Transport and degradation of Cry1Ab protein derived from genetically-engineered maize crop byproducts in agricultural streams

Headwater streams draining agricultural landscapes receive genetically-engineered maize detritus containing the insecticidal Cry1Ab protein through wind action and surface runoff.  Our previous research has shown that once in streams, maize leaves leach Cry1Ab protein at a detectable rate.  However, the fate of dissolved Cry1Ab has not been determined.  We used a combination of field and laboratory studies to assess the potential for transport and degradation of Cry1Ab in streams.  We collected water samples in 11 central Indiana streams during the summer growing season before and after pollen shed and bracketing maize harvest in autumn to explore the spatial and temporal distribution of Cry1Ab.  We detected Cry1Ab in streams and tile drains in all seasons, regardless of crop type planted adjacent to stream channels (e.g., genetically-engineered maize, traditional maize, or soybeans).  Maize leaching experiments in re-circulating light and dark artificial streams showed that Cry1Ab protein does not photodegrade and was detectable in water as long as maize leaves persisted (~70d).  Ongoing mesocosm studies will determine the relative influence of biotic and abiotic processes on Cry1Ab degradation.  It is essential to consider the fates of Cry1Ab in aquatic ecosystems in order to fully understand the influence of widespread planting of genetically-engineered crops.