To support management planning in Suisun Marsh, this project is developing a body of science and tools to understand past, present, and potential future changes to the Marsh’s ecological patterns, processes, and functions. This project builds on SFEI’s prior work in the Delta, extending historical ecology mapping, landscape change studies, and the Landscape Scenario Planning Tool to cover Suisun's historical and present-day landscapes. Through spatially explicit representations of the historical function and condition of the marsh and analyses of landscape metrics, this project is evaluating changes over time in landscape support for ecosystem functions and services in Suisun. In order to incorporate diverse perspectives into planning resources, project activities include engagement with local tribes and community members to understand community interests, priorities, and uses of the Marsh. Findings will be shared through a report and article for both technical and general audiences, and spatial analyses and data layers will be made available through the Landscape Scenario Planning Tool.
Water primrose (Ludwigia spp.) is a highly invasive, non-native floating macrophyte in the Delta. In recent years, water primrose has extended its niche into marsh habitat, causing extensive mortality of marsh macrophytes including tules and cattails. The goal of this project is to determine whether the growth strategy of water primrose, its allelopathic properties, or factors related to plant community structure are the cause of marsh loss following water primrose invasion in the Delta. Part of this study will identify and map the marshes most vulnerable to loss and quantify the spatial trajectory of marsh loss during the past 15 years. The ultimate benefit will be an improved understanding of the water primrose invasion processes in the Delta, which can be used to prioritize herbicide treatment of this highly invasive plant in marshes most vulnerable to invasion and with the highest habitat value.
Objectives:
Invasive aquatic macrophytes (aquatic weeds) cover increased dramatically in the Sacramento-San Joaquin Delta (Delta) during the 2013-2015 drought and the 2021-2023 drought. This trend toward increasing dominance of these invasive aquatic weeds has profound implications for delta/marsh habitat, as aquatic weeds are known to significantly alter the physical environment by slowing water velocities, increasing water clarity, providing habitat for invasive fishes, and reducing open water habitat. These habitat effects are thought to negatively impact the endangered Delta Smelt and other pelagic species that rely on turbid, open water habitat. During the drought of 2021- 2023, aquatic weeds have continued to spread into new habitats, therefore there is an urgent need to identify effective control measures, which requires increased understanding of ecosystem responses to drought and associated environmental conditions in the waterways (e.g., water temperature, flow rates, turbidity, etc.), and specific control measures.
The work covered in this contract includes the 2021-2023 Emergency Drought Salinity Barrier Monitoring Plan mandated under DWR’s Incidental Take Permit. Research has focused on understanding invasion patterns in Franks Tract and contrasting them with patterns in channels surrounding Liberty Island and restoration sites. We also analyze Suisun marsh to assess the condition near the salinity drought barrier on Montezuma Slough, and its impacts across the length of Montezuma Slough and relate observed patterns to salinity conditions in Suisun Slough.
Extensive field work has been conducted throughout the Delta and in Suisun Marsh to acquire data that is used to train and evaluate remotely sensed maps of aquatic weed distribution and link these to measurements of water quality. This project extends the time period of continued mapping of aquatic vegetation in the Delta through summer of 2027, for a time series that goes back to 2004, covering 19 years of high spatial resolution hyperspectral imagery data. This dataset now encompasses the full range of hydrologic conditions that extend from wet years to extremely dry years which can potentially form the basis for interpreting causal relationships and changes in trait distributions of aquatic weeds. Aquatic weed mapping combined with an extensive field campaign within the Suisun Marsh extends the Suisun time series to seven years. This growing time series of vegetation maps for both the Delta and Suisun Marsh can be leveraged to look at the evolution of tidal wetland restoration sites developed by DWR’s Fish Restoration Program (FRP) as part of the Incidental Take Permit. This analysis covers construction to current time period to see if different restoration strategies (pre-planting, no pre-action, treating invasive species outside the site, etc.) have an impact on the growth and maturity of a site, invasibility, etc. Additionally, the full time series will be evaluated for trends related to weather/climate, water conditions, and management actions.
