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.