Low colonisation on artificial substrata in arctic Spitsbergen

Abstract

High polar communities tend to be young because of the frequent and intense impact of ice (scour), so colonisation patterns are particularly important. Yet, despite a wealth of studies at temperate and tropical latitudes, we know of no hard substratum settlement/colonisation experiments reported north of 60°N, to date. Here we report on fauna encrusting square panels immersed at 12 m depth in Isforden, Spitsbergen (Svalbard) after 2 and 3 days, a week and a year. Arctic colonisation is slow but is not species poor. We found no colonists present after 2 and 3 days but two panels were colonised by a bryozoan and polychaetes after a week. After a year immersion, three panels were 3, 5 and 11% covered with a mean of ∼247 colonists. This is about an order of magnitude lower than has been described from most studies elsewhere, but not as low as has been recorded at an Antarctic locality. Most individual colonists (80–93%) were polychaetes (Spirorbis tridentatus) but most of the species were bryozoans. The Arctic is widely described as taxon poor compared with elsewhere, but at the local scale we investigated, species richness (20) was as high or higher than in many similar colonisation studies along the north Pacific or Atlantic coasts. In striking contrast, no settlement panel study has yielded fewer higher taxa (2 phyla, 3 classes) than this high arctic study.