Abstract
Several bacteria-based assays, notably Vibrio fischeri luminescence assays, are often used as environmental monitoring tool for toxicity in sediments that may serve as both sinks and secondary source of contamination in aquatic ecosystems. In this study, we used 30-s kinetic bioassays based on V. fischeri to evaluate the toxicity associated to sediments from five localities with different contamination inputs (Morava River and its tributary Drevnice River in the south-eastern part of the Czech Republic). Toxicity assessed as half maximal inhibitory concentration (IC50) over the course of a year-long sampling was compared in bottom sediments and freshly trapped particulate material. Standard approach based on testing of aqueous elutriates was compared with toxicity of whole sediments (contact suspension toxicity). Bottom sediments showed lower toxicity compared to freshly trapped suspended materials in all cases. On the other hand, standardized elutriates induced generally weaker effects than suspended sediments likely due to losses during the extraction process. Toxicity generally increased during winter reaching maximum peaks in early spring months in all five sites. Total organic carbon (TOC) was found to be highly correlated with toxic effects. Toxicity from sites with direct industrial and agricultural water inputs also correlated with concentrations of metals, polycyclic aromatic hydrocarbons (PAHs), and polychlorinated biphenyls (PCBs). Single time point sampling followed by the extraction and testing of elutriates, do not truly reflect the spatial and temporal variability in natural sediments and may lead to underestimation of ecotoxic risks.
Highlights
Natural compounds and anthropogenic pollutants such as organic compounds, pesticides, and heavy metals released into the environment accumulate in ecosystems, notably freshwater bodies, and pose risk to endogenous organisms
TOCc PAHs PCBs HCHs DDTs HCB V Cr Co Ni Cu Zn As Mo Cd Sb Pb Hg aMA, Malenovice; BE, Belov; SP, Spytihnev; CE, Certak; CR, Certak oxbow lake; All, all sampling sites. bNumber of paired values for correlation. cTOC, total organic carbon (%); PAHs, sum of polycyclic aromatic hydrocarbons; PCBs, sum of polychlorinated biphenyls; HCHs, hexachlorocyclohexane; DDTs, DDT and its metabolites; HCB, hexachlorobenzene; 1/IC50, inverse value of 50% inhibition concentration derived from the kinetic V. fischeri assay; INH75, decrease in light emission caused by 75 mg dry wt sediment in test with elutriates (%). dCorrelation is not possible here, because all toxicity values were >75 mg dry wt/ml
The V. fischeri kinetic assay was proved to be a suitable tool for the assessment of toxicity in solid and colorful samples such as fluvial sediments
Summary
Natural compounds and anthropogenic pollutants such as organic compounds, pesticides, and heavy metals released into the environment accumulate in ecosystems, notably freshwater bodies, and pose risk to endogenous organisms. Toxicity in water bodies, including rivers, can be evaluated by analyzing the structure and abundance of biological communities, by measuring concentrations. Bioluminescent V. fisheri Assays for Sediment Toxicity of chemicals that can be related to contaminant bioavailability and adverse effects and/or by direct assessing of toxicity using bioassays. The first approach is typically time-consuming and expensive, while the chemical measurements can be hard to extrapolate into biological systems and may lead to misinterpretation. There is a current need for the development of simple and inexpensive bioassays for the rapid assessment of environmental risks including aquatic matrices
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