Much research in the Delta has focused on foodweb dynamics, stimulated by evidence that low productivity of plankton is linked to declines in several fish species including the endangered delta smelt. Pseudodiaptomus forbesi is the most abundant copepod (small crustaceans) in the Delta in summer. It is an important food source for many fishes and makes up about half of the food of delta smelt. This study focuses on the feeding, reproduction, and growth of copepods as essential foodweb support for fishes. This work investigates four diverse habitats including two open-water channels and two shallow habitats. The researchers will measure copepods' feeding rates on microscopic plants and animals, and relate feeding to their rates of growth and reproduction. Computer models will be used to estimate their movement and death rates. These results will show the sources of nutrition used for growth and reproduction of these key organisms. Results will inform how food webs respond to large scale changes in the Delta ecosystem, for example, restoration and the Sacramento wastewater treatment plant upgrade.
Pesticide and nutrient inputs from human activities are present in the Sacramenot-San Joaquin Bay-Delta, but the impact of these stressors together on algae is not well known. This research will examine the impacts of herbicides and nutrients on the growth and stress responses of phytoplankton and cyanobacteria present in the San Francisco Estuary. The algae in the delta are diverse with critical ecological effects, ranging from toxin-producing cyanobacteria that form hazardous algal blooms to benthic diatoms and green algae that make up the bulk of the aquatic food web. Contaminants and herbicides can cause changes in algae cellular health which may impact population growth. Understanding algal sub-lethal stress responses will improve our understanding of stressors on the bay-delta food web and bloom formation.
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.
The Zooplankton Study has sampled macro-, meso-, and micro-zooplankton in the upper San Francisco Estuary since 1972. Samples are collected monthly at 19 stations, located from upper San Pablo Bay to the eastern Delta, using three gear types – a pump sampler for microzooplankton, such as copepod nauplii and rotifers, a CB net for mesozooplankton, such as adult copepods and cladocerans, and a mysid net for macrozooplankton. The Zooplankton Study provides data on zooplankton abundance and distribution to assess the food resources available to fish in the upper San Francisco Estuary, as zooplankton are an important trophic link between primary producers and upper trophic levels. This information is used by aquatic ecologists to investigate physical and biological drivers of the lower food web and relationships between food resources and fishes that feed on zooplankton in the upper estuary, including listed species such as Delta and Longfin Smelt.
The Zooplankton Study is conducted in compliance with the SWRCB’s Water Rights Decisions 1485 (Term 10a) and 1641 (Term 11a). This study may also inform the CDFW 2024 Incidental Take Permit, the operations of the State Water Project (Table 2), the 2024 NMFS and USFWS Biological Opinions for operations of the Central Valley Project, and the Summer-Fall Habitat Action Team.
