Science activity

Description

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.

Project Need

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.

Project Objectives

• Estimate abundance and distribution of micro-, meso-, and macro-zooplankton in the upper estuary, including San Pablo Bay, Suisun Bay, Grizzly Bay, Suisun Marsh, and the delta.
• Investigate relationships between zooplankton abundance and temperature, salinity, turbidity, and chlorophyll
• Monitor long-term abundance trends for various species of zooplankton and identify significant declines or increases
• Determine whether introduced species of zooplankton are becoming established in the estuary