Effects of Sunscreen Chemicals on Freshwater Algae

Roughly 14,000 tons of sunscreen enter the waterways across the entire globe every year. Sunscreens are released via human contact, runoff from sand, and spray-on sunscreens. Although sunscreen is effective against UV radiation, the active ingredients harm aquatic ecosystems and damage coral reefs. Sunscreens have been found in the cenotes in the Yucatan Peninsula, underground water systems that serve as safe drinking water and are home to marine life. The presence of these chemicals poses a risk to human health if consumed and is a hazard to the wildlife living in the freshwater ecosystem. In this study, we investigate three sunscreen chemicals found in the cenotes: ensulizole (PBSA), sulisobenzone (BP-4), and zinc oxide. Zinc oxide has been shown to be a safer alternative to PBSA and BP-4 in coral reefs but the impact on freshwater systems is less well understood. In this study, we investigate the impact of sunscreen chemicals on a freshwater green algae, Chlorella vulgaris. C. vulgaris was grown with different concentrations of each sunscreen, then algal growth was measured using spectrophotometry. It was found that PBSA and BP-4 did not significantly impact C. vulgaris growth, but increased zinc oxide concentrations significantly decreased algal growth.