I am writing to express strong opposition to the Virginia Department of Health’s (VDH) proposed edits to the Guidance for Cyanobacteria Recreational Advisory Management, specifically the proposal to eliminate the use of cyanobacteria cell counts as a criterion for issuing harmful algal bloom (HAB) alerts, as noted in the public comment period from April 21 to May 21, 2025. As a risk management professional and a concerned homeowner, I believe removing cell counts from the decision-making process undermines the scientific rigor, transparency, and precautionary approach necessary to protect Virginia’s residents, visitors, and pets from the risks posed by HABs. Below, I outline the critical role of cell counts in HAB monitoring and provide evidence-based arguments for retaining this metric in advisory determinations.

Importance of Cyanobacteria Cell Counts in HAB Monitoring

Cyanobacteria, often referred to as blue-green algae, are naturally occurring microorganisms that can proliferate rapidly under favorable conditions, forming HABs that pose significant risks to human and animal health. These blooms can produce cyanotoxins, such as microcystins and cylindrospermopsins, which are associated with skin irritation, gastrointestinal illness, neurological damage, and, in severe cases, liver damage or death. The decision to issue a recreational advisory must rely on robust, quantitative data to ensure timely and effective public health interventions.

Cell counts of cyanobacteria are a well-established, objective metric used by numerous state and federal agencies to assess the potential toxicity of a bloom. Eliminating cell counts as a criterion disregards this evidence-based framework and risks weakening the ability to detect potentially harmful blooms early. Cell counts provide a direct measure of cyanobacteria abundance, which is critical for assessing bloom severity before toxins reach dangerous levels. Unlike toxin concentrations, which may only become detectable after cell lysis or death, cell counts can serve as an early warning indicator, enabling proactive advisories that prevent exposure before toxins are released into the water column.

Scientific and Practical Limitations of Relying Solely on Toxin Concentrations

The proposed shift to rely primarily or exclusively on cyanotoxin concentrations for issuing HAB alerts is problematic for several reasons:

1. Delayed Detection of Risk: Cyanotoxins are often released into the water only after cyanobacteria cells die or rupture, meaning that toxin-based monitoring may fail to identify a bloom in its early stages. Cell counts, by contrast, can detect rising cyanobacteria populations before significant toxin release occurs, allowing for earlier public notification and intervention. For instance, the VDH’s own monitoring of the North Fork of the Shenandoah River in 2021 demonstrated that cell counts and visual observations of benthic cyanobacteria mats prompted advisories, even when toxin levels in the water column were below advisory thresholds. This proactive approach likely prevented human and animal exposure to potentially harmful conditions.
2. Variability in Toxin Production: Not all cyanobacteria blooms produce toxins consistently, and toxin production can vary based on environmental factors such as temperature, nutrient levels, and light intensity. A bloom with high cell counts but low detectable toxins at the time of sampling may still pose a future risk if conditions change. The EPA notes that cyanobacteria like Microcystis and Dolichospermum can produce toxins under specific conditions, and cell counts provide a reliable proxy for assessing this potential. Excluding cell counts ignores this latent risk and may lead to premature lifting of advisories.
3. Limited Accessibility of Toxin Testing: Toxin analysis, such as testing for microcystins or cylindrospermopsins, requires specialized laboratory equipment and expertise, which can be costly and time-consuming. In contrast, cell counts can be performed more rapidly through microscopic enumeration, often in collaboration with institutions like the Old Dominion University Phytoplankton Laboratory, which supports Virginia’s HAB Task Force. The VDH’s own protocols highlight the efficiency of cell count-based assessments in guiding initial responses to suspected blooms. Removing this metric could strain resources and delay advisories, particularly in rural areas with limited access to advanced testing facilities.
4. Incomplete Risk Assessment: Toxin concentrations alone do not capture the full ecological and health risks of HABs. Dense cyanobacteria blooms, even if non-toxic, can deplete dissolved oxygen, cause fish kills, and disrupt aquatic ecosystems, as noted by the EPA. High cell counts can also indicate excessive nutrient pollution, signaling the need for broader environmental management actions. By focusing solely on toxins, the VDH risks overlooking these secondary impacts, which have significant implications for recreation, tourism, and local economies.

Public Health and Safety Implications

The VDH’s mission is to protect public health, and the current hybrid approach—using both cell counts and toxin concentrations—ensures a precautionary stance that prioritizes safety. The proposed elimination of cell counts could erode public trust in advisories, particularly in light of past HAB events in Virginia, such as those in Lake Anna.

Pets and livestock are particularly vulnerable to cyanotoxins, with documented cases of fatalities in dogs that ingested contaminated water or licked algae from their fur. The VDH’s advisories, informed by cell counts, have been critical in preventing such incidents by warning pet owners to avoid affected areas. Removing cell counts could delay or prevent these warnings, increasing the risk of exposure for vulnerable populations, including children, who are more susceptible to cyanotoxins due to their lower body weight.

Economic and Community Impacts

Virginia’s waterways, including Lake Anna, are vital for recreation, tourism, and local economies. HABs pose a financial burden to communities reliant on water-based activities, as noted by the Virginia Department of Environmental Quality (DEQ). Accurate and timely advisories, supported by cell count data, help mitigate these impacts by clearly defining affected areas, allowing safe recreation to continue where possible. For instance, in the 2021 Shenandoah River advisory, the VDH noted that activities like kayaking could continue in areas with low contact risk, a determination informed by cell count and mat observations. Eliminating cell counts could lead to broader, less specific advisories, unnecessarily restricting access to unaffected areas and harming local businesses.

Recommendation

To maintain a robust and protective HAB advisory system, I urge the VDH to Retain Cell Counts as a Core Metric. Continue using cyanobacteria cell counts alongside toxin concentrations to ensure early detection and comprehensive risk assessment. The proposal to eliminate cyanobacteria cell counts from HAB advisory determinations is a step backward in protecting Virginia’s residents, visitors, and ecosystems. Cell counts are a scientifically validated, proactive, and accessible metric that complements toxin testing and ensures timely advisories. Retaining this metric aligns with national and international standards, and supports public health. I strongly urge the VDH to reconsider this proposal and maintain the current hybrid approach to HAB management.