Kelp forests are important to coastal ecosystems, where they support unique biodiversity and contribute considerably to the carbon budget in glacial fjords, such as Kongsfjorden in Svalbard.
By: Haakon Hop, Norwegian Polar Institute (NPI) and Karen Filbee-Dexter, Institute of Marine Research (IMR) / University of Western Australia (UWA)
Dive stations for collection of kelp. Red arrows indicate the historical sites sampled in 1996/98.
The BlueARC project aims to put Norway at the front on research and understanding effects of the climate change on kelp forests in northern areas. This project has included scientific diving campaigns in Kongsfjorden in May 2024 and September 2025. We revisited historical hard-bottom locations sampled in1996/98.
BlueARC dive team: Albert Pessarrodona and Kjell Magnus Norderhaug (IMR), Karen Filbee-Dexter (IMR/UWA), and Haakon Hop (NPI). Dive line support team: Jacob Nepper-Davidsen (ROS), and Hanna Scarlett Earp (IMR). Photo: Jan Ivar Pettersen / NPI
The climate-related questions we aim to answer are how the biophysical environment shape Arctic kelp forest habitats, to what extent sea urchins are increasing and grazing down these kelp forests, and how these ecosystems are expected to change in the future with consequences for coastal carbon sinks.
Scientific diver Kjell Magnus ready to dive to collect kelp. Photo: Haakon Hop / Norwegian Polar Institute
The dominant macroalgae in the Arctic are the brown seaweeds, which can grow several metres long and support high biodiversity. In Kongsfjorden, kelps have expanded and increased in biomass in some areas during the last 30 years since our first dive surveys. This increase is because of diminishing sea ice and less ice scouring, particularly in the shallows (< 5 m). However, increased run-off of turbid water from tidewater glaciers has reduced the depth distribution of brown seaweeds because of less light. In addition, a massive increase in sea urchin (Strongylocentrotus sp.) abundance has grazed down the kelp forest deeper than 10 metre in the outer and middle reaches of the fjord.
Albert and Karen with collections of large sugar kelp (Saccharina latissima). Photo: Haakon Hop / Norwegian Polar Institute
The kelp research in Kongsfjorden is part of a larger pan-Arctic project, BlueARC, funded by the Research Council of Norway. The project is led by Karen Filbee-Dexter, Institute of Marine Research (IMR), Norway, and aims to determine how Arctic kelp forests cycle and store carbon now and under future conditions.
Kelp collections ready to be processed in the marine laboratory. Photo: Jacob Nepper-Davidsen
The underwater surveys in the BlueArc project can only be done by scientific divers recording and collecting kelp at different locations around the fjord. The dive team was led by Haakon Hop (Norwegian Polar Institute), and Kjell Magnus Norderhaug (IMR), and included IMR and University of Western Australia (UWA) scientific divers Karen Filbee-Dexter and Albert Pessarrodona.
The oar weed (Laminaria digitata) can get as big as you! Photo: Jacob Nepper-Davidsen
Macroalgae collected were brought back on small boat to Kings Bay Marine Laboratory in Ny-Ålesund for further identification and processing, with carbon, age and genetic analyses led by researchers Morten Foldager Pedersen, Jacob Nepper-Davidsen, and Emma Brette from Roskilde University in Denmark, Luisa Düsedau from Danish Technical University (DTU) and Hannah Scarlett Earp (IMR) and Sidsel Pedersen (UWA). Genetic samples will be further processed as part of the GEcoKelp project led by Thomas Wernberg (IMR) to reveal genetic diversity and structure compared to samples from mainland Norway.
Kelp is being weighed and sampled by Hannah in the lab: Photo: Haakon Hop / Norwegian Polar Institute
The Blue ARC project aims to increase our understanding of the climate changes happening to our kelp forests in northern habitats. The project includes a pan-Arctic comparison of kelp forest structure with samples from nearly 100 sites across 3000 km of linear coastline, covering a latitudinal gradient from temperate to Arctic conditions. Svalbard is one of the few areas in the Arctic with historical measures of kelp forests, making it an essential window into these rapidly changing coasts. Diving-based research projects like BlueARC are essential to understand the consequences of these changes on Norway’s unique High Arctic marine ecosystem!
