Quantitative macroalgae survey and kelp morphometry data collected at Hansneset, Kongsfjorden, Spitsbergen in 2021

Surveys were performed for macroalgae fresh biomass, dry biomass, leaf area index and kelp morphometry at Hansneset, Blomstrand in Kongsfjorden, Svalbard, from the infralittoral fringe down to 15 m depth in June - August 2021. This dataset is part of a time series currently spanning over 25 years and complements the studies conducted in 1996/98 (Hop et al., 2012, doi:10.1515/bot-2012-0097) and 2012-14 (Bartsch et al., 2016, doi:10.1007/s00300-015-1870-1). The aim was to document changes in Arctic kelp forests dynamics in an Arctic fjord system influenced by glacial melt by repeatedly sampling the same site in a standardized manner. As ocean temperatures in the Arctic have risen substantially and underwater light climate continuously deteriorated over this time period, alterations were observed in the seaweed community, especially kelps as major coastal foundation species.