Benthic cyanobacteria in lakes and rivers: distribution, abundance, implications

科学界和媒体最近都把重点放在浮游蓝藻上，因为它们极大地影响了湖泊和河流用于娱乐和用水的使用。底栖生物的种类和阶段大多被忽视，因为它们只有在浮出水面时才能被看到。然而，越来越多的证据表明底栖蓝细菌在碳和氮的固定中发挥着重要的作用。此外，它们可能会通过与无脊椎动物相互作用，引发有害的浮游水华，释放毒素和产生气味的代谢物，从而影响营养链和供水。在这项研究中，我建议1)量化仍然知之甚少的水的物理和化学特征对底栖蓝细菌分布和丰度的影响，以及2)研究它们的存在对水资源的影响。我将在底栖蓝藻特别相关的两个环境中追求这些目标：a)我们最近报告在圣劳伦斯河的河流湖泊中存在大量有毒的丝状蓝藻lyngbya wollei，它覆盖了大约50平方公里的河底。本研究旨在模拟狼尾藻增殖的时间和空间动态。这一知识对圣劳伦斯河的管理将是重要的，因为商业和休闲渔业可能已经受到与L.wollei传播有关的水生维管植物和相关无脊椎动物减少的影响。毒素和气味化合物的释放可能会增加服务于数百万人口的水过滤厂的处理成本。B)尽管营养物质浓度很低，但在蒙特雷亚尔以北劳伦西亚地区的几个湖泊中，蓝藻水华越来越多。我们将测试这些水华是否开始于沿海地带，那里的底栖生物阶段可以通过利用湖泊周围土地开发导致的沉积物-水界面上增加的营养供应来开始生长。了解娱乐性湖泊有害水华的潜在机制将有助于保护加拿大遗产和水资源的这些重要元素的质量。

Both the scientific community and the media have recently focused on planktonic cyanobacteria because they greatly affect the use of lakes and rivers for the purposes of recreation and water consumption. Benthic species and stages are mostly ignored because they are only visible when they rise to the water surface. Nevertheless, there is increasing evidence that benthic cyanobacteria play an important role in carbon and nitrogen fixation. Moreover, they may affect the trophic chain and the water supply by interacting with invertebrates, initiating harmful planktonic blooms and releasing toxins and odour-producing metabolites. In this research, I propose to 1) quantify the still poorly understood role of physical and chemical water characteristics on the distribution and abundance of benthic cyanobacteria and 2) examine the implications of their presence for water resources. I will pursue these objectives in two environments where benthic cyanobacteria are especially relevant: A) We recently reported the presence of a significant amount of the noxious filamentous cyanobacterium Lyngbya wollei in the fluvial lakes of the St. Lawrence River, where it covers roughly 50 km2 of the river bottom. This research aims to model the temporal and spatial dynamics of L. wollei proliferation. This knowledge will be important in the management of the St. Lawrence River, as the commercial and recreational fishery may already be affected by the reduction in aquatic vascular plants and associated invertebrates linked to the spread of L. wollei. The release of toxins and taste and odour compounds may increase treatment costs for water filtration plants serving a population of several million. B) Cyanobacterial blooms are increasingly observed in several lakes of the Laurentian region north of Montréal, despite low nutrient concentrations. We will test whether these blooms initiate in the littoral zone, where benthic stages may start their growth by taking advantage of the increased nutrient supply at the sediment-water interface resulting from land development around the lakes. An understanding of the mechanisms underlying harmful blooms in recreational lakes will help preserve the quality of these important elements of Canada's heritage and water resources.