Mitigating and Managing Harmful Algae Blooms

Harmful algal blooms, or HABs, are a recurring and highly frustrating problem for source water managers and municipalities everywhere. Understanding this problem and reacting before the levels of certain algae become unmanageable is critical to the health of community drinking water supplies, lakes and ponds, and reservoirs. 

What are Harmful Algae Blooms? 

HABs can occur in fresh, marine (salt), and brackish (a mixture of fresh and salt) water bodies around the world. It refers to the excessive, rapid accumulation of algae in aquatic environments. Harmful algae or cyanobacteria can look like foam, scum, green mats, or a colorful paint-like film on the water surface. While not all algal blooms are harmful, certain types of algae, such as certain types of cyanobacteria (blue-green algae) and dinoflagellates commonly associated with “red tide”, produce toxins that can be detrimental to aquatic life, disrupt ecosystem food chains, and threaten animal and human health. 

Blooms often occur when conditions are favorable for algal growth. Extensive research has confirmed that climate controls many of the fundamental parameters regulating algal growth in surface waters, such as warm temperatures, abundant nutrients (such as nitrogen and phosphorus), and stagnant water. Agricultural runoff and the release of nutrients from sewage and industrial discharges to surface water bodies are common causes of the nutrient enrichment that triggers a bloom. The high levels of toxins produced by the rapid growth of certain algae lead to oxygen depletion and “dead zones” where aquatic life struggles to survive. During severe and persistent blooms, the shoreline may be littered with thousands of small fish washed ashore and, in severe conditions, including larger species of commercial fish, sharks, and sea turtles. 

The U.S. Centers for Disease Control and Prevention cautions that people who drink or swim in contaminated surface waters or consume certain seafood caught in contaminated waters may experience skin irritation, respiratory problems, gastrointestinal issues, or even more severe health effects. 

HABS have dire effects on local economies and property values. 

The economic consequences of HABs can be significant, as well. Red Tide and similar HAB alerts prompt the closure of fisheries, recreational areas, and summer camps. The loss of revenue and increased costs for water treatment facilities to contain and mitigate the dangers posed by the presence of toxins in drinking water can be significant, especially when unsafe conditions are prolonged. 

According to the National Centers for Coastal Ocean Science (NCCOS), the average economic impact of HABs in the U.S. is estimated at $10 to 100 million annually, and costs from a single major HAB event can reach tens of millions of dollars. The U.S. National Office for Harmful Algal Blooms claims a highly conservative nationwide estimate of the average annual socio-economic costs of HABs is $50 million. 

The economic consequences are notable along the U.S. Gulf Coast. Taxable sales data in Sarasota, Florida, data show monthly revenue losses by lodging and restaurants may be as much as 15% and 2%, respectively, during months when red tide was present. In nearby Pinellas County, Florida, persistent red tide blooms can decrease taxable sales receipts by 15% in the fishery and seafood sector. Surveys of the consumer reactions to information on health risks of commercial catches during an HAB suggest consumers’ unwillingness to purchase seafood rises by as much as 34% during a bloom. 

HABs are particularly costly for lakefront communities and property developers who include water features in their residential portfolios. In six Ohio counties between 2009 and 2015, the property values of lakefront homes located near HAB-infested lakes and ponds lost as much as 22% of their value. Property losses can exceed $50 million. Similar declines in property values are evident in Florida, where homes located within one mile of the coast typically sell for up to 30% less than similar homes sold in unaffected counties. 

How should property developers and municipalities prepare for HABs? 

It is crucial for municipalities and residential property developers to comprehend and prepare for the expenses and potential liabilities resulting from harmful algal blooms (HABs). Although a new study published in Nature Communications Earth and Environment, suggests there are no global trends that climate change is increasing the frequency of HABs throughout the world, increased nutrient loading from widespread local agricultural, commercial, and residential uses of fertilizers and weather-mediated loading to surface waters is worrisome. 

Today more than ever, HAB events are costly to mitigate. Property owners are dismayed when HAB events impair the enjoyment and value of their property. Tourism revenue from activity associated with accessible and pristine coastlines vanishes. Therefore, understanding the damages caused by periodic HAB events is essential and must be taken into account when making cost-benefit decisions regarding water treatment technologies and planning for large residential property developments. 

Early detection and public awareness can help mitigate the economic impacts. Stormwater nutrients are significantly increasing the lengths and severities of blooms, and if municipalities can better manage their stormwater and wastewater, that can help to lessen the nitrogen that is released into the ocean and feeds these blooms. 

There is also a large gap between scientific knowledge and public/community knowledge of HABs. Many residents and tourists alike do not fully understand HABs and their impacts. Knowing how to avoid red tide exposure, for example, would go a long way toward decreasing healthcare costs and visits to hospital urgent care facilities. Better communications by fishermen, grocers, and restaurants about the sources of their seafood can help mitigate revenue and sales losses when customers react to HAB alerts issued by state agencies and municipalities banning the sale and consumption of local seafood. 

How Montrose can partner with municipalities 

Economists, environmental scientists, and wastewater engineers at Montrose collaborate with municipalities, property developers, and a wide spectrum of industries to address the challenges posed by HABs. Our team includes experts in monitoring and testing drinking water intakes, stormwater runoff, and surface waters when red tide and other HAB concerns arise. Our economists are leading experts in the cost/benefit analysis of mitigation and treatment methods for mitigating the economic losses on local communities.  

By fostering collaboration, implementing innovative solutions, and prioritizing proactive measures, municipalities in Florida and elsewhere can take meaningful steps toward mitigating the impacts of HABs and protecting the natural resources that are integral to the vitality of their communities.