Interactive effects of temperature and copper on photosystem II photochemistry in Chlorella vulgaris.

In natural aquatic ecosystems, temperature conditions may undergo changes depending on the depth of the water column or micro-environmental conditions. In this study, copper effect on the photosynthetic performance of Chlorella vulgaris was investigated at different temperatures by using chlorophyll a fluorescence transients and fluorescence imaging parameters. Copper as a pollutant is known to be an inhibitor of photosystem II (PSII) photochemistry; therefore it was important to know how the change of temperature may alter this effect. PSII photochemistry was investigated when C. vulgaris, affected by different copper concentrations, was exposed to 24, 28 and 31 °C. Increase of temperature induced higher alterating effects to PSII quantum yield, primary photosynthetic electron transport from water splitting system and consequently higher decrease of total photosynthetic performance if compared to copper effect alone. Additional temperature effect to copper inhibition increased energy dissipation via non-photochemical pathway. In this study we indicated that, when C. vulgaris changes temperature conditions, inhibitory effect of copper also undergoes changes. For natural aquatic system we may suppose, when algae are distributed at different depths of water column, that toxicity effect will be dependent to the temperature conditions of the site.