The identification of macroalgal beds is a crucial component for the description of fjord ecosystems. Direct, biological sampling is still the most popular investigation technique but acoustic methods are becoming increasingly recognized as a very efficient tool for the assessment of benthic communities. In 2007 we carried out the first acoustic survey of the littoral areas in Kongsfjorden. A 2.68 km2 area comprised within a 12.40 km2 euphotic zone was mapped along the fjord's coast using single- and multi-beam echosounders. The singlebeam echosounder (SBES) proved to be a very efficient and reliable tool for macroalgae detection in Arctic conditions. The multibeam echosounder (MBES) was very useful in extending the SBES survey range, even though it's ability in discriminating benthic communities was limited. The final result of our investigation is a map of the macroalgae distribution around the fjord, showing 39% macroalgae coverage (1.09 km2) of investigated area between isobaths -0.70 m and -30 m. Zonation analysis showed that most of the studied macroalgae areas occur up to 15 m depth (93%). These results were confirmed by biological sampling and observation in key areas. The potential of acoustic imaging of macrophytes, and a proposed methodology for the processing of acoustic data, are presented in this paper along with preliminary studies on the acoustic reflectivity of macroalgae, also highlighting differences among species. These results can be applied to future monitoring of the evolution of kelp beds in different areas of the Arctic, and in the rest of the world.

Lacydonia (Polychaeta: Phyllodocida) is a poorly known genus containing 16 species that are sporadically collected in low densities all over the world oceans. During three cruises (in June 2014 in Ullsfjorden, northern Norway, in January 2015 in Kongsfjorden, and in June 2012 in Smeerenburg, Svalbard) nine specimens of Lacydonia eliasoni were found on sandy and muddy sediments at depths from 180 to 350 m. All specimens were incomplete and consisted of 10 to 29 chaetigers. This study presents the first record of the Lacydonia genus in the waters of Svalbard as well as the first record of L. eliasoni in coastal waters off northern Norway. This species has been reported previously in the Skagerrak and Trondheimsfjorden (southern Norway), our findings therefore may indicate a northward extension of its range, possibly due to climate changes.