Abstract
ABSTRACT: This study aimed to establish the mass cultivation of Wolffia brasiliensis under laboratory conditions, determine the sensitivity of reference substances (potassium dichromate, sodium chloride, and potassium chloride), and estimate the acute toxicity (LC50;7d) for the herbicide glyphosate, diquat, paraquat, imazapyr, 2,4-D, saflufenacil, imazamox, penoxsulam, metsulfuron-methyl, and atrazine. Three media were tested for culture establishment: Hoagland’s medium, 5.0 g L-1 NPK fertilizer (20-5-20), a mixture of Oxisol + organic substrate of decaying aquatic plant (2:1; v v-1). Sensitivity tests with reference substances and acute toxicity for herbicides were carried out after establishing the cultivation. The species W. brasiliensis presented an excellent sensitivity response to reference substances, with means of LC50;7d of 15.61±2.13 g L-1, 17.02±0.50 g L-1, and 52.54±4.27 mg L-1 for sodium chloride, potassium chloride, and potassium dichromate, respectively. The acute toxicity response indicated that W. brasiliensis was extremely sensitive to diquat (LC50;7d = 0.07 mg L-1) and paraquat (LC50;7d < 0.05 mg L-1), sensitive to imazapyr (LC50;7d = 21.10 mg L-1), and little sensitive to the other herbicides. The response capacity for the different groups of herbicides, the standardized response to reference substances, and ease of cultivation in the laboratory indicate the potential for using this aquatic plant in the assessment of herbicide risk in aquatic environments.
Highlights
Pollution caused by agriculture has caused severe problems in several countries due to the excessive use of fertilizers, herbicides, insecticides, and other chemicals during the production cycles
Toxicity tests with bioindicator organisms are essential during the entire environmental assessment process as they incorporate the interaction between contaminants and environmental properties and allow the ecological assessment of effects derived from exposure (Masese, 2013)
Due to the scarcity of bioindicator aquatic plants in the literature, especially in tropical environments, this study aimed to assess the establishment of W. brasiliensis cultivation under laboratory conditions, determine the sensitivity for reference substances, and estimate acute toxicity (LC50;7d) for the herbicides 2,4-D, atrazine, diquat, glyphosate, imazapyr, imazamox, metsulfuron-methyl, penoxsulam, paraquat, and saflufenacil
Summary
Pollution caused by agriculture has caused severe problems in several countries due to the excessive use of fertilizers, herbicides, insecticides, and other chemicals during the production cycles. Aquatic environments are hit by complex mixtures of chemicals, which may represent risks to ecosystems and human health (Brack et al, 2016). In this context, environmental monitoring has become a prominent tool (Brack et al, 2016), but a problem of chemical monitoring is the knowledge of the risk that each substance may represent, its carcinogenic and mutagenic properties, toxicity, potential bioaccumulation or persistence, hindering the real establishment of risk of environmental exposure (Johnson et al, 2017). Biomonitoring can be performed with organisms representing different ecological groups, such as algae, aquatic plants, aquatic invertebrates, benthic organisms, macroinvertebrates, fishes, and periphytic communities (Laini et al, 2018)
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