| dc.description.abstract | Multristressors have strong influence on aquatic ecosystems. Eutrophication is one of the main stressors in freshwater ecosystems, which can lead to the blooming of toxic species of cyanobacteria and microalgae. This study examines the effects of cyanobacteria and green microalgae on chironomid larvae under multistress conditions.
By using the HPLC method, it was determined that the strain Anabaena sp. produces microcystin-LR toxin; while the toxin production and the growth rate of Anabaena sp. is depending on the nutrients in the medium. Pure microcystin-LR, at an environmentally relevant concentration (10 μg/l), has no inhibitory effect on Gram-negative and Gram-positive bacteria, however, stimulates the growth of the microalgae Chlorella sp. By UV-VIS method it was determined that Anabaena sp. and Chlorella sp. are rich protein and carbohydrates sources, whereas the GC-MS method showed Chlorella sp. contains a large amount of fatty acids. Multiparameter bioassays, based on the OECD protocol, were performed on the test organism, Chironomidae (Diptera), Chironomus riparius. Lethal concentrations of environmental stressors (NO3-, NH4+, PO43-, Cd2+) and microcystin-LR were determined, as well as the lethal concentration of each stressor in combination with cyanotoxin. The following biomarkers were analyzed within the bioassay: survival, mortality, mass, stage of development, oxidative stress parameters (oxidation of proteins and lipids, catalase and superoxide dismutase activity), hemoglobin concentration, and genotoxicity (Comet assay). Microcystin-LR has an additive toxic effect under multistress conditions (NO3-, NH4+, PO43-, Cd2+). Chronic exposure of larvae to Anabaena sp. in the presence of the multistressors, showed all tested stressors enhance sublethal effects on larvae, based on: reduced mass, lower hemoglobin concentration and higher DNA damage in larvae.
Change in larval mass, hemoglobin concentration and DNA damage of somatic cells showed high sensitivity in the study of the toxic effect of phytoplankton and its metabolites on the model organism Chironomus riparius. This set of markers represents good parameters for improving the existing OECD protocol number 218. | en |
