The hidden influence of terrestrial groundwater on salt marsh function and resilience

Nature Portfolio (Springer Nature) | February 3rd, 2025

Salt marshes are hotspots of nutrient processing and carbon sequestration. So far, studies addressing spatiotemporal variability in and drivers of salt marsh biogeochemic

Salt marshes are hotspots of nutrient processing and carbon sequestration. So far, studies addressing spatiotemporal variability in and drivers of salt marsh biogeochemical function, carbon storage and resilience have focused on ocean-driven surface hydrologic influences, neglecting effects of terrestrial hydrology through subsurface connections. Here we evaluate drivers of salt marsh redox potential, a proxy for biogeochemical state, through wavelet analyses and information theory using data from seven marshes. The results point to terrestrial groundwater level as a dominant control on redox variability across all sites. Because redox is a key driver of biogeochemical processes, and specifically oxidation of organic matter that sequesters carbon and maintains marsh elevation, these terrestrial influences are critical to understanding marsh function and evolution. The newly identified links between onshore groundwater levels and marsh redox conditions shift the traditional paradigm and suggest that terrestrial hydrology is a primary control on salt marsh carbon sequestration potential and resilience.

The Influence of Zooplankton Availability on Delta Smelt Condition and Foraging Across Habitat Contexts

Publisher not available | December 19th, 2025

Strategies for endangered species conservation may have different outcomes depending on the habitat context in which they are implemented. Understanding these context-dep

Strategies for endangered species conservation may have different outcomes depending on the habitat context in which they are implemented. Understanding these context-dependent effects can help optimize and target management efforts. In this analysis, we investigate how environmental and food-web conditions interactively affect condition and foraging of Delta Smelt (Hypomesus transpacificus), an endangered fish endemic to the San Francisco Estuary (the estuary). Food limitation, in terms of pelagic zooplankton availability, is considered a main factor that contributes to the decline in Delta Smelt abundance. Our overarching objective was to examine whether the effect of zooplankton on Delta Smelt depended on habitat context. Specifically, we hypothesized that zooplankton would less positively effect Delta Smelt condition—as measured by hepatosomatic index (HSI)—and foraging success in areas with nearby tidal wetlands, because these adjacent habitats may provide access to prey items from the epibenthos and fringing vegetation. In contrast, in regions with limited proximity to wetlands, we hypothesized that Delta Smelt would rely more on pelagic prey, which would manifest as a more positive effect of zooplankton on body condition and foraging success for Delta Smelt. Using models that accounted for habitat in multiple ways, we found little evidence that zooplankton and habitat interactively influenced Delta Smelt condition or gut fullness. Rather, the influence of zooplankton on HSI and gut fullness was generally positive across habitat contexts. Given the well-documented food limitation in the estuary, promoting the availability of pelagic zooplankton is a rational, albeit complex, management aim. Furthermore, our results suggest that efforts to increase zooplankton would broadly benefit Delta Smelt across a wide range of habitat contexts.

The Once and Future Delta: Mending the broken heart of California

Bay Nature | April 1st, 2010

On March 30, 1772, Spanish explorer Pedro Pages was traveling east along the south shore of Suisun Bay, looking for a land route around the seemingly endless chain of b

On March 30, 1772, Spanish explorer Pedro Pages was traveling east along the south shore of Suisun Bay, looking for a land route around the seemingly endless chain of bays extending inland from the Golden Gate. Mounting to Willow Pass, the rise of land between present-day Concord and Pittsburg, he found himself staring at a new obstacle: an enormous expanse of marshland, threaded with bright channels. He had "discovered" the Sacramento-San Joaquin River Delta.

The Pulse of the Bay 2022: 50 Years after the Clean Water Act

San Francisco Estuary Institute (SFEI) | October 13th, 2022

This August an algal bloom of historic proportions blanketed San Francisco Bay. The most concerning aspect of the bloom was the death of thousands of fish across wide are

This August an algal bloom of historic proportions blanketed San Francisco Bay. The most concerning aspect of the bloom was the death of thousands of fish across wide areas of the Bay, including 10,000 yellowfin goby, hundreds of striped bass and white sturgeon, and other species like green sturgeon, bat rays, and sharks. This is the most widespread and deadliest fish kill in the Bay in recent memory.

The Pulse of the Bay: The 25th Anniversary of the RMP

San Francisco Estuary Institute (SFEI) | July 1st, 2017

San Francisco Bay is the defining feature of our region and a world-class ecosystem. The Bay Area is also known world-wide as a cradle of innovation, excellence, and succ

San Francisco Bay is the defining feature of our region and a world-class ecosystem. The Bay Area is also known world-wide as a cradle of innovation, excellence, and success, especially in the technology sector. Less well known is the fact that over the past 25 years the Bay Area has been a world leader in water quality monitoring, supporting a pioneering program for the Bay that demonstrates how regional collaboration can provide the science needed to protect and improve water quality in a treasured ecosystem. The Regional Monitoring Program for Water Quality in San Francisco Bay (RMP) was established in 1993 and, with sustained local funding and continuous improvement, is going stronger than ever a quarter century later.

The Reasonable Use Doctrine and Water Use Efficiency Report

Publisher not available | April 5th, 2011

The purpose of the report is to review the breadth of the Reasonable Use Doctrine, which can affect all water uses, including urban, hydropower, recreation, environment,

The purpose of the report is to review the breadth of the Reasonable Use Doctrine, which can affect all water uses, including urban, hydropower, recreation, environment, and agriculture, and then to focus on how the Reasonable Use Doctrine can be used promote efficient use of water in the agricultural sector. The underlying premise of this report is that the inefficient use of water is an unreasonable use of water. Accordingly, the Reasonable Use Doctrine is available prospectively to prevent general practices of inefficient water use. Indeed, the Reasonable Use Doctrine, as set forth in the State Constitution and California Statutes is broad and inviolate in scope. As interpreted by case law and administrative decisions and used to its full potential, it can comprehensively address the inefficient use of water in California.

The Regional Monitoring Program for Water Quality in San Francisco Bay, California, USA: Science in support of managing water quality

Regional Studies in Marine Science (Elsevier) | October 22nd, 2015

The Regional Monitoring Program for Water Quality in San Francisco Bay (RMP) is a novel partnership between regulatory agencies and the regulated community to provide the

The Regional Monitoring Program for Water Quality in San Francisco Bay (RMP) is a novel partnership between regulatory agencies and the regulated community to provide the scientific foundation to manage water quality in the largest Pacific estuary in the Americas. The RMP monitors water quality, sediment quality and bioaccumulation of priority pollutants in fish, bivalves and birds. To improve monitoring measurements or the interpretation of data, the RMP also regularly funds special studies. The success of the RMP stems from collaborative governance, clear objectives, and long-term institutional and monetary commitments. Over the past 22 years, high quality data and special studies from the RMP have guided dozens of important decisions about Bay water quality management. Moreover, the governing structure and the collaborative nature of the RMP have created an environment that allowed it to stay relevant as new issues emerged. With diverse participation, a foundation in scientific principles and a continual commitment to adaptation, the RMP is a model water qualitymonitoring program. This paper describes the characteristics of the RMP that have allowed it to grow and adapt over two decades and some of the ways in which it has influenced water quality management decisions for this important ecosystem.

The RMP Emerging Contaminants Program - Fact Sheet

San Francisco Estuary Institute (SFEI) | May 2nd, 2016

 RMP stakeholders believe that preventing a pollution problem is safer and more cost-effective than cleaning one up. For this reason, the RMP focuses on monitoring emerg

 RMP stakeholders believe that preventing a pollution problem is safer and more cost-effective than cleaning one up. For this reason, the RMP focuses on monitoring emerging contaminants, or CECs. Early identification of problem CECs and quick action to prevent their spread is the best way to protect water quality in San Francisco Bay. 

The Sacramento-San Joaquin Delta: The Evolution and Implementation of Water Policy: An Historical Perspective

University of California, Davis (UC Davis) | June 1st, 1977

This report is a history of the attempts to control the encroachment of salinity from San Francisco Bay into the Delta of the Sacramento and San Joaquin rivers from 1920

This report is a history of the attempts to control the encroachment of salinity from San Francisco Bay into the Delta of the Sacramento and San Joaquin rivers from 1920 to the present. Two basic solutions to the problem present themselves: the physical separation of salt water from fresh water by means of a barrier at some point downstream from the Delta, or the release of sufficient water from upstream storage reservoirs to drive back tidal salinity.

The San Francisco Bay-Delta Agreement: Principles for Agreement on Bay-Delta Standards Between the State of California and the Federal Government

California State Water Resources Control Board (SWRCB) | December 15th, 1994