http://hdl.handle.net/10854/6222 2026-04-17T10:27:10Z 2026-04-17T10:27:10Z Espinosa, Carme Abril, Meritxell Ponsá Salas, Sergio Ricart, Marta Vendrell Puigmitjà, Lidia Ordeix i Rigo, Marc Llenas, Laia Proia, Lorenzo http://hdl.handle.net/10854/6610 2025-11-28T11:28:54Z 2021-01-01T00:00:00Z

Effects of the interaction between nutrient concentration and DIN:SRP ratio on geosmin production by freshwater biofilms Espinosa, Carme; Abril, Meritxell; Ponsá Salas, Sergio; Ricart, Marta; Vendrell Puigmitjà, Lidia; Ordeix i Rigo, Marc; Llenas, Laia; Proia, Lorenzo The global increase of cyanobacterial blooms occurrence has been associated with the presence of compounds that generate earthy and musty odour in freshwater systems, among which geosmin stands out. The lack of information on the factors associated to geosmin production by benthic organisms has driven the development of this study, whose main goal is to determine the effects of nutrient concentration and DIN:SRP ratio on geosmin formation and release. The experiment was performed in 18 microcosms under controlled conditions for 21 days, using a natural biofilm suspension from Ter river (NE, Spain) to promote biofilm settlement. Six treatments were set crossing three DIN:SRP ratios (A = 4:1, B = 16:1 and C = 64:1) with two nutrient concentrations (Low and High). After 7 days of experiment, geosmin was detected in biofilm, being higher under high nutrient concentration and low DIN:SRP ratio conditions. In this treatment, geosmin in biofilm reached its maximum concentration at day 16 (3.8 ± 0.9 ng/mg), decreasing at the end of the experiment (21d) due to cyanobacteria detachment and geosmin release into the water (136 ± 6 ng/L). Overall, this experimental study showed that high nutrient concentration and low DIN:SRP ratio favoured the Oscillatoria genus development within biofilm communities, generating the optimal conditions for geosmin production. The interaction between these two factors was demonstrated to be a potential driver of benthic geosmin production and release, and should be monitored and controlled in rivers exploited for drinking water purposes.

2021-01-01T00:00:00Z Espinosa, Carme Abril, Meritxell Guasch, Helena Pou, Núria Proia, Lorenzo Ricart, Marta Ordeix i Rigo, Marc Llenas, Laia http://hdl.handle.net/10854/6224 2025-11-28T11:29:02Z 2020-01-01T00:00:00Z

Water Flow and Light Availability Influence on Intracellular Geosmin Production in River Biofilms Espinosa, Carme; Abril, Meritxell; Guasch, Helena; Pou, Núria; Proia, Lorenzo; Ricart, Marta; Ordeix i Rigo, Marc; Llenas, Laia Hydro-morphological alterations in water bodies caused by climate change and human activities affects the ecosystem functioning and generate important water quality problems. Some of these alterations can generate an increase in cyanobacterial blooms, which are associated with the appearance of bad taste and odorous compounds such as geosmin. The factors that trigger their production are still unclear, and this inability to predict geosmin episodes provokes economic problems for water supply companies. This study aims to evaluate the effects of water flow and light availability on biofilm development and intracellular geosmin formation. A mesocosm experiment was performed between February–April, 2019. The mesocosms were a set of 10 outdoor 3 m long flumes, with a continuous water supply from the Ter river (Catalonia, NE Spain). Two light intensities were established: natural light and light reduced to 80%, combined with five gradual water flows from 0.09 to 1.10 L/s. Water samples were taken to analyze nutrients, and biofilm samples, to analyze geosmin concentration, chlorophyll a and the community. Geosmin in biofilm was detected in those treatments in which Oscillatoria sp. appeared. The concentration of intracellular geosmin was higher at lower water flows (0.09 and 0.18 L/s), and the highest (2.12 mg/g) was found in the flume with the lowest water flow (0.09 L/s) and irradiation (20%). This flume was the one that presented a greater concentration of Oscillatoria sp. (21% of the community). It stands out that, when geosmin in biofilm was found, the dissolved inorganic nitrogen and soluble reactive phosphorus ratio decreased, from an average of 417:1 to 14:1. This was mainly due to an increase in inorganic phosphorus concentration generated by a change in the nutrient uptake capacity of the community’s biofilm. The results obtained in this study indicated the potential implications for stream ecosystem management to control geosmin appearance. Likewise, they could be used as an early warning system, establishing that in times of drought, which lead to a general decrease in river water flow, the situation could be optimal for the appearance and development of geosmin producing cyanobacteria in low-flow areas near the river banks.

2020-01-01T00:00:00Z