Quantifying Nutrient and Energy Flows in Aquatic Food Webs

气候变化正在改变生态系统。劳伦森五大湖的变暖速度是世界上第二快的，开发新模型和新技术使我们能够预测和测量气候变化对水生生态系统的影响是至关重要的。我们将通过进一步发展非稳态生物积累模型以及验证持久性有机污染物（POPs）和汞作为环境示踪剂的使用来量化水生食物网中的能量和营养流动来应对这一挑战。这两项研究是相互作用和相互依赖的，因为非稳态模型对数据的要求相对较高，需要关于生长速度、觅食策略和调节污染物吸收和消除过程的季节性代谢过程的信息。我们提出了四个项目。首先，我们将研究在休伦湖处于崩溃状态的食物网中湖鳟鱼和鲑鱼的化学积累动态。我们将使用非稳态模型方法来估计鱼类的能量需求，并测量这些鱼类对休伦湖营养循环和命运的相对贡献。据预测，湖鳟鱼在营养循环中起关键作用，而鲑鱼主要是营养损失载体。湖鳟鱼数量的减少加上鲑鱼的放养被认为是导致该系统食物网崩溃的原因。第二项研究旨在扩大持久性有机污染物非稳态模型的校准，将汞作为一种环境示踪剂纳入其中。汞的同化效率比持久性有机污染物高得多，但人们对鱼类从食物中吸收汞的调控机制知之甚少。我们将研究蛋白质动力学/动力学的作用，以更深入地了解是什么使汞在鱼类中成为超蓄积物。第三，鱼的消费量和体重之间有很强的关系，遵循四分之三次幂定律。我们将使用持久性有机污染物和汞作为鱼类消耗率的原位测量，以研究占据同一湖泊的温水和冷水物种消耗率的差异。我们预测消耗率和质量之间的斜率将是相似的，符合四分之三幂定律，但截距将显著不同。最后，基于原始稳态生物积累模型预测的鱼类消费指南假设个体差异很小。这一假设已被许多研究证明是错误的，因此有必要更好地了解调节污染物负担的高度个体变异性的过程。我们建议研究营养水平、生长速率和觅食策略作为伊利湖西部鱼类种群中污染物个体变异的调节因子的相对重要性，伊利湖是世界第二大商业渔业的所在地。

Ecological systems are being modified by climate change. The Laurentian Great Lakes have the second fastest rates of warming in the world, and it is essential to develop new models and novel techniques that allow us to predict and measure the effects of climate change on aquatic ecosystems. We will address this challenge with the further development of non-steady state bioaccumulation models as well as the verification of the use of persistent organic pollutants (POPs) and mercury as environmental tracers to quantify energy and nutrient flow in aquatic food webs. These two research initiatives are interactive and interdependent in that non-steady state models have relatively high data requirements, needing information on growth rates, foraging strategies and seasonal metabolic processes that regulate contaminant uptake and elimination processes. We propose four projects. First we will investigate chemical accumulation dynamics in lake trout and salmon in the food web of Lake Huron which is in a state of collapse. We will use the non-steady state model approach to estimate energy requirements of the fish and measure the relative contribution of these fish to nutrient recycling and fate in Lake Huron. It is predicted that lake trout provide a critical role in nutrient recycling whereas salmon are primarily a nutrient loss vector. The decline in lake trout populations combined with the stocking of salmon is suggested to have contributed to the food web collapse in this system. The second study aims to expand the calibration of the non-steady state model from POPs to include mercury as an environmental tracer. Mercury exhibits a much higher assimilation efficiency than POPs, but little is known what regulates the assimilation of Hg from food in fish. We will examine the role of protein dynamics/kinetics to gain more insight as to what makes Hg a super-accumulator in fish. Thirdly, there is a strong relationship between fish consumption rates and body mass which follows the Three Quarter Power Law. We will use both POPs and Hg as insitu measures of fish consumption rates to study differences in consumption rates of warm and cold water species occupying the same lakes. We predict the slope between consumption rate and mass will be similar, fitting the three quarter power law, but the intercepts will be significantly different. Lastly, fish consumption guidelines based on predictions of original steady state bioaccumulation models assume there is little individual variability. This assumption has been disproved by many studies, necessitating a better understanding of processes that regulate the high individual variability in contaminant burdens. We propose to examine the relative importance of trophic level, growth rates and foraging strategies as regulators of individual variability of contaminant in fish populations in Western Lake Erie, home to the second largest commercial fisheries in the world.