Year‐to‐year variability of epifaunal assemblages on a mobile hard substrate—Case study from high latitudes

Abstract Past polar regional studies on temporal trends of benthic systems have mostly been performed on soft bottom communities. Fewer studies have dealt with hard bottom, and none have been performed with mobile hard substrates, yet these are common, abundant and host high biodiversity—usually higher than similar substrates even if the latter were larger in size. In this study, we analysed the variability of epifaunal assemblages on a mobile hard substrate ( Buccinum sp. and Littorina sp. shells utilized by hermit crab Pagurus pubescens ) collected annually during 5 years (2005–2009) in Spitsbergen Island (Svalbard Archipelago, 78° N) and Northern Norway (68° N). The epifaunal assemblages were variable over the observed period, with differences in abundance, diversity ( S , H′ ) and assemblage structure. Among the species that contributed the most to the observed differences were barnacle Semibalanus balanoides , serpulid polychaetes ( Circeis armoricana , Spirobranchus triqueter ) and foraminiferans ( Discorbis rosacea , Lobatula lobatula ), which dominate the assemblages. Analyses indicated that epifauna found on hermit crab shells is mostly influenced by environmental effects linked to NAO, its seasonal values (esp. winter), sometimes lagged. Strong changes were coinciding with a NAO phase shift. Years with positive NAO tend do have higher number of species, abundance and diversity. Differences between Spitsbergen and Northern Norway are most likely driven by geographic setting of the sites and its implications (e.g., hydrography). By exploring the sensitivity to large‐scale climate variability and its direct consequences, the study helps assess the potential of environment monitoring through hermit crabs epifauna. It provides also a baseline data allowing comparative, or after disturbance, studies in future.