The Arctic Svalbard archipelago is one hotspot of global warming and Kongsfjorden (W- Svalbard) experiences a continuous increase in seawater temperature, glacial melt, freshwater run-off and sedimentation. In 1996/98, 2012-14 and 2021 seaweed biomass, species diversity and depth distribution of kelps were quantified at our study site in order to identify potential changes over time. We repeated the earlier studies by stratified random sampling along a sublittoral depth transect (0, 2.5, 5, 10 and 15 m; 1x1 m² frames; n=3) and documented the lower depth distribution of kelps at 2-20 m depth. With 21 biomass dominant species collected in 2021, the biodiversity along the depth transect remained stable. In contrast, the lower distribution limit and the relative abundance of all kelp species severely decreased. Between the 1st and 2nd study, the biomass maximum doubled and shifted upwards from 5m to 2.5m depth. Although this pattern did not change in 2021, the community structure shifted from a Laminaria digitata/Hedophyllum nigripes based community to an Alaria esculenta dominated kelp forest. In 2021, Alaria esculenta was the only kelp species present at 10m depth while the other kelps retreated to shallower waters. Comparison of kelp demography in 2013 and 2021 revealed a change in dominance relationships between age classes. Presently, a kelp forest with a balanced age distribution is only found at 2.5m depth. Our time series reveals consequences of increasing turbidity and decreasing light availability for Arctic kelp forests in an environment in transition.