Ecophysiological Responses of the Intertidal Seaweed Fucus Distichus to Temperature Changes and Reduced Light Driven by Tides and Glacial Input

Climate change is influencing the performance and distribution of macroalgae in the marine environment. Although intertidal seaweeds successfully adapt to extreme and rapid abiotic changes, exposure to persistent or prolonged potentially stressful conditions can affect their vitality and productivity. Rapid glacial melt can severely alter seawater physicochemical characteristics for shallow and intertidal seaweed communities on the Alaskan coasts. Understanding how intertidal macroalgae respond to this complex mosaic of stressors is key to assessing their ability to adapt to a climate change scenario. This study assessed whether specific stress responses and acclimation mechanisms were exhibited by the intertidal brown seaweed Fucus distichus subsp. evanescence may enable it to cope with changing temperatures and reduced light availability linked to tides and glacial inputs. We analyzed its physiological performance, including photobiological variables, nutrient content, nitrate uptake, and oxidative stress descriptors under strictly controlled laboratory conditions. Results show that this subspecies of Fucus distichus may be relatively unaffected by changes in light and temperature driven by glacial melt due to the presence of pre-adapted strategies that collectively express wide physiological tolerances. Outcomes provide insights into some of the mechanisms of stress tolerance of this major structuring seaweed across the Alaskan coast. Nonetheless, glacial melt would also lower salinity in coastal water, potentially resulting in osmotic stress and other physiological effects not explored here.