Methylmercury bioaccumulation among different food chain levels in the EEZ of Qatar (Arabian Gulf)

Methylmercury (MeHg) concentrations in three different species from different trophic levels with different amounts of Hg exposures were determined for the first time in the EEZ of Qatar. Sampling was conducted during autumn 2017 in two nearshore (Palm Tree and Al-Besheriya Islands) and two offshore locations (Sherawoo and Ishat Islands). Fish muscle and liver tissues were analyzed according to the US Environmental Protection Agency Method 1630. The lowest mean MeHg concentration was found to be 42.3 ppb wet weight in the lower trophic level fish Gerres oyena due to small fish size and trophic level; whereas, the highest MeHg concentration was found in higher trophic level sharks Rhizoprionodon oligolinx and Chiloscyllium arabicum with mean wet weight concentrations of 712 ppb and 166 ppb, respectively. Linear relationships were found between fish body size (weight, length, age) and MeHg concentrations. MeHg bioaccumulation was found to be higher in liver than in muscle tissue; however, there was no significant difference in tissue MeHg accumulation as well as, the concentrations between the four locations. The present study concludes that MeHg in most of the fish tissues is within the allowable limits and pose no threat to public health. Only the higher trophic level shark Rhizoprionodon oligolinx was found to have a MeHg concentration higher than the US EPA advisory level of 0.3 ppm. However, consumers should still be encouraged to eat smaller sized younger fish from lower trophic levels, which would be safer than larger older species from higher trophic levels.