Temperature Dependency of Population Dynamics and Trophic Cascades in a Model Aquatic System

Determining how temperature alters direct predation and indirect trophic cascade effects will be crucial in understanding how global climate change affects community structure and stability. While we are starting to comprehend the effects of warming on individual trophic interactions and underlying mechanisms, effects of warming on multilevel food webs are mostly unknown. This study sought to experimentally observe potential effects of temperature on population and community dynamics, and the magnitude of trophic cascades. To reach these objectives, a three-tiered food web (Scenedesmus, Daphnia and Hydra) was designed, maintained, and observed at two different temperatures (17°C and 21°C) for 37 days. Results found that Daphnia population dynamics shifted, with the 21°C treatments demonstrating higher density peaks, faster population declines, and an additional population cycle over the duration of the study. Scenedesmus populations showed no response to differential Daphnia population dynamics. While a strong trophic cascade effect was found, no differences were observed between temperatures. The experimental design may have been overly limited to accurately observe trophic cascade effects, so more research is encouraged. Mechanisms for Daphnia population dynamic shifts were hypothesized, including temperature-dependent rates of maturation and mortality, reproductive timing and capacity, and Scenedesmus productivity. Consequences of temperature-induced population dynamic shifts were explored, concluding that similar effects in vivo may contribute to uncoupling of predator-prey interactions, and increased community instability. Global climate change is set to be the most significant environmental, social and economic challenge in human history. It is also slated to become the most rapid change in climate in known geologic time, which presents a unique set of challenges for natural biological systems that have traditionally adapted to changing climates over hundreds of thousands of years, not decades. This study will focus on the effects of warming on one important component of ecosystems: food web dynamics. More specifically, it will attempt to determine the temperature dependency of predator-prey dynamics and trophic cascade effects in an aquatic model system. To best understand the relevance of this study, it is important to understand the role of predation in biological systems, and how alterations may induce system-wide effects. Global climate change (GCC) will affect biological systems in a region specific manner, as global climate change expresses itself in highly variable changes in regional temperatures, which may be more of less significant than the global average. Thus, it can be difficult to make generalized statements as to how GCC will affect biological systems. …