Effects of acute copper contamination on photosynthesis and biomass of periphyton determined with pulse amplitude modulated fluorescence

Summary

Shotr-term toxicity tests were performed on micro-phytobenthos from a branch of the Rhine river. The effects of copper (Cu) on photosynthesis were monitored using a PAM fluorometer. Photosynthetic efficiency (φ_PSII) was used to determine the effect level (EC₅₀) for the added CuCl₂. Suspended particles in the river water played an important role in lowering the copper toxicity for the microalgae; the structure of the biofilm also played a protective role against copper. Cu induced a fast degradation of chlorophyll, shown by the decrease of the fluorescence in the dark, in accordance with HPLC-determined pigments, which also showed a rapid destruction of the accessory pigments.