Influència de l'estrès múltiple sobre cianobacteris productors de geosmina

Abstract

The main cyanobacteria that produces geosmin in freshwater ecosystems is Oscillatoria sp.. Geosmin is a molecule with organoleptic features without harmful effect on humans, but it produces a nuisance odour on spring seasonally. Determining the environmental conditions in which this organism appears will be useful to avoid the problem before it starts. This study aims to check the effect of light and water velocity on Oscillatoria sp. trough experimental channels. The advantage of those in front of in situ experiments is that the variables can be modified. The channels, located in Manlleu in the CERM-UVic centre, received water directly from the Ter river, where previously other studies had found geosmin. To define the effect of the choosen factors, cyanobacteria and algae identification, counting and measurement were performed using an optical microscope. The obtained data was converted to biovolume to obtain an easy interpretation, and they were analysed with RStudio program. The photonic efficiency experiment was also performed in the laboratory to verify the photosynthetic production of the biofilm in different known light intensities. Due to the latter results, we had learned under which treatments Oscillatoria sp. growth is favourable, and by exposing all the biofilm samples to a light intensity range and measuring its photonic efficiency, the P/I curves were elaborated. Those results will describe their production under each light intensity. With the obtained results, we can define the light and water velocity conditions favourable to Oscillatoria’s growth. Specifically it was confirmed that its presence is significant in low light and low velocity conditions. Also it wasn’t expected the significant growth in high light and 1m/s water velocity conditions. Although its photosynthetic production is anomalously low, compared to other treatments in the first favourable conditions described. This may be the reason that leads Oscillatoria sp. to produce geosmin