Description Suisun Bay and Marsh are a key part of the habitat for Delta Smelt, but during drier periods such as summer, Delta Smelt may be at least partially excluded from Suisun Marsh due to high salinities. The purpose of this proposal is to provide scientific support a management action for Smelt, operation of the Suisun Marsh Salinity Control Gates (SMSCG). This facility is currently to tidally pump water into the Marsh to improve fall and winter habitat conditions for waterfowl, but could also provide a tool to manage aquatic habitat for Delta Smelt in other periods. Specifically, by using the SMSCG to direct more fresh water in Suisun Marsh, our prediction is that reduced salinities will improve habitat conditions for Delta Smelt in the region. Need The status of Delta Smelt is dire. As part of the Resources Agency's Delta Smelt Resiliency Strategy, in August 2018 we conducted pilot operations of the SMSCG to support Delta Smelt , with promising results. Based on this early success, we expect that the SMSCG will be used as a seasonal tool to support Delta Smelt in summer-fall in coming years as part of the coming FWS Biological Opinion and DFW ITP. Neither has been completed, but SMSCG operations for fish are expected to be required in each. Hence, the proposed study is intended to provide a scientific evaluation and guidance for an expected SMSCG action in 2020. Objectives The primary objective of this project is to evaluate the effectiveness of the SMSCG action. Questions to be addressed include: Did the action improve habitat conditions for Delta Smelt in the Suisun Region? Does the Suisun Region typically have better habitat and food web conditions than the upstream River Region? Do Delta Smelt respond favorably to the SMSCG flow action? Does operation of the SMSCG affect other fishes and clams?
Description In a collaborative effort between CA Department of Water Resources, US Bureau of Reclamation, CA Department of Fish and Wildlife, United States Geological Survey, San Francisco State University, and UC Davis, this study will investigate the role of augmented summer and fall flows in the Yolo Bypass and North Delta areas on lower trophic food web dynamics and the benefits to listed fish species. Using both continuous and discrete sampling approaches, this study will relate hydrologic patterns to chlorophyll-a, nutrients and primary productivity, plankton densities and composition (phytoplankton and zooplankton), contaminant concentrations, as well as water quality parameters such as electrical conductivity, turbidity, temperature, and dissolved oxygen. In addition, caged hatchery Delta Smelt will be monitored to determine the effects of the managed flow action and increased food web productivity on fish survival, growth, and behavior. Need Due to the food-limited nature of the San Francisco Estuary, it is critical to understand mechanisms that result in successful food web productivity including phytoplankton blooms. Food limitation is one of the primary hypothesized causes of the Pelagic Organism Decline. In 2011 and 2012 there was evidence that a moderate Yolo Bypass flow pulse during fall agricultural drainage periods was followed by phytoplankton blooms in the lower Sacramento River. Managed flow actions in the following years showed an increase in food web productivity could be repeated; however, results varied across years and flow actions indicating more research is warranted to understand correlations between flow and abiotic conditions, and the biological response of the food web. The increases of summer/fall flows in North Delta, has been considered a management strategy as part of complying with USFWS Delta Smelt Biological Opinion Action 4. The augmentation of flows through the Yolo Bypass/North Delta is also included as one of several Delta Smelt Resiliency Strategies by Natural Resources Agency. Objectives: Determine if managed flow actions through the Yolo Bypass stimulate increased primary productivity locally and downstream, and if it is repeatable. Characterize how nutrients, chlorophyll and plankton (composition and density) in the Toe Drain, Cache Slough Complex, and lower Sacramento River change in response to flow pulses. Determine if nutrient subsidies of the source water and downstream are limited by abiotic and biotic factors. Characterize spatial differences and transport of pesticide contaminants in the Yolo Bypass in response to the flow actions. Determine survival, growth and behavior of caged hatchery Delta Smelt before and after the flow action in the Yolo Bypass.
The Environmental Monitoring Program (EMP) began in 1975 to conduct baseline and compliance monitoring of water quality, phytoplankton, zooplankton, and benthic invertebrates in the San Francisco Bay-Delta estuary. This monitoring program was designed to track the impact of water diversions to the State Water Project (SWP) and Central Valley Project (CVP) on the Bay-Delta. In the decades since, EMP scientists have monitored these constituents at fixed and floating stations throughout the estuary and ensured compliance with state and federal mandates such as Water Right Decision 1641 (D-1641). In the years and decades since its inception, EMP has become one of the cornerstones for scientists' and managers' understanding of the pace and pattern of change in this critical ecosystem. By sampling water quality and biological communities concurrently, EMP has created a dataset that is uniquely useful in better understanding causal connections between physical, biological, and biogeochemical processes.
