By Julianne Murphy, intern, Environmental Health

Warm weather brings nature walks, picnics and sunny days by the shore, but it can also bring unwanted changes to your favorite beach. As the temperature rises, lake and ocean waters can turn from blue to mossy green as algae proliferates in unsightly and potentially harmful algal blooms.

What are harmful algal blooms?

Algae are plant-like organisms of one or more cells that use sunlight to make food. Together they can form colonies called algal blooms in both marine and freshwater systems. Some of these algal blooms are hazardous to health, but not all algal blooms are harmful.

Harmful algal blooms may release toxins at concentrations unsafe to humans and animals and may drastically reduce oxygen available to aquatic life. In fresh water bodies, cyanobacteria, aka “blue-green algae,” can produce dangerous cyanotoxins; in saltwater or brackish water, acid-generating plankton – dinoflagellates and diatoms – can pose a health threat.

Should I be concerned about algal blooms?

Algal blooms can pose a risk for human and animal health. People and animals can become ill through eating, drinking, breathing or having direct skin contact with harmful algal blooms and their toxins. Illnesses vary based on the exposure, toxins and toxin levels. Public health and environmental laboratories test samples from harmful algal blooms to confirm the presence and level of toxicity. Remember, not all algal blooms are harmful.

How are public health officials responding to the increase in algal bloom events?

As climate change events amplify conditions favorable to algal blooms, public health scientists are studying when and where associated illnesses are occurring and how to mitigate the effects of exposure. Their efforts have led to increased laboratory testing and electronic surveillance measures at the state and federal level.

For example, public health and environmental officials in Alaska have been tracking and testing harmful algal blooms. The Alaska Harmful Algal Bloom Network, a collaboration of the Alaska Department of Health and Social Services (DHSS) and regional monitoring programs, analyzes fish kills, unusual animal behaviors and other related phenomenon to provide early warning of developing coastal marine blooms. DHSS scientists analyze human specimens for illnesses associated with harmful algal blooms, such as paralytic shellfish poisoning (PSP) caused by saxitoxins. PSP is a potentially fatal poisoning with no treatment except supportive care. Samples from symptomatic patients are forwarded to the Centers for Disease Control and Prevention (CDC) for confirmatory testing as needed. Testing of asymptomatic individuals may be included in future studies.

In addition, Alaska Department of Environmental Conservation (DEC) laboratories test marine shellfish meat samples protect public health and safety as well as for regulatory purposes, illness investigations and non-commercial shellfish upon request. This monitoring literally saves lives.

David Verbrugge, chief chemist at the DHSS Division of Public Health, explains the value of Alaska’s testing of harmful algal blooms, “[Laboratory analysis] helps us to understand the nature of PSP exposures: frequency of occurrence, confirmation when lacking meals to test, and the presence or absence of toxins in asymptomatic co-exposed groups. It also allows us to let people know what they are eating before they eat it.”

Is the CDC involved in testing and surveillance for harmful algal blooms?

Yes, only for freshwater. In 2016, CDC created the One Health Harmful Algal Bloom System to provide a voluntary, electronic reporting system for states, federal agencies and their partners. Using the system, which integrates human, animal and environmental health data using a One Health approach, public health departments and their environmental and animal health partners can report bloom events, and human and animal cases of associated illness. Members of the public may report a bloom event or a case of human or animal illness to the One Health system by contacting their local or state health department.

What is the outlook for future testing and surveillance of harmful algal blooms?

As climatic conditions become more favorable to development of harmful algal blooms, state and local health departments will have to ramp up surveillance and testing to protect public health and to preserve local revenue from beaches. These actions will come with a price tag, requiring action at all levels of government. Resources can be leveraged through collaboration to research and expand clinical testing capacity for these persistent health threats.

Learn More:

• Rhode Island State Health Laboratory responds to toxic algae bloom, safeguarding health and the local economy [Blog post]
• APHL: A Freshwater Algal Toxin Guidance Document for Public Health Laboratories
• Water Research Foundation: Refinement and Standardization of Cyanotoxin Analytical Techniques for Drinking Water Funds. Eligible applicants include educational institutions, research organizations, federal, state or local government agencies, and for-profit entities, including consultants.

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