Arsenic toxicity effects on microbial communities and nutrient cycling in indoor experimental channels mimicking a fluvial system

Abstract

The toxicity of chemicals in the environment is influenced by many factors, such as the adsorption to mineral particles, active biological surfaces, biotransformation and/or nutrient concentration. In the present study, a simplified fluvial system including fish, periphyton and sediment was used to investigate the fate and effects of environmentally realistic concentration of arsenic (As) on biofilm growth and nutrient cycling. Total dissolved arsenic concentration decreased exponentially from 120 μg/L to 28.0 ± 1.5 μg/L during the experiment (60 days), mostly sinking to the sediment and a smaller percentage accumulated in the periphytic biofilm. Most P and N, which was provided by fish, was also retained in the epipsammic biofilm (growing on sediment grains). We conclude that exposure to this concentration of arsenic under oligotrophic conditions is changing the quality and quantity of the base of the aquatic food chain and its respective contribution to nutrient cycling, and normal functioning of the ecosystem. The effects include lowering the total biomass of biofilm and its potential ability to use organic P (i.e., phosphatase activity), inhibiting algal growth, especially that of diatoms, decreasing nitrogen content, and making the epipsammic biofilm more heterotrophic, thus reducing its ability to oxygenate the aquatic environment

Financial support was provided by the Spanish Science and Education Ministry (Project CTM2009-14111-CO2-01 and the Spanish Economy and Competitiveness Ministry (Project CGL2013-43822-R). Baigal-Amar Tuulaikhuu benefitted for a doctoral fellowship from the Techno 2 Program of the European Union ErasmusMundus partnership. Thanks to Kit Magellan for providing the fish and giving recommendations for maintaining and measuring them. Thanks also to Laura Barral for helping with the lab work, and Luisa Matas and Imma Arrom from the Technical Research Services of the University of Girona for guiding arsenic and elemental analyses