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POLARPROG-Polarforskningsprogram

Arctic marine mammals in a time of climate change: a Kongsfjorden Case Study ("ARK" – ARktiske Klima forandringer Konsekvenser)

Alternative title: Arktiske sjøpattedyr i en tid med klimaendringer: en Kongsfjorden "Case Study" ("ARK" – ARktiske Klima forandringer Konsekvenser)

Awarded: NOK 12.0 mill.

Declines in sea ice (volume, extent, seasonal coverage) and melting and retraction of tidewater glaciers in the Arctic are particularly visible signs of change that is occurring due to global warming. Degradation of these physical features in Arctic marine systems are happening more rapidly in the northern Barents Sea than elsewhere in the circumpolar Arctic, making the Norwegian High Arctic a bellwether of climate change for the entire region. Shrinking of sea-ice habitats and concomitant changes in Arctic food webs, will undoubtedly have profound implications for marine ecosystems in the High North; the expected implications for endemic Arctic marine mammal species have been described as ‘transformative’. In the period 2021-2026 the ARK research programme will test four principle theories/expectations regarding how marine mammals (especially resident endemic Arctic seals but also other species) are being impacted by global warming: 1) declining ice habitats will cause abundance declines in ice-dependent species and result in redistributions, and over longer time frames local extinctions; 2) Arctic endemic species will face increasing competition from temperate species that are expanding their ranges northward; 3) the health of Arctic endemic species will be negatively impacted by increasing exposure to diseases and increased impacts of contaminants and 4) warming-induced changes of food webs will affect Arctic marine mammals negatively, creating risks of cascading impacts through Arctic ecosystems. ARK is taking a case-study approach, using Kongsfjorden on the west coast of Svalbard to explore ecosystems change, employing state-of-the-art food web models and risk assessment models to produce management relevant assessments for conservation planning. In the first three years of ARK we have explored potential climate change impacts in Kongsfjorden using: 1) Passive Acoustic Monitoring (PAM) acoustics data 2) 15 years of sightings data and 3) started to explore fish community dynamics. The acoustics data shows that bearded seal singing rates have dropped dramatically and the peak vocal season for this species in Kongsfjorden now occurs after the local sea ice disappears, creating a problematic mismatch between breeding habitat availability and animal behaviour. We have also demonstrated that this west coast site is dramatically different than the east side of the archipelago in terms of "soundscape". In Kongsfjorden winter vocal presence of walruses is now strong as this species recovers and spreads into its pre-hunting range, but walruses are one of the few Arctic species strongly represented in Kongsfjorden - ship noise is now a dominant sound source throughout much of the year. This is marked contrast to the east, where bearded seals, walruses, narwhal and bowhead have long and strong seasons and ship noise is virtually non-existent. The sightings database analyses show that migratory whales have expanded their distribution northward and that they also are much more common in the fjords in recent years compared to in the past. These changes reflect the northward retraction of the Arctic ice cap and greater influxes of warm Atlantic Water onto the shelf and in the west coast fjords, which is bringing with it boreal fish and krill species on which the migrant whales feed. Specifically, in Kongsfjorden there are more sightings of white-beaked dolphins, blue whales, humpback whales and minke whales, while there are fewer sightings of resident white whales. Time series of active acoustics transects show that the fish community is also changing, with fewer small fish detected, while there are more medium- and large-sized fishes. These finding suggest that the small, Arctic, polar cod is declining, while the larger, boreal, Atlantic cod is increasing. We have paid particular attention to the salmonids to start our dietary, food-web studies in ARK, exploring the diet of the native char versus the invading (likely introduced) Pacific pink salmon. The diets of these two species overlap significantly, suggesting that the invading species will compete for food with the native species. In all three years of the study thus far we have also surveyed haul out locations for harbour seals and found that over the last decade they have become well established in Kongsfjorden, occupying all areas of the fjord, including areas deep into the fjord (where ringed and bearded seals feed and rest). We have now completed field campaigns capturing and equipping ringed seals, bearded seals, and harbour seals with GPS tracking devices to explore niche overlap and we have taken tissue samples to study their health and diet. Collections of possible prey species were also undertaken both in winter and summer, so that we can study the diet of the various seals, determining what they eat and whether they are competing for food. Analyses are now underway in ARK partner’s laboratories in several countries.

Declines in sea ice (volume, extent, seasonal coverage) and melting and retraction of tidewater glaciers in the Arctic are particularly visible signs of change that is occurring due to global warming. Degradation of both of these physical features of Arctic marine systems are happening more rapidly in the northern Barents Sea than elsewhere in the circumpolar Arctic making the Norwegian High Arctic is a bellwether of climate change for the entire region. The shrinking of sympagic habitats and concomitant Atlantification of Arctic food webs, will undoubtedly have profound implications for marine ecosystems in the High North; the expected implications for endemic Arctic marine mammal species have been described as “transformative”. The ARK research programme will use a variety of “captured” and extended data time series (abundance, ecology, diet, contaminant levels, disease/health, trophic interactions etc) to quantitatively test four principle hypotheses regarding how marine mammals (especially resident endemic Arctic seals but also other species) are being impacted by global warming: 1) H1 - Declining ice habitats will induce abundance declines in ice-dependent species and result in redistributions, and over longer time frames extirpations; 2) H1 - Arctic endemic species will face increasing competition from temperate species that are expanding their ranges; 3) H1 - the health of Arctic endemic species will be negatively impacted by increasing exposure to diseases and increased impacts of contaminants and 4) H1 - Atlantification of food webs will affect Arctic marine mammals negatively, creating risks of cascading impacts through Arctic ecosystems. ARK will take a case-study approach, using Kongsfjorden on the west coast of the Svalbard Archipelago to explore ecosystems change, employing state-of-the-art physical-biogeochemical food web models and complex adaptive systems risk assessment modelling to produce management relevant assessments and predictive capacity.

Funding scheme:

POLARPROG-Polarforskningsprogram