8 research outputs found
The Response of Lemna minor to Mixtures of Pesticides That Are Commonly Used in Thailand
In the field, aquatic organisms are exposed to multiple contaminants rather than to single compounds. It is therefore important to understand the toxic interactions of co-occurring substances in the environment. The aim of the study was to assess the effects of individual herbicides (atrazine, 2,4-D, alachlor and paraquat) that are commonly used in Thailand and their mixtures on Lemna minor. Plants were exposed to individual and binary mixtures for 7 days and the effects on plant growth rate were assesed based on frond area measurements. Experimental observations of mixture toxicity were compared with predictions based on single herbicide exposure data using concentration addition and independent action models. The single compound studies showed that paraquat and alachlor were most toxic to L. minor, followed by atrazine and then 2,4-D. For the mixtures, atrazine with 2,4-D appeared to act antagonistically, whereas alachlor and paraquat showed synergism
Proteomic Analysis of the Reproductive Organs of the Hermaphroditic Gastropod Lymnea stagnalis Exposed to Different Endocrine Disrupting Chemicals
Many studies have reported perturbations of mollusc reproduction following exposure to low concentrations (ng/L
range) of endocrine disrupting chemicals (EDCs). However, the mechanisms of action of these molecules on
molluscs are still poorly understood. Investigation of the modifications of protein expression in organisms exposed to
chemicals using proteomic methods can provide a broader and more comprehensive understanding of adverse
impacts of pollution on organisms than conventional biochemical biomarkers (e.g., heat-shock proteins,
metallothioneins, GST, EROD). In this study we have investigated the impacts of four chemicals, which exhibit
different endocrine disrupting properties in vertebrates, on the proteome of the hermaphroditic freshwater pulmonate
gastropod Lymnaea stagnalis after 21 days of exposure. Testosterone, tributyltin, chlordecone and cyproterone
acetate were chosen as tested compounds as they can induce adverse effects on the reproduction of this snail. The
2D-DIGE method was used to identify proteins whose expression was affected by these compounds. In addition to
modifying the expression of proteins involved in the structure and function of the cytoskeleton, chemicals had impacts
on the expression of proteins involved in the reproduction of L. stagnalis. Exposure to 19.2 ÎĽg/L of chlordecone
increased the abundance of ovipostatin, a peptide transmitted during mating through seminal fluid, which reduces
oviposition in this species. The expression of yolk ferritin, the vitellogenin equivalent in L. stagnalis, was reduced after
exposure to 94.2 ng Sn/L of tributyltin. The identification of yolk ferritin and the modification of its expression in snails
exposed to chemicals were refined using western blot analysis. Our results showed that the tested compounds
influenced the abundance of yolk ferritin in the reproductive organs. Alteration in proteins involved in reproductive
pathways (e.g., ovipostatin and yolk ferritin) could constitute relevant evidence of interaction of EDCs with
reproductive pathways that are under the control of the endocrine system of L. stagnalis
Herbicide Exposure and Toxicity to Aquatic Primary Producers
The aim of the present review was to give an overview of the current state of science concerning herbicide exposure and toxicity to aquatic primary producers. To this end we assessed the open literature, revealing the widespread presence of (mixtures of) herbicides, inevitably leading to the exposure of non-target primary producers. Yet, herbicide concentrations show strong temporal and spatial variations. Concerning herbicide toxicity, it was concluded that the most sensitive as well as the least sensitive species differed per herbicide and that the observed effect concentrations for some herbicides were rather independent from the exposure time. More extensive ecotoxicity testing is required, especially considering macrophytes and marine herbicide toxicity. Hence, it was concluded that the largest knowledge gap concerns the effects of sediment-associated herbicides on primary producers in the marine/estuarine environment. Generally, there is no actual risk of waterborne herbicides to aquatic primary producers. Still, median concentrations of atrazine and especially of diuron measured in China, the USA and Europe represented moderate risks for primary producers. Maximum concentrations due to misuse and accidents may even cause the exceedance of almost 60% of the effect concentrations plotted in SSDs. Using bioassays to determine the effect of contaminated water and sediment and to identify the herbicides of concern is a promising addition to chemical analysis, especially for the photosynthesis-inhibiting herbicides using photosynthesis as endpoint in the bioassays. This review concluded that to come to a reliable herbicide hazard and risk assessment, an extensive catch-up must be made concerning macrophytes, the marine environment and especially sediment as overlooked and understudied environmental compartments