The temporal and spatial distribution of krill (Meganyctiphanes norvegica) at the deep seabed of the Faroe–Shetland Channel, UK: A potential mechanism for rapid carbon flux to deep sea communities

Abstract

The temporal and spatial distribution of Meganyctiphanes norvegica near the seabed (<5 m above the seafloor) was investigated using remotely operated vehicle (ROV) video footage from eight sites in the Faroe–Shetland Channel. Meganyctiphanes norvegica was most abundant near the seabed at 400–600 m depth, which corresponds to a temperature transitional region between shallower warmer water and deeper cold water. Densities of M. norvegica were significantly lower in the warm water, and no krill were detected at 900–1500 m depth in the cold water. Meganyctiphanes norvegica densities declined at night owing to daily vertical migrations. Time-series analysis showed higher krill densities at 06:00–09:00 and 18:00–21:00 at a depth of 400–480 m and at 12:00–15:00 at a depth of 600 m. A great reduction in krill abundance in winter was detected from both ROV surveys and continuous plankton recorder records. Meganyctiphanes norvegica was observed feeding on benthic particulate organic matter on the seafloor and being consumed by benthic and epibenthic predators. The maximum density of M. norvegica at 480 m depth was 596 ± 261 individuals m^–3. This represents a standing stock of 12.8 ± 5.6 g C m^–3 with an egestion rate of 0.63 ± 0.28 g C m^–3 day^–1. Meganyctiphanes norvegica potentially provides an important source of carbon for communities in the deep waters of the Faroe–Shetland Channel.

Keywords:

• Carbon flux
• distribution
• Faroe-Shetland Channel
• Meganyctiphanes norvegica
• ROV imaging
• vertical migration

Published in collaboration with the University of Bergen and the Institute of Marine Research, Norway, and the Marine Biological Laboratory, University of Copenhagen, Denmark

Published in collaboration with the University of Bergen and the Institute of Marine Research, Norway, and the Marine Biological Laboratory, University of Copenhagen, Denmark

Acknowledgements

We wish to thank Statoil, Chevron, BP, Shell, Hurricane Exploration, OMV, Total E & P UK, the Total Corporate Foundation for Biodiversity and the Sea and Transocean for hosting this work and providing valuable assistance throughout. The work was carried out as part of the SERPENT (Scientific and Environmental Remotely operated vehicle Partnership using Existing industrial Technology) project. Thanks to Andrew Gates, Ian Hudson and Janne Kaariainen for collecting some of the ROV video data. We would like to thank SAHFOS (Sir Alister Hardy Foundation for Ocean Science) for providing CPR data. SERPENT was funded for this work by a grant from the Total Corporate Foundation for Biodiversity and the Sea. Comments by John Williams and Sven Thatje improved an early version of manuscript. We thank Mounir Lekouara for helping with data analysis.

Notes

Published in collaboration with the University of Bergen and the Institute of Marine Research, Norway, and the Marine Biological Laboratory, University of Copenhagen, Denmark