We have shown for the first time how arsenic is distributed in >90% of the biomass of a freshwater food web.
Our data vividly show the biodiminution of arsenic between three levels of a freshwater food web.
We report a living organism, Motobdella montezuma, with an exceptionally high arsenic content of 2810 mg kg−1.
Our data illustrate that the transformations of arsenic in the Montezuma Well ecosystem appear to be species specific.