Chlorinated paraffins (SCCPs and MCCPs) in corals and water-SPM-sediment system in the Persian Gulf, Iran: A potential global threat for coral reefs

Swift degradation of the coral reef ecosystems urges the need to identify the reef decline drivers. Due to their widespread use, bioaccumulative and toxic characteristics, chlorinated organic compounds, such as chlorinated paraffins (CPs), are regarded as specific pollutants of concern. Yet little is known about the occurrence of CPs in the coral reef ecosystems. This study focuses on the short-chain chlorinated paraffins (SCCPs) and medium-chain chlorinated paraffins (MCCPs). Their distribution and congener pattern were investigated in the water-SPM-sediment system and in the corals of the Larak coral reef for the first time. Chlorinated paraffins were detected in all the coral species. Their total loadings ranged from 42.1 to 178 ng g(-1) dw in coral tissue, from 6.0 to 144 ng g(-1) dw in the skeleton, and from 55.0 to 240 ng g(-1) dw in zooxanthellae. Soft corals were found to accumulate more CPs than Scleractinian corals. Zooxanthellae and mucus accumulated more CPs than tissue and skeleton. In most cases, congener group patterns were dominated by C-13 (for SCCPs) and C-17 (MCCPs) groups, respectively. The congener patterns of CPs altered to some extent between mucus and the remaining coral compartments. High loadings of CPs were detected in the skeleton of the bleached corals. Moreover, a significant negative correlation between the levels of CPs and the symbiodinium density was observed. (C) 2021 Elsevier Ltd. All rights reserved.

Automated summary

The study identified the presence of chlorinated paraffins in coral species at the Larak coral reef. Soft corals were found to accumulate more chlorinated paraffins than Scleractinian corals, with zooxanthellae and mucus accumulating more chlorinated paraffins than tissue and skeleton. Congener group patterns were dominated by C-13 for SCCPs and C-17 for MCCPs, with some alterations between mucus and other coral compartments. High loadings of chlorinated paraffins were detected in the skeletons of bleached corals, and a negative correlation between chlorinated paraffin levels and symbiodinium density was observed.