The freshwater phosophorus cycle and the fate of water-borne pathogens

在拟议的NSERC发现基金的任期内，三名博士生将进行湖泊和河流中磷循环的研究，一名博士生将研究河流中致病微生物的持久性。在多塞特环境科学中心，我们将使用以前NSERC DG资助开发的新技术来确定哪些环境因素决定浮游生物中细菌和藻类可用的磷酸盐浓度，从而确定它们的生产力。首先，我们将解决食物网结构和光（由混合深度和水透明度决定）是关键变量的假设。我们将在DESC上解决的第二个基本问题是磷在湖泊表层的停留时间，因此在给定的养分负荷下将存在的生物量总量。为了做到这一点，我们将利用自然产生的放射性同位素来测量磷元素的年龄。富营养化河流的一个主要环境问题是污水和农业的高磷负荷导致水生植物生物量过剩，导致夜间溶解氧低。为了了解夏季低流量期间植物可利用的磷酸盐浓度，当养分可能控制植物生长时，我们将估计夏季低流量期间不同群落中有多少磷被隔离，我们将确定每个群落是磷酸盐的净来源还是汇，作为磷酸盐浓度的函数。本研究将建立一个模型，预测这些群落相对丰度不同的河流在低流量时的磷酸盐浓度。地表水中病原体的浓度取决于负荷和持久性。我们将研究不同水生群落对病原体的去除，包括seston，沉积物，硬表面生物膜和与大型植物相关的生物膜。这些信息将告知河流群落如何与病原体负荷相互作用，以确定病原体水平。

During the tenure of the proposed NSERC Discovery Grant, three PhD students will conduct research on the phosphorus cycle in lakes and rivers, and one will work on the persistence of pathogenic microbes in rivers.  At the Dorset Environmental Science Centre we will use new techniques developed with previous NSERC DG funding to determine what environmental factors determine the concentration of phosphate available to bacteria and algae in the plankton, and hence their productivity.  Initially, we will address the hypothesis that food web structure and light (determined by mixing depth and water transparency) are the key variables.  The second fundamental problem we will address at DESC is the residence time of P in the epilimnion of lakes and therefore the total amount of biomass that will be present for a given nutrient loading.  To do this we will exploit naturally occurring radioisotopes that can be used to measure the age of P in the epilimnion.   A major environmental problem for eutrophic rivers is excess biomass of aquatic plants caused by high phosphorus loading from sewage and agriculture, leading to low dissolved oxygen at night.  To understand phosphate concentration available to plants during summer low flow periods, when nutrients likely control plant growth, we will estimate how much of the P at summer low flow is sequestered in different communities, and we will determine whether each of these is a net source or sink for phosphate as a function of phosphate concentration.  This research will lead to a model predicting phosphate concentrations at low flow for rivers with different relative abundances of these communities.   Concentrations of pathogens in surface waters are determined by both loading and persistence. We will study the removal of pathogens by different aquatic communities, including seston, sediments, biofilms on hard surfaces, and biofilms associated with macrophytes.  This information will inform as to how river communities interact with pathogen loading to determine pathogen levels.