Norwegian University of Life Sciences (UMB), Department of Ecology and Natural Resource Management (INA), P.O. Box 5003, N-1432 Ås, Norway.
Ecotoxicol Environ Saf. 2011 May;74(4):953-9. doi: 10.1016/j.ecoenv.2011.01.005. Epub 2011 Feb 5.
Stable isotope ratios of nitrogen (δ(15)N) and carbon (δ(13)C), complemented by stomach content data, were used to assess the food web structure and trophic transfer of mercury (Hg) in four commercial fish species of Lake Ziway, Ethiopia: Nile tilapia (Oreochromis niloticus), catfish (Clarias gariepinus), Tilapia zillii, and golden carp (Carassius auratus). Total mercury (THg in mg kg(-1), ww) concentrations were low, with mean values of 0.033, 0.034, 0.025, and 0.011, in C. gariepinus, T. zillii, C. auratus, and O. niloticus, respectively. The relationships between mercury concentrations against total length (TL) and total weight (TW) were positive and significant in T. zillii, C. auratus, and C. gariepinus (P<0.01), but not in O. niloticus, which even showed a decreasing tendency with increase in TL and TW. Regression of log THg vs. δ(15)N among all fish species showed a significant correlation, indicating that mercury is biomagnifying along the food web of Lake Ziway. Isotope ratios indicated that C. gariepinus occupied the highest trophic level of the food web of Lake Ziway; but contained similar THg concentrations as T. zillii, which is located at a lower trophic level, probably due to a faster growth rate of C. gariepinus, and thus an example of biodilution.
稳定同位素比值的氮（δ（15）N）和碳（δ（13）C），辅以胃内容物数据，用于评估食物网结构和埃塞俄比亚的 Ziway 湖的四种商业鱼类的汞（Hg）的营养转移：尼罗罗非鱼（Oreochromis niloticus），鲶鱼（Clarias gariepinus），Tilapia zillii 和金鱼（Carassius auratus）。总汞（THg 在毫克千克（-1），ww）浓度较低，C. gariepinus、T. zillii、C. auratus 和 O. niloticus 的平均值分别为 0.033、0.034、0.025 和 0.011。汞浓度与总长度（TL）和总重量（TW）之间的关系在 T. zillii、C. auratus 和 C. gariepinus 中呈正相关且显著（P<0.01），但在 O. niloticus 中却没有，甚至表现出随着 TL 和 TW 的增加而减少的趋势。所有鱼类的 log THg 与 δ（15）N 的回归显示出显著的相关性，表明汞在 Ziway 湖的食物网中生物放大。同位素比值表明，C. gariepinus 占据了 Ziway 湖食物网的最高营养级；但与位于较低营养级的 T. zillii 含有相似的 THg 浓度，这可能是由于 C. gariepinus 的生长速度较快，因此是生物稀释的一个例子。
