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1

Comparative toxicity of insecticides on thylakoids of intact Scenedesmus bijugatus [Turp.] Kutz. and Ankistrodesmus convolutus Corda cells: measurement of chlorophyll a fluorescence

100%
Mohapatra P. K., Mohanty R. C.
Acta Hydrobiologica
|
1996
|
tom 38
|
nr 3-4
A decrease in maximum fluorescence (Fm) and fluorescence yield (Fv/Fm) and increase in non-photochemical quenching (qN) were observed in the cultures treated with quinalphos, endosulfan, and carbaryl. The effects were time dependent but most of them were observed during the first 2 h. The insecticides also effectively increased the transthylakoid pH difference (ΔpH), this being attributed to inhibition of thylakoid ATPase. Acceleration of qN showed a direct correlation with the increase in ΔpH in all cases. A. convolutus was more sensitive to all insecticides. Carbaryl was less toxic than quinalphos and endosulfan.
2

Mercury toxicity to Chlorella vulgaris Beijerinck: protection by amino acids

80%
Mohanty L., Mohapatra D. K., Mohapatra P. K., Mohanty R. C.
Polish Journal of Environmental Studies
|
1998
|
tom 07
|
nr 1
Mercury is known to be toxic to a number of phytoplankton even at very low concentrations. The metal inhibited survival, growth and biosynthesis of chlorophyll, carbohydrate and lipid of the green alga Chlorella vulgaris at its toxic concentrations (≥ 0.1 μM), but induced the biosynthesis of proline. The addition of amino acids (Alanine, Aspargine, Glutamate, Histidine and Cysteine) to the growth medium had a significant impact on bioassay results. The toxicity was expressed differently depending on concentration and type of amino acid added to cultures. LC50s ranged from 0.68 ± 0.004 to 0.97 ± 0.008 μM and the acute toxicity of Hg2+ in amino acid supplemented media followed the order C > C + ALA > C + GLU > C + ASP > C + HIS > C + CYS. The static dose of the metal to the alga was found to be 1 + 0.006 μM but its inhibitory effect on the alga was drastically reduced with the addition of amino acids. There were positive correlations between growth and metabolic activities of the alga and concentration of amino acid added to cultures at the presence of static concentration of Hg2+. The results suggested that amino acids have moderating effects on toxicity of Hg2+ because of their ability to regulate the concentration of free Hg2+ ions in growth medium.
3

Effect of organic carbon sources on the toxicity of mercury to Chlorococcum infusionum [Schrank.] Menegh. and Ankistrodesmus falcatus [Corda] Ralfs

80%
Mohapatra P. K., Mohanty R. C., Sinha M.
Acta Hydrobiologica
|
1995
|
tom 37
|
nr 1
Abstract - Mercury at all tested concentrations was found to be less toxic to Chlorococcum infusionum than to Ankistrodesmus falcatus. Ankistrodesmus growth was inhibited at all the tested doses of the metal while Chlorococcum remained unaffected up to 0.005µM of Hg2+. A reduction of chlorophyll and protein content, decrease in Chl a/b ratio, and accumulation of glycolate was observed at inhibitory concentrations of Hg2+ whereas amino acid synthesis was not significantly affected. Both the used carbon sources caused a reduction of Hg2+ toxicity to the test algae, glucose being more effective than glutamate.
4

Effect of the pyrethroid insecticide cypermethrin on photosynthetic pigments of the cyanobacterium Anabaena doliolum Bhar.

80%
Mohapatra P. K., Patra S., Samantaray P. K., Mohanty R. C.
Polish Journal of Environmental Studies
|
2003
|
tom 12
|
nr 2
The degradation of chlorophyll a (Chl a), carotenoids and phycobiliproteins, and the fluorescence responses of the filamentous cyanobacterium Anabaena doliolum Bhar. were studied with short exposure (45 min-30 hours) to the pyrethroid insecticide cypermethrin by taking 20 μM and 50 μM of the chemical as treatment concentrations. There was significant reduction in Chl a, carotenoids and phycobiliprotein contents of cells in each of the selected concentrations of the insecticide. Pheophytin a and fluorescing and non-fluorescing chlorophyll catabolites (FCCs and NCCs) were produced as degradation products of Chl a during the exposure period. The amount of the degradation products gradually decreased with prolonged exposure of the cells to the insecticide. The pattern of degradation of carotenoids was similar to that of Chl a but the rate of degradation was less than for Chl a. The amount of lycopene also continuously decreased with increase of the insecticide concentration. There was gradual reduction of cellular phycocyanin and phycoerythrin contents of cells with rapid degradation during the first 6 hours of treatment. The fluorescence emission of phycobilisomes and photosystem II decreased with increased concentrations of insecticide and prolongation of treatment. The cyanobacterium did not show any recovery from insecticide stress during 30 hours of exposure.
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