Trophic decline and distribution of barium in a freshwater ecosystem

Abstract

Barium is generally considered a nonessential element with low toxicity, and with uptake from food sources balanced by excretion. Investigations into the dynamics of Ba in freshwater ecosystems have been limited. I show a 3-fold, trophic level-related decline in Ba in a freshwater ecosystem from a high of 60.9 µg/g for crayfish (Crustacea Orconectes virilis) to 0.438 µg/g for the largest individuals of a top predator (walleye Sander vitreus >3 kg). Barium concentrations were significantly higher in organisms (invertebrates and fish) associated with benthic substrates compared with those associated with pelagic environments. Thus, the concentration of Ba in muscle of 12 fish species was generally aligned along a pelagic to benthic food source gradient. These patterns may be related to relatively low concentration of Ba in water (77 µg/l) compared to the concentration of Ba in lake sediment (679 µg/g). Species level Ba assessments may provide a practical tool to assist with the identification of food web links and species specific routes of energy transfer in freshwater ecosystems.