Anthropogenic impacts on river food webs

南阿尔伯塔是一个严重缺水的地区，所有的水生资源都受到相当大的人为影响。 此外，由于缺乏湖泊，这是一个对水生食物网进行了大量研究的地区。 一个长期的目标是解决空间问题（方法和理论）与河流食物网的工作。 这些问题源于河流的线性几何形状，以及它们通常是开放式的等级系统，几乎每个属性（例如温度，营养物质和生产力）都具有很强的方向性和很强的上游/下游梯度。 因此，物种组成和动态的食物网是逐渐改变沿着河流连续。 该提案概述了与河流食物网结构和功能有关的三个项目 （1）SSRB食物网中的汞生物放大作用。 在流域内使用嵌套比较方法回答的问题是：（a）汞暴露沿着河流的梯度是什么，（B）采煤、集约农业、灌溉和污水处理等活动作为潜在汞来源的重要性如何，以及（c）在顶级捕食者中观察到的汞水平是否可以通过局部暴露和生物放大来解释，还是下游地区鱼类移动造成的生物迁移是一个重要因素。 （2）引进虹鳟鱼与本地锯喉鳟鱼杂交的生态后果。切喉鳟鱼在西部许多河流的源头地区的食物网中占主导地位。虹鳟鱼放养导致了杂交品种的形成和传播，这些杂交品种迅速扩大了它们的范围，只留下很少的遗传纯的割喉鳟鱼种群。本研究将探讨杂交和本地割喉鳟鱼及其功能后果之间的生态差异。3.）第三章生活和动物污水中的有机物和营养物及其对河流食物网的影响。 在这个项目中，我们将使用稳定同位素来追踪这些来源的食物网富集的程度和范围。

Southern Alberta is an area of acute water scarcity, where all aquatic resources are subjected to considerable anthropogenic influence.  In addition, it is an area, due to the shortage of lakes, where very work on aquatic foodwebs has been done.   A long-term goal is to address the spatial problems (both methodological and theoretical) of working with riverine food webs.  These arise from the linear geometry of rivers and the fact that they are usually open-ended hierarchical systems with strong directionality and strong upstream/downstream gradients in virtually every attribute (eg temperature, nutrients, and productivity).  As such the species compostion and dynamics  of the foodweb is gradually changing along the river continuum.   The proposal outlines three projects related to river food webs structure and function   (1)Mercury biomagnification in the SSRB food web.  The questions to be answered using a nested comparative approach within the watershed, are: (a) What is the gradient in mercury exposure along the river, (b) how important are activities such as coal mining, intensive agriculture, irrigation, and sewage as potential mercury sources, and (c) can levels of mercury seen in top predators be explained by local exposure and biomagnification, or is biotransport through fish movements from downstream areas an important factor.   (2)Ecological consequences of hybridization between introduced rainbow trout and native cutthroat trout. Cutthroat trout dominate the foodwebs of the headwater regions of many western rivers. Rainbow trout stocking has resulted in the formation and spread of hybrids that are rapidly expanding their range leaving very few genetically pure cutthroat trout populations. This study will explore ecological differences between hybrids and native cutthroat trout and their functional consequences. 3.)Organic matter and nutrients from domestic and animal sewage and its impact on river food webs.  In this project we will use stable isotopes to trace the magnitude and the extent of foodweb enrichment from these sources.