Unique data collection throughout the Arctic year
Top image: December 2008: At the height of the dark season sampling is conducted in Billefjorden from the UNIS boat “Viking Explorer”. Photo: Øystein Varpe/UNIS.
For the first time a team of UNIS scientists and students have been able to collect ice-, water and plankton samples through a full year to study the wintertime marine ecology in Svalbard. The data will be important in predicting future climate changes in marine productivity and behavior as a response to the thinning and withdrawal of Arctic sea ice.
23 July 2009
Text: Eva Therese Jenssen
For the first time a team of UNIS scientists and students have been able to collect samples through a full year to study the wintertime marine ecology in Svalbard. Knowledge about the wintertime marine ecology in Svalbard is limited, due to the difficulty of obtaining data during the long Polar night.
The ArcWin project (The Arctic sea in Wintertime: ecosystem structuring due to environmental variability during the polar night) in cooperation with the CLEOPATRA project (Climate effects on planktonic food quality and trophic transfer in the Arctic marginal ice zone) are aiming at obtaining important data about what goes on in the ocean ecosystem during the winter dark season.
Specifically, the ecology of the seasonal vertically migrating Calanus copepods throughout the winter is of interest. This research is part of the bigger Ice Edge programme which focuses on the ecological key processes in the Arctic ice edge ecosystem.
Influence of sea ice on the marine ecology
– The timing of the descent and ascent of overwintering Calanus glacialis and Calanus finmarchicus as well as the lipid storage status and developmental composition of the population throughout the year, is important to investigate. It will give us important information about the influence of sea ice on the feeding and reproduction of these important components of the Arctic marine food web, according to Janne Søreide and Øystein Varpe, UNIS Post Docs in marine biology.
– The aim is to study in detail the seasonal development and behavior of Calanus glacialis, as it is one of the most important zooplankton species, Søreide says.
C. glacialis constitute up to 80% of the zooplankton biomass in Arctic shelf seas, and constitute thus the key link between primary producers and higher trophic levels such as fish, whales and sea birds in Arctic marine ecosystems.
In particular, the scientists want to study the seasonal adaptations of Calanus, especially what triggers their seasonal ascend and descend in the ocean column in connection to food availability, ice and light conditions and their physiological state in terms of fat deposits, Varpe explains.
– We have photographed the lipid sacs of individual specimens from different depths throughout the year to follow their seasonal fluctuations in fat content, he says. These small (~5 mm) but lipid-rich specimens can have up to 70% fat of their dry weight.
All these factors are important to document and study in order to understand how zooplankton will cope with and respond to the thinning and withdrawal of the Arctic sea ice. Much of the Arctic marine food chain, from the Polar cod up to the Polar bear, will be influenced by changes at the zooplankton level.
Marine predators feed on zooplankton, such as the Calanus spp. Most predators depend on visual contact in order to identify their prey. Thus, many zooplankton species have developed strategies to escape these predators. Such strategies include the seasonal migration to the deep overwintering habitat, and on a daily timescale, so called diel vertical migrations (DVM); ascending into the food-rich surface waters during darkness and retreating to deeper waters during day.
A DVM study was recently conducted in Rijpfjorden and Kongsfjorden. These locations are difficult to perform year-long sampling in due remote locations and sea ice conditions, and although exciting DVM patterns were observed, it was difficult to decide which plankton species performed the migrations.
Thus, Søreide and Varpe, UNIS students and colleagues from the mainland, decided to investigate this also in Billefjorden, closer to Longyearbyen.
– We chose Billefjorden because it is an Arctic oasis in the otherwise Atlantic water influenced ocean on the west coast of Spitsbergen, Søreide explains.
Billefjorden is a threshold fjord, which means that there is less transportation of water in and out of the fjord than other fjords along the western coast. As such, it is more suitable to do population studies than for instance Kongsfjorden which is an open fjord with lots of water mass and thus zooplankton exchange.
The UNIS team has been taking samples throughout a full year, starting last summer and completing the field period on July 15th 2009.
Unique research opportunity
– This is probably the first time scientists have been able to collect monthly water and plankton samples in such a High Arctic fjord throughout a winter season, says Søreide.
– It gives us a unique opportunity to observe how things change in the ocean throughout the seasons, from mid-summer with midnightsun through the wintertime, where the sun is more than 12 degrees below the horizon and humans perceive complete darkness, she says.
Throughout the year, the scientists visited Billefjorden one or more times each month to collect samples. This kind of fieldwork presents logistically challenges and the scientists have had to be creative in order to get their work done.
– We have used all kinds of transportation methods, from boats of all sizes, to snow scooters and even in spring, with treacherous sea ice conditions, we used sled dogs and skis in order to reach our destination, Varpe says.
The samples and tests are still being performed and this study will be the source for several master theses and scientific papers in the coming years.