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Chlorophyll-a fluorescence allows detection of rapid alterations in the photosynthetic activity of biofilms


The researcher at the University of Girona Natàlia Corcoll has focused her thesis on assessing the appropriateness of using chlorophyll-a fluorescence parameters in biofilms as biomarkers for metal toxicity. The researcher has found that in many European rivers zinc is found in concentrations that have negative effects on the biofilm.

Heavy metals contamination in river ecosystems is an environmental problem of great concern and it is mainly linked to industrial and urban activities that take place in river basins and that can severely alter the ecological condition of rivers. Biofilms, known as good biological indicators of rivers, are complex communities composed of algae, cyanobacteria, bacteria and fungi living on river cobbles and playing a major role in primary production and self-purification capacity of rivers.

In this context, the thesis of the researcher at the University of Girona (UdG) Natàlia Corcoll has focused on assessing the appropriateness of using chlorophyll-a fluorescence parameters in biofilms as biomarkers for metal toxicity. The researcher has also assessed the cause-effect relationships between metal contamination and the effects on the structure and function of fluvial biofilms. Chlorophyll-a fluorescence parameters allow to estimate the photosynthetic activity of algae and cyanobacteria living in biofilms.

Riou Mort and Riera d’Osor
The ecotoxicological studies with biofilms were performed under experimental conditions in a microcosm (by means of artificial canals) and in rivers contaminated with zinc such as the Riou Mort river in France and the Riera d’Osor stream in Catalonia. Working with biofilms has allowed performing studies of ecotoxicology of communities which have a much higher ecological relevance than standard toxicity tests performed with algal monocultures.

Natàlia Corcoll’s thesis, entitled “The use of pulse amplitude modulated fluorescence of techniques for metal toxicity assessment in fluvial biofilms”, proves that chlorophyll-a fluorescence parameters allow detection of alterations caused by the toxicity of zinc a few hours after its exposure, both in the laboratory and in contaminated rivers.

The researcher has also proved that, in artificial rivers, chlorophyll-a fluorescence parameters allow to assess structural changes in the photosynthetic apparatus and in the composition of algal groups when biofilms are exposed to toxic concentrations of zinc for several weeks. So as to assess the effects of chronic metal contamination in rivers, the researcher recommends performing on-the-spot experiments of biofilm translocation and using a multi-biomarker approach including chlorophyll-a fluorescence parameters.

Negative effects of zinc
In this thesis, Natàlia Corcoll has found that zinc has adverse effects on the structure and function of biofilms in concentrations which are found in many European rivers such as the Osor stream, where the biofilm shows a strong impact caused by the discharges from the old mines located in the area. For this reason, the researcher recommends its restoration.

The results of this thesis, directed by Dr. Helena Guasch Padró (University of Girona) and Dr. Manel Leira Campos (University of Lisbon), have been published in internationally recognized scientific journals and books.


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