This report has examined in detail bioaccumulation of elements in freshwater aquatic biota and selected species of terrestrial plants (mosses) and wildlife (caribou). The elements chosen are those that have sufficiently long-lived radioactive isotopes that they could reasonably be expected to cycle through the Great Lakes biotic communities and exert both the chemical effects associated with the element as well as any harm from alpha, beta, and gamma radiation that accompanies the isotope. The only alpha emitter for which any biotic data existed that met the tests of quality assurance and reportability of the Task Force was thorium. Most of the remaining isotopes covered are beta emitters.

The report examined aquatic plants, zooplankton, and a terrestrial insect. Appropriate data for fishes were not available, although some model analyses of fish data supplied by Dr. Jack Cornett of the Chalk River Laboratory in Canada give a possible snapshot as to what bioaccumulation figures might be for fishes. In addition, selected fish data from Ontario Hydro's nuclear power stations on the Great Lakes were available for ⁴⁰ K and ¹³⁷ Cs. From these data, selected bioaccumulation factors were suggested.

The various data strongly suggest that bioaccumulation within freshwater food chains requires careful study. The behavior of many elements which have radioactive isotopes of half-lives greater than 40 days is often anomalous and unexpected. Many elements perform their physiological function as part of interconnected metabolic systems, and therefore, one must examine the behavior of several elements as a suite before assuming that a given bioaccumulation factor is appropriate. This is especially true when using data from marine species to make judgments about freshwater species.