Ecological change in freshwater ecosystems during the Anthropocene: The impacts of legacy pollution and emerging environmental stressors

人类活动正在对水生生态系统产生深远影响，使水质恶化，生物多样性减少。事实上，湖泊和河流是地球上受影响最大的生态系统之一，人们越来越需要了解人类的行动是如何改变这些环境的，特别是在数据稀缺的较长时间尺度(几十年或更长时间)。这项拟议的计划将使用古生态技术和现代采样来调查人类活动如何改变湖泊生态系统，特别是高度生物多样性和生产力的近岸环境(滨海区)。具体地说，该计划将1)调查受到遗留污染的湖泊生态系统的生态弹性和恢复(如果有的话)，2)确定微塑料在淡水环境中的运输路径和命运，并评估微塑料如何与沿海栖息地(大型植物、周生硅藻)相互作用。*历史采矿活动造成的遗留污染是一个全球性的环境问题，加拿大各地有数百个受污染的地点。我们已经证明，在采矿停止近一个世纪后，澳大利亚钴的许多湖泊仍然受到砷和其他金属(固体)的高度污染。我们还表明，生物指示剂在景观尺度上对这种遗留污染的反应是复杂的。为了解决这一复杂性，我们将量化来自过时沉积物岩心的关键生物指标组(硅藻、摇蚊类、枝角类)多样性的时间变化，以确定历史污染和气候变化的多重压力因素如何影响水生生物多样性。我们还将研究湖泊中金属(LOID)浓度的空间变化，大型植物床是否充当这些金属(LOID)的汇或源，以及围生硅藻的丰度和组成在砷污染的梯度上是如何改变的。虽然了解遗留污染的长期影响仍然是一个优先事项，但也需要增加我们对微塑料等新出现的污染物对水生生态系统影响的了解。为了解决这一研究重点，我们将调查微塑料浓度和组成如何随湖泊中的水深、河流中的空间和时间变化而变化，并使用大直径测年沉积物岩心来确定微塑料浓度和组成的历史趋势。我们将在这一知识的基础上，还研究微塑料如何与这些系统的生物成分相互作用，例如确定微塑料是否是湖泊和河流系统中大型植物群落的一部分。该计划将提供有关人类活动如何在广阔的空间和时间尺度上改变加拿大淡水生态系统的重要新数据，还可以用于为遗留受污染地点设定现实的恢复目标，并为未来的新兴污染物监测计划提供信息。

Human activities are having a profound impact on aquatic ecosystems degrading water quality and reducing biodiversity. In fact, lakes and rivers are some of the most impacted ecosystems on the planet and there is a growing need to understand how human actions are altering these environments, particularly over longer time scales (decades or longer) where data are scarce. This proposed program will employ both paleoecological techniques and modern sampling to investigate how human actions are altering lake ecosystems, with special focus on the highly biodiverse and productive nearshore environment (littoral zone). Specifically, this program will 1) investigate ecological resilience and recovery (if any) in lake ecosystems contaminated with legacy pollution and 2) determine the transport pathways and fate of microplastics in freshwater environments and assess how microplastics are interacting with littoral habitat (macrophytes, periphytic diatoms). Legacy pollution from historical mining activities is a global environmental problem with hundreds of contaminated sites across Canada. We have shown that many lakes in Cobalt, ON remain highly contaminated with arsenic and other metal(loids) nearly a century after mining has stopped. We have also shown that the response of bioindicators to this legacy contamination at a landscape scale is complex. To address this complexity, we will quantify temporal shifts in diversity in key bioindicator groups (diatoms, chironomids, Cladocera) from dated sediment cores to determine how the multiple stressors of historical contamination and climate change are impacting aquatic biodiversity. We will also examine how metal(loid) concentrations vary spatially within lakes, if macrophyte beds are serving as a sink or source of these metal(loids), and how periphytic diatom abundance and composition is altered over a gradient of arsenic contamination. Although understanding the long-term impacts of legacy pollution remains a priority there is also a need to increase our understanding of the impacts of emerging contaminants such a microplastics on aquatic ecosystems. To address this research priority we will investigate how microplastic concentrations and composition changes with water depth in lakes, varies spatially and temporally within rivers, and use large-diameter dated sediment cores to determine historical trends in microplastic concentration and composition. We will build on this knowledge by also examining how microplastics are interacting with biological components of these systems such as determining if microplastics are part of the periphytic community on macrophytes in lake and river systems. This program will provide important new data on how human activities are altering Canadian freshwater ecosystems across broad spatial and temporal scales and can also be used to set realistic restoration targets for legacy contaminated sites and inform future monitoring programs for emerging contaminants.