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

Abstract

The soft bottom macrofauna of three fjords in NorthernNorway is presented and compared. One fjord is open,with gradually decreasing water depth from mouth tohead, and two fjords possess shallow sills, splittingthe fjords into two and three basins respectively. Themost southerly samples were collected from Rombaken inthe innermost part of the Vestfjord, at approximately68° 23′ N; 17°32 ′ E, close to the city ofNarvik. The northernmost samples were collected fromAkkarfjord at 70° 46′ N; 23°25 ′ E, nearNorthCape, Europe's northernmost tip.The ten numerically most abundant taxa at each stationare listed, together with a description of bottomtopography, sediment composition and the extent ofanthropogenic impact on the fjord. Data are presentedon species diversity related to water depth,sedimentary TOC content and presence/absence ofshallow sill(s). The dominant faunal groups presentare the Polychaeta and Mollusca. In sill basinsechinoderms are absent or poorly presented. Speciescomposition generally appears to be most influenced bybottom topography and sediment composition. Wastedischarge appears to have only local effects on thefaunal assemblages investigated. The TOC content ofthe bottom sediments tends to increase from exposed,outer parts to the landward parts near the head of thefjord basins. Faunal diversity decreased from openareas (mouth of fjords) towards the sill basins.