Magnetized vermiculite as a tool for the treatment of produced water generated by oil companies: Effects on aquatic organisms before and after treatment.

Produced water (PW) generated by oil companies is a highly impacting waste that contains chemicals such as metals and organic and inorganic compounds. Given its polluting potential, PW requires effective treatment before being discharged into the environment. Conventional treatments have limited efficiency in removing PW toxicity, so alternative approaches must be developed and standardized. In this context, treatment with adsorbent materials like magnetized vermiculite (VMT-mag) is highlighted. This work aimed to evaluate the efficiency of treatment with VMT-mag in reducing PW toxicity to aquatic biota. For this purpose, three aquatic species (the midge Chironomus riparius, the planarian Girardia tigrina, and the crustacean Daphnia magna) were exposed to untreated PW and to PW treated with VMT-mag at laboratory conditions. The assessed endpoints included mortality, growth, emergence, and developmental time of C. riparius; mortality, locomotion, feeding, and head regeneration of G. tigrina; and intrinsic population growth rate (r) and reproductive output of D. magna. The results showed that all the species exposed to raw PW were impaired: C. riparius had delayed development, G. tigrina had reduced locomotor activity and delayed head regeneration, and D. magna had reduced reproduction and delayed intrinsic population growth rate (r). Most of the analyzed parameters showed that treatment with VMT-mag diminished PW toxicity. Therefore, using VMT-mag to treat PW may be the key to reducing the PW effects on aquatic organisms.

The combined effects of microbial insecticides and sodium chloride on the development and emergence of Chironomus xanthus.

BACKGROUND: Freshwater organisms are facing increasing salinity levels, not only due to natural environmental processes, but also human activities, which can cause several physiological adaptations to osmotic stress. Additionally, these organisms might also have to deal with contamination by microbial insecticides. Our main goal was to use Chironomus xanthus to assess the chronic effects of increasing the salinity and commercial formulations of the microbial insecticides based on Bacillus thuringiensis subs. kurstaki (Btk) and Beauveria bassiana (Bb) as active ingredients, respectively. RESULTS: A significant interaction of growth was observed between the biopesticide based on Bb and NaCl on the larvae of C. xanthus. Single exposure to NaCl and each one of the formulations demonstrated deleterious impacts not only on larval development, but also on the emergence success and emergence time of this nontarget insect, with potential consequences for freshwater ecosystems due to cascading effects. CONCLUSION: The chronic effects induced by both bioinsecticides show that these formulations can have environmental impacts on nontarget freshwater insects. © 2023 Society of Chemical Industry.

Do bio-insecticides affect only insect species? Behavior, regeneration, and sexual reproduction of a non-target freshwater planarian.

Bio-insecticides have been increasingly used worldwide as ecofriendly alternatives to pesticides, but data on their effects in non-target freshwater organisms is still scarce and limited to insects. The aim of this study was to determine the lethal and sub-lethal effects of the bio-insecticides Bac Control (based on Bacillus thuringiensis kurstaki-Btk) and Boveril (based on Beauveria bassiana-Bb) on regeneration, behavioral, and reproductive endpoints of the freshwater planarian Girardia tigrina. The estimated LC50-48h were > 800 mg a.i./L for Btk and 60.74 mg a.i./L for Bb. In addition, exposure to Btk significantly decreased locomotion and feeding activities of planarians (lowest observed effect concentration (LOEC) of 12.5 mg a.i./L Btk) and fecundity rate (LOEC = 3.12 mg a.i./L Btk), whereas exposure to Bb significantly delayed regeneration (LOEC = 0.75 mg a.i./L Bb) and decreased fecundity rate (1.5 mg a.i./L Bb) of planarians. Thus, both bio-insecticides induced deleterious sub-lethal effects on a non-insect freshwater invertebrate species. However, only Bb-based formulation affected the survival, fecundity rate, and regeneration at concentrations below the maximum predicted environmental concentration (PEC = 247 mg/L). Thus, care should be taken when using such formulations as alternatives to chemical insecticides near aquatic ecosystems.

Lethal and sublethal effects of the saline stressor sodium chloride on Chironomus xanthus and Girardia tigrina.

Salinization in freshwaters is gradually increasing as a result of human activities and climatic changes. Higher salt content causes stress for freshwater organisms. Sodium chloride (NaCl) is among the most frequently occurring salts in freshwater ecosystems. The objective of the present study was to investigate the lethal and sublethal effects of NaCl on freshwater ecosystems, using as test organism the dipteran Chironomus xanthus and the planarian Girardia tigrina. Acute tests showed that C. xanthus was more sensitive (48-h LC50 (median lethal concentration) of 2.97 g NaCl L-1) than G. tigrina (48-h LC50 of 7.77 g NaCl L-1). C. xanthus larvae growth rate (larvae length and head capsule width) was significantly reduced under exposure to concentrations as low as 0.19 g L-1 NaCl and higher. A delay in the emergence time (EmT50) was also demonstrated for the same concentration. Sublethal NaCl effects in G. tigrina included feeding inhibition (LOEC (lowest observed effect concentration) of 0.4 g L-1), reduced locomotion (LOEC = 0.2 g L-1), and 24-48-h blastema regeneration (LOEC = 0.2 g L-1 and 0.1 g L-1, respectively). The results demonstrated the toxicity of NaCl to C. xanthus and G. tigrina including sublethal effects that can result in negative consequences for populations in natural freshwaters under salinization.

Toxicity of microbial insecticides toward the non-target freshwater insect Chironomus xanthus.

BACKGROUND: Commercial formulations based on Bacillus thuringiensis subs. kurstaki (Btk) and Beauveria bassiana (Bb) are commonly used microbial insecticides in Brazil and other tropical regions. However, and despite being considered environmentally friendly, their use generates concerns regarding possible adverse ecological effects in freshwater ecosystems. Here, we evaluate the effects of these bioinsecticides on the tropical aquatic dipteran Chironomus xanthus under laboratory conditions. RESULTS: After laboratory exposures to these compounds 48-h median lethal concentration (LC50 ) values of 1534 µg a.i./L for Btk and of 6.35 µg a.i./L for Bb were estimated. Chronic assays revealed different sublethal effects: Btk-based bioinsecticide exposure reduced C. xanthus growth [lowest observed effect concentration (LOEC) was 126 µg a.i./L for head width], decreased emergence rate (LOEC = 8 µg a.i./L) and increased immunological response (LOEC = 50 µg a.i./L) measured as total hemocyte count in larvae hemolymph. Exposure to low concentrations of Bb-based insecticide also reduced C. xanthus growth (LOEC = 0.07 µg a.i./L for larvae body length measurements), and emergence rate (LOEC = 0.28 µg a.i./L), despite no clear effects on the total hemocyte counts. CONCLUSION: Our results suggest that low concentrations of Btk and Bb bioinsecticides are toxic to C. xanthus. Given their widespread use and occurrence in tropical freshwater systems, research is needed to evaluate the potential effects of these compounds concerning natural freshwater insect communities and ecosystem functioning. © 2019 Society of Chemical Industry.

Lethal and sub-lethal effects of cyproconazole on freshwater organisms: a case study with Chironomus riparius and Dugesia tigrina.

The fungicide cyproconazole (CPZ) inhibits the biosynthesis of ergosterol, an essential sterol component in fungal cell membrane and can also affect non-target organisms by its inhibitory effects on P450 monooxygenases. The predicted environmental concentration of CPZ is up to 49.05 µg/L and 145.89 µg/kg in surface waters and sediments, respectively, and information about CPZ toxicity towards non-target aquatic organisms is still limited. This study aimed to address the lack of ecotoxicological data for CPZ, and thus, an evaluation of the lethal and sub-lethal effects of CPZ was performed using two freshwater invertebrates (the midge Chironomus riparius and the planarian Dugesia tigrina). The estimated CPZ 48 h LC50 (95% CI) was 17.46 mg/L for C. riparius and 47.38 mg/L for D. tigrina. The emergence time (EmT50) of C. riparius was delayed by CPZ exposure from 0.76 mg/L. On the other hand, planarians showed higher tolerance to CPZ exposure. Sub-lethal effects of CPZ on planarians included reductions in locomotion (1.8 mg/L), delayed photoreceptors regeneration (from 0.45 mg/L), and feeding inhibition (5.6 mg/L). Our results confirm the moderate toxicity of CPZ towards aquatic invertebrates but sub-lethal effects observed also suggest potential chronic effects of CPZ with consequences for population dynamics.