A wide range of anthropogenic chemicals, including pharmaceuticals and personal care products (PPCPs) and pesticides, have been reported to be potentially toxic to hermatypic corals. Among PPCPs; oxybenzone (BP-3), used as a UV absorber in sunscreens, has been detected in coral reef areas at concentrations greater than 1000 µg/L. While initial studies reported toxic effects on corals at low concentrations, the toxicity-inducing concentration has varied between studies. Here, we report the effects of BP-3 on the transcriptome of hermatypic coral Acropora tenuis, one of the most representative species in the Indo-Pacific region.
Four treatments of cultured A. tenuis (7 d at 27.5 °C) were performed using an artificial seawater control, an acetone control, and 50 µg/L or 500 µg/L BP-3. Coral colour and maximum effective quantum yield (ΔF/Fm') were measured daily during the experiment. After seven days of exposure, transcriptome analysis of the corals and their symbiotic dinoflagellates was performed using next-generation sequencing. Genes with expression log2-fold changes (logFC) -1 ≥ logFC ≥1 and a false discovery rate ≤ 0.05 were identified as differentially expressed genes (DEGs). Gene ontology (GO) enrichment and pathway analyses of these DEGs were also performed.
Exposure to 50 µg/L and 500 µg/L BP-3 for seven days had no effect on coral colour or ΔF/Fm'. Transcriptome analysis revealed less than 50 DEGs among the predicted genes (> 20000 genes) in both 50 µg/L and 500 µg/L treatments compared to the acetone treatment control. While DEGs in the 500 µg/L BP-3 group included fluorescent protein genes, no enriched GO terms or pathways were detected at either concentration. Transcriptome analysis of symbiotic dinoflagellates showed no DEGs at either concentration compared to the acetone control treatment. Therefore, seven-day exposure to 50 µg/L and 500 µg/L BP-3 had very limited effects on Acropora tenuis and its symbiotic dinoflagellates.