Biostimulation and Biological Condition
California faces significant water quality challenges from excess nutrients, biostimulation, and harmful algal blooms (HABs). Nutrients, such as nitrogen and phosphorus, can cause HABs and biostimulation. HABs and biostimulation in turn, have detrimental effects on a variety of human health and aquatic life beneficial uses. Common detrimental effects include the depletion of dissolved oxygen; floating algal mats that block sunlight and reduce the growth of submerged aquatic vegetation; altered aquatic communities; foul taste and odors; and the production of cyanotoxins that are harmful to aquatic life, wildlife, and humans. Excess nutrients and biostimulation have also been shown to negatively impact biological conditions in wadeable streams.
In California, many waterbodies are impaired due to impacts from nutrients and biostimulation. Since 2021, reports of HABs have increased by about 200 percent.
Project Updates
The State Water Resources Control Board (State Water Board) is considering statewide water quality objectives for harmful algal blooms (HABs) and a program of implementation to reduce the risk and occurrence of HABs in California’s inland surface waters, enclosed bays, estuaries, and coastal lagoons. More information on that project is available by going to the HABs Provisions project.
The State Water Board is continuing to develop tools and resources to measure and mitigate the effects of nutrients and other biostimulatory substances in inland surface waters, enclosed bays, estuaries, and coastal lagoons. The State Water Board is also continuing to develop and use tools to measure Biological Condition in wadeable streams. Although the State Water Board is not currently developing a project establish statewide water quality objectives for nutrients, other indicators of biostimulation, or biological metrics, a Regional Water Quality Control Board (regional board) may establish regional or site-specific water quality objectives for these parameters.
Technical Documents & Tools
- A Technical Foundation for Biointegrity and Eutrophication Indicators and Thresholds for Modified Channels, Intermittent Streams, and Streams on the Central Valley Floor – 2025 Update
- A Technical Foundation for Biointegrity and Eutrophication Indicators and Thresholds for Modified Channels, Intermittent Streams, and Streams on the Central Valley Floor (2024 - Old Version)
- Science Supporting the Provisions
Archived Nutrient Objective Workplans and Technical Documents
Archived Information from the Biological Integrity Plan Project
Public Meetings
July 14, 2022 Biostimulation, Cyanotoxins, and Biological Conditions Public Workshop
July 14, 2022 Public Workshop
Presentations
- State Water Board
- Southern California Coastal Water Research Project (SCCWRP)
Advisory Groups Information
Other Nutrient Related Efforts:
- San Francisco Bay Nutrients Project
- Delta Nutrient Research Plan
- San Diego Regional Water Quality Control Board Biological Objectives
- SWAMP Bioassessment Program
- U.S. EPA Nutrient Criteria Webpage
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Contact
For additional information
Recorded Webinars
- Science Supporting Cyanotoxin Thresholds
Part 1: Humans and Domestic Animals - Science Supporting Cyanotoxin Thresholds
Part 2: Aquatic Life - Satellite Remote Sensing Assessment of HABs in Lakes and Reservoirs: Progress Report
- Statewide Wadeable Streams (38 min)
- Watershed Wadeable Streams (17 min)
- Estuaries (21 min)
- Stress-Response Models to Support Selection of Biostimulatory Thresholds for California Lakes and Reservoirs (54 min)
