ANTROPOGEN PÅVERKAN OCH REGIONAL VARIATION I BIODIVERSITETEN HOS EUROPEISKA MAERLBÄDDAR

Sammanfattning

Maerl beds consist of free-living red coralline algae that create structurally complex and three dimensional habitats on the seabed. Maerl beds occur across large parts of the world, with occurrences along Europe’s western coastlines and in the Mediterranean Sea. By creating substrates on sea bottoms, the beds provide habitats for many associated species, making them hotspots for biodiversity. At the same time, maerl has a slow growth rate, which makes maerl beds vulnerable to anthropogenic disturbances such as bottom trawling, dredging, maerl extraction, eutrophication and organic enrichment among other things. In this study, data from the BIOMAERL-project from the late 1990s was used to analyze the biodiversity of invertebrates in European maerl bed, with a focus on species richness and species composition. The dataset consisted of species-level occurrence-data from control and impacted sites in six different European regions. Differences in species richness and species composition between sites and regions were studied using statistical tests and visual analyses. The results indicate that anthropogenic disturbances can affect biodiversity in European maerl beds, mostly though lower species richness of invertebrates in impacted sites compared with control sites. However, no significant difference in species composition could be detected between types of sites. This suggests that the effect of anthropogenic impact was primarily visible in the number of unique species, rather than a systematic and consistent change in which species occurred. In contrast, species composition varied significantly between European regions, indicating that regional factors are of great importance for the faunal community in maerl beds. Despite increased measures of protection and management in recent decades, status assessments show that maerl beds remain exposed to threats. This, together with the results of this study, highlights the need for continued research and conservation efforts to preserve maerl beds and their associated biodiversity.