Soft-bottom macro invertebrate fauna of North Norwegian coastal waters with particular reference to sill-basins. Part one: Bottom topography and species diversity

The soft bottom macrofauna of three fjords in Northern Norway is presented and compared. One fjord is open, with gradually decreasing water depth from mouth to head, and two fjords possess shallow sills, splitting the fjords into two and three basins respectively. The most southerly samples were collected from Rombaken in the innermost part of the Vestfjord, at approximately 68 degrees 23' N; 17 degrees 32' E, close to the city of Narvik. The northernmost samples were collected from Akkarfjord at 70 degrees 46' N; 23 degrees 25' E, near North Cape, Europe's northernmost tip. The ten numerically most abundant taxa at each station are listed, together with a description of bottom topography, sediment composition and the extent of anthropogenic impact on the fjord. Data are presented on species diversity related to water depth, sedimentary TOC content and presence/absence of shallow sill(s). The dominant faunal groups present are the Polychaeta and Mollusca. In sill basins echinoderms are absent or poorly presented. Species composition generally appears to be most influenced by bottom topography and sediment composition. Waste discharge appears to have only local effects on the faunal assemblages investigated. The TOC content of the bottom sediments tends to increase from exposed, outer parts to the landward parts near the head of the fjord basins. Faunal diversity decreased from open areas (mouth of fjords) towards the sill basins.