Say hello to Kongsfjorden, Svalbard
Kongsfjorden is a glacial fjord in Svalbard that harbours a mixture of Arctic flora and fauna. It is an open fjord with no sill at its entrance, meaning the Atlantic waters that flow in make it a sub-Arctic rather than Arctic environment. Kongsfjorden represents a border area between the Atlantic and Arctic biogeographic zones and the biodiversity and animal populations found in its waters is influenced by the cooler and warmer waters coming together.
A rich photoplankton environment
In the fjord scientists have found a pronounced seasonal growth pattern in photoplankton and distribution. In the polar winter, photoplankton stops production while in spring more than 60 photoplankton taxa spring to life culminating in a bloom that coincides with similar blooms along the northern Norwegian coast, indicating a strong light or day length control. The summer season in Kongsfjorden is characterised by a very diverse range of photoplankton communities with over 130 taxa recorded.
Shrimp and fishes, mammals and birds
The most common shrimp in Kongsfjorden is Pandalus borealis while the most common fish is the polar cod and capelin. Meanwhile, Kongsfjorden has diverse, abundant marine mammal and seabird communities. Marine mammals found there include pinnipeds (seals and walruses), cetaceans (whales) and the polar bear. Seabirds include fulmars, marine ducks, gulls and some shorebirds. The number of birds found at Kongsfjorden varies according to the seasons with a marked seasonal peak in the spring-summer season. This is attributed to migratory species that regularly pass through the fjord. However, there are a few resident bird species that call Kongsfjorden home throughout the year.
A variable food supply
Within and between the seasons there are changes in food availability in various parts of the fjord that determine the spatial and temporal distribution of foraging by the top predators. The retreating ice normally creates a highly productive area with an extensive photoplankton bloom in spring that results in prey organisms being concentrated in the upper water layers. These animals then attract both marine mammals and birds in these areas. When the short-fast ice has melted, glacier fronts, which act as upwelling areas for zooplankton due to freshwater discharging from the bottom of the glacier, become the main feeding areas for marine mammals and birds during late summer and early autumn.
The sunbathing ringer seals
Ringed seals are distributed throughout the circumpolar Arctic and they are the most abundant Arctic seal in the area. Kongsfjorden is an important breeding site for these species with the seals building lairs in this habitat to protect themselves and their offspring from the harsh, winter weather as well as predators. Snow depth is one of the limiting factors for the location of the lairs as the average snow depth of 20 centimetres is quite shallow for the Arctic and so it provides limited resources for lair construction. This means the prime location for ringed seals in Kongsfjorden occurs in the inner fjord area that contains glacier-ice pieces frozen into the annual ice. Because these ice structures tend to cause accumulation of drifting snow it provides good snow depth for ringed seal lairs. During the March-April time some 50-100 pups are born. As spring comes around, the seals are visible as they lay out to rest and sun themselves on the ice surface. During June, adults and young adults spend most of their time out in the water while they undergo their annual moult. At this time, there is high concentrations of ringed seals on the limited remaining sea ice in Kongsfjorden. After moulting the seals leave the fjord and move along the coast or more northward to the pack ice. Breeding-aged animals return in early winter the fjord and maintain holes in the ice as the inner part of the fjord becomes ice-covered.
The water-loving bearded seals
Meanwhile, bearded seals also call Kongsfjorden home but the species prefer the drifting pack ice as its breeding habitat. Because of the seals’ large body size it has protection from both the cold weather while its aquatic nature protects it from predators. Bearded seals are very seldom found more than a metre away from the water and their young swim and dive within hours of their birth. Bearded seals are found at low densities with often only around 25 pups born each year. Pups remain with their mothers for around 3-4 weeks and then females mate with males that have managed to attract them via their singing behaviour. During June, bearded seals moult and can often be found on land-fast ice in clusters.
There are even walruses there
Walruses too are found in Svalbard and are part of a population that breeds mainly in the Franz Josef Land area. They spend their winter on pack ice in southern parts of Svalbard and in north-eastern Svalbard and eastwards near Russia. Walruses are often found in Kongsfjorden during the spring months until late summer.
Whales cruising around
White whales are the most commonly sighted whales in the Kongsfjorden area and are the most numerous whale species in the wider Svalbard area. Pods of these whales can be seen in the area for days at a time from early spring through the summer months. These whales prefer ice edges during spring and the glacier fronts become their prime feeding spots in the summer. Minke whales have also been spotted in the outer areas of Kongsfjorden from late spring to the summer months with the occasional minke making its way into the inner fjord area. Fin whales too have been known to forage at times in Kongsfjorden but they usually remain in coastal and offshore waters as opposed to inside the fjords.
The sea-birds making the fjord home
There are nine species of sea birds that call Kongsfjorden home. The common eider is the largest contributor to the area’s total bird population followed by black-legged kittiwake. Nearly all the birds are migratory, leaving the fjord during the winter months. Their arrival time in spring and departure time in autumn varies among the species meaning the peak time for birds in the area is during a three-month period from mid-May to mid-August. Other seabird species breed in the Kongsfjorden area including the Arctic skua, long-tailed skua, greater black-backed gull, long-tailed duck and red-throated diver.
The foragers and the divers
The seabird species present can be broken into two groups based on their foraging behaviour. There are the pursuit divers that catch zooplankton and small fish while diving at sea. The diving depth of each bird is related to body size with the largest of these species, the Brunnich’s guillemot, making the deepest dives at around 200 metres while the smallest bird, the little auk, dives to much shallower depths of around 30 metres at most. Meanwhile, the common eider is mainly a benthic feeder that forages in shallow waters and dives to depths of no less than 15 metres. The other group of bird species is the surface feeders or near-surface feeds. This group is dominated by the northern fulmar, kittiwake, glaucous gull and Arctic tern. The first three of which mainly feed on zooplankton and pelagic fish from the sea surface while the Arctic tern sometimes goes below the water to catch prey.