Zooplankton community composition in Svartnes, Balsfjord, Norway in June 2017 and June 2018 (sampled with a WP-2)

Study Extent

All samples were taken at the same station in Balsfjorden. However, samples were taken in two different years (2017 and 2018).

Sampling

The zooplankton community was sampled with a WP-2 type net (Hydrobios Apparatebau GmbH, Altenholz, Germany) in two depth intervals (50-0 m and 170-50 m). Five vertical profiles (at approximately 6 h intervals) were sampled in 2017 to quantify differences in vertical abundance distributions over a 24 h cycle. In 2018, one profile for abundance quantification was sampled during daytime. The net and its cod end had a mesh size of 64 µm and was used with a closing mechanism for stratified sampling. Due to the small mesh-size, the net was hauled vertically at low speed, 0.2-0.3 m s-1. On deck, the content of the cod-end was gently rinsed onto a 64 µm sieve, transferred to 100 mL PVC bottles and preserved with sodium tetraborate buffered formaldehyde in filtered seawater at 4 % final concentration.

Method steps

1. Zooplankton samples were examined with an Olympus model SZX7 stereomicroscope according to the procedures described in Postel et al. (2000., Biomass and abundance, p. 83-192. In R. Harris, J. Lenz, M. Huntley, P. Wiebe and H. R. Skjoldal (eds.), ICES Zooplankton Methodology Manual. Academic Press.) and Kwasniewski et al. (2010, doi: 10.1016/j.pocean.2010.06.004).
2. Zooplankton identification and counting was performed on sub-samples obtained from the whole sample by splitting with a box splitter. From each sample, a sub-sample of at least 500 individuals was examined. The remainder of the sample was screened in its entirety for the presence of individuals of rare species and ephemeral taxa.

The samples were collected at station Svartnes, Balsfjorden, Northern Norway (bottom depth 190 m).