AUTHOR=Wiktor Józef M. , Tatarek Agnieszka , Kruss Aleksandra , Singh Rakesh Kumar , Wiktor Józef M. , Søreide Janne E. 

TITLE=Comparison of macroalgae meadows in warm Atlantic versus cold Arctic regimes in the high-Arctic Svalbard

JOURNAL=Frontiers in Marine Science

VOLUME=Volume 9 - 2022

YEAR=2022

URL=https://www.frontiersin.org/journals/marine-science/articles/10.3389/fmars.2022.1021675

DOI=10.3389/fmars.2022.1021675

ISSN=2296-7745

ABSTRACT=A warmer Arctic with less sea ice will likely improve macroalgae growth conditions, but observational data to support this idea is scarce. In this study, we combined hydroacoustic and video inspections to compare the depth of growth, density and thickness of macroalgae (>10 cm) meadows in two contrasting climate regimes in Svalbard 1) the warm, ice free, Atlantic influenced West Spitsbergen and 2) the cold, Arctic and seasonal ice covered East Spitsbergen.  Both places have similar insolation and comparable turbidity levels. Macroalgae communities at both places were similar and were formed mainly by common north Atlantic kelp species: Saccharina latissima, Alaria esculenta, Laminaria digitata and L. hyperborea. However, the density of the bottom coverage and thalli condition were strikingly different between the two sites. High-Arctic kelp species Laminaria solidongula was observed solely on the colder site. Algae at the warmer site were intact and fully developed and occupied most of the available hard substrate. At the colder site, only patchy macroalgae canopies were found and most thallies were physically damaged and trimmed at an uniform height due to physical ice scouring. These differences in macroalgal density and thalli condition were only found at depths down to 5 m. Deeper, no distinct differences were observed between the warm and cold sites. Sea urchins were only observed at the warm site, but in few numbers with no visible negative top-down control on macroalgae growth. In a future warmer Arctic, the macroalgae will experience less physical constraints in the upper 5 m and expand its growth here if not grazing by sea urchin will increase and severely constrain macroalgae growth as seen at lower latitudes in the Arctic.