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

沿海海洋系统中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。据推测，这是由于与上升流相关的营养物浓度增加造成的，从而使初级产量增加，从而使常绿藻类生物量增加。然而，上升流也会导致水温急剧下降。由于鱼类和无脊椎食草动物的代谢依赖于温度，较冷的上升水可能会降低消费者的代谢和放牧强度。这反过来又会导致站立藻类生物量的增加。因此，上升流可能影响对初级生产者群体和社区自下而上和自上而下的控制。本研究的目的是验证一个假设，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到温度调节的。更广泛的影响包括通过北卡罗来纳大学基于课程的本科研究计划培训和保留少数民族学生，支持本科研究，教师培训和各种外展活动。研究人员将利用Galápagos群岛独特的强烈的水温时空差异，在自然温度梯度上比较放牧强度和初级生产。他们将结合野外监测、统计建模、放牧分析、种群特定代谢测量、就地食草动物排除和营养添加来测量温度对浅海潮下群落模式和过程的影响。研究人员还将测试一个假设，即在温暖的地区和/或温暖的季节，食草动物的种群对热的敏感度较低，这可能是由于适应或适应。最后，研究人员将进行一系列中生态实验，以测量近期温度对食草动物、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，特别是初级生产是如何调节的，以及能量在营养水平上转移的温度依赖性。

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.