Cycling of Novel Allochthonous Carbon in Midwestern Agricultural Streams

在美国中西部以农业为主的景观中，小型水源溪流是一种重要的淡水资源，但相对于更原始的水生生态系统，研究不足。去除天然河岸植被的农业做法可能会改变为生态系统过程提供燃料的能源基础。作物副产品（如未收获的叶子）可能是受农业影响的水源中主要的碳源。这种新型碳源对河流生态系统功能的作用尚未确定。我们将量化中西部18条河流中玉米叶屑和花粉的投入、存量、分解和运输。2000年，北美玉米带种植了大约2800万公顷的玉米，其中18%种植了Bt玉米。由于Bt -内毒素在整个植物中产生，分散的花粉和未收获的叶子进入农业溪流可能被各种水生生物消耗，从而对环境构成威胁。转基因作物对水生生态系统中非目标物种的潜在影响很少受到关注，而对水源流作为Bt -内毒素在环境中意外扩散的机制的考虑一直被忽视。我们将确定Bt -内毒素是否存在于食物网中并影响水生生物群。Bt玉米叶片碎屑可能对水生生物和溪流中的能量流动产生不利影响，值得进一步研究。

Small headwater streams are a critical freshwater resource in the agriculturally-dominated landscape of the Midwestern US, yet are understudied relative to more pristine aquatic ecosystems. Agricultural practices that remove natural streamside vegetation may change the energy base that fuels ecosystem processes. Crop byproducts (e.g., non-harvested foliage) may represent a dominant carbon source in agriculturally-influenced headwater streams. The role of this novel carbon source to stream ecosystem function has not been determined. We will quantify input, standing stocks, decomposition and transport of corn foliar detritus and pollen in 18 streams across the Midwest.In 2000, approximately 28 million hectares of corn were planted in the North American corn-belt, with 18% of this area planted with Bt corn. Because the Bt d-endotoxin is produced throughout the plant, dispersing pollen and non-harvested foliage that enters agricultural streams may be consumed by various aquatic organisms, and thus pose a threat to the environment. The potential effect of genetically modified crops on non-target species in aquatic ecosystems has received little attention, and consideration of headwater streams as a mechanism for the unintended dispersal of Bt d-endotoxin through the environment has been overlooked. We will determine if Bt d-endotoxin is present in the food web and affecting aquatic biota. Bt corn foliar detritus may detrimentally influence aquatic organisms and energy flow in streams, and merits further study.