Abstract Heavy metal contamination is considered one of the most serious environmental threats, posing significant risks to human health, aquatic ecosystems, and animal life. The marine microalga Dunaliella salina is of high nutritional and ecological importance and serves as a valuable bioindicator for assessing aquatic pollution. This study investigates the spatial distribution and risk assessment of three heavy metals (Ni, Zn, and Cu) in Manzala Lake, Egypt, and examines their ecotoxicological effects on D. salina . The spatial suitability of Manzala Lake for algal growth was evaluated using Landsat imagery and geospatial analyses based on the obtained results. The alga was employed as a biological monitor to evaluate the stress induced by metal exposure through measurements of growth rate, chlorophyll content, cellular ultrastructure, and antioxidant enzyme activities (peroxidase, superoxide dismutase, and catalase). The results revealed that the EC 50 values for the three metals were approximately 15 mg/L. Lower concentrations of Ni, Zn, and Cu stimulated algal growth and chlorophyll content, whereas higher concentrations inhibited both parameters, with the extent of inhibition varying according to the metal type and dosage. Among the three analyzed metals, copper exhibited the highest toxicity under all tested concentrations, followed by zinc and nickel. Ultrastructural examination of D. salina cells revealed distinct morphological alterations, further confirming the greater toxicity of copper compared with the other metals. The southern parts of the lake exhibited the highest concentrations of all investigated metals, primarily due to the inflow of wastewater from multiple drainage sources. Seasonal variations significantly influenced metal concentrations, resulting in fluctuating suitability between summer and winter. Nevertheless, the analysis indicated that nearly 70% of Manzala Lake remains suitable for D. salina growth with respect to Ni, Cu, and Zn levels, except for a few scattered unsuitable patches. Overall, the study aligns with Sustainable Development Goal (SDG) 6 by contributing to scalable solutions aimed at reducing pollution, protecting aquatic ecosystems, and promoting the sustainable management of water resources. Graphical abstract
Kaamoush et al. (Tue,) studied this question.