Anthropogenic impacts on river food webs

阿尔伯塔省南部是一个严重缺水的地区，那里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。长期目标是解决河流食物网的空间问题（方法和理论）。这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，具有很强的方向性，并且在几乎所有属性（例如温度、营养物质和生产力）上都有很强的上游/下游梯度。因此，食物网的物种组成和动态是沿着河流连续体逐渐变化的。该提案概述了与河流食物网结构和功能相关的三个项目(1)SSRB食物网中的汞生物放大。在流域内使用嵌套比较方法要回答的问题是：(a)沿河汞暴露的梯度是什么，(b)煤矿开采、集约化农业、灌溉和污水等活动作为潜在汞源的重要性有多大，以及(c)在顶级捕食者身上看到的汞水平是否可以用局部暴露和生物放大来解释，或者通过下游地区的鱼类运动进行的生物运输是否是一个重要因素。(2)引进虹鳟鱼与本地切喉鳟鱼杂交的生态后果。切喉鳟鱼主宰着许多西部河流源头地区的食物网。放养虹鳟鱼导致了杂交鳟鱼的形成和传播，这些杂交鳟鱼迅速扩大了它们的活动范围，只留下了很少的基因纯正的切喉鳟鱼种群。本研究将探讨杂交和本地切喉鳟鱼之间的生态差异及其功能后果。3)。来自家庭和动物污水的有机物质和营养物质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幅度和程度。

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.