Comparison of tropical, temperate and arctic coastal, soft-bottom regions

Local diversity (alpha diversity) of macrobenthos in tropical, temperate and arctic soft-bottom regions was investigated. Macrobenthos are here defined as animals retained on a1mm sieve. Species abundance data from the Pechora Sea (arctic), the Oslofjord (temperate) and Espiritu Santo (tropical) were used in the analyses. Six sites were selected in each of the three regions and the depth ranged from 11 m to 94 m. The Pechora Sea had the highest species richness with 182 taxa, followed by Espiritu Santo (170 taxa) and the Oslofjord (80 taxa). Polychaeta was the most abundant group and had the highest number of taxa in all three regions. The multivariate methods revealed differences in composition of fauna at family level between the three regions probably due to geographical position. Espiritu Santo had the highest species diversity (measured as 1/ Simpson) and greatest evenness (measured as J´), followed by the Pechora Sea and the Oslofjord. Espiritu Santo and the Pechora Sea were not statistical different from each other when diversity was measured as species richness (S) and Shannon-Wiener (ExpH´). The Oslofjord had lowest diversity for all indices applied. The heterogeneity indices applied gave additional information than what could be obtained by species richness alone. The results clearly illustrated that applying species richness as an only measure of diversity had limited value. Espiritu Santo had highest “true” species richness (measured as Chao 1) followed by the Pechora Sea and the Oslofjord. The curve for Espiritu Santo differed from the Pechora Sea and the Oslofjord by being steeper indicating that a greater sampling effort is needed for adequately sample all the species in this region. In all three regions species abundances were strongly right skewed, and most of the species were found within the two first bins. Espiritu Santo had highest number of singletons and few species occurred with more than 15 individuals. This study revealed differences in local diversity between tropical, temperate and arctic coastal, soft-bottom regions. As predicted, highest diversity was observed in Espiritu Santo. Lowest species richness and species diversity were found in the Oslofjord probably due to physical conditions that exist there. In addition nutrient loading from the land and limited water exchange may have a great effect on the composition of fauna. The high species richness and diversity observed in the Pechora Sea indicate that a simple latitudinal