NOAA recommends a site-specific approach that focuses on determining the availability of mercury and the potential for toxic effects. The accumulation of mercury in aquatic biota is often the primary concern at mercury sites and is useful for assessing availability. Bioaccumulation studies should measure tissue concentrations in more than one resident and/or transplanted caged species, preferably with species representing different trophic levels or different food web pathways. It may not be possible to correlate sediment mercury concentrations with concentrations in biota. However, correlations between mercury concentrations in predator and prey species may be useful in determining pathways of mercury transfer.
Toxicity tests such as the standard amphipod tests should also be conducted to assess mercury toxicity to benthic organisms. At major mercury sites, chronic toxicity endpoints should be included in the assessment - in particular, fish early life stage or reproductive endpoint tests. Because of the persistence of mercury in aquatic systems, source control alone may not be sufficient to permit recovery. Additional remedial actions may be required to reduce the total mercury burden in the system. Long-term monitoring of tissue concentrations of mercury in aquatic biota is needed to assess remedial effectiveness.