The effect of ultraviolet radiation on cellular ultrastructure and photosystem II quantum yield of Alaria esculenta (L.) Greville from Spitsbergen (Norway)

Abstract

Large brown seaweeds (kelps) represent ecologically important habitats in coastal systems. Along the western shores of the Svalbard archipelago, the kelp Alaria esculenta forms dense stands and provides habitat to a multitude of associated organisms. At the growth site in shallow waters, kelp sporophytes can be exposed to high irradiances of harmful ultraviolet (UV-B) radiation resulting from a thinning of the stratospheric ozone layer over the Arctic. Here, we tested to what extent UV-B-induced impairment of photophysiology is accompanied by changes in the cellular ultrastructure of A. esculenta and characterizes sites of cellular damage after UV exposure. Adverse effects on cellular components mostly manifest in chloroplast thylakoid membrane integrity, which is accompanied by a decrease in maximal quantum yield of photosystem II. At the applied irradiances of UV radiation, A. esculenta is stressed to an intermediate extent confirming its adaptability to a moderately increased UV-B climate.