Trace element accumulation in fish and their prey: Comparing essential and non-essential elements

We measured tissue concentrations of essential (As, Se, and Zn) and non-essential (Cd, Cs, Hg, Pb) trace elements in tissues of stream-dwelling fish and their macroinvertebrate prey from 15 sites in New England streams.  All streams were in forested watersheds with no industrial point sources.  Spatial variation in essential element tissue concentrations in fish (2.2 to 3.6-fold range in site means) was much lower than variation in non-essential element concentrations (10 to 240-fold variation in site means), suggesting greater physiological control of essential elements even though concentrations were well above physiological requirements.  Cd, Cs, Hg, and Se concentrations in fish closely tracked those in their macroinvertebrate prey, consistent with dietary accumulation of these elements.  Only Hg biomagnified from invertebrates to fish, other element concentrations in fish were similar to (As, Pb, Zn) or lower than (As, Cd, Cs) their prey.  Fish tissue concentrations of most elements were reduced at sites with high pH, likely due to reduced bioavailability, and high individual growth rates, likely due to growth dilution.