Catchment-fueled cyanobacteria blooms

全球变化速率最高的是北部生态系统。气候变暖、水文强化和酸化恢复与陆地溶解有机质（DOM）进入北部湖泊的增加（即褐变）有关，这反过来又对藻类的生产力和多样性产生影响，而藻类是湖泊食物网能量转移的主要途径。蓝藻华（蓝藻）威胁着全世界的淡水资源。以前在北方的原始清澈的湖泊意外地经历了蓝藻，也许是未来更频繁，更强烈的蓝藻的早期预警。随着居住在北部湖泊沿岸的人们向政府报告的蓝藻数量显著增加，公众对蓝藻的关注程度有所提高。普遍接受的概念模型是，蓝藻与磷(P)和/或氮(N)管理不善有关。然而，我们现在收到了“新的”报告，在北部农村和偏远的湖泊，没有已知的蓝藻历史。我们需要一个新的蓝藻形成的概念模型。我推测，气候引起的北部湖泊褐变为蓝藻的特殊生长创造了光照和营养条件。虽然DOM对湖泊光照和营养（如氮、磷和铁）条件的影响是已知的，但需要进一步了解藻类对褐变的特定适应。DOM作为从周边流域运输P、N、Fe的营养载体，作为防止P、Fe沉淀并保持在水柱中的营养海绵。为了验证这一假设，我将(1)描述北纬地区的气候变化特征，重点关注那些导致湖泊褐变的变化以及与之相关的湖泊光照和营养条件的变化；(2)褐变与藻类生物量变化和蓝藻相对于其他藻类的富集有关；(3)探索蓝藻优势增加对湖泊食物网中必需脂肪酸（预计减少）和蓝藻毒素（预计增加）转移的影响。从人类的角度来看，蓝藻没有任何积极的一面。淡水资源与人类活动之间的密切联系使人类处于蓝藻毒素暴露途径中。直接影响包括人类通过饮用水或气溶胶暴露于蓝藻毒素，可引起神经和肝脏疾病。间接影响包括蓝藻引发一系列改变的生物学结果，因为蓝藻可能会减少鱼类膳食中必需脂肪酸的组成，增加毒素含量，或导致湖泊缺氧和鱼类或鱼类繁殖地的损失。我的研究项目将创造知识，形成必要的“早期预警”系统的基础，从而预防和减轻北部湖泊的蓝藻。

The highest rates of global change are occurring in northern ecosystems. Climate warming, hydrological intensification, and acidification recovery are linked to increased inputs of terrestrial dissolved organic matter (DOM) into northern lakes (i.e., browning) which in turn have consequences to the productivity and diversity of algae that form a major pathway of energy transfer to food webs in lakes. Cyanobacterial blooms (cyanoblooms) threaten freshwater resources worldwide. Formerly pristine clear water lakes in the north are unexpectantly experiencing cyanoblooms, perhaps an early warning of more frequent, intense cyanoblooms in the future. Heightened public concern for cyanoblooms has been observed with a significant increase in the number of cyanobloom reports to governments by people living on the shores of northern lakes. The commonly accepted conceptual model is that cyanoblooms are associated with phosphorus (P) and/or nitrogen (N) mismanagement. However, we are now receiving “new” reports in northern rural and remote lakes with no known history of cyanoblooms. A new conceptual model of what forms cyanoblooms is needed. I hypothesize that the climate-induced browning of northern lakes creates light and nutrient conditions for exceptional cyanobacterial growth. While the effects of DOM on lake light and nutrient (e.g., N, P, and iron (Fe)) conditions is known, further knowledge is needed to understand algae species-specific adaptations to browning. DOM functions as a nutrient vector transporting P, N, and Fe from the surrounding catchment, and as a nutrient sponge preventing the precipitation of P and Fe and keeping them in the water column. To test this hypothesis, I will (1) Characterize climate changes at northern latitudes, focusing on those changes that lead to lake browning and the associated alterations to lake light and nutrient conditions; (2) Link browning to changes in algal biomass and the enrichment of cyanobacteria over other algae; and (3) Explore consequences of an increase in cyanobacteria dominance on the transfer of essential fatty acids (predicted to decrease) and cyanotoxins (to increase) in lake food webs. From a human perspective, there is nothing positive about cyanoblooms. The close association between freshwater resources and human activities place humans in the cyanotoxin exposure path. Direct effects include human exposure to cyanotoxins through drinking water or aerosols that can cause neurological and hepatological disorders. Indirect effects include cyanobacteria initiating a cascade of altered biological outcomes, as cyanobacteria may reduce the essential fatty acid composition and increase the toxin content in dietary fish or lead to lake hypoxia and the loss of fish or fish breeding grounds. My research program will create knowledge that will form the basis of essential “early warning” systems that can lead to the prevention and mitigation of cyanoblooms in northern lakes.