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Dive behavior represents multiple ecological functions for marine mammals, but our understanding of dive characteristics is typically limited by the resolution or longevity of tagging studies. Knowledge on the time-depth structures of dives can provide insight into the behaviors represented by vertical movements; furthering our understanding of the ecological importance of habitats occupied, seasonal shifts in activity, and the energetic consequences of targeting prey at a given depth. Given our incomplete understanding of Eastern Beaufort Sea (EBS) beluga whale behavior over an annual cycle, we aimed to characterize dives made by belugas, with a focus on analyzing shifts in foraging strategies. Objectives were to (i) characterize and classify the range of beluga-specific dive types over an annual cycle, (ii) propose dive functions based on optimal foraging theory, physiology, and association with environmental variables, and (iii) identify whether belugas undergo seasonal shifts in the frequency of dives associated with variable foraging strategies. Satellite-linked time-depth-recorders (TDRs) were attached to 13 male belugas from the EBS population in 2018 and 2019, and depth data were collected in time series at a 75 s sampling interval. Tags collected data for between 13 and 357 days, including three tags which collected data across all months. A total of 90,211 dives were identified and characterized by twelve time and depth metrics and classified into eight dive types using a Gaussian mixed modeling and hierarchical clustering analysis approach. Dive structures identify various seasonal behaviors and indicate year-round foraging. Shallower and more frequent diving during winter in the Bering Sea indicate foraging may be energetically cheaper, but less rewarding than deeper diving during summer in the Beaufort Sea and Arctic Archipelago, which frequently exceeded the aerobic dive limit previously calculated for this population. Structure, frequency and association with environmental variables supports the use of other dives in recovery, transiting, and navigating through sea ice. The current study provides the first comprehensive description of the year-round dive structures of any beluga population, providing baseline information to allow improved characterization and to monitor how this population may respond to environmental change and increasing anthropogenic stressors.

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Climate-driven impacts on marine trophic pathways worldwide are compounded by sea-ice loss at northern latitudes. For the Arctic, current information describing food web linkages is fragmented, and there is a need for tools that can describe overarching trophic structure despite limited species-specific data. Here, we tested the ability of a mass-balanced ecosystem model (Ecopath with Ecosim, EwE) to reconstruct the trophic hierarchy of 31 groups, from primary producers to polar bears, in the Canadian Beaufort Sea continental shelf. Trophic level (TL) estimates from EwE were compared with those derived from two nitrogen stable isotope (SI) modelling approaches (SI linear and scaled) to assess EwE accuracy, using a dataset of 642 δ15N observations across 282 taxa. TLs from EwE were strongly, positively related to those from both SI models (R2 > 0.80). EwE performed well (within 0.2 TL) for groups with relatively well-known diets or for taxa characterized by fewer trophic connections (e.g., primary consumers). Performance was worse (> 0.5 TL) for species groups aggregated at coarse taxonomic levels, those with poorly documented diets, and for anadromous fishes. Comparisons with SI models suggested that the scaled approach can overestimate the TL of top predators if ecosystem-specific information is not considered.

The Eastern Beaufort Sea (EBS) beluga (Delphinapterus leucas) population are an important traditional food for the Inuit of the Inuvialuit Settlement Region, Northwest Territories (NT) Canada. In 2014, over 30 beluga whales were harvested at Ulukhaktok, NT, the first occurrence of a large harvest in the area on record. Unlike observations from the established beluga harvest monitoring program in the Mackenzie Estuary, these belugas had numerous prey and prey items in their stomachs. Our study objectives were to combine traditional and local knowledge (TLK) from beluga hunters with the analysis of dissected stomachs to identify EBS beluga diet, feeding behaviour, as well as gain insights into potential drivers of the event. TLK holders witnessed foraging behaviors such as herding schools of fish. Stomach dissections revealed Sandlance (Ammodytes sp.) to be the predominant prey species, comprising 90% of identified otoliths, occurring in 92% of stomachs. The low presence of Arctic Cod (Boreogadus saida), a preferred prey types, raised questions about prey availability/accessibility and if alternative prey types can sustain beluga energetic needs. Based on interviews of TLK holders, avoidance of noise due to human activity, killer whale presence, and shifts in prey were factors that may have led to the increased beluga sightings near Ulukhaktok, NT.

We examined monthly changes in crustacean zooplankton community composition during the initial colonisation period of a newly constructed pond (LWL pond), and in the littoral zone of an adjacent lake (Ramsey lake). In addition, four unconnected constructed ponds aged ≥20 years with established zooplankton communities were sampled and compared to the LWL pond. The species richness of both LWL pond and Ramsey lake increased over the ice-free season, although Ramsey lake always had more species. Almost half of all species sampled occurred in both pond and lake. None of the zooplankton communities in the ponds used in the spatial analysis resembled communities of the LWL pond or one another. Taken together, these results indicate a lack of dispersal limitation, which suggests that differing local habitat factors had a strong influence in structuring the zooplankton communities.

With increased warming and open water due to climate change, the frequency and intensity of storm surges is expected to increase. Although studies have shown that strong storms can negatively impact Arctic ecosystems, the impact of storms on Arctic marine mammals is relatively unknown. In July 2016, an unusually large storm occurred in the Mackenzie Delta while instrumented seabed moorings equipped with hydrophones and oceanographic sensors were in place to study environmental drivers of beluga habitat use during their summer aggregation. The storm lasted up to 88 h, with maximum wind speeds reaching 60 km/h; historical wind data from Tuktoyaktuk revealed a storm of similar duration has not occurred in July in at least the past 28 years. This provided a unique opportunity to study the impacts of large storms on oceanographic conditions, beluga habitat use, and the traditional subsistence hunt that occurs annually in the delta. The storm resulted in increased water levels and localized flooding as well as a significant drop in water temperature (∼10 °C) and caused belugas to leave the area for 5 days. Although belugas returned after the storm ended, the subsistence hunt was halted resulting in the lowest beluga harvest between 1978 and 2017.