Novel Biogeochemical Pathways, Patterns and Measurements of Nitrogen and Phosphorus in Lakes and Reservoirs

该建议审查了影响水生生态系统中生物地球化学过程和水质的非生物和生物因素，包括人类因素。引起蓝藻水华的因素及其毒素正在紧张的研究中。对生态系统服务丧失(例如，水质)的关注一直是一个主要焦点。然而，直到最近才考虑到蓝藻对生态系统功能的影响。蓝藻通过产生毒素、抵抗放牧以及作为食草动物的食物质量差，对食物网产生广泛影响。因此，当湖泊被蓝藻主导时，它们的浮游食物网应该不会有效地发挥作用。我将用直接测量食物网周转效率的新技术来检验这一假设。我的下一个目标是比较迪芬贝克湖(SK)磷的两条重要的生物地球化学途径。从河流到水库的磷负荷往往是水质的主要决定因素。同样，浮游磷的再生对维持生产力也很重要。然而，尽管这些过程对湖泊和水库管理具有潜在的意义，但每条路径相对于另一条路径的重要性尚不清楚。因此，我建议对迪芬贝克湖的这两条小径进行测量和比较。我的第三个目标是确定整个湖泊的光氨化速率。这是水体中溶解的有机氮(DON)被光分解为生物可利用的营养物质NH4的过程。我的初步研究表明，这一过程在春季和夏季可能会很明显。然而，DON转化为NH4的速率作为湖泊深度的函数尚未确定，这是估计整个系统速率的必要步骤。因此，我将测量一组不同的草原和前寒武纪屏蔽湖的深度综合光氨化作用，以确定这一途径的相关性。我的下一个目标是测量硝酸盐，这是一种影响湖泊水质的重要营养物质。硝酸根通常用比色法测定。然而，比色法需要很多步骤，而且容易受到干扰。作为一种替代方法，二阶导数紫外法正在兴起，它具有快速、不易受到干扰、产生的废物少等优点。然而，这项技术还没有在草原地区典型的更具挑战性的水域(例如，更高的传导性和更高的溶解有机碳浓度)中进行测试。我的初步分析表明，这两种技术在估计这类水域的三氧化二氮方面存在很大差异。因此，我将对它们的性能进行比较，确定二阶导数技术是否适用于草原水体中的NO_3测量。这些研究将促进我们对湖泊和水库中生物地球化学过程的了解，并最终有助于内陆水域的管理和保护。

This proposal examines the abiotic and biotic factors, including human, that affect biogeochemical processes and water quality in aquatic ecosystems. The factors giving rise to cyanobacterial blooms and their toxins are under intense research. Concern over the loss of ecosystem services (e.g., water quality) has been a major focus. However, only recently has the effect of cyanobacteria on ecosystem function been considered. Cyanobacteria have widespread impacts on food webs through toxin production, resistance to grazing and as poor food quality for grazers. Hence, when lakes are dominated by cyanobacteria their planktonic food webs should be functioning inefficiently. I will test this hypothesis with novel techniques that directly measure food web turnover efficiency. My next objective is to compare two important biogeochemical pathways of P in Lake Diefenbaker (SK). Loading of P from rivers into reservoirs is often a major determinant of water quality. Similarly, planktonic P regeneration is known to be important to maintain productivity. However, the importance of each pathway relative to the other is unknown, despite the potential significance of these processes for lake and reservoir management. Therefore, I propose to measure and compare both pathways in Lake Diefenbaker. My third objective is to determine whole-lake rates of photoammonification. This is a process by which dissolved organic nitrogen (DON) is photodecomposed to the bioavailable nutrient NH4 in waterbodies. My preliminary research suggests that this process may be significant in spring and summer. However, the rate at which DON is converted to NH4 as a function of depth in lakes has not been determined, a necessary step to estimate whole system rates. Therefore, I will measure depth integrated photoammonification in a diverse set of prairie and Precambrian Shield lakes in order to establish the relevance of this pathway. My next objective concerns the measurement of NO3, an important nutrient affecting water quality in lakes. NO3 is usually measured with colorimetric methods. However, colorimetric methods entail many steps and are prone to interferences. The second derivative UV technique for NO3 measurement is emerging as an alternative method; it is rapid, less prone to interferences, and generates less waste. However, this technique has not been tested in more challenging waters typical of prairie regions (e.g., of greater conductivity and higher dissolved organic carbon concentration). My preliminary analyses indicate that both techniques differ greatly in estimating NO3 in such waters. Therefore, I will compare their performance and determine if the second derivative technique is suitable for NO3 measurement in prairie waterbodies. These studies will advance our understanding of biogeochemical processes in lakes and reservoirs, and ultimately aid in the management and protection of inland waters.