Reliability of benthic indices in health assessment of coral reefs subjected to oil pollution

Coral reefs provide humans with numerous ecosystem services and therefore the need for sustainable use of their resources is evident. Oil pollution introduces numerous hazardous pollutants into the marine environment, which could easily influence the viability, assemblage structure, and species composition of benthic organisms. Consequently, any alteration in benthic communities can provide a warning of stress and ecosystem decline. Using powerful statistical tools, the main objective of the present study was to evaluate the reliability of benthic indices to detect possible impacts of oil pollution on coral reefs across an oil pollution gradient in Kharg Island. In this regard, multiple indices including the bioaccumulation of polycyclic aromatic hydrocarbons (PAHs) in coral tissues, live coral cover, alpha and beta diversity of macroinvertebrates, as well as a new index called "Sediment Constituent Index" (SEDCON) were investigated. Live coral cover was estimated by video transects. Five cm of surface sediment was collected and immediately fixed with ethanol and Rose Bengal solution for macrobenthic communities and SEDCON measurements. The reliability of each index was assessed using estimations of the effect size (using omega-squared), and decision trees (Classification and Regression Tree (CART)). The findings suggest that PAHs concentration more than ۱۳۶ ng.g-۱ in massive corals, live coral cover less than ۲۹%, and the SEDCON values below ۴.۲۵ may reflect the adverse effect of oil contamination and provide warning of degradation in a coral reef area. This encourages decision-makers to execute routine monitoring and mitigation practices to maintain healthy reefs in the study areas.

کلیدواژه ها:

Persian Gulf ، Polycyclic aromatic hydrocarbons ، Bioaccumulation ، Hard coral ، Benthic communities