Linking climate change and watershed responses to emerging cyanobacterial blooms in lakes on forested landscapes

将气候变化和流域响应与森林景观湖泊中出现的蓝藻水华联系起来

• 批准号: RGPIN-2014-06579
• 负责人: Creed, Irena
• 金额: $ 3.79万
• 依托单位: University of Western Ontario
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2015
• 资助国家: 加拿大
• 起止时间: 2015-01-01 至 2016-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=589097
• 关键词: Linking; climate; change; watershed; responses

Fundamental changes are occurring on Canada’s forested landscapes. The Great Lakes-St. Lawrence forest region supplies 18% of the world’s drinking water. The formerly pristine clear waters of cottage country appear to be experiencing an incipient rise in cyanobacterial blooms (cyanoblooms), including potentially harmful ones that have the capacity to produce potent neural and liver toxins. Recently, there has been a significant increase in the number of cyanobloom reports by the public to regional governments, resulting in heightened public concern for cyanoblooms. We may be at an ecological tipping point. The frequency and intensity of cyanoblooms are increasing in nutrient-rich lakes, but the majority of “new” bloom reports are in nutrient-poor lakes with no prior bloom history. Based on our current understanding these lakes should not have the capacity to support blooms. It is time to challenge our understanding. We propose that climate change is leading to fundamental changes in the hydrology and biogeochemistry of forested landscapes, and thus nutrient delivery from land to lakes, from which the rise of cyanoblooms may be a consequence. This proposal focuses on nutrient sources in forested landscapes, their potential for transformation along pathways of transport, and their contributions to receiving lakes and consequences on phytoplankton communities in lakes. Our hypothesis is that climate-induced changes in iron (Fe) and dissolved organic matter (DOM) create conditions for exceptional cyanobacterial growth compared with their eukaryotic competitors. We will test this hypothesis at multiple scales – from coarse-scale monitoring of entire landscapes with many lakes to fine-scale experimental incubations. The role of phosphorus (P) and nitrogen (N) in regulating cyanoblooms is widely acknowledged; however, the role of micronutrients such as Fe is less known, although Fe has been shown to regulate P and N use efficiency in phytoplankton. We will (1) confirm whether there exists a rising trend in phytoplankton blooms by constructing a 30-year satellite survey of 1,000 lake phytoplankton pigment concentrations combined with contemporary ground surveys of cyanobacteria and determining if the peak annual phytoplankton concentrations in lakes is on the rise across the region (or if it is restricted to a few lakes), (2) identify critical features of the land-lake system affected by either humans (generally well understood) or climate change (far less understood) that lead to changes in Fe storage or export – the purported catalytic and stimulatory element associated with the emerging cyanobloom problem, (3) characterize Fe concentration and composition as it is transported from the catchment to lake by documenting rates of binding to DOM, and (4) describe the selective impact of DOM form and Fe that enters lakes from catchments and stimulates the development and toxicity of cyanoblooms. Using a subset of lakes, the land-stream-lake processing and export of DOM-Fe will be assessed in conjunction with cyanoblooms. This biogeochemical land-lake model of cyanobloom formation will be tested in three different bioassay procedures: low-volume “grow outs”, flow-through continuous cultures (“ecostats”) that enable cells to outcompete others through small changes in growth rate, and multi-trophic within-lake mesocosm experiments. The outcome of this work will provide fundamental insights to the mechanistic relationship between climate-driven forest hydrological and biogeochemical changes, the consequences of these changes to cyanoblooms, and the resultant threat of toxin production to human and ecosystem health.

加拿大的森林景观正在发生根本性的变化。圣劳伦斯大湖森林地区提供了世界上18%的饮用水。农舍乡村以前清澈的沃茨似乎正在经历蓝藻水华（蓝藻）的初期上升，其中包括具有产生强效神经和肝脏毒素能力的潜在有害蓝藻。最近，公众向地方政府报告的蓝藻数量显著增加，导致公众对蓝藻的关注度提高。我们可能正处于一个生态临界点。在营养丰富的湖泊中，蓝藻水华的频率和强度正在增加，但大多数“新”水华报告都发生在营养缺乏的湖泊中，以前没有水华历史。根据我们目前的理解，这些湖泊不应该有能力支持水华。是时候挑战我们的理解了。 我们认为，气候变化正在导致森林景观的水文和地球化学发生根本性变化，从而导致从陆地到湖泊的营养物质输送，从而导致蓝藻的增加。 该提案的重点是森林景观中的营养源、它们沿运输路径沿着转化的潜力、它们对接收湖泊的贡献以及对湖泊中浮游植物群落的影响。我们的假设是，气候引起的铁（Fe）和溶解有机物（DOM）的变化创造了特殊的蓝藻生长条件相比，它们的真核竞争对手。我们将在多个尺度上测试这一假设-从粗尺度监测整个景观与许多湖泊到细尺度实验孵化。磷（P）和氮（N）在调节蓝藻中的作用得到了广泛的认可;然而，微量营养素（如铁）的作用却鲜为人知，尽管铁已被证明可以调节浮游植物对磷和氮的利用效率。我们将（1）通过对1,000个湖泊的浮游植物色素浓度进行30年的卫星调查，结合对蓝藻的当代地面调查，并确定湖泊中浮游植物浓度的年度峰值是否在整个地区呈上升趋势，来确认浮游植物水华是否存在上升趋势（或者仅限于几个湖泊），（2）确定受人类活动影响的陆地-湖泊系统的关键特征，（一般都很好理解）或气候变化（远不太了解），导致铁的储存或输出的变化-据称与新出现的蓝藻问题相关的催化和刺激元素，（3）通过记录与DOM结合的速率，表征Fe从集水区输送到湖泊的浓度和组成，（4）描述DOM形式和Fe从集水区进入湖泊并刺激蓝藻生长和毒性的选择性影响。使用一个子集的湖泊，土地流湖处理和出口的DOM-Fe将与cyanobloom一起评估。这种蓝藻形成的陆地-湖泊生态化学模型将在三种不同的生物测定程序中进行测试：低容量“生长”，流通连续培养（“生态稳定器”），使细胞能够通过生长速率的微小变化胜过其他细胞，以及多营养湖泊内围隔生态系统实验。 这项工作的结果将提供基本的见解，气候驱动的森林水文和生物地球化学变化，这些变化的后果，蓝藻，以及由此产生的毒素生产对人类和生态系统健康的威胁之间的机械关系。