EXAMINING THE ROLE OF IRON IN PROMOTING CYANOBACTERIA DOMINANCE

营养丰富(富营养化)湖泊中的蓝藻水华仍然是一个重大的全球问题，包括加拿大，尽管几十年的科学研究和数十亿美元的资金用于去除营养物质以降低水华形成的风险。水华对环境健康构成威胁，因为许多细菌会产生肝脏和神经毒素，它们会损害饮用水的味道和气味。很明显，营养、磷(P)向湖泊和河流的过量输入是导致水生初级生产力增加的原因，并且P是水华形成和良性藻类物种置换的一个非常强烈的风险因素。然而，磷导致富营养化水域蓝藻水华的原因尚不清楚。此外，磷本身不能解释近年来在被认为处于低风险的低磷水平的湖泊中水华发生率的增加。我的实验室最近的证据表明，一种特殊形式的铁--亚铁的可获得性增加，促进了蓝藻对浮游植物(藻类)群落的优势地位，而且水华发生的时间受到控制亚铁从缺氧沉积物中释放的物理和化学因素的影响。这项建议解决了新兴模型中关于磷和铁如何共同作用以增加水华形成风险的几个知识空白。它还研究了水华形成的发生率增加是否可能是气候变化的信号。

Cyanobacteria blooms in nutrient-rich (eutrophic) lakes remain a significant global problem including Canada, in spite of decades of scientific research and billions of dollars spent on nutrient removal to reduce the risk of bloom formation. Blooms pose a threat to environmental health because many strains produce liver and nerve toxins and they can impair the taste and odour of drinking waters. It is clear that excessive input of the nutrient, phosphorus (P) to lakes and rivers is responsible for increased aquatic primary productivity and that P is a very strong risk factor for bloom formation and displacement of benign algal species. However, the reason why P leads to blooms of cyanobacteria in eutrophic waters has not been clearly established. In addition, P alone does not explain increasing incidence of blooms in recent years in lakes with low P levels that were considered to be at low risk. Recent evidence from my lab shows that increased availability of a particular form of iron, ferrous iron, promotes dominance of phytoplankton (algal) communities by cyanobacteria and that the timing of blooms is influenced by physical and chemical factors that control release of ferrous iron from oxygen-depleted sediments. This proposal addresses several knowledge gaps in the emerging model about how P and iron work together to increase the risk of bloom formation. It also examines whether increasing incidence of bloom formation may be a climate change signal.