Abstract
This study was conducted as part of a kelp forest project which aim is to acquire knowledge about biodiversity and productivity in kelp forest areas. The epiphytic algae associated with the stipe of Laminaria hyperborea (Gunnerus) Foslie are important as habitat and food source for numerous faunal species along the Norwegian coastline. My investigations were performed on samples taken from kelp stipes in the area of Finnøy, Norway, in April, June, September and November 2005. I address questions of how the epiphytic community structure and primary production relates to a gradient of wave exposure, and the seasonal aspects of these relationships were also brought into the analyses. Both univariate and multivariate statistical methods were used in this approach. The amount of biomass found on a stipe was first of all related to the length of the stipe, and stipe lengths increased with increasing levels of wave exposure. A definite peak in total biomass was found in September. The species composition of epiphytes on the kelp stipes showed variation with increasing exposure. However, the variation within sites with the same index of exposure was also very high, suggesting that differences on a smaller scale may be of great importance. Differences in the species composition between sampling periods were also found. I conclude that both epiphyte species composition and productivity in kelp forest areas are affected by wave exposure, or some factors related to wave exposure, and that the structures of these epiphytic communities change through the season.