Henny Charles J, Kaiser James L, Packard Heidi A, Grove Robert A, Taft Michael R
USGS-Forest and Rangeland Ecosystem Science Center, Corvallis, OR 97331, USA.
Ecotoxicology. 2005 Oct;14(7):709-25. doi: 10.1007/s10646-005-0023-7. Epub 2005 Sep 28.
To evaluate mercury (Hg) exposure and possible adverse effects of Hg on American dipper (Cinclus mexicanus) reproduction, we collected eggs and nestling feathers and the larval/nymph form of three Orders of aquatic macroinvertebrates (Ephemeroptera, Plecoptera and Trichoptera = EPT) important in their diet from three major headwater tributaries of the upper Willamette River, Oregon in 2002. The Coast Fork Willamette River is contaminated with Hg due to historical cinnabar (HgS) mining at the Black Butte Mine; the Row River is affected by past gold-mining operations located within the Bohemia Mining District, where Hg was used in the amalgamation process to recover gold; and the Middle Fork Willamette River is the reference area with no known mining. Methyl mercury (MeHg) concentrations (geometric mean) in composite EPT larvae (111.9 ng/g dry weight [dw] or 19.8 ng/g wet weight [ww]), dipper eggs (38.5 ng/g ww) and nestling feathers (1158 ng/g ww) collected from the Coast Fork Willamette were significantly higher than MeHg concentrations in EPT and dipper samples from other streams. Total mercury (THg) concentrations in surface sediments along the same Hg-impacted streams were investigated by others in 1999 (Row River tributaries) and 2002 (Coast Fork). The reported sediment THg concentrations paralleled our biological findings. Dipper breeding territories at higher elevations had fewer second clutches; however, dipper reproductive success along all streams (including the lower elevation and most Hg-contaminated Coast Fork), was judged excellent compared to other studies reviewed. Furthermore, MeHg concentrations in EPT samples from this study were well below dietary concentrations in other aquatic bird species, such as loons and ducks, reported to cause Hg-related reproductive problems. Our data suggest that either dipper feathers or EPT composites used to project MeHg concentrations in dipper feathers (with biomagnification factor of 10-20x) may be used, but with caution, to screen headwater streams for potential Hg-related effects on dippers. When actual feather concentrations or projected feather concentrations are equal to or lower than concentrations reported for the Coast Fork, dippers are expected to reproduce well (assuming adequate prey and suitable nest sites). When Hg concentrations are substantially higher, more detailed investigations may be required. Birds feeding almost exclusively on fish (e.g., osprey [Pandion haliaetus]) and usually found further downstream from the headwaters would not be adequately represented by dippers given the higher MeHg concentrations in fish resulting from biomagnification, compared to lower trophic level invertebrates.
为了评估汞（Hg）暴露情况以及汞对美洲河乌（Cinclus mexicanus）繁殖可能产生的不利影响，我们于2002年从俄勒冈州威拉米特河上游的三条主要源头支流收集了河乌的卵和雏鸟羽毛，以及在其饮食中很重要的三个水生大型无脊椎动物目（蜉蝣目、襀翅目和毛翅目=EPT）的幼虫/若虫形态。威拉米特河的海岸支流因黑丘矿历史上的朱砂（HgS）开采而受到汞污染；罗河受到位于波希米亚矿区过去的金矿开采作业影响，在那里汞被用于汞齐化过程以回收黄金；而威拉米特河的中支流是没有已知采矿活动的对照区域。从威拉米特河海岸支流收集的EPT幼虫（111.9纳克/克干重[dw]或19.8纳克/克湿重[ww]）、河乌卵（38.5纳克/克湿重）和雏鸟羽毛（1158纳克/克湿重）中的甲基汞（MeHg）浓度（几何平均值）显著高于从其他溪流收集的EPT和河乌样本中的MeHg浓度。1999年（罗河支流）和2002年（海岸支流）其他人对沿同样受汞影响溪流的表层沉积物中的总汞（THg）浓度进行了调查。报告的沉积物THg浓度与我们的生物学发现一致。海拔较高处的河乌繁殖领地内的二次窝卵数较少；然而，与所审查的其他研究相比，所有溪流（包括海拔较低且汞污染最严重的海岸支流）中的河乌繁殖成功率都被判定为良好。此外，本研究中EPT样本中的MeHg浓度远低于其他水鸟物种（如潜鸟和鸭子）的饮食浓度，据报道这些物种会出现与汞相关的繁殖问题。我们的数据表明，可以使用河乌羽毛或用于推算河乌羽毛中MeHg浓度（生物放大系数为10 - 20倍）的EPT组合，但要谨慎使用，以筛查源头溪流对河乌可能产生的与汞相关的影响。当实际羽毛浓度或推算的羽毛浓度等于或低于海岸支流报告的浓度时，预计河乌能顺利繁殖（假设猎物充足且巢址适宜）。当汞浓度显著更高时，可能需要进行更详细的调查。与营养级较低的无脊椎动物相比，几乎完全以鱼类为食（如鹗[Pandion haliaetus]）且通常在源头下游更远处发现的鸟类，由于生物放大作用，鱼类中MeHg浓度较高，河乌无法充分代表它们。
