This study aimed to characterize changes in surface morphology of the marine microalga Dunaliella salina following lead acetate exposure using Scanning Electron Microscopy (SEM) and to determine its elemental composition using Energy Dispersive Spectroscopy (EDS). The work is intended to improve understanding of D. salina responses to lead contamination and to support environmental monitoring and management of heavy-metal pollution. The D. salina culture was obtained from a laboratory stock maintained at the Laboratory of Molecular Biology and Marine Pharmaceutics, FPIK UNSRAT. Cells were motile and displayed morphological variability, ranging from elliptical to cylindrical forms, with radially symmetric cells measuring approximately 2.8-40 µm. Seawater for the culture medium was collected from an unpolluted coastal area, filtered through a 0.45 µm membrane using an aspirator and diluted with distilled water to a salinity of 20 ppt. Cultivation was conducted in Walne medium at 25°C and 20 ppt under continuous illumination from a 20 Watt fluorescent lamp. Cultures were harvested during the exponential growth phase, which was monitored daily by hemocytometer counts under a light microscope and then exposed to lead acetate at 30, 50 and 80 ppm respectively. Harvested biomass was centrifuged prior to SEM analysis, while cell density was quantified microscopically using a hemocytometer. The results showed no significant differences in cell density among the tested lead acetate concentrations and cell density was not associated with the observed structural characteristics across treatments. However, SEM observations demonstrated that lead acetate exposure caused evident cell-wall damage and measurable alterations in the surface morphology of D. salina. The mineral content found in D. salina consisted of carbon (C), oxygen (O), sodium (Na), magnesium (Mg), silicon (Si), sulfur (S), chlorine (Cl), potassium (K) and lead (Pb).
