الفهرس 
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Abstract
5- Summary
The nannoplanktons are considered to be the most important marine phytoplankton components since they constitute the basic food of almost all the marine larval organisms and other marine creatures which are considered to be the first organisms affected by heavy metals pollutant discharged in aquatic environment because they are directly in contact with the medium separated only by the cell wall and the cytoplasmic membrane. The distribution and diversity of several algal species were correlated with type and concentration of metal ion in the environment .Consequently information about the role of these heavy metals and related physiological activities must be investigated. So this work aims to study the growth of the filamentous blue green alga Spirulina platensis and synthesis of some important metabolites under normal conditions as well as under the effect of different concentrations of three heavy metals namely nickel, zinc and copper. The work was also extended to study the effect of these three elements on the activity of total antioxidants together with the atomic absorption of the biophasic uptake of those heavy metals. The results obtained from all the experiments that have been conducted in this study could be summarized in the following:
1- Anent effect of Ni2+, Zn2+ and Cu2+ions on growth of Spirulina platensis and its related metabolic activities, the results indicated that lower concentrations of these elements stimulated the growth of S. platensis measured as optical density and content of chlorophylls a, total carotenoids and total proteins. On the contrary, higher concentrations inhibited these algal parameters. The toxicity of these elements on growth was more prominent in case of copper than in case of zinc and nickel and at the end of the culturing periods.
2- Regarding content of protein, carbohydrates and amino acids under the effect of the different concentrations of these elements (Ni2+, Zn2+ and Cu2+) the results proved that they affected the content of these metabolites with different degrees. Under lower concentrations of these elements the content of the measured metabolites increased but with different responses. The increase in content of these metabolic products with low concentrations of the tested heavy metals may be attributed to inhibition to export out these metabolites from the cells by heavy metals. On the other hand, inhibition in their accumulation induced by higher concentrations of heavy metals may be attributed to the toxic action of these heavy metals on the enzymatic reactions responsible for biosynthesis of these metabolites.
3- Concerning fatty acids content of the tested alga after 10 days of culturing under the effect of the different concentrations of the three chosen elements, it is clear that, by gradual increase in the concentration of the element, the total content of the three fatty acids groups gradually decreased. The toxic effect of Ni2+, Zn2+ and Cu2+ was found to be concentration dependent i.e. the toxic effect increased with increasing the element concentration. The toxic effect was more prominent in case of mono-unsaturated and poly-unsaturated fatty acids than in case of saturated one.
4- The effect of the different concentrations of Ni2+, Zn2+ and Cu2+ on growth, synthesis of protein, carbohydrates, amino acids and fatty acids content of S. platensis proved that Ni2+ ions were less toxic than both Zn2+ and Cu2+ ions.
5- The obtained Infrared peaks of the major cell constituents of the treated Spirulina platensis cultured for 8 days with the five concentrations of the tested metals showed the appearance of new peaks and the disappearance of others. At the same time few peaks remained unchanged when compared to control. Most of the new peaks appeared in the region between 4000 and 2010 cm-1, and between 700 and 250cm-1 which contained the asymmetric and symmetric C-H of methylene groups and also V C-O-C of polysaccharides. On the other hand, most of the absorption peaks that disappeared were in the region between 1650 and 1000 cm-1, which constituted the V C=O and δ N-H of amides associated with proteins, δas CH3 and Sas CH2 of proteins, δs CH3 and Ss CH2 of proteins and VS C-O of COO- groups, Vas P=O and Vs P=O of phosphodiester backbone of nucleic acids. At 1.0 mg/L Ni2+the obtained number of peaks were the same as in case of control i.e. 59 absorption peaks, while in case of Zn2+ and Cu2+ under the same concentration, the number of peaks increased to 69 and 86 respectively. This increase of peaks significantly increased at 2.0 and 3.0 mg/L of Cu2+, Zn2+ and Ni2+. For example, at 3.0 mg/L Cu2+ the total absorption peaks that obtained increased by 81.4% while in case of Zn2+ and Ni2+ the percentage of increase in absorption peaks reached 23.7% and 5.1% respectively compared to control.
6- Concerning atomic absorption, the results cleared that the more the concentration of the element and the period of culturing, the less in the passive uptake and the more in the active uptake of the element. This in turn will cause reduction in the percent of residual metal ions.
7- The gel plate of the total soluble protein profile of S. platensis at control and under the effect of different concentrations of Ni2+, Zn2+ and Cu2+ showed different bands with similar and different RF values. In nearly all the lanes most of bands appeared in the region between 13 and 241KDa. The number of bands obtained for control was 17 bands, while in case of the treated organism this number increased or decreased depending on type and concentration of the metal ion. The protein profile cleared that Spirulina platensis is more sensitive to Cu2+ than both Ni2+ and Zn2+.
8- The effect of different concentrations of Ni2+, Zn2+ and Cu2+ on the total antioxidants activities revealed that: the antioxidant activity increased gradually under the stress of all the concentrations used, but at the most higher concentrations of these elements, their activities slightly decreased but still slightly higher than control.