| In the Midwestern US, corn byproducts enter streams draining agricultural land. Genetically modified Bt corn is commonly planted along streams, but the potential effects of Bt toxins on freshwater ecosystems are unknown. The objective of this study was to assess the effects of Bt corn detritus on aquatic invertebrates in agricultural headwater streams.;I sampled benthic macroinvertebrates in streams surrounded by Bt corn and non-Bt corn and found no significant differences in community composition. I used litterbags to measure decomposition rates for Bt and non-Bt corn in streams and to identify differences in taxa colonizing Bt and non- Bt litterbags and found no difference in decomposition rates or invertebrates colonizing litterbags. I conducted laboratory Bt and non- Bt corn detritus feeding trials on common invertebrate taxa and found that the shredding Trichopteran, Lepidopstoma liba, grew significantly slower when fed Bt corn compared to non- Bt corn, while other taxa examined did not show a Bt effect.;In-situ findings did not support laboratory results in this study. This is likely because agricultural streams are highly disturbed systems, with multiple stressors occurring over long periods of time. Invertebrate communities in these systems are already highly stressed and reflective of degraded conditions, and this may not show effects from a single stressor such as Bt toxin. |
