Cooperative Ecosystem Studies Unit

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The U.S. Geological Survey (USGS) California Water Science Center (CAWSC) is offering a funding opportunity to one or more member universities of the Cooperative Ecosystems Studies Unit (CESU) Program. The project is titled Molecular-level Decomposition Studies in Sacramento-San Joaquin Delta Wetlands. This USGS-funded project will coordinate closely with a project titled Modeling Carbon and Greenhouse Gas Dynamics in Sacramento-San Joaquin Delta Wetlands. The USGS effort is comprised of several interrelated study components, three of which are included in this announcement [conduct molecular-level analyses (primarily lignin) on decomposition bag samples from a series of experiments conducted on the Twitchell Island demonstration ponds; prepare a final report focusing on preservation mechanisms, as revealed by molecular level compositions and concentrations, along with interannual variability; and perform associated project management functions]. For the past decade Carbon Farm pilot program has used a pilot wetland facility on Twitchell Island in the Sacramento-San Joaquin Delta to study the capacity of wetlands to sequester carbon and reverse subsidence. Past experiments on pilot wetland plant decomposition have revealed slower decomposition rates as the wetland matured, which in turn led to greater sequestration of carbon and accretion of peat. One goal of this project is to characterize the controls on the rates of accretion with a goal of actively manipulating these controls. Development of anoxic conditions in mature wetlands is generally considered the main control on decreased decomposition and increased preservation in wetlands. However, this mechanism is most effective for biochemicals with significant differences in aerobic vs. anaerobic decomposition rates, such as lignin. However, it is also known that production of biochemicals in plants changes as a function of environmental stressors, and maturation of a wetland could also lead to greater or lower allocation of plant resources toward production of oxygen-sensitive biochemicals such as lignin. This study will determine the extent to which increased preservation of lignin indicates anoxia as a control vs. compositional controls. The analytical work will be carried out over the course of approximately three months. Data will be analyzed and a final report will be produced in collaboration with USGS CAWSC team members. Specific objectives are: • Conduct molecular-level analyses (primarily lignin) on approximately 40 decomposition bag samples from a series of yearly experiments conducted on the Twitchell Island pilot wetland site to determine the extent to which increased preservation of lignin is responsible for or otherwise indicates mechanisms for this slower decomposition. • Prepare a final report focusing on preservation mechanisms, as revealed by molecular level compositions and concentrations, along with interannual variability. • Perform all associated project management functions.

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