The data set covers the marine biological transect from Kongsfjorden to Fram Strait (KongHau transect) within the framework of the Environmental monitoring of Svalbard and Jan Mayen (http://www.mosj.no/en/) program. The data set covers summers 2009-2014 for nutrients and chlorophyll a (Chl a) and summer 2009-2013 for protist (including phytoplankton and protozooplankton) abundance. The results published in Hegseth et al. 2019 (see the "Citation Custom" field) are based on this data set. Norwegian Polar Institute"s marine database will contain extended data from the KongHau transect, and any users post-2019 are encouraged to use the extended data set instead.

The data show concentrations of total mercury (THg) in hair from female adult (>4 years, n= 185) and sub-adult (1-4 years; n= 14) polar bears from the Barents Sea subpopulation management regime. The samples were collected in spring of each year between 1995 and 2016 (except 2001 and 2002). Additionally, the samples were analysed for stable isotopes of carbon (δ13C), sulfur (δ34S), and nitrogen (δ15N) to approximate feeding habits (δ13C and δ34S: marine vs. terrestrial diet, δ15N: trophic level). It was assumed that δ34S could be a potential indicator for bacterial mercury methylation. The data were used to explore temporal trend of THg, and how they were affected by changes in feeding habits, and changes in body condition, breeding status, and age. The THg concentrations are given in µg/g hair; and values of all stable isotopes in ‰. Polar bear length and girth are given in cm, and weight in kg. Breeding status refers to females captured alone (n), with cubs of the year (c), or with one or two year old offspring (y, 2y).

Zooplankton dataset over the Kongsfjorden to Fram Strait marine biological transect collected in connection with Environmental monitoring of Svalbard and Jan Mayen (http://www.mosj.no/en/) programme. The dataset covers summers 1996-2016 except for 1998 when summer samples were not taken. The dataset contains only zooplankton collected with the MultiNet plankton sampler. The results published in Hop et al. 2019 (see the "Citation Custom" field) are based on this exact dataset. Norwegian Polar Institute"s database will contain extended data based on this dataset, and any users post-2019 are encouraged to use the extended dataset instead. The dataset is compiled in three files: **kf_zooplankton_abundance_data** contains zooplankton abundance data in *individuals per cubic meter*. The columns of the dataset consists of species and stage codes specified in the species metadata, while the rows consist of samples indicate in the sample metadata **kf_zooplankton_sampling_meta** contains row metadata for zooplankton abundance. Columns: id = row name in zooplankton abundance data; expedition = expedition/cruise name; station = standard station name across the MOSJ transect; sample_name = internal sample name for backwards compatibility; region = region category used in Hop et al. 2019; longitude = longitude as decimal degrees (WGS84); latitude = latitude as decimal degrees (WGS84); date = date in yyyy-mm-dd format; from = depth in meters where the MultiNet opened ; to = depth in meters where the MultiNet closed; comment = specific comments concerning the sample. **kf_zooplankton_species_meta** contains column metadata for zooplankton abundance. Columns: id = column name in zooplankton abundance data; species = scientific taxa name; stage = life stage; length = length group; origin = the assumed origin of species (Atlantic, Arctic, Both or Unknown); taxa = used for grouping of species data based on taxonomy in Hop et al. 2019; biomass_conv = abundance to biomass conversion factor, see Hop et al. 2019.

This dataset contains results from seawater column samples collected in Rijpfjorden (80°N, 22°30’E) and northern coast of Svalbard during three years in July 2012-2014 using R/V Lance. Measured variables include seawater total alkalinity (AT), total dissolved inorganic carbon (DIC), salinity, and temperature.

This dataset contains results from seawater column samples collected in Kongsfjorden (between 78°50' and 79°04'N and 11°20' and 12°30'E) and West-Spitsbergen shelf (Svalbard) during three years in July 2012-2014 using R/V Lance. Measured variables include seawater total alkalinity (AT), total dissolved inorganic carbon (DIC), salinity, and temperature.