The Role of Temperature in Regulating Herbivory and Algal Biomass in Upwelling Systems

沿海海洋系统的一个众所周知的模式是初级生产者的生物量与上升流的发生或强度之间存在正相关关系。这被认为是由于与上升流相关的营养浓度增加所致，从而使初级生产力更高，从而使藻类生物量更大。然而，上升流也会导致水温大幅快速下降。由于鱼类和无脊椎动物的新陈代谢依赖于温度，较凉爽的上升水可能会降低消费者的新陈代谢和放牧强度。这反过来又可能导致海藻生物量的增加。因此，上升流可能会影响对人口和初级生产者社区的自下而上和自上而下的控制。这项研究的目的是检验这样一种假设，即放牧强度和藻类生物量在一定程度上是通过代谢率的温度依赖性受温度调节的。更广泛的影响包括通过北卡罗来纳大学以课程为基础的本科生研究计划培训和留住少数族裔学生，支持本科生研究，教师培训和各种外展活动。调查人员将利用加拉帕戈斯群岛水温独特的强烈时空变化来比较放牧强度和自然温度梯度上的初级生产力。他们将结合现场监测、统计模型、放牧分析、特定种群的新陈代谢测量、就地草食动物排除和营养添加来衡量温度对浅潮下群落格局和过程的影响。研究人员还将测试这一假设，即较温暖地点和/或较温暖季节的食草动物种群对温度不那么敏感，这可能是由于驯化或适应。最后，研究人员将进行一系列中游实验，以测量不久的将来气温对食草动物、藻类和食草动物的影响。这项工作可能会改变我们对上升流系统的看法，特别是初级生产力是如何被调节的，以及营养水平之间能量转移的温度依赖性。

A well-known pattern in coastal marine systems is a positive association between the biomass of primary producers and the occurrence or intensity of upwelling. This is assumed to be caused by the increase in nutrient concentration associated with upwelling, enabling higher primary production and thus greater standing algal biomass. However, upwelling also causes large, rapid declines in water temperature. Because the metabolism of fish and invertebrate herbivores is temperature-dependent, cooler upwelled water could reduce consumer metabolism and grazing intensity. This could in turn lead to increased standing algal biomass. Thus upwelling could influence both bottom-up and top-down control of populations and communities of primary producers. The purpose of this study is to test the hypothesis that grazing intensity and algal biomass are, in part, regulated by temperature via the temperature-dependence of metabolic rates. Broader impacts include the training and retention of minority students through UNC's Course Based Undergraduate Research program, support of undergraduate research, teacher training, and various outreach activities. The investigators will take advantage of the uniquely strong spatiotemporal variance in water temperature in the Galápagos Islands to compare grazing intensity and primary production across a natural temperature gradient. They will combine field monitoring, statistical modeling, grazing assays, populations-specific metabolic measurements, and in situ herbivore exclusion and nutrient addition to measure the effects of temperature on pattern and process in shallow subtidal communities. The researchers will also test the hypothesis that grazer populations at warmer sites and/or during warmer seasons are less thermally sensitive, potentially due to acclimatization or adaptation. Finally, the investigators will perform a series of mesocosm experiments to measure the effect of near-future temperatures on herbivores, algae, and herbivory. This work could change the way we view upwelling systems, particularly how primary production is regulated and the temperature-dependence of energy transfer across trophic levels.