Managing ground and surface waters together to limit pollution

Past research has revealed that impaired water quality in Elkhorn Slough—California’s third-largest estuary and a National Estuarine Research Reserve (NERR)—is linked to salt marsh loss and decreased flatfish production within the estuary and catch offshore. The region’s Water Quality Control Board is working with agricultural farmers and scientists to better understand these pollution issues and is actively seeking solutions. However, comprehensive studies of how nutrient pollution moves through this system are lacking. University of Southern California (USC) Sea Grant funded a study to quantify the extent to which nutrient removal and transport processes occur naturally in this salt marsh system.

Key Results:

  • Results show that ocean tides dominate the salt marsh hydrology and biogeochemistry in the dry growing season (summer) and that freshwater inputs mix with tidal inputs during the wet dormant season (winter)
  • The hydrological model of Elkhorn Slough is complete; the biogeochemical model to understand how nutrients move throughout groundwater and the water-sediment interface is underway; pollution modeling is underway

Project Impacts & Application:

  • Hosted a public workshop in collaboration with Elkhorn Slough NERR staff in June 2023
  • Presented at the American Geophysical Union Meeting, Coastal and Estuarine Research Federation Conference, and Goldschmidt Conference
  • Organized an undergraduate research course where students partnered with Elkhorn Slough National Estuarine Research Reserve to identify regional water quality needs
  • Began collaborating with the Department of Energy’s Lawrence Berkeley National Lab for data analysis


Principal Investigator:

Margaret Zimmer, Ph.D., University of California Santa Cruz 



California Ocean Protection Council, 2018-2021

Additional Info


Access our Publications Database to view publications from this project or other related topics

N2 flux in sediment incubation experiments conducted with sediments from different salt marsh positions

Graphic showing N2 flux in sediment incubation experiments conducted with sediments from different salt marsh positions