Development of photosynthetic biofilms affected by dissolved and sorbed copper in a eutrophic river

• Published in: Environmental toxicology and chemistry 2002-09, Vol.21 (9), p.1955-1965
• Main Authors: Barranguet, Christiane, Plans, Marc, Van Der Grinten, Esther, Sinke, Jan J., Admiraal, Wim
• Format: Article
• Language: English
• Subjects: Adsorption; Algae; Animal, plant and microbial ecology; Applied ecology; Bacillariophyceae; Biofilms; Biofilms - drug effects; Biological and medical sciences; Biological Availability; Copper - adverse effects; Copper - chemistry; Copper Diatoms; Diatoms - physiology; Ecotoxicology, biological effects of pollution; Effects of pollution and side effects of pesticides on plants and fungi; Eutrophication; Fluorescence; Fresh water environment; Fundamental and applied biological sciences. Psychology; Netherlands, Meuse R; Particle Size; Photosynthesis - drug effects; Photosynthesis - physiology; River Meuse; Solubility
• ISSN: 0730-7268; 1552-8618
• DOI: 10.1002/etc.5620210925

Photosynthetic biofilms are capable of immobilizing important concentrations of metals, therefore reducing bioavailability to organisms. But also metal pollution is believed to produce changes in the microalgal species composition of biofilms. We investigated the changes undergone by natural photosynthetic biofilms from the River Meuse, The Netherlands, under chronic copper (Cu) exposure. The suspended particles in the river water had only a minor effect on reduction of sorption and toxicity of Cu to algae. Biofilms accumulated Cu proportionally to the added concentration, also at the highest concentration used (9 μM Cu). The physiognomy of the biofilms was affected through the growth of the chain‐forming diatom Melosira varians, changing from long filaments to short tufts, although species composition was not affected by the Cu exposure. The Cu decreased phosphate uptake and algal biomass measured as chl a, which degraded exponentially in time. Photosynthetic activity was always less sensitive than algal biomass; the photon yield decreased linearly in time. The protective and insulating role of the biofilm, supported by ongoing autotrophic activity, was indicated as essential in resisting metal toxicity. We discuss the hypothesis that the toxic effects of Cu progress almost independently of the species composition, counteracting ongoing growth, and conclude that autotrophic biofilms act as vertical heterogeneous units. Effective feedback mechanisms and density dependence explain several discrepancies observed earlier.