Kongsfjorden Seasonal Baseline Zooplankton Dataset

The Kongsfjorden Seasonal Baseline Zooplankton Dataset presents hydrographic and zooplankton data collected in Kongsfjorden, Svalbard, during spring (Julian days 107–133), summer (Julian days 208–214), and autumn (Julian days 240–277) in 2002, 2006, and 2007. Kongsfjorden is a high-Arctic fjord located in the transition zone between Arctic and Atlantic water masses, and serves as a reference site for long-term ecological monitoring.

Sampling was conducted along a transect extending from the central fjord through the outlet areas (stations K1–K2–K3–K4) to the adjacent shelf (stations K5–K6). Samples were collected aboard the research vessels Oceania and Jan Mayen (currently Helmer Hanssen) as part of a collaborative effort between the Institute of Oceanology, Polish Academy of Sciences (IO PAN), the Norwegian Polar Institute (NPI), and the Arctic University of Norway.

The dataset includes temperature and salinity profiles obtained with a Sea-Bird Electronics SBE 911plus CTD system, along with zooplankton data collected using a MultiNet Multiple Plankton Sampler (Type Midi, Hydro-Bios, Germany; 0.25 m² mouth opening; five nets with 180 µm mesh size). Zooplankton samples were preserved in a 4% formaldehyde solution in seawater buffered with borax. In total, the dataset contains information from 230 zooplankton samples collected over the three study years.

Zooplankton were identified in the laboratory following standard analytical procedures (see Gluchowska et al., 2025). Organisms were identified to the lowest possible taxonomic level (most often species), with copepodid stages distinguished for key Calanus species. Identification of Calanus was based on prosome size distribution criteria established for Svalbard fjord populations (Kwaśniewski et al., 2003; Weydmann & Kwaśniewski, 2008).

The resulting dataset comprises records for 64 taxa belonging to 9 phyla, including 50 species/genera and 14 taxa identified at higher taxonomic levels. Abundance is expressed as the number of individuals per cubic meter (ind. m⁻³) for each sampled depth stratum. Source data for the functional traits of each taxon are available in Table S1 of the supplementary information in Gluchowska et al. (2025).

A study based on this dataset (Gluchowska et al., 2025) examined the seasonal succession and interannual variability of zooplankton in Kongsfjorden, providing a quantitative description of both taxonomic and functional community dynamics (using ecological trait-based approaches) across years characterized by contrasting hydrographic conditions.

Variables Measured
• Hydrography: temperature and salinity
• Zooplankton: abundance (ind. m⁻³), including copepodid stage identification for key Copepoda species

Zooplankton Sampling Design
• Study years: 2002, 2006, and 2007 — each representing distinct environmental conditions, especially in spring, with notable variation in seawater temperature and salinity
• Seasons:
Spring: Julian days 107–133
Summer: Julian days 208–214
Autumn: Julian days 240–277
• Stations: six sampling sites along a transect from the central fjord (K1–K2–K3–K4) to the adjacent shelf (K5–K6)
• Depth strata: five discrete layers, typically:
I: 0–25 (20) m
II: 25 (20)–50 m
III: 50–100 m
IV: 100–150 (200) m
V: 150 (200) m to the bottom

Literature:
• Kwasniewski S., Hop H., Falk-Petersen S., Pedersen G. (2003) Distribution of Calanus species in Kongsfjorden, a glacial fjord in Svalbard. Journal of Plankton Research 25: 1–20.
https://doi.org/10.1093/plankt/25.1.1
• Weydmann A., Kwasniewski S. (2008) Distribution of Calanus populations in a glaciated fjord in the Arctic (Hornsund, Spitsbergen) – the interplay between biological and physical factors. Polar Biology 31: 1023-1035.
https://doi.org/10.1007/s00300-008-0441-0
• Gluchowska M., Falk-Petersen S., Hop H., Olszewska A., Walkusz W., Kwaśniewski S. (2025) Zooplankton seasonal variability in Arctic fjord during cold and warm events – taxonomic and trait-based approaches (Kongsfjorden, Svalbard), Journal of Marine Systems 252, 104144.
https://doi.org/10.1016/j.jmarsys.2025.104144.