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This study screened binary mixtures of pesticides for potential synergistic interaction effects on growth of the marine microalgae Tisochrysis lutea and Skeletonema marinoi. It also examined the single and combined effects of three of the most toxic substances on microalgal physiology. Single substances were first tested on each microalgal species to determine their respective EC and concentration-response relationships. The toxicity of six and seven binary mixtures was then evaluated in microplate experiments on the growth of T. lutea and S. marinoi, respectively, using two mixture modelling approaches: isobolograms and the MIXTOX tool, based on Concentration Addition (CA) or Independent Action (IA) models. Significant cases of antagonism (for both species) and synergism (for S. marinoi) were observed for the mixtures of isoproturon and spiroxamine, and isoproturon and metazachlor, respectively. These two mixtures, together with that of isoproturon and diuron, for which additivity was observed, were further studied for their impacts on the physiology of each species. Exposures were thus made in culture flasks at three concentrations, or concentration combinations for mixtures, selected to cause 25%, 50% and 75% growth rate inhibition. The effects of the selected pesticides singly and in combination were evaluated at three perceived effect concentrations on esterase metabolic activity, relative lipid content, cytoplasmic membrane potential and reactive oxygen species (ROS) content by flow cytometry, and on photosynthetic quantum yield (ϕ') by PAM-fluorescence. Isoproturon and diuron singly and in mixtures induced 20-40% decreases in ϕ' which was in turn responsible for a significant decrease in relative lipid content for both species. Spiroxamine and metazachlor were individually responsible for an increase in relative lipid content (up to nearly 300% for metazachlor on S. marinoi), as well as cell depolarization and increased ROS content. The mixture of isoproturon and metazachlor tested on S. marinoi caused a 28-34% decrease in ϕ' that was significantly higher than levels induced by each of substances when tested alone. This strong decrease in ϕ' could be due to a combined effect of these substances on the photosynthetic apparatus, which is likely the cause of the synergy found for this mixture.
This article was published in the following journal.
Name: Aquatic toxicology (Amsterdam, Netherlands)
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A non-taxonomic term for unicellular microscopic algae which are found in both freshwater and marine environments. Some authors consider DIATOMS; CYANOBACTERIA; HAPTOPHYTA; and DINOFLAGELLATES as part of microalgae, even though they are not algae.
Such mixtures of amphoteric electrolytes or buffers that provide a continuous range of pH in an electric field; used for separating proteins by their isoelectric points, i.e., by isoelectric focusing.
Mixtures of many components in inexact proportions, usually natural, such as PLANT EXTRACTS; VENOMS; and MANURE. These are distinguished from DRUG COMBINATIONS which have only a few components in definite proportions.
The measurement of infection-blocking titer of ANTISERA by testing a series of dilutions for a given virus-antiserum interaction end-point, which is generally the dilution at which tissue cultures inoculated with the serum-virus mixtures demonstrate cytopathology (CPE) or the dilution at which 50% of test animals injected with serum-virus mixtures show infectivity (ID50) or die (LD50).
A species of green microalgae in the family Chlorellaceae. It is used as a model organism for PHOTOSYNTHESIS, and as a food supplement (DIETARY SUPPLEMENTS).