Contaminants of emerging concern fate and fluvial biofilm status as pollution markers in an urban river.

Contaminants of emerging concern (CEC) are still under research given the vast diversity of compounds reaching freshwater ecosystems and adverse effects they might cause. In this study, the environmental fate of 73 CEC, comprising sweeteners, stimulants and several pharmaceutical therapeutic classes, and changes in fluvial biofilm photosynthetic parameters were evaluated in a semi-arid urban river receiving diffuse and point sources of pollution (Suquía river, Argentina). Out of the 37 CEC detected, 30 were quantified in surface water (n.d. - 9826 ng/L), 10 in biofilm (n.d. - 204 ng/gd.w.) and 9 in the clay fraction of sediments (n.d. - 64 ng/gd.w.). CEC distribute differently among the 3 matrices: water phase presents the biggest diversity of compounds (14 CEC families), being analgesic/anti-inflammatories the most abundant family. Antibiotics largely predominated in biofilms (7 CEC families), while the stimulant caffeine and some antibiotics where the most abundant in sediments (6 CEC families). Different CEC accumulated in biofilms and sediments upstream and downstream the city, and big shifts of biofilm community occurred downstream WWTP. The shift of biofilm community upstream (F0 > 0) and downstream the WWTP (F0 = 0) shows a sensitive response of F0 to the impact of WWTP. Biofilm photosynthetic parameters responded in less impacted urban sites (sites 1, 2 and 3), where significant correlations were found between ketoprofen and some antibiotics and biofilm parameters. The diversity and amount of CEC found in the urban section of Suquía river alert to the magnitude of point and non-point sources of pollution.

Influence of the interaction between phosphate and arsenate on periphyton's growth and its nutrient uptake capacity.

Periphyton communities grown in microcosms were studied under the exposure to different arsenate (As) and phosphate (P) regimes with the aim of revealing the effect of chronic exposure to As on periphyton physiological and structural characteristics. Also, we aimed to study periphyton changes on sensitivity to As, exposed to different P and As regimes. As affected structural and functional parameters of periphyton communities starved of P, inhibiting algal growth, photosynthetic capacity, changing community composition and reducing the ability of the community to retain P. The effects of As on these parameters were only detected in P starved communities, showing that chronic exposure to As led to changes in the photosynthetic apparatus under the conditions of P-limitation, but not when P-availability was higher. This fact reveals a lower toxicity and/or a higher adaptation of the P-amended community. Intracellular As contents were higher in communities starved of P. However, As tolerance was only induced by the combination of As and P but not by As or P alone indicating that tolerance induction may be an ATP-dependent mechanism. This study reveals that chronic exposure of natural communities to environmentally realistic As concentrations will damage periphyton communities affecting key ecosystem processes, as P uptake, leading to changes in stream ecosystems, as these organisms play a key role in nutrient cycling through nutrient uptake and transfer to higher trophic levels.