Toxicity of atrazine to Scenedesmus quadricauda under different nitrogen concentrations

Abstract

Herbicides constitute a serious environmental problem because they can affect nontarget organisms. The toxicity of these chemicals depends on their interaction with prevailing environmental conditions. In this study, the effect of atrazine (ATR) (0.05, 0.5 and 5.0 mg L -1 ) at different nitrogen concentrations (1.8 9 10 -4 and 1.8 9 10 -5 M) on the growth, morphological variation, biomass production and antioxidant enzyme activities of the freshwater microalga Scenedesmus quadricauda was investigated. Compared with the control, growth rate, dry weight and cell density were lower under limited nitrogen with or without ATR exposure. The proportion of multicelled coenobial structures was generally higher in the control and ATR treatments with replete (1.8 9 10 -4 M) nitrogen than that under limited nitrogen. Catalase and peroxidase activities decreased under nitrogen limitation and atrazine exposure. In conclusion, our results revealed that nitrogen levels influence the toxicity of atrazine to S. quadricauda and possibly other algae in aquatic ecosystems.

Impacts of chemical contamination on bacterio-phytoplankton coupling

“…The contaminants cocktail was designed from the main compounds identified and analysed in sediment elutriate (Table S1, supplementary materials) in order to assess the toxic effects of these contaminants without confounding chemical factors, nutrients and/or dissolved organic matter that are released during sediment resuspension (Pringault et al, 2016). Nutrients and organic matter are known to strongly mitigate the toxicity of pesticides and TME against microorganisms, mainly attributed to a decrease of contaminant bioavailability by adsorption on dissolved organic matter (Boyd et al, 2005;Coquillé et al, 2018;Lorenzo et al, 2002) and changes in the nutrient status, toxicity increasing under nutrient limitation (Chia et al, 2016;Miao and Wang, 2006). For offshore waters, spiking with pesticides and MTE resulted in an inhibition of phytoplankton biomass as well as a reduction of metabolic activities involved in the carbon cycle (PP and BCD).…”

Seasonal changes of chemical contamination in coastal waters during sediment resuspension

“…Nevertheless, the concomitant release of nutrients and dissolved organic matter with toxic compounds (pesticides and trace metal elements) upon sediment resuspension can alleviate the potential toxicity of the toxic elements (Pringault et al, 2016), nutrients and organic matter are known to decrease the toxicity of trace metal elements (Anu et al, 2018;Huang et al, 2016) or pesticides for phytoplankton (Chia et al, 2016;Coquillé et al, 2018). The structure and diversity of phytoplankton (Lafabrie et al, 2013) and bacterioplankton (Pringault et al, 2016) can be strongly impacted by sediment resuspension in shallow waters with significant consequences on the primary production as well on the microbial biomass (Ding et al, 2017;McSweeney et al, 2017;Pringault et al, 2016).…”