Nordkoster Urchin Fields

The northern tip of Nordkoster island is where the Kosterfjord current meets the open Skagerrak, creating ideal conditions for filter-feeding communities. Dense carpets of green sea urchins cover the bedrock from 5 metres down, and their grazing creates openings colonised by tunicates, bryozoans, and the brilliantly coloured Coryphella nudibranchs that feed on them. Edible crabs and velvet swimming crabs are abundant in the crevices. The site experiences stronger tidal movement than the sheltered southern sites, which brings nutrients but requires careful timing — slack water dives are the most productive.