Assessing interacting stressors in lakes

评估湖泊中相互作用的压力源

• 批准号: RGPIN-2022-03173
• 负责人: MacIsaac, Hugh
• 金额: $ 4.01万
• 依托单位: University of Windsor
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2022
• 资助国家: 加拿大
• 起止时间: 2022-01-01 至 2023-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=755163
• 关键词: Assessing; interacting; stressors; lakes

Lakes are among Canada's most defining landscapes and most our sensitive sentinels of environmental change. Stressors of these systems include cultural eutrophication, habitat loss, species introductions, and climate change. Identifying the impact of an individual stressor on a lake's plankton community is often challenging because stressors commonly occur in combination. Previous work identified that interacting stressors may encompass everything from additive effects to more complex situations in which they enhance (synergism) or damp one another (antagonistic effects). In this proposal I will use a combination of lake sampling over space and time, experimental mesocosms, and modeling to create a landscape of expected responses to major interacting stressors. The main field site for development of the model will be western Lake Erie. This basin can experience gradients in cyanobacteria (mainly Microcystis aeruginosa) blooms near major inflowing rivers that foster blooms while other sections of the basin are bloom-free. At the same time, the basin experiences annual development of a key introduced predator, the waterflea Bythotrephes longimanus, whose abundance and impact vary seasonally and spatially. Major zooplankton groups vary with respect to sensitivity to presence of cyanobacteria colonies, with specialist feeders (e.g. rotifers) little affected, while others, like the major herbivore Daphnia spp., are strongly and negatively impacted. These same zooplankton groups also vary with respect to vulnerability to ingestion by Bythotrephes, with rotifers not affected and Daphnia heavily impacted. Interestingly, then, the same two co-occurring stressors that harm populations of grazers like Daphnia could simultaneously either neutrally or positively affect rotifers (owing to insensitivity and competitive release). The complexity of these responses indicates that defining the impact of interacting stressors will be a challenging problem. In this proposal we will assess zooplankton community composition and abundance spatially and seasonally in conjunction with development of cyanobacteria blooms and Bythotrephes populations, with the expectation that shifts in community composition and abundance will reflect sensitivity to the interacting stressors. Mesocosm experiments will be conducted across a gradient of Microcystis and Bythotrephes densities with lab-reared mixed community of a key cladoceran (Daphnia) and rotifers (Keratella). Modeling exercises will explore the nature of the interactions between this mixed community in the absence of stressors, and with one or both stressors present. Finally, we will validate our models using inland lakes and other areas of the Great Lakes where both Bythotrephes populations and Microcystis blooms co-occur. Our projects will shed light on the complexity of interacting stressors that are expected as co-occurring Bythotrephes and Microcystis blooms spread to more lakes across Canada.

湖泊是加拿大最具特色的景观之一，也是我们对环境变化最敏感的哨兵。这些系统的压力源包括文化富营养化、栖息地丧失、物种引入和气候变化。确定单个压力源对湖泊浮游生物群落的影响通常具有挑战性，因为压力源通常组合出现。之前的研究发现，相互作用的压力源可能涵盖从相加效应到相互增强（协同）或抑制（拮抗作用）的更复杂情况的各种情况。在本提案中，我将结合使用空间和时间上的湖泊采样、实验中生态系统和建模来创建对主要相互作用压力源的预期响应的景观。该模型开发的主要场地将是伊利湖西部。该盆地在主要流入河流附近可能会经历蓝藻（主要是铜绿微囊藻）水华的梯度，从而促进水华，而该盆地的其他部分则没有水华。与此同时，该盆地每年都会出现一种重要的外来捕食者水蚤Bythotrephes longimanus，其数量和影响随季节和空间的变化而变化。主要浮游动物群体对蓝藻菌落存在的敏感性各不相同，专业饲养者（例如轮虫）几乎不受影响，而其他动物，如主要食草动物水蚤，则受到强烈的负面影响。这些相同的浮游动物群体在被白蛉虫摄入的脆弱性方面也有所不同，轮虫不受影响，而水蚤则受到严重影响。有趣的是，伤害水蚤等食草动物种群的两个同时发生的压力源可能同时对轮虫产生中性或积极的影响（由于不敏感和竞争性释放）。这些反应的复杂性表明，定义相互作用的压力源的影响将是一个具有挑战性的问题。在本提案中，我们将结合蓝藻水华和Bythotrephes种群的发展，在空间和季节上评估浮游动物群落的组成和丰度，期望群落组成和丰度的变化将反映对相互作用的压力源的敏感性。中生态系统实验将在微囊藻和白藻密度梯度上进行，实验室饲养的关键枝角动物（水蚤）和轮虫（Keratella）混合群落。建模练习将探索在没有压力源以及存在一个或两个压力源的情况下这个混合社区之间相互作用的性质。最后，我们将使用内陆湖泊和五大湖的其他地区来验证我们的模型，这些地区白蛉虫种群和微囊藻同时出现。我们的项目将揭示相互作用的压力源的复杂性，预计随着同时发生的白头藻和微囊藻华蔓延到加拿大更多的湖泊。