Ecological Modeling Laboratory, Department of Physical and Environmental Sciences, University of Toronto, Toronto, Ontario M1C 1A4, Canada.
Environ Sci Technol. 2011 Mar 15;45(6):2217-26. doi: 10.1021/es103054q. Epub 2011 Feb 17.
The temporal trends of total mercury (THg) in four fish species in Lake Erie were evaluated based on 35 years of fish contaminant data. Our Bayesian statistical approach consists of three steps aiming to address different questions. First, we used the exponential and mixed-order decay models to assess the declining rates in four intensively sampled fish species, i.e., walleye (Stizostedion vitreum), yellow perch (Perca flavescens), smallmouth bass (Micropterus dolomieui), and white bass (Morone chrysops). Because the two models postulate monotonic decrease of the THg levels, we included first- and second-order random walk terms in our statistical formulations to accommodate nonmonotonic patterns in the data time series. Our analysis identified a recent increase in the THg concentrations, particularly after the mid-1990s. In the second step, we used double exponential models to quantify the relative magnitude of the THg trends depending on the type of data used (skinless-boneless fillet versus whole fish data) and the fish species examined. The observed THg concentrations were significantly higher in skinless boneless fillet than in whole fish portions, while the whole fish portions of walleye exhibited faster decline rates and slower rates of increase relative to the skinless boneless fillet data. Our analysis also shows lower decline rates and higher rates of increase in walleye relative to the other three fish species examined. The food web structural shifts induced by the invasive species (dreissenid mussels and round goby) may be associated with the recent THg trends in Lake Erie fish.
基于 35 年的鱼类污染物数据，评估了安大略湖四种鱼类中总汞 (THg) 的时间趋势。我们的贝叶斯统计方法包括三个步骤，旨在解决不同的问题。首先，我们使用指数和混合阶衰减模型来评估四种密集采样鱼类（大眼梭鲈、黄鲈、小口黑鲈和白鲈）的下降率。由于这两个模型假设 THg 水平呈单调下降，因此我们在统计公式中包含了一阶和二阶随机游走项，以适应数据时间序列中的非单调模式。我们的分析确定了 THg 浓度的近期增加，特别是在 20 世纪 90 年代中期之后。在第二步中，我们使用双指数模型来量化 THg 趋势的相对幅度，具体取决于所使用的数据类型（去皮去骨鱼片与整条鱼数据）和所检查的鱼类。去皮去骨鱼片的观察到的 THg 浓度明显高于整条鱼部分，而大眼梭鲈的整条鱼部分相对于去皮去骨鱼片数据表现出更快的下降率和更慢的上升率。我们的分析还表明，相对于其他三种检查的鱼类，大眼梭鲈的下降率更低，上升率更高。入侵物种（双壳贻贝和圆鳍鱼）引起的食物网结构变化可能与安大略湖鱼类近期的 THg 趋势有关。
