Sadinski Walt, Roth Mark, Hayes Tyrone, Jones Perry, Gallant Alisa
Upper Midwest Environmental Sciences Center, U.S. Geological Survey, La Crosse, Wisconsin, United States of America.
Laboratory for Integrative Studies in Amphibian Biology, Molecular Toxicology, Energy and Resources Group, Group in Endocrinology, Museum of Vertebrate Zoology, and Department of Integrative Biology, University of California, Berkeley, California, United States of America.
PLoS One. 2014 Sep 12;9(9):e107018. doi: 10.1371/journal.pone.0107018. eCollection 2014.
Extensive corn production in the midwestern United States has physically eliminated or fragmented vast areas of historical amphibian habitat. Midwestern corn farmers also apply large quantities of fertilizers and herbicides, which can cause direct and indirect effects on amphibians. Limited field research regarding the statuses of midwestern amphibian populations near areas of corn production has left resource managers, conservation planners, and other stakeholders needing more information to improve conservation strategies and management plans. We repeatedly sampled amphibians in wetlands in four conservation areas along a gradient of proximity to corn production in Illinois, Iowa, Minnesota, and Wisconsin from 2002 to 2005 and estimated site occupancy. We measured frequencies of gross physical deformities in recent metamorphs and triazine concentrations in the water at breeding sites. We also measured trematode infection rates in kidneys of recently metamorphosed Lithobates pipiens collected from nine wetlands in 2003 and 2004. We detected all possible amphibian species in each study area. The amount of nearby row crops was limited in importance as a covariate for estimating site occupancy. We observed deformities in <5% of metamorphs sampled and proportions were not associated with triazine concentrations. Trematode infections were high in metamorphs from all sites we sampled, but not associated with site triazine concentrations, except perhaps for a subset of sites sampled in both years. We detected triazines more often and in higher concentrations in breeding wetlands closer to corn production. Triazine concentrations increased in floodplain wetlands as water levels rose after rainfall and were similar among lotic and lentic sites. Overall, our results suggest amphibian populations were not faring differently among these four conservation areas, regardless of their proximity to corn production, and that the ecological dynamics of atrazine exposure were complex.
美国中西部广泛的玉米种植实际上已经消除或分割了大片历史悠久的两栖动物栖息地。中西部的玉米种植户还大量使用化肥和除草剂，这可能对两栖动物产生直接和间接影响。关于玉米种植区附近中西部两栖动物种群状况的实地研究有限，这使得资源管理者、保护规划者和其他利益相关者需要更多信息来改进保护策略和管理计划。从2002年到2005年，我们在伊利诺伊州、爱荷华州、明尼苏达州和威斯康星州沿着与玉米生产的接近梯度，对四个保护区湿地中的两栖动物进行了多次采样，并估计了栖息地占有率。我们测量了近期变态幼体的总体身体畸形频率以及繁殖地水中的三嗪浓度。我们还测量了2003年和2004年从九个湿地采集的近期变态的北美豹蛙肾脏中的吸虫感染率。我们在每个研究区域都检测到了所有可能的两栖动物物种。附近的大田作物数量作为估计栖息地占有率的协变量，其重要性有限。我们在采样的变态幼体中观察到畸形的比例不到5%，且该比例与三嗪浓度无关。我们采样的所有地点的变态幼体中吸虫感染率都很高，但与地点的三嗪浓度无关，也许除了两年都采样的一部分地点。在离玉米生产较近的繁殖湿地中，我们更频繁地检测到三嗪，且浓度更高。洪泛平原湿地中的三嗪浓度在降雨后水位上升时增加，在流水和静水区域中相似。总体而言，我们的结果表明，这四个保护区的两栖动物种群无论与玉米生产的距离远近，情况并无不同，而且阿特拉津暴露的生态动态很复杂。
