Differential acclimation responses to irradiance and temperature in two co-occurring seaweed species in Arctic fjords

Arctic fjord systems experience large amplitudes of change in temperature and radiation regime due to climate warming the related decrease sea ice. The resultant increase irradiance entering water column influences photosynthetic activity benthic pelagic primary producers. subtidal brown alga Desmarestia aculeata and intertidal red alga Palmaria palmata populate cold-temperate coasts North Atlantic, reaching polar zone. To evaluate their acclimation potential, we collected both species Kongsfjorden, Svalbard (78.9°N, 11.9°E), during summer exposed specimens two different PAR levels (50 500 μmol photons m−2 s−1) temperatures (0, 4 8 °C) for 21 days. Photosynthetic parameters biochemical features (pigment concentration antioxidants) were assessed. In general, high was factor that generated a negative effect for D. aculeata and P. palmata in photosynthesis–irradiance curve and Fv/Fm. pigment tended with increasing irradiance. Antioxidant level showed trends species: in D. aculeata, antioxidant potential increased temperature, while in P. palmata, it only Both responses interaction although D. aculeata was more sensitive than P. palmata. Our study shows how these species, which have similar geographical distribution Atlantic but belong taxonomic lineages, strategies acclimation, although they respond differently ecophysiological parameters.