Ecological benefits and toxicological consequences of flooding in river ecosystems

洪灾是一种自然事件，由于其对人的财产以及极端情况下对人的生命的负面影响，公众往往认为其具有一致的危害性。但洪水也可以通过影响生态系统服务间接造福人类。这项研究的目标是确定洪水对生活在河流中的鱼类和其他动物的好处和后果。它将使用一个模型生态系统--艾伯塔省落基山脉山脚下的一系列河狸池塘--以及萨斯喀彻温河中一个容易发生洪水的大型三角洲，来检验这样一个假设：与河流自由流动的部分相比，河流浅水泛滥地区的初级生产力更高，鱼产量更多、更大，食物链也更长。这些好处预计将被更高浓度的潜在有毒微量元素所抵消，这些元素从土壤中释放出来，并被洪水腐烂的有机物所抵消。我的实验室将在新老河狸池塘中进行定量采样，以与自由流动的河流河段进行比较，并开发预测洪水周期不同阶段藻类、无脊椎动物和鱼类生产力变化的模型。碳和氮的稳定同位素比率将用于检查藻类和碎屑有机物向无脊椎动物和鱼类的转移，并评估微量元素的暴露途径。在萨斯喀彻温河三角洲，我们将采集大型老鱼，并使用老化结构的新微采样技术(微细研磨、激光烧蚀电感耦合等离子体质谱)来询问个别鱼类过去的摄食、生长和存活情况，以及它们与河流水文条件有关的微量元素暴露情况。通过增加我们对洪水脉冲的积极和消极影响的了解，它将有助于了解围绕通过拆除堤坝和重建和保护湿地来恢复自然水流状况的辩论。

Floods are natural events that are often perceived by the public as uniformly harmful because of their negative effects on human property and in extreme cases, human life. But floods can also indirectly benefit humans via their influence on ecosystem services. The goal of this research is to determine the benefits and consequences of flooding for fish and other animals that live in rivers. It will use a model ecosystem - a series of beaver ponds in the Rocky Mountain foothills of Alberta - and a large, flood-prone delta in the Saskatchewan River to test the hypothesis that shallow, flooded areas of the river have higher rates of primary productivity, produce more and larger fish and have longer food chains than free-flowing sections of the river. These benefits are expected to be offset by higher concentrations of potentially toxic trace elements that result from their liberation from soils and decaying organic matter by floodwaters.My lab will use quantitative sampling in new and old beaver ponds to draw comparisons to free-flowing river reaches and develop models that predict changes in algal, invertebrate and fish productivity at various phases of the flood cycle. Stable isotope ratios of carbon and nitrogen will be used to examine the transfer of algal and detrital organic matter to invertebrates and fishes and assess exposure pathways for trace elements. In the Saskatchewan River delta, we will collect large, old fish and use new microsampling techniques of ageing structures (micromilling, laser ablation inductively-coupled plasma mass spectrometry) to interrogate the past feeding, growth and survival of individual fish and their exposure to trace elements in relation to hydrological conditions in the river. By increasing our understanding of both positive and negative effects of the flood pulse, it will help inform the debate surrounding the restoration of natural flow regimes via dam removal and wetland re-establishment and protection.