Efectes d’un gradient de salinitat en l’estructura i el funcionament del biofilm epilític en una riera salada

Torres i Roig, Meritxell
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The Riera Salada is an aquatic ecosystem characterized by having a high content of dissolved salts in some sections which come sediment basin where drift. The closest site to the birth of the stream has been sampled has a conductivity of 43.53 mS/cm and most distant (about 4 km downstream) of 0.60 mS/cm respectively. The objective of this study was to analyze the effect of the salinity gradient on the biomass of different microbial groups (bacteria, algae and fungi) that form the stream epilithic biofilm. It also focused on determining its function by analyzing the enzymatic activities (phosphatase, β-gluco-sidase and leucineaminopeptidasa) that carried out bacteria, fungi and algae in order to compare whether there is a relationship between the function and structure of this biofilm. To reinforce the ob-tained data were analyzed the water nutrients and the dissolved organic matter (MOD). It has been found that the composition of the microbial groups in % has been favored by the algae, which has been the group most represented at each site, then by bacteria and finally the fungi. The results determined that there is an inhibition of microbial biomass micro-by salinity, being algae and bacteria, the most affected groups, and fungi, the group has presented more resistance throughout the gradient. However, in the section with higher salinity has been observed that there was a high microbial biomass due to the high content of nutrients because in this site there is a local eutrophication that probably counteracts the effect of salinity. Regarding the role of biofilms determined by the enzymatic activity has been seen that these were not seen very affected by the salinity gradient, being the β-glucosidase the most sensi-tive and less sensitive the phosphatase. Finally, leucineaminopeptidasa also presents certain relation-ship with the salinity but also is related nitrate content of the medium. The results suggest changes in the composition of microbial biofilm along the gradient studied, and therefore, further studies would be interesting to analyze microbial diversity and richness to see which species can be more or less re-sistant to salinity ​
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