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The projects listed below give brief descriptions of some of our current research in ecology at UTA. Please see individual faculty webpages for additional research areas.

Plant Species Diversity and Trophic Interactions in Alaskan Tundra

Dr. Laura Gough has been investigating the determinants of plant species composition in arctic tundra in northern Alaska since 1996. She has two currently funded research projects. The first is an NSF-funded collaborative project with Dr. John Moore, Colorado State University. Previously, Gough and Moore examined the direct linkages among soil nutrients, plants, small mammals, insects, and soil fauna in two common Alaskan tundra types, moist acidic tussock and dry heath. As the Arctic continues to warm, soil nutrient availability increases as soil microbes are able to decompose organic matter at a higher rate, making more nutrients available to plants. The effect of these changes on the plant community have been documented, but subsequent effects on mammalian herbivores have not been studied nor have direct feedbacks between soil organisms and plants. Gough and Moore’s current project focuses on the plant-soil linkages within moist acidic tundra when nutrients are no longer limiting, and will involve a modification of the DAYCENT model of soil organic matter to better understand how changes in soil nutrient availability affect carbon exchange with the atmosphere. Gough’s second project is an NSF-funded collaborative award to investigate how increased shrubbiness associated with climate warming is affecting migratory songbird breeding success in arctic Alaska. Please see Gough’s lab webpage for more information.

Golden Algae in Texas Reservoirs

Prymnesium parvum, also called “golden algae”, occurs worldwide and is responsible for large fish kills in coastal and inland water environments. Blooms of golden algae have been identified in fresh and brackish water environments from Australia to Texas, where they have impacted community revenues from tourism, fishing, and hatchery production. Blooms in Texas have affected over 20 reservoirs in five river basins, killing over 17.5 million fish with economic losses of several million dollars. Dr. James Grover and colleagues at UT-Austin, Texas A&M University and Baylor University are investigating the ecology of golden algae, with sponsorship from the Texas Parks & Wildlife Department (http://www.tpwd.state.tx.us/landwater/water/environconcerns/hab/ga/). This research integrates laboratory and field experiments with mathematical modeling and toxicology. Previous research has established that blooms in Texas occur in winter, under conditions of temperature and salinity that are not optimal for growth of the algae, but which do enhance the toxicity of golden algae to fish. The absence of golden algae blooms in warmer weather, which supports more rapid growth, remains unexplained. Ongoing research will address hypotheses that the competitors (other algae) and grazers present in summer suppress the growth of golden algae.

Effects of Stoichiometry on Microbial Competition and Predation

Drs. James Grover and Thomas Chrzanowski are investigating the impact of variable stoichiometry on predation and competition by developing microbial experimental models, in a project funded by NSF (2005-2008). This project addresses how variations in the chemical composition (“stoichiometry”) of microorganisms affect their interactions with other species. In theory, variations in composition of the nutrient elements carbon, nitrogen, and phosphorus, affect competition between bacterial species, and also affect the relationship of bacterial prey with the larger microorganisms that consume them. Recently developed mathematical models of these processes are being tested using laboratory cultures of two bacterial species and a consumer microorganism, a chrysophyte flagellate. Specific predictions being tested include the proposal that the capability to reduce the cellular content of a nutrient indicates efficient nutrient use and can improve a species’ competitive ability, the proposal that consumers alter the outcome of competition between prey species, and the notion that this effect depends on details of chemical composition and the processing and recycling of nutrients on the part of the consumer. This project will provide insights into processes governing abundances of microorganisms in nature, including some species of “harmful algae” whose lifestyle includes feeding upon bacteria.

Lake Granbury Water Quality Study

Lake Granbury Water Quality Study. This project is sponsored by the US Department of Energy through a contract with the Texas Water Resources Institute, and involves investigators from Texas A&M University, Baylor University and the University of Texas at Arlington. The goal is to use high resolution spatial mapping of lake characteristics and mathematical modeling to identify factors affecting two water quality problems within the lake. Problems under investigation involve outbreaks of high numbers of bacteria indicating low water quality (E. coli, other fecal bacteria indicators), and harmful blooms of "golden algae" (Prymnesium parvum). Lake Granbury is a long, narrow reservoir whose shoreline is essentially completely developed, mostly as residential property. Only a minority of the residences around the lake is hooked to municipal sewage, and most homes rely on septic systems for sewage disposal. Leakage from these systems is one potential factor contributing to water quality problems.

Algal biodiversity in streams: Exploring the mechanisms of coexistence under resource limitation

Dr. Passy has been funded by the Norman Hackerman Advanced Research Program (2010-2012) to test experimentally two theories developed in her lab and recently published in PNAS and Ecology. The first theory opposes over 80 years of ecological thinking, viewing species coexistence as a result of resource limitation. Contrary to this prediction, Dr. Passy’s investigations with algae revealed that resource abundance rather than resource limitation promoted producer biodiversity in streams. The second theory builds on over 20 years of extensive oceanographic research, showing that iron limits phytoplankton growth in 40% of the world’s ocean. This theory suggests that iron limitation is not restricted to oceans but reduces algal biodiversity in the continental stream network as well. It further links explicitly stream iron supply to the area of wetlands in the watershed, which implies that continuing wetlands degradation and loss, already exceeding 52 million hectares in the conterminous US alone, may cause algal biodiversity decline across stream ecosystems. This can lead to harmful environmental and economic consequences, such as deterioration of water quality and diminishing of fish resources. Therefore, in testing these ideas, Dr. Passy’s future research will deepen the understanding of biodiversity, promote a holistic and integrative approach to the study of freshwaters, and potentially lead to the development and adoption of new practices of wetland restoration and creation, which have become a nation-wide industry under the current US policy of “no net loss”