Natural stable isotopes of iron: a new tool to trace Fe cycling for management of risk from harmful cyanobacterial blooms in lakes and reservoirs

湖泊和水库中有害的藻类水华对人类健康构成了重大威胁，进而对加拿大经济的各个方面都构成了威胁。有害藻华，特别是与蓝藻有关的藻华，除了引起味道和气味问题外，还会产生各种肝脏和神经毒素，直接影响饮用水供应的安全。近年来，从纽芬兰到不列颠哥伦比亚省，加拿大各地的氰基哈布斯一直在增加。这种增加的原因尚不清楚，但已经提出了各种加剧作用，其中包括营养物质的变化、酸雨的减少和气候变化。目前迫切需要评估科学和管理与氰基-哈布斯有关的风险。主要营养物质磷(P)和氮(N)的输入一直是许多研究和管理工作的重点。最近，一个新的理论集中在以铁(II)的形式存在的铁(Fe)作为蓝藻水华的关键的重要性。然而，确定蓝藻可利用的铁(II)的来源是有问题的。地表水中的铁含量很低，因为铁(III)很难溶解，氧气能迅速将Fe(II)转化为Fe(III)。我们发现，铁的天然稳定同位素在破译蓝藻使用的铁的来源方面有很大的希望。我们的项目将对这一新的同位素工具进行评估，以了解面临氰基赤潮风险的湖泊和水库中的铁循环。这项工作将集中在实验湖地区，在那里，过去47年来收集了关于湖泊化学、生物和物理的背景信息。其中一个关键组成部分是正在进行的一项全球独一无二的全湖实验的密集研究，其中一个湖接受了47年的营养添加，并反复出现蓝藻水华。ELA的一系列实地活动和实验室实验将评估天然稳定铁同位素的使用。此外，将对合作科学家从加拿大各地其他湖泊和水库收集的精心挑选的样本进行分析，以评估这项前景光明的新技术广泛应用的潜力。

Harmful algal blooms in lakes and reservoirs constitute a major threat to human health and, by extension, to all aspects of the Canadian economy. Harmful algal blooms (HABs), especially those associated with cyanobacteria (cyano-HABs) have direct impacts on the safety of drinking water supplies by producing a variety of liver and nerve toxins in addition to causing taste and odour problems. Cyano-HABs have been increasing in recent years across Canada from Newfoundland to British Columbia. Causes of this increase are unknown but various exacerbating effects have been suggested, among these are changes in nutrients, a decrease in acid precipitation and climate change. There is an urgent need to evaluate the science and to manage risk with regard to cyano-HABs. Inputs of the main nutrients, phosphorus (P) and nitrogen (N), have been the focus of much research and management effort. Recently a new theory centres on the importance of the availability of iron (Fe) in the form of Fe(II) as the key to cyanobacterial blooms. Determining the source of Fe(II) available to cyanobacteria is, however, problematic. Fe is low in surface waters because Fe(III) is very insoluble and oxygen quickly changes Fe(II) to Fe(III). We have discovered that the natural stable isotopes of Fe hold great promise to decipher the source of Fe used by cyanobacteria. Our project will evaluate this novel isotopic tool for understanding Fe cycling in lakes and reservoirs at risk from cyano-HABs. The work will be focussed at the Experimental Lakes Area (ELA) where background information on chemistry, biology and physics of lakes has been collected over the past 47 years. One of the key components is the intensive research ongoing at a globally unique whole lake experiment where one lake has received nutrient additions for 47 years and has recurring cyanobacterial blooms. A series of field campaigns at ELA and laboratory experiments will evaluate the use of natural stable Fe isotopes. In addition, carefully selected samples from other lakes and reservoirs across Canada, collected by collaborating scientists, will be analyzed to evaluate the potential for widespread application of this promising novel technique.****