Standardized Calanus glacialis and Calanus hyperboreus Abundance Data with Spatiotemporally Matched Environmental Variables

Overview This dataset contains standardized abundance records of the pre-diapause C1–C2 copepodite stages of Calanus glacialis and Calanus hyperboreus across Arctic and sub-Arctic regions between 55°N and 90°N from 1993 to 2022.Biological observations were matched with environmental variables according to sampling location and date. The dataset was prepared for ecological niche modelling and habitat suitability reconstruction of Arctic Calanus species. File included Cgla_Chyp_c1c2_EnviVar.xlsxThe workbook contains standardized C1–C2 abundance records of Calanus glacialis and Calanus hyperboreus together with environmental covariates matched to each biological sampling record. Variable description lat: Sampling latitudelon: Sampling longitudeyear: Sampling yearmonth: Sampling monthday: Sampling daySIC: Sea-ice concentrationCHL: Surface chlorophyll-a concentrationSST: Sea-surface temperatureSal: Sea-surface salinityu: Zonal ocean-current velocityv: Meridional ocean-current velocitynpp: Net primary productionnitrat: Nitrate concentrationSIT: Sea-ice thicknessmlotst_glor: Mixed-layer depthCgla_c1c2: Standardized abundance of Calanus glacialis C1–C2 stagesChyp_c1c2: Standardized abundance of Calanus hyperboreus C1–C2 stagesMLDaverCHL: Mixed-layer-averaged chlorophyll-a concentrationMLDaverSal: Mixed-layer-averaged salinityMLDaverSST: Mixed-layer-averaged temperaturep60dmSIC: Mean sea-ice concentration during the 60 days preceding sampling Data preparation Biological abundance records were standardized to reduce inconsistencies associated with sampling depth, sampling gear and life-stage reporting.Environmental variables were matched to each biological observation using sampling coordinates and date. Both surface and mixed-layer-averaged environmental variables were retained to represent environmental conditions at different vertical scales.For habitat suitability modelling, abundance values greater than zero were treated as presence records, while zero abundance values represent observed absences from actual biological sampling events. Unsampled locations were not treated as absences. Environmental data Environmental predictors describe sea-ice conditions, upper-ocean temperature and salinity, ocean circulation, biological productivity, nutrient availability and mixed-layer conditions.The environmental variables were derived from ocean reanalysis, biogeochemical and sea-ice products used in the associated study, including Copernicus Marine datasets.Intended useThis dataset was prepared primarily for ecological niche modelling, habitat suitability reconstruction and analysis of environmental controls on Arctic Calanus distributions and climate-driven habitat shifts. Limitations Sampling coverage is spatially and temporally uneven across the Arctic because biological observations are concentrated in regions and periods with greater survey effort. Some regions, particularly parts of the central Arctic Basin, are therefore more sparsely represented.The dataset focuses specifically on pre-diapause C1–C2 stages and should not be interpreted as representing the habitat requirements or distribution of later developmental stages.Habitat suitability derived from these data should not be interpreted as a direct estimate of abundance, because realized distributions may also depend on processes such as advection, recruitment, mortality, food availability and growth-season duration.