Department of Biological Sciences, Dartmouth College, Hanover, NH 03755, USA.
Sci Total Environ. 2012 Apr 1;421-422:230-7. doi: 10.1016/j.scitotenv.2012.01.058. Epub 2012 Feb 21.
Little is known about differences among trace elements in patterns of bioaccumulation in freshwater food webs. Our goal was to identify patterns in bioaccumulation of different elements that are large and consistent enough to discern despite variation across lakes. We measured methylmercury (MeHg) and trace element (As, Cd, Hg, Pb, and Zn) concentrations in food web components of seven New England lakes on 3-5 dates per lake, and contrasted patterns of bioaccumulation across lakes, metals and seasons. In each lake, trace element concentrations were compared across trophic levels, including three size fractions of zooplankton, planktivorous fish, and piscivorous fish. The trophic position of each food web component was estimated from N isotope analysis. Trace element concentrations varied widely among taxa, lakes and sampling dates. Yet, we identified four consistent patterns of bioaccumulation that were consistent across lakes: (1) MeHg concentration increased (i.e., was biomagnified) and Pb concentration decreased (i.e., was biodiminished) with increased trophic position. (2) Zinc concentration (as with MeHg) was higher in fish than in zooplankton, but overall variation in Zn concentration (unlike MeHg) was low. (3) Arsenic and Cd concentrations (as with Pb) were lower in fish than in zooplankton, but (unlike Pb) were not significantly correlated with trophic position within zooplankton or fish groups. (4) Average summer concentrations of As, Pb, Hg, and MeHg in zooplankton significantly predicted their concentrations in either planktivorous or piscivorous fish. Our secondary goal was to review sampling approaches in forty-five published studies to determine the extent to which current sampling programs facilitate cross-lake and cross-study comparisons of bioaccumulation. We found that studies include different components of the food web and sample too infrequently to enable strong cross-lake and cross-study comparisons. We discuss sampling strategies that would improve our capacity to identify consistent patterns of bioaccumulation and drivers of elevated trace element concentrations under naturally high levels of variability.
关于痕量元素在淡水食物网生物累积模式中的差异，人们知之甚少。我们的目标是确定生物累积不同元素的模式，这些模式要足够大且一致，以便在不同湖泊之间存在差异的情况下能够识别。我们在新英格兰的 7 个湖泊中，每个湖泊测量了 3-5 次，测量了食物网成分中的甲基汞（MeHg）和痕量元素（As、Cd、Hg、Pb 和 Zn）浓度，并对比了湖泊、金属和季节之间的生物累积模式。在每个湖泊中，痕量元素浓度在包括三个浮游动物大小的营养级进行了比较，分别为浮游动物、食浮游动物的鱼类和食鱼的鱼类。每个食物网成分的营养位置是通过 N 同位素分析来估计的。痕量元素浓度在类群、湖泊和采样日期之间差异很大。然而，我们确定了四个一致的生物累积模式，这些模式在湖泊之间是一致的：（1）随着营养位置的增加，MeHg 浓度增加（即生物放大），Pb 浓度降低（即生物稀释）。（2）锌浓度（与 MeHg 一样）在鱼类中高于浮游动物，但锌浓度的整体变化（与 MeHg 不同）较低。（3）与 Pb 一样，砷和 Cd 浓度（与 Pb 一样）在鱼类中低于浮游动物，但（与 Pb 不同）与浮游动物或鱼类群体内部的营养位置没有显著相关性。（4）浮游动物中 As、Pb、Hg 和 MeHg 的平均夏季浓度显著预测了它们在食浮游动物或食鱼鱼类中的浓度。我们的次要目标是审查 45 项已发表研究中的采样方法，以确定当前采样方案在多大程度上促进了湖泊之间和研究之间的生物累积比较。我们发现，研究包括了食物网的不同组成部分，并且采样频率太低，无法进行强有力的湖泊间和研究间比较。我们讨论了采样策略，这些策略将提高我们识别生物累积的一致模式和在自然高变异性下痕量元素浓度升高的驱动因素的能力。
