If you want to estimate how much methylmercury is present in marine animals look to the water, not the sediment to do it. That was the findings of a paper published earlier this week in the journal PLOS one.
The researchers looked at methylmercury (MeHg) levels in the sediment and in water at 10 sites in the Northeast US. They found that the level of MeHg detected in the sediment was only correlated with the levels found in bottom feeders such as worms and that it was the level in the water that correlated more with what was detected in fish.
The data suggests that the theory of MeHg accumulation from the “bottom up” does not seem to fit with what they observed.
Currently most water systems are managed based on the MeHg detected in the sediment, the researchers advise that water column levels should also be taken into account.