|Soft-bottom fauna and oxygen minima in sub-arctic north Norwegian marine sill basins|
Holte, B.; Oug, E.; Dahle, S. (2005). Soft-bottom fauna and oxygen minima in sub-arctic north Norwegian marine sill basins. Mar. Biol. Res. 1(2): 85-96
In: Marine Biology Research. Taylor & Francis: Oslo; Basingstoke. ISSN 1745-1000, more
Benthos; Feeding behaviour; Oxygen demand; ANE, Norway [Marine Regions]; Marine
Marine sill basins are generally characterized by vertically stratified water masses. During periods of water stagnation, the bottom fauna may be severely affected by the depletion of oxygen. In northern Norway, stratification is less and water exchange processes stronger than in topographically similar boreal basins, which would generally imply better oxygen conditions. In this study the soft-bottom macrofauna (> 1 mm) of three northern Norwegian sill basins was examined with respect to species diversity, abundance and functional relationships. Simultaneous data for hydrographical parameters (salinity, temperature, dissolved oxygen) and sediments (total organic carbon, fine fraction) were recorded. All basins were subject to discharges of municipal wastewater. In the basins, the water masses were stratified from spring to late autumn, but apparently freely circulating in winter. During stratification the oxygen content fell to 22-55% saturation in the bottom water. The fauna was generally species rich and diverse, but the number of species was lower than outside the basins. Polychaetes feeding at or just above the sediment surface were numerically dominant. The proportion of detrivorous polychaetes feeding below the sediment surface decreased in relation to oxygen minimum levels. The study suggests that, due to relatively strong water exchange dynamics, northern sill fjords are less vulnerable to organic discharges than more southerly located sill fjords.