Monitor toxicity levels in aquatic invertebrates to assess the Delta's ecosystem health.

The Measure

Measurable reduction in positive toxicity test using standard methods, for pesticides and other pollutants in Delta waters. 

  • Expectations

    Achieve measurable reduction in toxicity, using standard testing methods, for pesticides and other pollutants in Delta waters.

  • Performance Metrics

    Toxicity in sediments using invertebrates determined by standard methods approved by the United States Environmental Protection Agency (USEPA) as measured by the State Water Resources Control Board.

Stream Pollution Trends Monitoring Program

There are five sites in the Central Valley that have been identified as toxic in the Stream Pollution Trends Monitoring Program (SPOT). One of these sites (Marsh Creek) is located within the Delta boundary. The other sites are out of the scope of this performance measure.

Click on the points to view a station's mean percent survival (lower %= Higher toxicity)* between the 2014 and 2016 SPOT reports.

Sampling Sites Identified

To Quote the 2016 SPOT report

The majority of the sites in Region 5 have never been toxic and generally have low concentrations of measured chemicals, including pesticides. Only seven sites in the region have ever been toxic, but two sites are consistently highly toxic (Marsh Creek and Del Puerto Creek)

*Toxicity tests with Hyalella azteca, a widespread and abundant species of amphipod crustacean, were conducted following U.S. EPA standard methods and the toxicity of sediment samples was determined using the U.S. EPA’s test of significant toxicity-TST. More information about USEPA standard methods below.

Link to the SPOT reports

Next Data Update: This visualization will not be updated until the next SPOT report is released. In addition, we anticipate additional toxicity data (e.g. Delta RMP or other programs sampling toxicity) to be made available that will enable us to create new data visualizations.

Delta Regional Monitoring Program

The Delta Regional Monitoring Program (Delta RMP) released a report regarding pesticides and toxicity monitoring in the Delta for 2015-16. The report shows results from monthly water samples conducted (July '15-June '16) at fixed sites that represented key inflows to the Delta . There are also other water quality efforts that the Delta RMP is currently conducting, which can be found on the Delta RMP Web Page.

An overview of the Delta RMP quoted from their website:

The Delta RMP is a stakeholder-directed project formed to develop water quality data necessary for improving our understanding of Delta water quality issues. The goal of this effort is to better coordinate and design current and future monitoring activities in and around the Delta to create a cost effective approach for providing critically needed water quality information to better inform policy and regulatory decisions of the Central Valley Regional Water Quality Control Board and other Federal, State and local agencies and organizations.

Also Available: Data visualization of the RMP's first two years of Current Use Pesticides data.

It is important to measure toxicity in Delta water bodies because the Delta ecosystem is affected by a variety of discharged constituents, including contaminants of emerging concern—such as neonicotinoids, pyrethroids and phenylpyrazoles. These contaminants can affect key Delta species, ecosystem health, and water bodies that are used for recreation and human consumption.

Contaminant toxicity is a growing concern because it adversely affects all organisms and people who rely on water bodies—impacting water quality, ecosystem health, and the reproduction and viability of organisms coming in contact with the water. Even at low concentrations, these chemicals can have negative effects over longer periods of exposure for larger organisms. Long-term exposure can present itself in many forms, but a prime example would be high levels of selenium or mercury in predatory fish species.

Moreover, toxicity in Delta water is especially a concern for threatened and endangered species, as certain chemicals have detrimental effects on reproduction and offspring viability. It is important that toxicity is measured using organisms sensitive to the contaminants present and representative of the environment being sampled.

United States Environmental Protection Agency (USEPA) Standard Methods are guidelines on how to measure the toxicity of waterbodies and sediments. The USEPA methods use specific invertebrates and monitor and evaluate their responses to associated contaminants in freshwater sediments.

Stream Pollution and Monitoring Program (SPOT) monitors trends in sediment toxicity and contaminant concentrations in selected large rivers throughout California, and relates it to watershed land uses. The overall goal of this long-term trends assessment is to detect meaningful change in the concentrations of contaminants and their biological effects in large watersheds at time scales appropriate to management decision making (Direct quote from SPOT website).

Each chapter of the Delta plan includes strategies to achieve the goals of the plan. These strategies are general guidance on achieving the objective laid out in the plan and in the Delta Reform Act of 2009. Associated with these strategies are recommendations. The recommendations describe more specific and implementable actions to support the achievement of Delta Plan strategies. Strategies and recommendations may also have associated performance measures. Delta Plan performance measures track progress in achieving desired outcomes for the Delta Plan. Below are the strategies and recommendations associated with this performance measure.

Delta Plan Strategy

  • Improve environmental water quality

Delta Plan Recommendations

  • Completion of regulatory processes, research, and monitoring for water quality improvements
  • Implement Delta Regional Monitoring Program
  • Evaluate wastewater recycling, reuse, or treatment
  • Manage dissolved oxygen in Stockton Deep Water Ship Channel
  • Manage dissolved oxygen in Suisun Marsh

Toxicity in sediments using invertebrates determined by standard methods approved by the USEPA as measured by the State Water Resources Control Board.


The 2008-2012 averaged levels of toxicity using combined Toxic and highly toxic sites from the Stream Pollution and Monitoring Program Report (18.8 percent toxicity).


Less than one percent toxicity in sediment samples from pesticides and other contaminants, using invertebrates testing, by 2034.

Data is retrieved directly from the Stream Pollution Trends Monitoring Program report. Locations of sampling locations are retrieved from California Environmental Data Exchange Network (CEDEN).

Data Sources

2016 SPOT report

California Environmental Data Exchange Network

Have questions or comments about this measure? Contact Us