Potential degradation of polyaromatic hydrocarbons under anaerobic conditions of mangrove ecosystem

Mangroves are vulnerable habitats to pollution and accumulation of polycyclic aromatic hydrocarbons (PAHs).Many studies have reported the aerobic biochemical pathways of PAH degradation by bacteria and fungi but little is known about the anaerobic ones.In this paper,naphthalene was used as a model compound for PAHs demonstrating the possible anaerobic degradation pathways in mangrove environments.Oxidation of naphthalene was firstly found under anaerobic conditions in sediment columns and subsequently under strict anaerobic conditions and the processes were proved to be sulfate-reducing dependent by testing with sodium molybdate,a specific inhibitor of sulfate reduction.Further detailed studies isolated and identified several intermediates such as 2-naphthoate,5,6,7,8-tetrahydro-2-NA and decalin-2-carboxylate during the transformation processes of naphthalene.In these studies,different initial steps (hydroxylation or carboxylation) were proposed for naphthalene degradation.However,specific transformation steps for naphthalene will need further investigation to elucidate if degradation pathway of benzoate is involved.