Recipient Organization
UNIVERSITY OF CALIFORNIA, DAVIS
410 MRAK HALL
DAVIS,CA 95616-8671
Performing Department
Environmental Science and Policy
Non Technical Summary
Wetlands are, without doubt, important ecosystems fulfilling many critical roles in natural as well as anthropogenic environments. This research focuses on improving our understanding of growth, nutrient cycling and decomposition in wetland ecosystems and interaction of macrophytes (macroscopic plants) and microphytes (bacteria) in these processes. These research questions will advance our general scientific knowledge and, more importantly, contribute to better management strategies designed to utilize wetland macrophytes in restoration and water quality improvement. Specifically, we propose to apply the gained knowledge to restoration of Mojavi Desert bulrush dominated wetlands, which provide a unique habitat for several endangered species. We also propose to test the capabilities of wetland macrophytes to intercept pathogen detrimental to human health.
Animal Health Component
80%
Research Effort Categories
Basic
10%
Applied
80%
Developmental
10%
Goals / Objectives
Ecological restoration in conjunction with conservation and natural resource management programs can only be successful if they are based on a thorough understanding of ecosystem processes in the respective systems. This project aims at understanding the wetland ecosystem processes in order to provide better guidance for restoration of ecologically and economically important wetlands. In addition, the role of macrophytes in interception of pollutants and improvement of water quality can be properly utilized only if the processes involved are fully understood.Growth of terrestrial as well as wetland plants in non-agricultural settings is often limited by the availability of nutrients, specifically nitrogen (N) and phosphorus (P) (Aerts and Chapin 2000; Bedford et al. 1999). Plants have evolved two broad strategies to deal with nutrient-limiting environment: (1) conservation of use; and (2) enhanced acquisition (Vance et al. 2003, Ticconi and Abel 2004; Rejmánková and Snyder 2008). Resorption of nutrients from senescing to newly growing or storage organs is a typical example of a conservation of use strategy. The enhanced acquisition involves production and secretion of hydrolytical enzymes such as phosphatases in case of P imitation, or utilization of rhizosphere bacteria that can increase the bioavailability of N through N2-fixation (Jurelevicius et al. 2010). Ecosystems dominated by species long-term adapted to shortage of nutrients are threatened and often eliminated under conditions of increased nutrient input through (anthropogenicaly caused) eutrophication. Among wetland ecosystems, hydrological changes are often equally important to changes in nutrient content. The project focuses on emergent macrophytes from genus Schoenoplectus, S. americanus, Olney's three-square bulrush) and S. californicus, California bulrush (Cyperaceae). Both species form critical habitats for endangered and/or economically important species. Schoenoplectus americanus is a critical habitat for an Amargosa vole (Microtus californicus scirpensis) - a federally and State endangered rodent species endemic to the Mojave Desert with a highly restricted geographic range on the Amargosa Wild and Scenic River (AWSR) and an obligate dependence upon three-square bulrush for food and protection from predators. Recent intensive studies of vole occupancy, health, and habitat availability indicate that only a few hundred individuals of this species remain. Due to long-term drought coupled with human land use, quality habitat for Amargosa voles continues to decline, with decreased plant productivity, smaller habitat area, and less connectivity between habitat patches, all exacerbated by changing climate. Of particular concern are the climate change exacerbated long-term drought impacts to the single habitat patch historically housing the largest proportion of the overall vole population. Schoenoplectus californicus, California bulrush, is a large, perennial, rhizomatous wetland sedge reaching up to 6 meters in height. As a dominant producer of biomass, S. californicus can impact biogeochemical cycles by providing a source of organic material and by oxygenating the rhizosphere (Thullen et al. 2008). In many regions, it plays an important role in the human economy, providing raw materials for livestock feed (Dejoux 1992) and the construction of boats and all-purpose mats (Rondon et al. 2003). It is also an important habitat for small fish and crabs forming an important part of human diet at Lake Atitlan, Guatemala. Currently, both bulrush species are in decline in some of their native areas, specifically, the Mojave desert for S. americanus and Lake Atitlan for S. californicus.The overall objective of this project is to research conditions most conducive to restoration of the two species in their respective home habitats. In addition, we want to research the pollutant interception capabilities of dominant species of Lake Atitlan macrophytes. The specific objectives are:Mojave Wetlands1) Explore the conditions, such as flooding level, removal of litter, seedling establishment, of reestablishment of Schoenplectus americanus.2) Determine what limits vegetation establishment and persistence in potential corridors, for the dominant plant species of vole habitat, bulrush (Schoenoplectus americanus).Macrophytes at Lake Atitlan3) Determine the conditions for reestablishment of S. californicus in the areas where it has been replaced by Hydrilla verticillata.4) Research the interception capabilities of S. californicus x Hydrilla verticillata for water pollutants (pathogens, heavy metals, pesticide residua)5) Verify the conditions conducive to N fixation by both epiphytic and endophytic N fixers associated with S. californicus and potential auto- and heterotrophic fixers in the lake.6) Evaluate the contribution of nitrogen contributed through hydrolysis of organic N molecules in the decomposing litter and sediments by extracellular enzymes.
Project Methods
Mojave Wetlands1) Explore the conditions, such as flooding level, removal of litter, seedling establishment, of reestablishment of Schoenplectus americanus.For the restoration management of Olney's three-square bulrush (Schoenoplectus americanus), we will collect information such as viability of seed bank and nutrient levels in water and soil is that will guide restoration management. Ultimately, we intend to correlate the data on bulrush performance with vole population data to show direct links between management of bulrush and rehabilitation of vole populations within the degraded habitat area.2) Determine what limits vegetation establishment and persistence in potential corridors, for the dominant plant species of vole habitat, bulrush (Schoenoplectus americanus).While the initial restoration trials by a graduate student, Stephanie Castle, proved highly successful, important information will need to be collected in order to successfully expand and restore habitat corridors for the Amargosa vole. Key questions involve whether such corridors must be vegetated, which plant species should be used for vegetated corridors, what limits corridors at present, and how such corridors can be enhanced for the vole but to also benefit other listed species that utilize AWSR such as southwest willow flycatcher and least Bell's vireo. We will determine what limits vegetation establishment and persistence in potential corridors, specifically for the two dominant plant species of vole habitat, bulrush (Schoenoplectus americanus) and salt-grass (Distichlis spicata). We will use greenhouse manipulation of salinity, nutrients, and soil moisture to determine the ecolophysio- logical limits of both species and conditions in which each would be the better competitor. We will initiate enhancement of inter-marsh corridors. Following data collection regarding ecological suitability of potential corridor sites (to include detailed documentation of salinity, soil type, soil moisture, pH, nutrient condition, and hydrological conditions and dynamics at candidate sites), we will develop and begin implementation of a specific plan to create corridors at two experimental marsh clusters.Macrophytes at Lake Atitlan3) Determine the conditions for reestablishment of S. californicus, bulrush, in the areas where it has been replaced by Hydrilla verticillata.Currently used methods for restoration of bulrush are labor-intensive and not very efficient. Establishment of bulrush nurseries, removal of hydrilla, planting the bulrush, and assessment of necessary maintenance will be tested at selected locations around the lake. This will be done in cooperation with "tuleros" (local group specilizied in bulrush management and utilization).4) Research the interception capabilities of S. californicus x Hydrilla verticillata for water pollutants (pathogens, heavy metals, pesticide residua)There are many papers indicating the role of aquatic macrophytes in sequestering various types of contaminants. Many of these are done in short time experiments, small volumes, with often unrealistically high concentrations. What seems to be missing is the connection to the real field situation. Therefore, we will first survey the concentration of specific pollutants in the lake water and lake organisms (macrophytes, fish and snails), and based on this information, set up mesocosm experiments testing the interception capability of macrophytes. We will expose a Semipermeable Membrane Device (SPMD) and the Polar Organic Chemical Integrative Sampler (POCIS) to the lake water for a month. Analyzing these samplers will allow us to determine which pesticides (and pharmaceutical products if we want to include those) are the most important in the lake water, and therefore where we should focus our future research and specific aims for grant proposals. We have collected macrophyte and fish tissue material for analyses of heavy metals - the results will also guide future experiments. And, finally, we have preliminary data indicating different interception capabilities of macrophytes for coliform and Escherichia coli pathogens. Some of the mesocosm experiments will be conducted as a part of the "hands-on" UC Davis Summer Abroad program.5) Verify the conditions conducive to N fixation by both epiphytic and endophytic N fixers associated with S. californicusBecause of the lake's relatively low concentrations of nitrogen - and thus a low nitrogen to phosphorus (N:P) ratio - the situation remains favorable for N-fixing cyanobacteria, Limnoraphis (the species that formed the bloom in 2009) Aphanizomenon, and Dolichospermum, with the latter two species being a potential toxin producers. Because the process of N-fixation has important implications for the lake ecosystem functioning, we are trying to get a good understanding of conditions that promote/prevent the fixation. Heterotrophic N-fixers - rhizosphere and endophytic fixers in Schoenoplectus; bacterial fixers in the water column; epiphytic cyanobacteria and heterotrophs on submersed macrophytes and filamentous algae. To obtain samples for N2-fixation, plants will be extracted from sediments to prevent extensive root damage and roots and rhizomes will be rinsed in surface water to remove adhered larger particles and sealed in a plastic bag. In the lab, an equivalent of ~ 200 mg DW will be transferred to fixation vials. Rhizome tissue will be surface sterilized, the outer, coarse surface layer of rhizomes will be removed after surface sterilization. The acetylene reduction technique, ARA, will be employed to estimate N2-fixation by the reduction of acetylene to ethylene by nitrogenase. Acetylene gas, freshly generated from calcium carbide, will be injected into assay bottles and the bottles will be incubated for 24 hours at 28 degrees C. At the end of the exposure, several mL of headspace will be withdrawn with an airtight syringe and analyzed by gas chromatograph. The results will be reported as the nitrogenase activity in nmol C2H4 g-1 d-1. 6) Evaluate the contribution of nitrogen contributed through hydrolysis of organic N molecules in the decomposing litter and sediments by extracellular enzymesNitrogen cycling begins with the hydrolysis of protein materials by peptidases. In aquatic environments, peptidases are secreted by various microorganisms as well as roots of some aquatic macrophytes. In order to evaluate the contribution of nitrogen released by peptidase activities of different origin, we will evaluate the peptidase activity of microorganisms associated with roots of the main macrophyte species, bulrush and hydrilla, as well as aquatic bacteria and phytoplankton. The highest activity is expected in the decomposing material of phytoplankton and aquatic macrophytes. The samples will be collected in the field and transported on ice to our lab at UC Davis. The molecular analysis of the samples conducted by Dr. Dagmara Sirova from the University of South Bohemia, Czech Republic will reveal which bacteria are mostly responsible for peptidase release.