Integrating top-down control by parasitic protists and fungi into the ecological dynamics of freshwater phytoplankton blooms

淡水湖为我们提供了许多服务，如为我们的家庭和娱乐提供淡水供应。在淡水湖中，进行光合作用的单细胞微藻在整个春季和夏季数量都在增加。不同种类的藻类在一年中的不同时间“开花”，通常是湖泊生态系统的正常组成部分。然而，有时这些水华会成为一种滋扰，产生有毒的化学物质(如蓝藻)，或者只是把水变成绿色的豌豆汤，遮盖了其他植物。藻类的大量繁殖可能会影响湖泊内的所有生命。随着来自污水和农业的养分输入的增加，气温的上升和极端气候事件的发生，藻类水华发生的频率更高，持续时间更长。控制水华的因素很大程度上归因于自下而上的因素(光、温度、营养的可用性)或自上而下的因素(浮游动物的捕食和觅食)。另一种鲜为人知的自上而下控制藻类的方法是寄生。藻类被许多不同的生物寄生。最广为人知的是微小的单细胞真菌种类，称为合胞菌，它会感染藻类细胞，杀死它们。还有不同种类的其他生命，例如不同种类的单细胞原生动物，它们可能通过寄生来控制藻类的数量。英国境内的许多藻类寄生虫并不为人所知，仅在上个世纪通过显微镜观察进行了描述。该项目将使用尖端DNA测序技术结合显微镜和流式细胞仪来识别和计数英国湖区湖泊内的藻类寄生虫。它将研究来自20个不同湖泊的不同季节的样本。它还将在藻类大量繁殖的整个生命周期内跟踪寄生虫的丰度和多样性。该项目将研究这些寄生虫对藻类大量繁殖的影响，展示它们的数量如何与藻类宿主有关的增加和减少。这将使我们能够增加我们对藻类水华的自上而下控制的知识，了解更多关于它们的生态学，并将帮助我们更好地了解、预测和管理藻类以及淡水生态系统的健康。

Freshwater lakes provide us with many services such as a supply of freshwater for our homes and recreation. Within freshwater lakes, microalgae, photosynthesising single cells, increase in numbers throughout the spring and summer. Different species of algae "bloom" at different times of the year and are usually a normal part of the lake ecosystem. However, sometimes these blooms can become a nuisance, produce toxic chemicals (such as blue-green algae), or simply turn the water a green pea soup colour, shading out other plants. Blooms of algae may impact on all life within the lakes. With increasing nutrient inputs from sewage and agriculture, increasing temperature and extreme whether events, algal blooms are happening more frequently and with longer duration. What controls these blooms is largely attributed either bottom-up factors (availability of light, temperature, nutrients) or top-down factor (predation and grazing by zooplankton). One less known top-down control of algae is parasitism. Algae are parasitised by many different organisms. The most well-known are tiny single-celled species of fungi called Chytrids that infect cells of algae killing them. There are also diverse groups of other life such as different species of single celled protozoa that may control algae numbers through parasitism. Many parasites of algae within the UK are not well known and only described from microscope observations in the last century. This project will use cutting edge DNA sequencing technology combined with microscopy and flow cytometry to identify and count parasites of algae within the lakes of Lake district UK. It will look at samples across different seasons and from 20 different lakes. It also will track parasite abundance and diversity across the lifetime of an algal bloom. The project will look at the impact these parasites have on blooms of algae, showing how their numbers increase and decrease in relation to their algal hosts. This will enable us to increase our knowledge of top-down controls on blooms of algae, learning more about their ecology and will helpi us to better understand, predict and manage algae and the health of freshwater ecosystems.