Microcystin is a deadly toxin produced during algal blooms. The cells release MCLR which can cause significant neurological and behavioral damage to organisms exposed to the toxin. MCLR can exist in the water column and in the sediment and through normal ecological processes move between those two states or location. Given the location of the toxin, it is possible that MCLR in the sediment could have different adverse effects on organisms as opposed to when the toxin is in the water column. We tested that idea using crayfish that were exposed to either nothing, a vehicle to carry the mclr, and mclr. In addition, the toxin and vehicle were dosed either in the water column or in the sediment. Behavioral and physiological measures were taken after 4 days of exposure, The results indicate that at both the behavioral and physiological level, the location of the toxin has different adverse effects.