Aarhus University Seal / Aarhus Universitets segl

No. 361: Benthic macrofauna communities on the Northeast Greenland shelf 2017

Hansen JLS, Sejr MK, Holm-Hansen TH, Andersen OGN. 2019. Benthic macrofauna communities on the Northeast Greenland shelf 2017. Results and data from the NEG Dana cruise 2017. Aarhus University, DCE – Danish Centre for Environment and Energy, 35 pp. Scientific Report No. 361. http://dce2.au.dk/pub/SR361.pdf

Summary

Benthic macrofauna was sampled from 21 stations on the Northeast Greenland shelf between the 74° N and 78° N latitude during the NEG R/V Dana cruise in August-September 2017. At all stations on the shelf and on the eastern shelf slopes down to 1,400 m depth, the sediment consisted of fine mud. On most of the stations on the shelf, the sediment surface was furthermore covered with a layer of stones suggesting erosion of the sediment. Quantitative sampling of infauna communities with 0.1 m2 Van Veen grabs and a 0.0143 m2 Haps-corer generally showed low densities of arthropods and annelids with about 400 individuals m-2 as an average for the area, and the corresponding biomass was even lower with an average biomass of 10 g m-2. Compared to the West Greenland shelfs, from where corresponding and comparable data exist, the biomass of the infauna was about 30 times lower at the NEG shelf and the abundance was about 7 times lower than on the WG shelfs. The differences in the benthic fauna communities between the western and eastern shelfs are in agreement with the differences in productivity of the two shelf ecosystems. Species densities in the samples (0.1 m2 sample) were also lower, about two thirds of comparable species densities on the WG shelfs. However, the Shannon diversity showed about the same values for the two shelfs and species accumulation plots of the two phyla suggest that the total species pools of the systems could be of the same sizes or larger on the NEG shelf. Qualitative sampling of epibenthic megafauna included observations of an iconic giant > 2 m high sea pen Umbellula encrinus retrieved from bottom trawling and observed on the underwater video. Furthermore, dense gardens of the cold-water corals Keratoisis sp. were observed on the continental slopes. From counting of year rings, the population of Umbellula encrinus was determined to be more than 30 years old and literature values of growth rates of Keratoisis suggest that these populations were considerably older. These epifauna communities document the pristine conditions of the NEG shelf and emphasise the extreme vulnerability of these communities to disturbance.