Similarity in phytoplankton photophysiology among under-ice, marginal ice, and open water environments of Baffin Bay (Arctic Ocean)

Abstract

As sea ice is declining rapidly in the Arctic, phytoplankton are being exposed to very different light regimes. Here we investigated how phytoplankton photoacclimate in three different irradiance regimes: under the ice, in the marginal ice zone, and in open water. We sampled from these three regimes in spring-summer 2016 during the Green Edge cruise in Baffin Bay. We also conducted experiments to investigate the impact of short-term surface light exposure on phytoplankton photophysiology, focusing on processes related to photoprotection and photodamage. These experiments were designed to simulate phytoplankton mixing to the surface or sea ice rapidly disappearing. Despite differences in hydrography, nutrient concentrations, light conditions, and phytoplankton biomass in each regime, the phytoplankton community was similar in terms of photophysiological state. Photoprotective pigments (including the xanthophyll cycle) were high in all three regimes sampled. As with the in situ measurements, ice conditions and light history had little impact on how phytoplankton responded to high light exposure, leading us to conclude that phytoplankton are largely prepared for a high light transition, even when originating from low light environments under sea ice.