Defense Date

5-9-2022

Document Type

Thesis

Degree Type

Master of Science

Degree Name

Marine Science

First Advisor

D. Abigail Renegar

Second Advisor

Bernhard M. Riegl

Third Advisor

Nicholas R. Turner

Keywords

zinc oxide, titanium dioxide, toxicity, Acropora cervicornis, sunscreen, mineral filters

Abstract

Coral reefs are one of the most diverse and biologically significant ecosystems on the planet. However, anthropogenic impacts have led to a global decline in overall reef health in recent years. To address concerns that organic ultraviolet filters in sunscreen may contribute to reduced coral health, the mineral UV filters, zinc oxide (ZnO) and titanium dioxide (TiO2), have become more common in sunscreen formulas as they are often considered “reef safe” despite limited information on the toxicological effects of these compounds in corals. This study evaluated the effects of exposure to unmodified forms of zinc oxide or titanium dioxide compared to the commercial products ZinClear IM® 50CCT (ZnO 50%) and UV Cut (TiO2 40%) on the threatened Atlantic scleractinian coral, Acropora cervicornis. Exposure-associated stress on coral fragments was determined utilizing measurements of photosynthetic efficiency, behavioral responses, and calcification in 48-h exposure assays. Corals exposed to TiO2 were observed to have mild to moderate response during the 48 h exposure but ultimately returned to normal behavior at the end of the 48-h exposure. Corals exposed to ZnO had moderate to severe responses, with a high percentage of tissue mortality at concentrations > 190.7 µg/L. Exposure to ZinClearIM® 50CCT or UV Cut resulted in no significant response and no mortality. Corals had a significantly greater response to ZnO in comparison to TiO2.

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