Differential bioaccumulation and tolerances of massive and branching scleractinian corals to polycyclic aromatic hydrocarbons in situ

Scleractinian corals are capable of accumulating polycyclic aromatic hydrocarbons (PAHs) in reef environments; however, the mechanism behind their PAHs tolerance is unknown. This study investigated the occurrence and bioaccumulation of PAHs in coral reef ecosystems and examined the physiological responses induced by PAHs in coral hosts and their algal symbionts, the massive coral Galaxea fascicularis and branching coral Pocillopora damicornis. G. fascicularis had a higher PAHs accumulation capacity than P. damicornis. Both the coral hosts and algal symbionts preferentially accumulated acenaphthene, dibenzo(a,h)anthracene, and benzo(a)pyrene. The accumulated PAHs by G. fascicularis and P. damicornis hosts was accompanied by a reduction in detoxification ability. The accumulated PAHs could induce oxidative stress in P. damicorni hosts, thus G. fascicularis demonstrated a greater tolerance to PAHs compared to P. damicornis. Meanwhile, their algal symbionts had fewer physiological responses to accumulated PAHs than the coral hosts. Negative effects were not observed with benzo(a)pyrene. Taken together, these results suggest massive and branching scleractinian corals have different PAHs bioaccumulation and tolerance mechanisms, and indicate that long-term PAHs pollution could cause significant alterations of community structures in coral reef ecosystems.