Cyanobacteria harmful algal blooms (CHABs) have long been a persistent water quality issue in the Delta, affecting ecosystems and public health for decades. Despite numerous studies highlighting their impacts, the Delta lacks a formal regulatory framework for monitoring CHABs. The Delta CHABs Monitoring Strategy was developed to fill this critical gap, driven by input from the science community and a public workshop held in Fall 2022.
The Delta CHAB strategy establishes a community-informed approach to better manage CHABs in the Delta. Its key objectives include coordinating the collection of priority data, developing collaborative approaches to sharing data, and implementing effective mitigation techniques. By aligning scientific expertise with community involvement, the Delta CHABs Monitoring Strategy aims to advance both understanding and management of these harmful blooms.
The development of the strategy was facilitated by the Delta Science Program and authored by Dr. Ellen Preece (Department of Water Resources), Dr. Mine Berg (Environmental Science Associates), Tricia Lee (DSP), Dr. Karen Odkins (Department of Fish and Wildlife), and Jenna Rinde (Department of Fish and Wildlife).
Background
Harmful algal blooms (HABs) are a recurring issue across the Delta, affecting a range of water bodies—from coastal waters to brackish zones and freshwater areas. In 2022, the brackish waters of San Francisco Bay experienced a significant HAB caused by Heterosigma akashiwo, a type of algae known to thrive in such environments. Meanwhile, in the freshwater regions of the Delta, cyanobacteria—primarily Microcystis—are the main culprits behind these harmful blooms. Each type of HAB poses challenges to the ecosystem and highlights the complex nature of water quality issues in the region.
Harmful algal blooms (HABs) can produce toxins that pose serious risks to both animals and humans. If large enough, these blooms can also deplete oxygen levels in the water, threatening aquatic life. When water affected by HABs is used for crop irrigation, the toxins may accumulate in the crops, creating potential health hazards. Additionally, HABs present significant challenges for drinking water treatment.
The graphic on the slide below illustrates the key variables and drivers behind the formation of harmful algal blooms (HABs). Factors such as water flow, residence time, and temperature play a significant role in HAB development.
The characteristics of these blooms vary depending on their environment. For instance, dense blooms often thrive in slow-moving waters like dead-end channels or marinas, where limited circulation allows algae to accumulate. Conversely, blooms in fast-flowing rivers with deeper waters tend to be sparser due to greater water movement and depth that disrupt algae growth. Flooded islands fall somewhere in between, offering conditions that support moderate HAB formation. The interplay of these factors shapes the unique patterns of HABs in each setting.
Although some factors driving HABs are understood, there is still a significant gap in detailed, site-specific data on their status, trends, and causes. This information is crucial for developing strategies to mitigate and monitor these blooms. Unfortunately, the lack of dedicated funding and regulatory requirements for consistent data collection remains a major obstacle.
Developing the strategy
With the growing problem, the Delta science community recognized the importance of a collaborative approach to monitoring and addressing HABs. To address these challenges, stakeholders developed a coordinated strategy to align the needs and priorities of all involved. However, its success depends on the community’s collective effort to implement it, especially without reliable funding to support the process.
Development of the strategy was a three-year effort that included a public workshop and targeted outreach to agencies, community-based organizations, tribes, and environmental justice groups. A draft strategy was released for public comment in early 2024, allowing stakeholders to provide input. In April, the Delta Plan Interagency Implementation Committee endorsed the strategy. After incorporating feedback, the final version of the strategy was published in October 2024.
The strategy
The Delta CHABs Monitoring Strategy establishes a community-informed approach to address and advance the management of CHABs in the Delta by coordinating the collection of priority data, developing collaborative approaches to sharing data, and ultimately implementing CHAB mitigation techniques.
The Strategy includes five goals, 15 objectives, and recommendations for 20 special studies. These recommendations primarily focus on enhancing collaboration and data sharing, and informing CHABs-related decision-making in the Delta.
The strategy includes five goals:
- Enhance Delta CHAB Collaboration: The strategy includes several recommendations to enhance collaboration, including creating a CHAB working group and an annual CHAB meeting to share information and training.
- Identify monitoring questions, goals, and objectives: Feedback received indicated that the community wanted to have a voice on the monitoring questions and goals, so the strategy does not finalize these but rather provides examples of what the questions could be, such as what are the status and trends of Habs in the Delta?
- Develop a Delta CHAB monitoring program: Once the monitoring questions and goals are finalized, a Delta CHAB monitoring program will be developed, including 19 special studies to address identified knowledge gaps.
- Develop collaborative reporting protocols that include standardized operating procedures and data collection.
- Utilize a data-sharing platform to make Delta CHAB data publicly available.
Implementation
Now that the HAB strategy is finalized, implementation can begin, but Dr. Preece reminded that there is no dedicated funding for the strategy, so the success of implementation falls to the ongoing coordination and collaboration of the Delta science community.
Four co-chairs of the Delta CHAB workgroup have been identified, and they have coordinating with the Interagency Ecological Program project work team. They are working towards the first annual CHAB workshop, tentatively scheduled for March at the IEP Annual Meeting.
The State Water Board has provided funding to the USGS to develop the monitoring design. The management questions are still being finalized, but the USGS is beginning the initial design. Some of the recommended special studies are starting up.
NOAA study
NOAA’s Monitoring and Event Response for Harmful Algal Blooms (MERHAB) Research Program builds capacity along the coasts for enhanced harmful algal bloom (HAB) monitoring and response. In October of 2023, the program awarded a $3 million grant over five years to support the development of a HAB monitoring program for the San Francisco Estuary.
The project, led by scientists at the San Francisco Estuary Institute (SFEI), US Geological Survey, and California Department of Water Resources (DWR), will leverage ongoing research and monitoring activities in the Bay and Delta to build a robust system-wide HAB monitoring program for the Estuary. The project includes specific tasks for the San Francisco Baykeeper, Restore the Delta, Cal State Maritime Academy, and the California Department of Public Health.
The MERHAB project includes independent research projects to address HABs across the San Francisco Estuary, some of which overlap with the 19 special studies in the HAB strategy. A data dashboard will be developed to provide a single location for all the HAB resources. New visualizations and tools will be built for researchers and communities can monitor and learn about HABS across the Estuary.
There is also a management transition advisory group that will bring managers from across the Estuary to discuss how to use the tools from the project in the future and how those will be implemented into monitoring programs once the funding ends. The group includes managers from state and federal agencies and local advocacy groups such as Restore the Delta and San Francisco Baykeeper.
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