Manganese is introduced into water sources by mine runoff, fracking, and industrial waste processes. Overexposure to Mn leads to a variety of health issues in humans, including progressive, irreversible neurodegenerative effects, increased heart rate and blood pressure, liver damage, decreased fertility, and increased fetal abnormalities. Contaminated freshwater sources could be improved using phytoremediation, a growing field of research that has shown success in removing nitrate and phosphate contamination from water sources. However, published studies regarding metal removal are limited. Chlorella vulgaris is a unicellular green microalga that can absorb heavy metals. However, in published studies of Cd, Cu, and Zn, C. vulgaris experienced metal toxicity with symptoms including reduced cell growth, pigment concentrations, and production of proteins and carbohydrates, limiting the potential to use C. vulgaris for phytoremediation. No published research has looked at Mn toxicity in microalgae. The objective of this study was to physiologically characterize the effect of elevated Mn on C. vulgaris and to determine if C. vulgaris could be used in phytoremediation of Mn-contaminated freshwater. The algae was grown in increased Mn concentrations and assayed for metabolic changes by monitoring its biochemical composition and photosynthetic activity before determining intracellular and extracellular Mn concentrations using inductively coupled plasma optical emission spectroscopy. Results show that C. vulgaris has the capacity to bioaccumulate up to 1.25 mg/mL of Mn while showing a maximum of a 25% reduction in terminal turbidity. Additionally, increased Mn exposure results in a delay of maximum photosynthetic efficiency in the alga, but maintains the peak photosynthetic efficiency for a greater amount of time. While the cells also exhibit a decrease in lipid and carbohydrate production, cell viability studies show that prolonged Mn exposure is not toxic to C. vulgaris. Based on this work, C. vulgaris could be a good candidate for phytoremediation of Mn-contaminated freshwater.

Bioaccumulation capacity and physiological characterization of Chlorella vulgaris exposed to elevated Mn concentrations

2019 Spring National Meeting

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