Characterization of river biofilm responses to the exposure with heavy metals using a novel micro fluorometer biosensor.

River biofilms are a suitable indicator of toxic stress in aquatic ecosystems commonly exposed to various anthropogenic pollutants from industrial, domestic, and agricultural sources. Among these pollutants, heavy metals are of particular concern as they are known to interfere with various physiological processes of river biofilm, directly or indirectly related to photosynthetic performance. Nevertheless, only limited toxicological data are available on the mechanisms and toxicodynamics of heavy metals in biofilms. Pulse Amplitude Modulated (PAM) fluorometry is a rapid, non-disruptive, well-established technique to monitor toxic responses on photosynthetic performance, fluorescence-kinetics, and changes in yield in other non-photochemical processes. In this study, a new micro-PAM-sensor was tested to assess potential acute and chronic effects of heavy metals in river biofilm. Toxicity values across the three parameters considered in this study (photosynthetic yield YII, non-photochemical quenching NPQ, and basal fluorescence F0) were comparable, as determined EC50 were within one order of magnitude (EC50 ∼1-10 mg L-1). However, the stimulation of NPQ was more clearly associated with early acute effects, especially in illuminated samples, while depression of YII and F0 were more prevalent in chronic tests. These results have implications for the development of functional indicators for the biomonitoring of aquatic health, in particular for the use of river biofilm as a bioindicator of water quality. In conclusion, the approach proposed seems promising to characterize and monitor the exposure and impact of heavy metals on river periphyton communities. Furthermore, this study provides a fast, highly sensitive, inexpensive, and accurate laboratory method to test effects of pollutants on complex periphyton communities that can also give insights regarding the probable toxicological mechanisms of heavy metals on photosynthetic performance in the river biofilm.

Hemodialysis Water Parameters as Predisposing Factors for Anemia in Patients in Dialytic Treatment: Application of Mixed Regression Models.

Contamination by metals and microbiological agents in hemodialysis water can cause clinical intercurrences in hemodialysis patients. Evaluating and assuring minimum levels of contamination from metals and microorganisms in hemodialysis water can improve patient safety. The objective of this study was to assess hemodialysis water quality in a major tertiary hospital in Brazil and investigate the relationship between hemodialysis water quality and clinical intercurrences in hemodialysis patients. A prospective-observational cohort study for evaluation of water quality parameters and clinical intercurrences present by patients (n = 52) were performed from May 2014 to April 2015. Mixed linear regression models and binary regression models were fitted for water quality parameters and patients' clinical parameters. The increase in the levels of copper and nitrate in hemodialysis water was significant (p < 0.05) to explain anemia. Bone pain was related to age, sex (female), and hemodialysis treatment duration (years). Hypotensive episodes were related to serum sodium decrease. Aluminum in hemodialysis water was present in an average concentration higher than the permitted threshold (15.35 ± 14.53 µg/L). Cadmium, total coliforms, Escherichia coli, and endotoxins in hemodialysis water were not detected and the heterotrophic bacteria count was below the reference limit. These parameters' concentrations varied during the study, evidencing the need for continuous monitoring.