Mercury Magnification In Riverine Food Webs In The Northern Rocky Mountains: Clark Fork River Basin, Montana, U.S.A.

Scientific Disciplines
Environmental Sciences & Engineering
Biological Sciences - Aquatic
food web
University of Montana
trophic levels
Volume 17, No. 1-4

Mercury magnification in riverine food webs in the 
Northern rocky mountains: clark fork river basin, 
Montana, u.s.a.
Molly F. Staats,* University of Montana, Geosciences Department,
Heiko Langner, University of Montana, Geosciences Department, 
At a local scale, such as the Clark Fork River Basin (CFRB), historic gold mining 
contributes the majority of mercury (Hg) found in the environment. Mercury enters aquatic 
systems in inorganic forms and is transformed to methylmercury (MeHg) by bacteria. MeHg 
has the ability to bioaccumulate within higher trophic levels, causing severe neurotoxic 
diseases and mortality. Hg concentrations observed within an aquatic food web are controlled 
by two factors, a source of inorganic mercury and the potential for that Hg to become 
methylated (methylation controlled by environmental conditions i.e.: water velocity, organic 
matter, etc.). A sufficient source of inorganic mercury and environmental conditions which 
promote Hg methylation can lead to maximum MeHg biomagnification. This study presents 
a comprehensive look at food web Hg biomagnification within the CFRB. Hg concentrations 
are characterized through blood or tissue samples from osprey, fish, and aquatic 
macroinvertebrates. Additionally we look at controlling Hg biomagnification factors, Hg of 
fine-grained sediment, percentage of wetlands and riparian land cover, and mean monthly 
discharge, to access the biomagnification process within the watershed and thus the Hg levels 
observed throughout these three trophic levels. Preliminary results show Hg levels of aquatic 
invertebrates have been found to be heavily influenced by the source of Hg (fine-grained 
sediment), while upper trophic level species exhibit a strong correlation to environmental 
characteristics of the sample reach.