of biological amplification of an initial response at shallower depths. We present a 3D simulation of the light field generated by lights mounted on the R/V Helmer Hansen using measured IOPs for Barents Sea waters in winter. We show that absorption and scattering levels in these waters are typically very low during polar night due to low light levels inhibiting primary production. By propagating measured hyperspectral surface light fields to depth and convolving with known animal spectral sensitivity curves, we show that light levels at 300m are indeed sufficient to stimulate a direct animal response. These results have significant implications for understanding the potential impact of shipping on underwater lightscapes, with further work required to address variability in animal sensitivity, optical water properties and development of alternative lighting strategies for the industry. Further consideration of potential impact on night time surveying of fish and other animal populations is also required.

David McKee, University of Strathclyde, United Kingdom, https://orcid.org/0000-0001-8023-5923

Emlyn Davies, SINTEF, Norway

Bernhard Schartmuller, University of the Arctic in Tromso, Norway

Jorgen Berge, University of the Arctic in Tromso, Norway

Maxime Geoffroy, Memorial University, Canada

Tom Langbehn, University of Bergen, Norway

Malin Daase, University of the Arctic in Tromso, Norway

Kim Last, Scottish Association for Marine Science, United Kingdom

Jonathan Cohen, University of Delaware, USA

Geir Johnsen, Norwegian University of Science and Technology (NTNU), Norway

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