Watanabe Kozo, Monaghan Michael T, Takemon Yasuhiro, Omura Tatsuo
Department of Civil Engineering, Graduate School of Engineering, Tohoku University, Aoba 6-6-06, Sendai, 980-8579, Japan.
Sci Total Environ. 2008 May 1;394(1):57-67. doi: 10.1016/j.scitotenv.2008.01.006. Epub 2008 Feb 15.
Analysis of carbon (delta13C) and nitrogen (delta15N) stable isotopes provides an increasingly important means of understanding the complex trophic structure of macroinvertebrate communities in streams. We coupled a stable isotope approach with a contaminant analysis of six metals (Pb, Ag, Zn, Hg, Cu, As) to trace the accumulation and dilution of metals from an abandoned mine across trophic levels of the benthic community in Ginzan Creek, Japan. The delta15N signature increased with trophic level, with mean increases of 4.70 per thousand from producers to primary consumers and 3.06 per thousand from primary to secondary consumers. Tissue Pb and Ag concentrations were negatively correlated with delta15N, indicating biodilution of both metals through the food web. Although macroinvertebrate taxon body mass was negatively correlated with tissue metal concentration at several sites, it did not increase with trophic level (as delta15N) in any of the sites, suggesting that changes in body mass were not the cause of biodilution. Our findings suggest invertebrates at higher trophic levels may exhibit increasingly efficient excretion of metals. Autotrophic epilithon (mean delta13C= -21.3 per thousand) had a much higher concentration of mined metals than did riparian vegetation (mean delta13C= -29.3 per thousand); nonetheless, a carbon-mixing model indicated that taxa feeding on autochthonous carbon sources did not accumulate more metal than allochthonous feeders. It is likely that the notably high metal concentration of allochthonous FPOM plays an important role in the trophic transfer of metals. Our data suggest the strong potential for stable isotope analysis to enhance our understanding of metal transfer through stream macroinvertebrate food webs.
碳（δ13C）和氮（δ15N）稳定同位素分析为理解溪流中大型无脊椎动物群落复杂的营养结构提供了一种日益重要的方法。我们将稳定同位素方法与六种金属（铅、银、锌、汞、铜、砷）的污染物分析相结合，以追踪日本银山溪中废弃矿山的金属在底栖生物群落营养级中的积累和稀释情况。δ15N特征随营养级升高而增加，从生产者到初级消费者平均每千分增加4.70，从初级消费者到次级消费者平均每千分增加3.06。组织中的铅和银浓度与δ15N呈负相关，表明这两种金属在食物网中发生了生物稀释。尽管在几个地点大型无脊椎动物分类单元的体重与组织金属浓度呈负相关，但在任何地点其体重都没有随营养级（如δ15N）增加，这表明体重变化不是生物稀释的原因。我们的研究结果表明，营养级较高的无脊椎动物可能表现出越来越高效的金属排泄。自养附生藻类（平均δ13C = -21.3‰）的开采金属浓度比河岸植被（平均δ13C = -29.3‰）高得多；尽管如此，碳混合模型表明，以本地碳源为食的分类单元积累的金属并不比以异地碳源为食的分类单元多。很可能异地漂浮植物残体中显著高的金属浓度在金属的营养传递中起重要作用。我们的数据表明，稳定同位素分析在增强我们对溪流大型无脊椎动物食物网中金属转移的理解方面具有强大潜力。
