Effects of environmentally relevant concentrations of atrazine and glyphosate herbicides, isolated and in mixture, on two generation of the freshwater microcrustacean Daphnia magna

Biological-based techniques for real-time water-quality studies: Assessment of non-invasive (swimming consistency and respiration) and toxicity (antioxidants) biomarkers of zebrafish

Swimming consistency and respiration of fish are recognized as the non-invasive stress biomarkers. Their alterations could directly indicate the presence of pollutants in the water ecosystem. Since these biomarkers are a routine process for fish, it is difficult to monitor their activity manually. For this reason, experts employ engineering technologies to create sensors that can monitor the regular activities of fish. Knowing the importance of these non-invasive stress biomarkers, we developed online biological behavior monitoring system-OBBMS and online biological respiratory response monitoring system-OBRRMS to monitor real-time swimming consistency and respiratory response of fish, respectively. We continuously monitored the swimming consistency and respiration (OCR, CER and RQ) of zebrafish (control and atrazine-treatments) for 7 days using our homemade real-time biological response monitoring systems. Furthermore, we analyzed oxidative stress indicators (SOD, CAT and POD) within the vital tissues (gills, brain and muscle) of zebrafish during stipulated sampling periods. The differences in the swimming consistency and respiratory rate of zebrafish between the control and atrazine treatments could be precisely differentiated on the real-time datasets of OBBMS and OBRRMS. The zebrafish exposed to atrazine toxin showed a concentration-dependent effect (hypoactivity). The OCR and CER were increased in the atrazine treated zebrafish. Both Treatment I and II received a negative response for RQ. Atrazine toxicity let to a rise in the levels of SOD, CAT and POD in the vital tissues of zebrafish. The continuous acquisition of fish signals is achieved which is one of the main merits of our OBBMS and OBRRMS. Additionally, no special data processing was done, the real-time data sets were directly used on statistical tools and the differences between the factors (groups, photoperiods, exposure periods and their interactions) were identified precisely. Hence, our OBBMS and OBRRMS could be a promising tool for biological response-based real-time water quality monitoring studies.

Dissipation of pesticides by stream biofilms is influenced by hydrological histories

To evaluate the effects of hydrological variability on pesticide dissipation capacity by stream biofilms, we conducted a microcosm study. We exposed biofilms to short and frequent droughts (daily frequency), long and less frequent droughts (weekly frequency) and permanently immersed controls, prior to test their capacities to dissipate a cocktail of pesticides composed of tebuconazole, terbuthylazine, imidacloprid, glyphosate and its metabolite aminomethylphosphonic acid. A range of structural and functional descriptors of biofilms (algal and bacterial biomass, extracellular polymeric matrix (EPS) concentration, microbial respiration, phosphorus uptake and community-level physiological profiles) were measured to assess drought effects. In addition, various parameters were measured to characterise the dynamics of pesticide dissipation by biofilms in the different hydrological treatments (% dissipation, peak asymmetry, bioconcentration factor, among others). Results showed higher pesticide dissipation rates in biofilms exposed to short and frequent droughts, despite of their lower biomass and EPS concentration, compared to biofilms in immersed controls or exposed to long and less frequent droughts. High accumulation of hydrophobic pesticides (tebuconazole and terbuthylazine) was measured in biofilms despite the short exposure time (few minutes) in our open-flow microcosm approach. This research demonstrated the stream biofilms capacity to adsorb hydrophobic pesticides even in stressed drought environments.