As the planted acreage of genetically-modified crops increases annually around the world, so will the debris entering waterways containing plant incorporated protectants (PIPs). Valued for their high specificity and low impact on the environment, the activity and impact of crop PIPs on non-target terrestrial organisms are studied thoroughly. However, these parameters are relatively unexplored in flowing water systems. Since headwater streams near agricultural areas tend to have lower input, storage, and transport of organic matter, windblown crop debris may provide a disproportionately high source of allochthonous energy and nutrients for the biota. In this subsection of a multi-investigator study, the effects of the PIP delta endotoxins Cry1Ab and Cry3Bb from Bacillus thuringiensis var. kurstaki expressed in corn will be examined on non-target stream invertebrates in the laboratory. Five different invertebrates shredder taxa will be collected from the field and monitored for sub-lethal responses to three corn isolines: a non-Bt hybrid, a hybrid expressing the Cry1Ab toxin, and a stacked hybrid expressing both the Cry1Ab and Cry3Bb toxins. The potential ecological implications of the sublethal responses will be discussed. In addition we will discuss the incorporation of this study into new protocols being developed for assessing the future risk to stream biota and their ecological function.