Hothem R L, Crayon J J, Law M A
Dixon Field Station, Western Ecological Research Center, United States Geological Survey, 6924 Tremont Rd, Dixon, CA 95620, USA.
Arch Environ Contam Toxicol. 2006 Nov;51(4):711-9. doi: 10.1007/s00244-005-0226-1. Epub 2006 Sep 4.
Contamination by organochlorine pesticides (OCs), polychlorinated biphenyls, metals, and trace elements at Edwards Air Force Base (EAFB), located in the Mojave Desert, could adversely affect nesting aquatic birds, especially at the sewage lagoons that comprise Piute Ponds. Estimates of avian reproduction, in conjunction with analyses of eggs and avian foods for contaminant residues, may indicate the potential for negative effects on avian populations. From 1996 to 1999, we conducted studies at the Piute Ponds area of EAFB to evaluate the impacts of contaminants on nesting birds. Avian reproduction was evaluated in 1999. Eggs were collected for chemical analyses in 1996 and 1999, and African clawed frogs (Xenopus laevis), a likely food source, were collected for chemical analyses in 1998. Avian species occupying the higher trophic levels--black-crowned night-heron (Nycticorax nycticorax), white-faced ibis (Plegadis chihi), and American avocet (Recurvirostra americana)--generally bioaccumulated higher concentrations of contaminants in their eggs. Reproductive success and egg hatchability of night-herons and white-faced ibises in the Piute Ponds were similar to results observed at other western colonies. Deformities were observed in only one embryo in this study, but concentrations of contaminants evaluated in this ibis embryo were considered insufficient to have caused the deformities. Because clawed frogs, a primary prey item for night-herons at Piute Ponds, had no detectable levels of any OCs, it is likely that OCs found in night-heron eggs were acquired from the wintering grounds rather than from EAFB. The presence of isomers of dichlorodiphenyltrichloroethane (DDT) in ibis eggs indicated recent exposure, but invertebrates used for food by ibises were not sampled at Piute Ponds, and conclusions about the source of OCs in ibis eggs could not be made. Concentrations of contaminants in random and failed eggs of individual species were not different, and we concluded that contaminants did not cause the observed egg failures.
位于莫哈韦沙漠的爱德华兹空军基地（EAFB）受到有机氯农药（OCs）、多氯联苯、金属和微量元素的污染，可能会对筑巢的水鸟产生不利影响，尤其是在构成皮尤特池塘的污水塘。对鸟类繁殖的估计，以及对鸟蛋和鸟类食物中污染物残留的分析，可能表明对鸟类种群产生负面影响的可能性。1996年至1999年，我们在EAFB的皮尤特池塘地区进行了研究，以评估污染物对筑巢鸟类的影响。1999年对鸟类繁殖进行了评估。1996年和1999年收集鸟蛋进行化学分析，1998年收集非洲爪蟾（非洲爪蟾）作为可能的食物来源进行化学分析。处于较高营养级的鸟类物种——黑冠夜鹭（夜鹭）、白脸朱鹭（白脸朱鹭）和美国反嘴鹬（反嘴鹬）——其鸟蛋中通常会生物累积更高浓度的污染物。皮尤特池塘中夜鹭和白脸朱鹭的繁殖成功率和鸟蛋孵化率与在其他西部繁殖地观察到的结果相似。在本研究中仅在一个胚胎中观察到畸形，但该朱鹭胚胎中评估的污染物浓度被认为不足以导致畸形。由于爪蟾是皮尤特池塘夜鹭的主要猎物，未检测到任何OCs水平，夜鹭蛋中发现的OCs很可能是从越冬地获得的，而不是从EAFB获得的。朱鹭蛋中存在二氯二苯三氯乙烷（DDT）异构体表明近期有接触，但皮尤特池塘未对朱鹭用作食物的无脊椎动物进行采样，因此无法得出朱鹭蛋中OCs来源的结论。单个物种的随机鸟蛋和未孵化鸟蛋中的污染物浓度没有差异，我们得出结论，污染物不会导致观察到的鸟蛋未孵化。
