Coral reefs are at risk of exposure to petroleum hydrocarbons from shipping spills and uncontrolled discharges during extraction. The toxicity of petroleum hydrocarbons can substantially increase in the presence of ultraviolet radiation (UVR), therefore spills in shallow coral reef environments may be particularly hazardous to reef species. Here we investigated the sensitivity of coral larvae (Acropora tenuis) to dissolved hydrocarbons from heavy fuel oil (HFO) and diesel in the absence and presence of UVR. Larval settlement success decreased with increasing concentrations of dissolved HFO, and co-exposure to UVR doubled the toxicity: 50% effect concentrations (EC50) decreased from 96 (-UVR) to 51 (+UVR) total petroleum aromatic hydrocarbons (TPAH). Toxic thresholds for HFO were similar to concentrations reported during marine spills: EC10s of 24 (-UVR) and 15 (+UVR) μg l-1. While less toxic, diesel also reduced settlement and exhibited phototoxicity: EC10s of 122 (+UVR) and 302 (-UVR) μg l-1. This study demonstrates that the presence of UVR increases the hazard posed by oil pollution to tropical, shallow-water coral reefs. Further research on the effects of oils in the presence of UVR is needed to improve the environmental relevance of risk assessments and ensure appropriate protection for shallow reef environments against oil pollution.
Bibliographical noteFunding Information:
The authors would like to thank the Australian Institute of Marine Science Townsville (AIMS) and the National Sea Simulator (SeaSim), Tristan Lever and Edith Strecker for logistical support as well as Gerard Ricardo and Patricia Menendez for their advice regarding statistical analysis. This work was supported by a research grant set up as part of the collaborative research project between the Red Sea Research Center (RSRC) at King Abdullah University of Science and Technology (KAUST) and the AIMS.
© 2018 The Author(s).
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