Absence of photophysiological response to iron addition in autumn phytoplankton in the Antarctic sea-ice zone

Abstract. The high nutrient–low chlorophyll condition of the Southern Ocean is generally thought to be caused by low bioavailability micronutrients, particularly iron, which plays an integral role in phytoplankton photosynthesis. Nevertheless, experiences seasonal blooms that initiate austral spring, peak summer, and extend into autumn. This increase primary productivity typically linked characteristics nutrient light supply. To better understand potential limitations on Antarctic sea-ice zone (SIZ), photophysiological response iron addition (2.0 nM FeCl3) was investigated during autumn along coast off Dronning Maud Land. Five short-term (24 h) incubation experiments were conducted around Astrid Ridge (68∘ S) a 6∘ E transect, where bloom identified region western SIZ. Surface concentrations ranged from 0.27 1.39 Ridge, 0.56 0.63 transect. Contrary expectation, addition, measured through photosynthetic efficiency absorption cross-section for photosystem II, showed no significant responses. It thus proposed since SIZ exhibited lack limitation at time sampling, ambient may have been sufficient fulfil cellular requirements. provides new insights extended replete post-bloom conditions assumed deficient Ocean.