Seasonal ecophysiology of <i>Fucus vesiculosus</i> (Phaeophyceae) in the Northern Baltic Sea

The brown macroalga Fucus vesiculosus is a foundation species in temperate rocky shores, subjected to seasonally fluctuating environmental conditions. To obtain more complete picture of the seasonality F. ecophysiology northern Baltic Sea, situ photochemistry, elemental ratios and chlorophyll c content alga were investigated field campaigns conducted different months throughout year during 2017. Carbon, nitrogen, carbon nitrogen ratio varied substantially year, with highest observed summer, winter. C:N apical tissue ranged from 8.6 February 48.3 July. Chlorophyll followed inversely seasonal patterns ambient irradiance. High winter was associated higher maximum photosynthetic efficiency energy conversion (Fv/Fm), but not under light limitation (?). Electron transport rate correlated strongly seawater temperature, electron rates summer internal alga. Redundancy analysis on measured variables against physiological responses identified day temperature macronutrients as most important driving ecophysiology. results suggest elevated temperatures may increase growth photosynthesis study area.Highlights Two distinct states identified.The season, macronutrients.Fucus shows substantial Sea.