Defense Date

8-7-2025

Document Type

Thesis

Degree Type

Master of Science

Degree Name

Marine Science

First Advisor

D. Abigail Renegar, Ph.D

Second Advisor

Carys Mitchelmore, Ph.D.

Third Advisor

Dimitrios Giarikos, Ph.D

Keywords

arsenite As(III), arsenate As(V), half maximal lethal concentration (LC50), half-lethal effect concentration (EC50), half-maximal inhibitory concentration (IC50), NOEC, LOEC, Acropora cervicornis, Orbicella faveolata

Abstract

Inorganic arsenic (As), specifically arsenate (As(V)) and arsenite (As(III)) are well-documented toxicants to a range of marine organisms. However, their specific impacts on coral reef species remain largely unstudied. This study is the first to assess the acute and subacute toxicity of inorganic arsenic on two threatened scleractinian coral species, Acropora cervicornis and Orbicella faveolata. Corals were exposed for 96 hours to five analytically verified concentrations and a negative control of either arsenate or arsenite. Toxicity was evaluated through three endpoints: mortality (LC50), coral condition (EC50), and photosynthetic efficiency (IC50). The lethal concentrations to result in 50% mortality (LC50) were 0.0367 mg L-1 (95% CI 0.0342-0.0393 mg L-1) arsenate and 0.111 mg L-1 (95% CI 0.09992-0.131 mg L-1) arsenite for A. cervicornis and 0.315 mg L-1 (95% CI 0.304 -0.326 mg L-1) arsenate and 0.235 mg L-1 (95% CI 0.223-0.250 mg L-1) arsenite for O. faveolata. Additionally, significant adverse effects were observed with the subacute endpoints in both coral species and inorganic arsenic exposures. Orbicella faveolata exhibited significantly greater sensitivity to arsenite, whereas Acropora cervicornis showed greater sensitivity to arsenate, indicating species-specific responses that challenge the prevailing assumption of universally higher toxicity of arsenite across taxa. Species sensitivity distributions were developed highlighting the lower LC50 values for these corals compared to previously reported marine organisms’ LC50s. These findings underscore the ecological risk that inorganic arsenic poses to coral reef ecosystems and offer critical data to inform sediment quality guidelines and environmental management strategies, particularly in anticipation of coastal dredging activities.

ORCID ID

0009-0002-2260-6858

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