Bioluminescence as an ecological factor during high Arctic polar night.

Heather A Cronin,Geir Johnsen,Jonathan H Cohen,Mark A Moline,Jørgen Berge

doi:10.1038/srep36374

Abstract

Bioluminescence commonly influences pelagic trophic interactions at mesopelagic depths. Here we characterize a vertical gradient in structure of a generally low species diversity bioluminescent community at shallower epipelagic depths during the polar night period in a high Arctic fjord with in situ bathyphotometric sampling. Bioluminescence potential of the community increased with depth to a peak at 80 m. Community composition changed over this range, with an ecotone at 20–40 m where a dinoflagellate-dominated community transitioned to dominance by the copepod Metridia longa. Coincident at this depth was bioluminescence exceeding atmospheric light in the ambient pelagic photon budget, which we term the bioluminescence compensation depth. Collectively, we show a winter bioluminescent community in the high Arctic with vertical structure linked to attenuation of atmospheric light, which has the potential to influence pelagic ecology during the light-limited polar night.

Highlights

Bioluminescence commonly influences pelagic trophic interactions at mesopelagic depths
In Kongsfjord during polar night, the luminescent community composition transitioned between 20 m and 40 m, and concomitantly the source of photons changed from atmospheric light to bioluminescence (Fig. 5)
Over this small depth range bioluminescence potential transitioned from contributing less than 3% of the pelagic photon budget to over 85%, and below 60 m bioluminescence contributed over 98% of the pelagic photon budget

Summary

Introduction

Bioluminescence commonly influences pelagic trophic interactions at mesopelagic depths. The decline in organismal metabolic rate across pelagic depth gradients (and light gradients) has been related to a decline in visual predation risk and with it a reduction in necessary locomotory capacity[9,10] In all of these cases, the underwater light field impacts pelagic organisms through trophic interactions. Plankton, with sizes ranging from dinoflagellates through meso- and macrozooplankton and micronekton, based on their differential emission intensity and flash kinetics[27,28,29] (Fig. 1) This approach is best-suited for use in luminescent communities with relatively low taxonomic diversity, such as thin layers[18] and polar waters[29]. In coastal fjords, dinoflagellates have been found to dominate the bioluminescence budget with copepods contributing relatively little light[32]

Methods

Results

Conclusion