Marine life has received less attention than the land areas in the archipelago. Under water, we have the 470-meter-deep Hvaler Trench, which brings in saltwater from the Atlantic Ocean. In this deep-water trench, oceanic conditions prevail, with high salinity and low temperatures.
Smooth shoreline rocks at Pølsesund, Vesterøy. Photo: Ottar Krohn
In Ytre Hvaler National Park, you can experience a magnificent coastal landscape that hasn’t been subjected to technical encroachments. The landscape is characterized by smooth shoreline rocks and wind-swept coastal forests. There is great variation, from the smooth and rounded granite and gneiss areas on the Hvaler islands to the rugged rhomb-porphyry conglomerate (a globally rare conglomerate rock) on the Søster islands in Fredrikstad. Glomma, Norway’s largest river, influences the marine environment in parts of the national park, as does a section of the Norwegian Atlantic Current.
Here, everyone has the opportunity to experience traditional, simple outdoor life and beautiful experiences of nature.
In the sea, there are hard and soft seabed areas, rich kelp forests, and coral reefs. Ytre Hvaler National Park is home to what is considered one of the largest inshore cold-water coral reefs in the world. Tisler reef is 1200 meters long, 200 meters wide and grows at depths between 74 and 160 meters. The reef is over 8000 years old and provides a habitat for a variety of different fish species, crustaceans and sponges.
Coral reefs are large colonies and complex structures of bottom-dwelling cnidarians, and are habitats for thousands of other species. They can be very old and they grow slowly; just a few millimeters per year.
A coral reef of Lophelia pertusa at Tisler. Photo: Lisbeth Jonsson/Thomas Lundälv
Goldsinny wrasse among the soft coral called dead man’s fingers. Photo: Lisbeth Jonsson/Thomas Lundälv
Sponges, soft corals, cold-water corals, and other species attached to the substrate grow under water on hard substrates like bedrock and large stones at depths ranging from 30 to 470 meters. Hard substrate is most often found on steep slopes.