Owing to the increase of pollutant sources in oceans, seas, and lakes, there is an expected effect on growth and metabolism of planktonic algae which are considered primary producers in the ecosystem. Therefore, it becomes urgent to carry out laboratory studies to test to what extent these pollutants can affect the growth of algae which is necessary as a food for marine fishes. Spirulina is considered the most important algal species due to its high nutritional value for humans and animals. Therefore, this work investigated the effect of different concentrations of Ni2+, Zn2+, and Cu2+ metal ion pollutants on growth of the blue-green alga Spirulina platensis. EC50 was identified to be around 2 mg/l for the three heavy metals. The suitability of Idku Lake for Spirulina platensis growth was investigated using multi-criteria spatial modeling integrated with remotely sensed data processing. Spatial distribution maps of turbidity, water nutrients, and phytoplankton were the input criteria used to assess Idku Lake’s suitability. The results obtained proved that low concentrations of the tested heavy metals stimulated growth and pigment fractions (chlorophyll a, carotenoids, and total phycobilins content) but to different degrees. The inhibitory effect was more prominent in the case of copper ions than zinc and nickel ions with all concentrations used. The overall suitability map of Spirulina platensis in Idku Lake showed that the whole lake is suitable for growth and proliferation except for the northwestern corner due to the high salinity levels. The present paper helps to understand the behavior of algae responding to environmental pollution, which supports environmental planners with the necessary baseline for investigating the fate of pollutants and the potential risk.

The presence of heavy metal ions in water is hazardous to one's health and the environment. Algae are frequently exposed to heavy metal pollution as a result of industrial waste dumping into water environments. Spirulina platensis, a significant kind of algae utilized commercially (especially for fish feeding) as a good source of protein, amino acids, minerals, vital unsaturated fatty acids, and a number of vitamins, was selected for this study because of its high nutritional value. This study examined how S. platensis responded to five different concentrations of the three heavy metals (nickel, copper, and zinc) in terms of its growth, fatty acid IR spectra, content, and total soluble protein profile. The remaining four doses (two higher and two lower) for each element were selected to evaluate the findings of 5 different concentrations of the three heavy metals because the EC50 for those three was almost at 2.0 mg/l. Compared to zinc and nickel, copper demonstrated a greater growth inhibitory impact as determined by optical density. Cu 2+ was more noticeable than Zn 2+ and Ni 2+ when compared to control cells in the IR spectra, which showed the creation of new molecules and the lack of other compounds. Total fatty acids decreased under stress at all concentrations examined, while saturated fatty acids outnumbered unsaturated fatty acids. Cu 2+ stress resulted in a more marked destructive effect of the heavy metal ions the protein profile than Zn 2+ or Ni 2+ stress.

This study focused on the effect of five different concentrations of three heavy metals (Nickel, Copper and Zinc) on growth, IR spectra, the content of fatty acids and total soluble protein profile in Spirulina platensis. Spirulina platensis was selected for this study because of its high nutritional value as an important form of algae that is used commercially (especially for fish feeding) as a source of proteins, minerals, amino acids, vital unsaturated fatty acids, and a range of vitamins. EC50 of the three heavy metals was recorded nearly at concentration 2.0 mg/l. The inhibitory effect of growth measured in optical density was more prominent in case of copper than zinc and nickel. IR spectra showed formation of new compounds and absence of other compounds when compared to untreated cells, it was clearer in case of Cu2+ than in case of Zn2+ and Ni2. Grand total fatty acids decreased under all the tested concentrations, saturated fatty acids were more dominant than unsaturated ones under stress conditions. The destructive effect of the heavy metal ions on protein profile was more prominent under the stress effect of Cu2+ than in case of Zn2+ and Ni2+.