Importance of wave and current exposure to fauna communities in Laminaria hyperborea kelp forests

Abstract

Hydrodynamic forces from waves and currents may have strong but different impacts on benthic diversity. In order to study the relative importance of current and wave expo- sure to the diversity of macrofauna associated with the kelp Laminaria hyperborea, we sampled fauna on epiphytic algae of 4 different morphological types from 27 stations in a crossed design with 3 levels of wave exposure and current speed. Fauna species number (S) was determined by morphology and amount (weight) of epiphyte and the interaction between wave exposure and current speed. Shannon-Wiener diversity H ' was determined by the epiphyte morphology and amount and degree of wave exposure. The most important factors for faunal community composi- tion were epiphyte morphology and wave exposure, and the effect of wave exposure was different for algae of different morphology. The most diverse fauna communities were found at intermit- tently wave-exposed sites and on large, rough epiphytic algae. The study shows that waves and currents influence kelp fauna communities very differently. Within our study area, waves had a stronger overall effect compared to currents.