Integrated water quality assessment of two Rivers Basins from a semiarid region of Argentina.

The Tunuyán and Mendoza River Basins (Province of Mendoza, Argentina) have been selected as a representative semiarid region to test the applicability of an integrated water quality evaluation. To detect spatio-temporal variations of anthropic contamination, physicochemical and bacteriological parameters, as well as three ecotoxicological assays, were assessed in reference sites for 3 years. Bioassays based on the nematode Caenorhabditis elegans, the vascular plant Lactuca sativa, and the algae Pseudokirchneriella subcapitata were performed and toxicological categories were established. Our results showed that water quality, as well as water toxicity, deteriorates as both river systems run through urban areas. Interestingly, monitoring sites with good physicochemical and bacteriological qualities but with toxicity were identified, illustrating that traditional water quality studies do not predict potential toxic effects on living organisms. In addition, a multivariate statistical analysis was performed to detect clusters of monitoring sites according to the water quality status. In the context of climate change, this study provides information to support that integrated water monitoring is an essential tool to ensure sustainable water management and to guarantee economic growth, human health, food security, and environmental protection.

Glyphosate-based herbicides modulate oxidative stress response in the nematode Caenorhabditis elegans.

Glyphosate-based formulation is used as non-selective and post-emergent herbicides in urban and rural activities. In view of its recurring applications in agricultural producing countries, the increase of glyphosate concentration in the environment stresses the need to test the adverse effects on non-target organisms and assess the risk of its use. This paper analyzes the toxicological and oxidative stress and modulatory effects of a glyphosate commercial formulation (glyphosate F) on the nematode Caenorhabditis elegans. We detected ROS production and enhancement of oxidative stress response in glyphosate F-treated nematodes. Particularly, we found an increased ctl-1 catalase gene expression of a catalase specific activity. In addition, we showed that glyphosate F treatment activated the FOXO transcription factor DAF-16, a critical target of the insulin/IGF-1 signaling pathway, which modulates the transcription of a broad range of genes involved in stress resistance, reproductive development, dauer formation, and longevity. In summary, the exposure of glyphosate F induces an oxidative imbalance in C. elegans that leads to the DAF-16 activation and consequently to the expression of genes that boost the antioxidant defense system. In this regard, clt-1 gene and catalase activity proved to be excellent biomarkers to develop more sensitive protocols to assess the environmental risk of glyphosate use.

The nematode Caenorhabditis elegans as an integrated toxicological tool to assess water quality and pollution.

Determination of water quality status in rivers is critical to establish a sustainable water management policy. For this reason, over the last decades it has been recommended to perform integrated water assessments that include water quantities and physicochemical, ecological and toxicological tests. However, sometimes resources are limited and it is not possible to perform large-scale chemical determinations of pollutants or conduct numerous ecotoxicological tests. To overcome this problem we use and measure the growth, as a response parameter, of the soil nematode Caenorhabditis elegans to assess water quality in rivers. The C. elegans is a ubiquitous organism that has emerged as an important model organism in aquatic and soil toxicology research. The Tunuyán River Basin (Province of Mendoza, Argentina) has been selected as a representative traditional water monitoring system to test the applicability of the C. elegans toxicological bioassay to generate an integrated water quality evaluation. Jointly with the C. elegans toxic assays, physicochemical and bacteriological parameters were determined for each monitoring site. C. elegans bioassays help to identify different water qualities in the river basin. Multivariate statistical analysis (PCA and linear regression models) has allowed us to confirm that traditional water quality studies do not predict potential toxic effects on living organisms. On the contrary, physicochemical and bacteriological analyzes explain <62% of the C. elegans growth response variability, showing that ecotoxicological bioassays are important to obtain a realistic scenario of water quality threats. Our results confirm that the C. elegans bioassay is a sensible and suitable tool to assess toxicity and should be implemented in routine water quality monitoring.

Aerobic degradation of 3-chlorobenzoic acid by an indigenous strain isolated from a polluted river.

An indigenous strain of Pseudomonas putida capable of degrading 3-chlorobenzoic acid as the sole carbon source was isolated from the Riachuelo, a polluted river in Buenos Aires. Aerobic biodegradation assays were performed using a 2-l microfermentor. Biodegradation was evaluated by spectrophotometry, chloride release, gas chromatography and microbial growth. Detoxification was evaluated by using Vibrio fischeri, Pseudokirchneriella subcapitata and Lactuca sativa as test organisms. The indigenous bacterial strain degrades 100 mg l(-1) 3-chlorobenzoic acid in 14 h with a removal efficiency of 92.0 and 86.1% expressed as compound and chemical oxygen demand removal, respectively. The strain was capable of degrading up to 1,000 mg of the compound l(-1). Toxicity was not detected at the end of the biodegradation process. Besides initial concentration, the effect of different factors, such as initial pH, initial inoculum, adaptation to the compound and presence of other substrates and toxic related compounds, was studied.

CS-US delay does not impair appetitive conditioning in Chasmagnathus.

Habituation and appetitive conditioning have been already described in the crab Chasmagnathus. The purpose of this work is to study whether associative learning can be obtained despite a long conditioned stimulus-unconditioned stimulus interval. Results of the first experiment show that the weakening of temporal contiguity does not prevent appetitive conditioning to occur while after a long 4-h delay, conditioning wanes completely. A second experiment was conducted, after one and three days of training respectively, confirming the above results. Though initially neutral the context trace may be still available immediately after training and for the period of two but not after 4:00 h, demonstrating a forward limit for the conditioning window. After 3 days of training, a further decrease in the exploratory activity suggested that a longer training could increase the relative weight of habituation. Conditioning and habituation seem to work as opponent processes in the crab CHASMAGNATHUS GRANULATUS: if habituation training in the box is followed by the administration of reinforcement after a short period of time, appetitive conditioning will take place. However, as this interval is increased, habituation prevails. A persistent effect of the exposure to a given environment that may underlie trace conditioning in this crab is discussed in adaptive terms.