| 英文摘要: | Wetlands are dynamic habitats that are found at the interface of terrestrial and aquatic ecosystems. They function to cleanse polluted water, ameliorate floods, recharge groundwater aquifers, and support diverse flora and fauna. Regretfully, half of Earth's wetlands have been lost in recent times due to population expansion, pollution, coastal development, and other human activities. In addition to the ecosystem services mentioned above, wetlands are among the most biogeochemically active habitats on Earth. They have been identified as key sites for carbon sequestration and regulation of greenhouse gas emissions. These environments are very sensitive to environmental perturbation, and the effects of global climate change - especially sea level rise - are already evident. Sea level rise can bring saltwater into historically freshwater wetlands, changing the chemical reactions that take place in the sediment and the composition of soil microbial communities. This research provides a better understanding of freshwater wetland response to saltwater intrusion and specifically focuses on soil microorganisms and their roles in carbon sequestration and greenhouse gas emissions. In addition to its scientific contributions, this project advances both science education and public awareness of the threats facing tidal freshwater wetlands, and includes activities intended to educate the community (grade school children through adults) on basic aspects of environmental science.
Microbial communities have historically been treated as a "black box" due to assumptions that there is a high level of functional redundancy and that microbial population dynamics (e.g., in response to global change) are unimportant. However, numerous recent studies have demonstrated that changes in microbial community composition can directly influence ecosystem process rates, motivating this study of the responses of microbial consortia to disturbance. The overall goal of this research is to link genomics-based characterization of soil microbial communities with process-level measurements of important ecosystem carbon transformations, and to examine their collective responses to environmental change. This research project includes both observational and manipulative experiments in the tidal freshwater and oligohaline marshes of the Pamunkey/York River system in Virginia, a major tributary of Chesapeake Bay. The project combines assessment of wetlands along an existing riverine salinity gradient, as a space-for-time substitution for future saltwater intrusion, with an in situ saltwater addition experiment that characterizes changes in the coupled microbe-plant-soil system. Molecular genetic analyses (16S sequencing, qPCR, and RT-qPCR) of the soil microbial communities, process rate measurements (iron and sulfate reduction, methanogenesis), and ecosystem carbon dioxide and methane exchanges are being used to develop a detailed mechanistic understanding of how compositional changes in microbial communities affect biogeochemical processes. This fundamental knowledge will pave the way for future research that effectively incorporates microbial communities into ecosystem process models. |