Biodilution of heavy metals in a stream macroinvertebrate food web: Evidence from stable isotope analysis

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• 作者：Kozo Watanabe ; Michael T. Monaghan ; Yasuhiro Takemon ; Tatsuo Omura
• 关键词：Stream macroinvertebrates ; Abandoned mine ; Metal accumulation ; Carbon and nitrogen stable isotopes ; Trophic level ; Autochthonous and allochthonous organic matters
• 刊名：Science of the Total Environment
• 出版年：2008
• 期刊代码：63_00489697
• 类别：env
• 出版时间：1 May 2008
• 卷：394
• 期：1
• 页码：57-67
• 文件大小：414 K

摘要

Analysis of carbon (δ¹³C) and nitrogen (δ¹⁵N) 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 δ¹⁵N signature increased with trophic level, with mean increases of 4.70‰ from producers to primary consumers and 3.06‰ from primary to secondary consumers. Tissue Pb and Ag concentrations were negatively correlated with δ¹⁵N, 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 δ¹⁵N) 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 δ¹³C = − 21.3‰) had a much higher concentration of mined metals than did riparian vegetation (mean δ¹³C = −29.3‰); 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.