16 years of gelatinous zooplankton seasonal abundances reveal food availability and temperature as key drivers in Arctic latitudes

Abstract

Abstract Year-round long-term monitoring programs are essential for assessing ecosystem functioning and change. In the Arctic, however, continuous multi-year sampling covering all seasons remains scarce. Using monthly observations from the Greenland Ecosystem Monitoring program (2005–2021) in Nuup Kangerlua (SW Greenland), collected with triplicate 0–100 m net hauls and concurrent environmental profiling, we characterized seasonal and multiannual abundance patterns of major gelatinous zooplankton (GZP) groups (Ctenophora, Appendicularia, Cnidaria, and Chaetognatha) and assessed their responses to temperature and salinity, as well as food availability (i.e., chlorophyll a , biomass of small copepods, small Calanus spp. (CI–CIII), large Calanus spp. (CIV–CVI) and copepod nauplii abundance), the latter being drivers rarely included in long-term studies. All GZP groups showed strong seasonal variability in abundances, with peak abundances in summer. Hereby, copepod availability showed correlations with GZP abundance that were equal to or stronger than those of temperature. Chlorophyll a correlated weakly with GZP abundance directly, but remained a central driving factor of prey availability and therefore still indirectly influenced carnivorous GZP dynamics. Salinity showed mostly negative associations. Indicator species analyses identified Oikopleura spp., Parasagitta spp., Aglantha digitale , and undetermined Hydromedusae as characteristic of warm, food-rich summer conditions. Additionally, undetermined Chaetognatha were an indicator taxon for the entire productive season. These findings demonstrate that resolving Arctic change requires year-round observations that integrate trophic context, as food availability can rival or exceed physical drivers in structuring GZP communities, as demonstrated here with copepods and primary production.