Animals living in aquatic habitats regularly encounter anthropogenic chemical pollution. Typically, the toxicity
of a chemical toxicant is determined by the median lethal concentration (LC50) through a static exposure test.
However, LC50 values and static tests do not provide an accurate representation of exposure to pollutants within
natural stream systems. In their native habitats, animals experience exposure as a fluctuating concentration due
to turbulent mixing, temporal variations of contamination (seasonal inputs), and contaminant input type (point
vs. non-point). Research has shown that turbulent environments produce exposures with a high degree of
fluctuation in frequency, duration, and intensity. In order to more effectively evaluate the effects of pollutants,
we created a dynamic exposure paradigm, utilizing both flow and substrate within a small mesocosm. A
commonly used pharmaceutical, naproxen, was used as the toxicant and female crayfish (Orconectes virilis) as
the target organism to investigate changes in fighting behavior as a result of dynamic exposure. Crayfish
underwent either a 23 h long static or a dynamic exposure to naproxen. Following exposure, the target crayfish
and an unexposed size matched opponent underwent a 15 min fight trial. These fight trials were recorded and
later analyzed using a standard ethogram. Results indicate that exposure to sublethal concentrations of
naproxen, in both static and flowing conditions, negatively impact aggressive behavior. Results also indicate that
a dynamic exposure paradigm has a greater negative impact on behavior than a static exposure. Turbulence and
habitat structure play important roles in shaping chemical exposure. Future research should incorporate
features of dynamic chemical exposure in order to form a more comprehensive image of chemical exposure and
predict the resulting sublethal effects from exposure. Possible techniques for assessment include utilizing flowthrough
experimental set-ups in tandem with behavioral or physiological endpoints as opposed to acute toxicity.
Other possibilities of assessment could involve utilizing fine-scale chemical measurements of pollutants to
determine the actual concentrations animals encounter during an exposure event.