Effects of Anthropogenic Chemicals on Hermatypic Corals with Special Reference to Gene Expression

Abstract

Many studies have reported the adverse effects of various anthropogenic activities, including climate change and ocean acidification, on coral reefs. While the molecular effects of these environmental stressors on corals and symbionts have been well studied, the effect of anthropogenic chemicals on corals remains poorly understood. In this review, we investigated the potential toxic effects including bleaching by heavy metals (copper and cadmium), organotins (TBT, tributyltin), polycyclic aromatic carbons (PAHs) (anthracene, phenanthrene, and benzo[a]pyrene), polychlorinated biphenyls (PCBs, PCB118, representative congener of PCBs, and Aroclor 1254, representative PCB products), photosystem II herbicides (Diuron and Irgarol 1051), and other contaminants (caffeine, 4-nonylphenol, and oxybenzone) on gene expression biomarkers. The potential biomarkers mainly included chaperones (heat shock proteins HSP70 and HSP90 and calreticulin), components of the cytochrome P450 monooxygenase system, antioxidant enzymes (glutathione S-transferase [GST], catalase [CAT], and superoxide dismutase [SOD]), and green and red fluorescent proteins (GFP and RFP). Another survey using DNA microarray and RNA sequencing (RNA-seq) identified hundreds to thousands of differentially expressed genes (DEGs) in corals and the symbiotic dinoflagellates. Bioinformatics analyses using DEGs also documented the potential effects of various gene ontology terms, pathways, and protein interaction networks. These findings using transcriptomic approach provide new insights into the potential molecular mechanisms underlying the toxic and bleaching effects of anthropogenic chemicals on corals and symbiotic dinoflagellates.