DISSERTATION RESEARCH: Effects of multiple invasive species on nutrient cycling in Lake Seminole: effects of warmer winters on ecosystem dynamics

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Human activities are causing major changes in species distributions globally. These changes have led to the development of new combinations of plants and animals as new species have invaded a wide range of ecosystems. In many cases, multiple species have invaded the same areas, and their interactive effects on ecosystem processes are not well understood. The overarching objective of this project is to investigate the interactive effects of multiple invaders on nutrient cycling in Lake Seminole, on the border of Georgia and Florida. Experiments will document the effects of a highly productive species of aquatic plant from Asia, Hydrilla verticillata, living together with an abundant Asian clam, Corbicula fluminea, and two newly established snail species (Pomacea maculata, from South America and Pomacea paludosa from Florida). These experiments are designed to simulate natural conditions of light and temperature and determine differences in rates of nutrient uptake, storage, and release by Hydrilla with and without Corbicula and the two Pomacea species. To determine larger scale changes in abundance and distribution of aquatic vegetation due to the presence of the other non-native species, remote sensing methods will be developed for tracking rapid changes among non-native aquatic vegetation. Results from mesocosm experiments and remote sensing analyses will be integrated into a general conceptual model to forecast likely future impacts on nutrient cycling as these invasive species move northward to other lakes and rivers. Recent climate change and increased organism movement by humans are dispersing many species into new locations, resulting in novel species combinations in many ecosystems. Understanding how non-native aquatic plants and animals interact allows for projection of their effects on specific ecosystem services, such as nutrient cycling, provision of sustainable supplies of high-quality drinking water, and recreational boating and fishing. The recent invasion of Lake Seminole by Pomacea, where two other abundant invasive species (Hydrilla and Corbicula) were already established, provides a unique opportunity to study multi-species invasions at an early stage and to investigate effects on ecosystem services, specifically their impact on water quality. Lake Seminole currently plays a critical role in nutrient and contaminant storage as well as in providing high-quality water to downstream communities. However, little is known about the interactions or combined effects of invasive species within the lake, nor how recent introductions will affect lake production and nutrient cycling. This project will help to fill these knowledge gaps and to inform local and regional stakeholders of the effects of invasive species on lake ecosystems. A workshop will be organized to facilitate communication with stakeholders on the effects of invasive species. The conceptual model will help to create an early warning network to inform residents on how to reduce the spread of invasive species, the potential risks of toxicity, and wildlife diseases. Local students will benefit from direct participation in research and workshops.