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

Informations

Funding country

Norway

Acronym

-

URL

-

Start date

1/1/2021

End date

12/31/2026

Budget

1,472,556 EUR

Fundings

Abstract

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 two years of ARK we have explored potential climate change impacts in Kongsfjorden using 1) Passive Acoustic Monitoring (PAM) data and 2) 15 years of sightings data. The PAM data shows that this previously important breeding site for bearded seals has declined in usage; male bearded seal singing rates have dropped dramatically and the peak vocal season in Kongsfjorden now occurs after the local sea ice disappears, creating a problematic mismatch between habitat availability and animal behaviour. The sightings database was analyses with respect to whale distribution and their usage of coastal and fjord habitats. We found 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 on the shelf and in the fjords, which is bringing with it boreal fish and krill species that the migrant whales are feeding on. Specifically, in Kongsfjorden there are more sightings of white-beaked dolphins, blue whales, humpback whales and minke whales, while there are fewer sightings of the Arctic endemic white whales. In 2021 and 2022, we have also surveyed potential haul out locations for harbour seals and found that over the last decade they have become well established, using several colony sites and occupying all areas of the fjord, including aquatic areas deep into the fjord (where ringed and bearded seals feed and rest). We also ran field campaigns in each year (late summer), capturing and equipping ringed seals, bearded seals, and harbour seals with satellite tracking devices to explore niche overlap and we took 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 undertake non-invasive studies of the diet of the various seals, determining what they eat and whether they are competing for food.