The main determinate of bioaccumulation could be sulfur concentrations, but Lucotte does not say this. When Hg is found in aquatic wildlife, it is mostly in predatory fish. Lacustic Hg will decrease if the source is eliminated, such as in European lakes surrounding closed FSU facilities. In Canada, most soil Hg is in the top 5-10 cm of dirt. Most of this Hg is natural.
Animals have a difficult time eliminating methylmercury from their systems.
In contrast, reactive mercury can be excreted while natural mercury can be exhaled. A lot of fish exceed the consumption guidelines of 0.5 ppm. These contaminated fish can be found even in lakes without a direct discharge of mercury. Atmospheric mercury enters these lakes as wet and dry precipitation of reactive mercury. Most of the mercury remains as reactive mercury, but a small proportion is either methylated or volatilized.