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

湖泊和水库中的有害藻类大量繁殖对人类健康构成重大威胁，进而对加拿大经济的各个方面构成重大威胁。有害藻华，特别是与蓝细菌有关的藻华，除了造成味道和气味问题外，还产生各种肝脏和神经毒素，对饮用水供应的安全产生直接影响。近年来，从纽芬兰到不列颠哥伦比亚省，加拿大各地的氰基有害生物一直在增加。这种增加的原因尚不清楚，但已经提出了各种加剧影响，其中包括营养物质的变化，酸雨的减少和气候变化。目前迫切需要对氰基有害生物进行科学评估和风险管理。主要营养元素磷（P）和氮（N）的输入一直是许多研究和管理工作的焦点。最近，一个新的理论中心的重要性，铁（Fe）的可用性的形式铁（II）作为关键的蓝藻水华。然而，确定蓝藻可用的Fe（II）的来源是有问题的。Fe在表面沃茨中含量低，因为Fe（III）非常不溶，氧气会迅速将Fe（II）转化为Fe（III）。我们已经发现，铁的天然稳定同位素具有很大的希望破译蓝藻所使用的铁的来源。我们的项目将评估这种新的同位素工具，以了解铁循环在湖泊和水库的风险，从氰基有害生物。这项工作将集中在实验湖区（ELA），在那里收集了过去47年来有关湖泊化学，生物学和物理学的背景信息。其中一个关键组成部分是正在进行的一项全球独特的全湖实验的深入研究，其中一个湖泊已经接受了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其他湖泊和水库中精心挑选的样本进行分析，以评估这项有前途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.