Effects of carbaryl, diazinon and malathion on native aquatic populations of microorganisms

Toxicological effects of chlorpyrifos on growth, enzyme activity and chlorophyll a synthesis of freshwater microalgae

This paper aims to acquire the experimental data on the eco-toxicological effects of agricultural pollutants on the aquatic plants and the data can support the assessment of toxicity on the phytoplankton. The pesticide of Chlorpyrifos used as a good model to investigate its eco-toxicological effect on the different microalgae in freshwater. In order to address the pollutants derived from forestry and agricultural applications, freshwater microalgae were considered as a good sample to investigate the impact of pesticides such as Chlorpyrifos on aquatic life species. Two microalgae of Chlorella pyrenoidosa and Merismopedia sp. were employed to evaluate toxicity of Chlorpyrifos in short time and long time by means of measuring the growth inhibition rate, the redox system and the content of chlorophyll a, respectively. In this study, the results showed that EC50 values ranging from 7.63 to 19.64mg/L, indicating the Chlorpyrifos had a relatively limited to the growth of algae during the period of the acute toxicity experiment. Moreover, when two kinds of algae were exposed to a medium level of Chlorpyrifos, SOD and CAT activities were importantly advanced. Therefore, the growth rate and SOD and CAT activities can be highly recommended for the eco-toxicological assessment. In addition, chlorophyll a also could be used as a targeted parameter for assessing the eco-toxicity of Chlorpyrifos on both Chlorella pyrenoidosa and Merismopedia sp.

Effect of insecticides on plankton and fish of Ignacio Ramirez reservoir (Mexico): a biochemical and biomagnification study

Studies on the limnology, plankton, and biomagnification of pesticides at Ignacio Ramírez (IR) reservoir (Mexico) were undertaken. The reservoir is located in central Mexico, in an agricultural zone with high soil erosion. Acetylcholinesterase (AchE), gamma-glutamyl transpeptidase (GGTP), and lipid peroxidation were assayed in fish. Organochlorines (0.024-0.279 mg/liter) and organophosphates (0.02 x 10(-3)-0.21 x 10(-3) mg/liter) were present at high concentrations in water and the biota assayed. In the IR dam the plankton fluctuated depending on the dry and wet seasons. The dominant group of phytoplankton was Bacillariophyta (20-85%) in May, Cyanophyta (22-65%) in September, and Cyanophycean (10-65%), Chlorophycean (10-60%), and Bacyllariophycean (5-80%) species in March. The zooplankton were dominated by cladoceran species (40-70%). Organochlorine and organophosphate insecticides were bioconcentrated (2- to 10-fold) from water to algae, 10- to 25-fold in zooplankton, and 8- to 140-fold in fish. GGTP activity and lipid peroxidation increased and AchE activity in fish decreased in response to the environmental stress caused by the elevated biomagnification of pesticides. The bioaccumulation of these contaminants in fish and the potential for biomagnification in humans are perceived as threats.

Effects of pyridaphenthion on growth of five freshwater species of phytoplankton. A laboratory study

The acute toxicity of the insecticide and acaricide pyridaphenthion to five species of freshwater phytoplankton, Scenedesmus acutus, Scenedesmus subspicatus, Chlorella vulgaris, Chlorella saccharophila and Pseudanabaena galeata was determined. Insecticide concentrations eliciting a 50% growth reduction over 96 h (EC50) ranged from 2.2 to 30.9 mg/l. The two species of Chlorella and the cyanobacteria P. galeata were more tolerant than the two species of Scenedesmus. Concentrations of pyridaphenthion detected in some natural waters were less than the toxic threshold for these species.

The effects of 2,4-D herbicide and organophosphorus insecticides on growth, photosynthesis, and chlorophyll a synthesis of Chlamydomonas reinhardtii (mt +)

The effects of the herbicide (2,4-D) and six organophosphorus insecticides (Diazinon, Dimethoate, Fenitrothion, Malathion, Phenthoate and Quinalphos) on growth, photosynthesis and chlorophyll a synthesis of the fresh water green alga Chlamydomonas reinhardtii (mt +) were studied. At low concentrations (1 and 5 ppm), the herbicide and all six orgnophosphorus insecticides stimulated photosynthesis of the alga. The stimulating effects on algal growth and chlorophyll a synthesis were only observed in the presence of low concentration (1 ppm) of 2,4-D and Fenitrothion, Growth, photosynthesis and chlorophyll a synthesis of the alga were inhibited in the presence of high concentrations (10, 20 and 40 ppm) of the herbicide and all the six organophosphorus insecticides. Results also indicated that the toxicities of these organophosphorus insecticides on the tested alga were dependent on their chemical structures.