Individuals of solitary specimens were counted (anterior parts) and the biomass of all species weighed (wet). Biomass was included to avoid having to estimate the numbers of individuals in colonial species, and for comparison of solitary and colonial species distributions. The fauna was characterised by total species richness, solitary species richness, individual numbers (solitary species) and biomass (all species). Shannon–Wiener diversity indices were calculated from both the biomass composition of all species and from the abundance

AZD4547 composition of solitary species using the function H′ = Σ (pi × (log2 pi)) where pi is the proportion of the i’th species of the total sample (Krebs 1989). Relationships of the above parameters with aggregation volume were investigated through regression. Since space often is limiting on hard substrate and new additional space colonised immediately (Jackson 1977), linear trend

lines intersecting the origin were used for individual numbers and biomass, which were believed to increase continuously with the additional substrate and cavities provided by larger aggregations. Habitat number is not expected to increase 4SC-202 molecular weight continuously with additional substrate and cavities but rather reach a maximum involving a certain amount of associated species, and geometric trend lines were therefore used for solitary and total species richness regression against aggregation volume. Results In totally 4.4 l of Filograna implexa aggregations (n = 8) we identified 61 solitary species (4663 individuals) and 38 colonial species that weighed 160.3 g together (Table 2). However, many different crustacean specimens were not identified to the species level but rather merged in congregated taxonomic groups (Caprellida, Gammaridea, Isopoda; Table 1, Appendix Table 2), and the total species number was therefore even higher. The Filograna aggregations protruded approximately 10 cm from the substrate and covered in total less than 0.05 m2. The observed species

richness is therefore very high. There were few predominating species. On average, only 16 species were represented by more than three individuals, and eight species with find more more than 0.5 g of biomass per aggregation. This reflects the very high biodiversity within the small aggregations. Only the congregated taxon Gammaridea spp. was present with more than 100 individuals on average per aggregation (Table 1), but these represented many species. The average Filograna aggregate volume was 0.55 l (SE = 0.14), the Shannon–Wiener diversities 2.8 (abundance, SE = 0.29) and 2.7 (biomass, SE = 0.27), the solitary species number 30.4 (SE = 4.0), the total species number 46.9 (SE = 5.6), the individual number 582.9 (SE = 263.1), and the biomass 20.04 g (SE = 5.1) per aggregation. Shannon–Wiener indices varied from low (1.3) to high (3.5), demonstrating from skew to even SB-715992 distributions of species.