Photosynthesis and photoinhibition at low temperatures: D1-turnover in Antarctic rhodophytes

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Performing photosynthesis under high light but low temperature conditions poses the problem of slowed down enzymatic reactions and increased generation of reactive oxygen species. However, these are the abiotic conditions, macroalgae from Antarctica are usually exposed to during the Antarctic spring/summer season. In this project, the interactive effects of high light and low temperature will be evaluated in laboratory and field experiments on endemic Antarctic rhodophytes. During the previous expedition marked interactive effects under low temperature (0 °C) and high light conditions were found on photosynthesis of Palmaria decipiens. The maximum electron transport rate (ETRmax) decreased under high PAR (400μmol photons m-2s-1) and 0°C whereas ETRmax was more or less constant at 8° C compared to initial values. The following steps of investigation during the ongoing second and the applied third year of funding will focus on the generation and scavenging of reactive oxygen species, as well as the related damage and turnover of the reaction centre protein of photosystem II (D1). Moreover, changes in the abundance of D1 will be related to species-specific lipid composition and expression of psbA genes encoding for D1. Furthermore, the effect of salinity changes due to increased glacier melting will be included as an additional factor modulating physiological responses. This will add new information on both algal physiology and polar ecosystem function.