5. Conclusion
In this novel Arctic time series,
we report considerable changes in kelp forest dynamics over the past 25
years in Kongsfjorden on Svalbard which are likely the result of global
climate change. At our study site kelp demography, biomass and species
dominance along the depth transect were influenced by the prevailing
counteracting environmental drivers related to Arctic warming (Schlegel
et al., 2023). In contrast to proposed assumptions (Assis et al., 2022;
Krause-Jensen et al., 2012; Krause-Jensen & Duarte, 2014) we observed a
decrease of depth expansion of the investigated kelp forest despite its
release from ice scouring pressure and shading by thick sea ice
coverage. The documented retreat of the kelp forest to the uppermost
depth level reflects the decline of key engineer species exposed to
coastal darkening with potentially large impacts on all associated
higher trophic levels. As kelp communities represent complex marine
ecosystems our investigation aims to serve as an example study that
quantifies the negative consequences of increasing glacier loss (Geyman
et al., 2022) to facilitate future predictions for wider stretches of
Arctic coastline. We propose that in Arctic fjord systems influenced by
strong melt water runoff, kelp forest communities will decline further
as long as glaciers retreat and coastal darkening intensifies. The
effects of the rapidly shrinking Arctic cryosphere on marine primary
producers and their highly valuable ecosystem services are extensive and
will continue in a changing future Arctic.