Ecotoxicological assessment of Uruguay River and affluents pre- and post-pesticides’ application using Caenorhabditis elegans for biomonitoring

Abstract

Uruguay River is the most important river in western Rio Grande do Sul, separating Brazil from Argentina and Uruguay. However, its pollution is of great concern due to agricultural activities in the region and the extensive use of pesticides. In a long term, this practice leads to environmental pollution, especially to the aquatic system. The objective of this study was to analyze the physicochemical characteristics, metals and pesticides levels in water samples obtained before and after the planting and pesticides' application season from three sites: Uruguay River and two minor affluents, Mezomo Dam and Salso Stream. For biomonitoring, the free-living nematode Caenorhabditis elegans was used, which were exposed for 24 h. We did not find any significant alteration in physicochemical parameters. In the pre-and post-pesticides' samples we observed a residual presence of three pesticides (tebuconazole, imazethapyr, and clomazone) and metals which levels were above the recommended (As, Hg, Fe, and Mn). Exposure to both pre-and post-pesticides' samples impaired C. elegans reproduction and post-pesticides samples reduced worms' survival rate and lifespan. PCA analysis indicated that the presence of metals and pesticides are important variables that impacted C. elegans biological endpoints. Our data demonstrates that Uruguay River and two affluents are contaminated independent whether before or after pesticides' application season. In addition, it reinforces the usefulness of biological indicators, since simple physicochemical analyses are not sufficient to attest water quality and ecological safety.

Water quality assessment in the region of Vale dos Sinos trough the alternative model Caenorhabditis elegans

“…Similar study was conducted by Kuhn et al (2021) in Uruguay River, located in Brazil. The authors used C. elegans as a bioassay to evaluate the quality and ecological safety of water before and after pesticides application in the region.…”

“…Corroborating with our results, the authors did not find alteration in physicochemical parameters, however, it was observed toxic effects in C. elegans. These results reinforce the need for bioindicators in water quality assessment and ecotoxicological safety (Kuhn et al, 2021).…”

Biomonitoring in a fish farm in the Legal Amazon revealed physiological alterations in Caenorhabditis elegans

“…These differences in samplings were also observed in a previous study from our group when monitoring the Uruguay River. Pesticides and metals levels also varied in each sample, even though collections were done on consecutive days (Kuhn et al, 2021). Differences in worms exposed to different tanks were also observed in the present study, since each one has a function and may contain different chemicals that may contribute to the findings.…”

“…Notably, the nematode Caenorhabditis elegans has been inserted into this field and widely used in water and sediment analysis, emerging as a great model in environmental toxicology due to its sensitivity to toxicants (Leung et al, 2008). For instance, C. elegans has been used to evaluate the water quality of important Rivers such as Uruguay/ Brazil (Kuhn et al, 2021), Magdalena/Colombia (Tejeda-Benítez et al, 2018), Tunuyán River Basin/Argentina (Clavijo et al, 2016) and Yangtze River/China (Xiao et al, 2018). Samples collected from sites near industrial or agricultural activities caused significant toxicity to worms even in short-term exposures, particularly by affecting development and reproduction.…”

Biomonitoring of Alterations in Fish That Inhabit Anthropic Aquatic Environments in a Basin from Semi-Arid Regions

“…Recently, studies suggest that pressures on aquatic ecosystems have increased due to the widespread presence of environmental stressors affecting the normal functioning of living organisms [ 2 , 6 , 9 , 11 , 12 , 13 ]. The longitudinal connectivity along the stream or river (from the lower to the upper parts of the basin) can be compromised or interrupted by anthropic activity, creating a fragmentation of the aquatic habitat, similar to what can be found in a dammed site, but produced by a pollution barrier [ 2 , 14 ].…”