Coral reef systems are a special type of aquatic environment and an ecologically critical zone in tropical and subtropical oceans. They provide valuable ecosystem service functions, such as high primary productivity, supply of multiple natural resources, and high-quality seafood, as well as conservation of coastal environments. However, coral reef ecosystems have been widely contaminated by chemicals released from intense human activities.
Polycyclic aromatic hydrocarbons (PAHs), generated mainly from human activities, are ubiquitous environmental contaminants. PAHs of high toxicity, mutagenicity, carcinogenicity, and persistence may exert highly negative effects on corals, flora, and fauna in the coral reef ecosystem and even human health via trophic transfer through food webs.
To date, our understanding of the trophodynamics of PAHs in coral reef ecosystems is lacking. The coral reef system in the South China Sea is one of the most diverse and well-developed systems in the world but, due to aggravating factors such as chemical contamination, it is becoming increasingly damaged. In order to reveal the pollution status and composition pattern of PAHs in sediments, fish, corals, and other invertebrates and clarify the trophic transfer characteristics of PAHs in the coral reef ecosystems, the authors of the latest Editor's Choice paper explore the PAHs in a typical coral reef ecosystem in the South China Sea.
Based on a series of investigations of PAHs in the coral reef ecosystems of the Xisha and Nansha Islands in the South China Sea, the authors found that the concentrations of the total PAHs are 9.00-32.48ng g-1 dw (dry weight) in sediments, 6.77-69.40 ng g-1 dw in corals, 3.60-28.70 ng g-1 dw in invertebrates and 12.79-409.28 ng g-1 dw in fish, and their PAHs composition are different. Combing with results from stable isotope analyses and the trophic magnification factors (TMFs) method, a limited trophic transfer of PAHs is found in the Xisha food web while a trophic magnification of PAHs is shown in the Nansha food web. Trophic biodilution seems not very likely to occur in these two coral reef ecosystems.
By comparison with other ecosystems, it is speculated that the reasons for differences in trophodynamics among ecosystems may be attributed to different ecosystem characteristics (e.g. the food chain length). Octanol-water partition coefficient of PAHs may have positive influences on the PAH biomagnification.
This study provides the first comprehensive assessment of the pollution status, composition pattern, and particular trophodynamics of PAHs in tropical coral reef ecosystems and serves as a first step towards ecological risk assessment, biodiversity conservation and coastal function management in global coral reef systems. By examining the potential risk of biomagnification of PAHs in high-trophic-level marine life via trophic transfer, the authors hope to raise public awareness that the pollutants we have produced and are producing may poison numerous marine lives and eventually ourselves!