Columbia Environmental Research Center, US Geological Survey, 4200 New Haven Road, Columbia, MO 65201, USA.
Ecotoxicol Environ Saf. 2011 Nov;74(8):2215-24. doi: 10.1016/j.ecoenv.2011.08.008. Epub 2011 Aug 25.
Crayfish (Orconectes spp.), Asian clam (Corbicula fluminea), northern hog sucker (hog sucker; Hypentelium nigricans), and smallmouth bass (smallmouth; Micropterus dolomieu) from streams in southeastern Missouri (USA) were analyzed for total mercury (HgT) and for stable isotopes of carbon (δ¹³C), nitrogen (δ¹⁵N), and sulfur (δ³⁴S) to discern Hg transfer pathways. HgT concentrations were generally lowest in crayfish (0.005-0.112 μg/g dw) and highest in smallmouth (0.093-4.041 μg/g dw), as was δ¹⁵N. HgT was also lower and δ¹⁵N was higher in all biota from a stream draining a more heavily populated historical lead-zinc mining area than from similar sites with mostly undeveloped forested watersheds. δ¹³C in biota was lowest at spring-influenced sites, reflecting CO₂ inputs and temperature influences, and δ³⁴S increased from south to north in all taxa. However, HgT was not strongly correlated with either δ¹³C or δ³⁴S in biota. Trophic position (TP) computed from crayfish δ¹⁵N was lower in hog suckers (mean=2.8) than in smallmouth (mean=3.2), but not at all sites. HgT, δ¹³C, δ³⁴S, and TP in hog suckers increased with total length (length) at some sites, indicating site-specific ontogenetic diet shifts. Changes with length were less evident in smallmouth. Length-adjusted HgT site means in both species were strongly correlated with HgT in crayfish (r²=0.97, P<0.01), but not with HgT in Corbicula (r²=0.02, P>0.05). ANCOVA and regression models incorporating only TP and, for hog suckers, length, accurately and precisely predicted HgT concentrations in both fish species from all locations. Although low compared to many areas of the USA, HgT (and therefore methylmercury) concentrations in smallmouth and hog suckers are sufficiently high to represent a threat to human health and wildlife. Our data indicate that in Ozark streams, Hg concentrations in crayfish are at least partly determined by their diet, with concentrations in hog suckers, smallmouth, and possibly other higher-level consumers largely determined by concentrations in crayfish and other primary and secondary consumers, fish growth rates, and TP.
来自美国密苏里州东南部溪流的小龙虾（Orconectes spp.）、亚洲蛤蜊（Corbicula fluminea）、北方猪鼻鱼（hog sucker；Hypentelium nigricans）和小口黑鲈（小口；Micropterus dolomieu）被分析了总汞（HgT）和碳（δ¹³C）、氮（δ¹⁵N）和硫（δ³⁴S）的稳定同位素，以辨别汞的转移途径。HgT 浓度通常在小龙虾中最低（0.005-0.112μg/g dw），在小口黑鲈中最高（0.093-4.041μg/g dw），δ¹⁵N 也是如此。与主要为未开发森林流域的类似地点相比，来自溪流的所有生物体内的 HgT 都较低，而 δ¹⁵N 则较高，这些溪流的排水区都有一个人口密集的历史铅锌矿区。在受泉水影响的地点，生物体内的 δ¹³C 最低，反映了 CO₂的输入和温度的影响，而在所有分类群中，δ³⁴S 从南向北增加。然而，HgT 在生物体内与 δ¹³C 或 δ³⁴S 并没有很强的相关性。根据小龙虾 δ¹⁵N 计算的营养位（TP）在猪鼻鱼（平均值=2.8）中低于小口黑鲈（平均值=3.2），但并非在所有地点都是如此。在一些地点，猪鼻鱼的 HgT、δ¹³C、δ³⁴S 和 TP 随着总长度（长度）的增加而增加，表明存在特定于地点的个体发育饮食变化。在小口黑鲈中，随着长度的变化不太明显。两种物种中经长度调整后的 HgT 点平均值与小龙虾中的 HgT （r²=0.97，P<0.01）强烈相关，但与 Corbicul 的 HgT （r²=0.02，P>0.05）不相关。仅包含 TP 的协方差分析和回归模型，以及对于猪鼻鱼，仅包含长度的回归模型，可以准确而精确地预测来自所有地点的两种鱼类的 HgT 浓度。尽管与美国许多地区相比，小口黑鲈和猪鼻鱼中的 HgT（因此是甲基汞）浓度相对较低，但足以对人类健康和野生动物构成威胁。我们的数据表明，在欧扎克溪流中，小龙虾中的 Hg 浓度至少部分取决于其饮食，而猪鼻鱼、小口黑鲈和可能其他更高营养级消费者的浓度主要取决于小龙虾和其他初级和次级消费者、鱼类生长速度和 TP 的浓度。
