HABs (Harmful Algal Blooms)
The lakes and ponds of North Carolina are increasingly impacted by HABs – harmful algal blooms. These naturally occurring, microbiotic bacteria (commonly referred to as “blue-green algae”) turn our slow-moving waters into neon green pools that can be toxic to aquatic life, pets and, potentially, humans.
These HABs can not only impact people, pets and wildlife. They can also affect local economies, drinking water supplies, property values, fishing and recreational water activities.
So, why are our ponds and lakes turning green, and what can you do about it?
Why do HABs happen?
Algal blooms are due to excess nutrients from farm and urban runoff pouring into our lakes and rivers. Cyanobacteria can produce cyanotoxins, which are the most dangerous impact on our drinking water and endanger human health, fish and animals.
Algal growth is caused by numerous factors, including available nutrients, water-flow rates and water temperature.
Nutrient Loading - Increased nutrient loading from wastewater treatment plants, urban stormwater, residential fertilizer and agricultural runoff is fueling the growth of HABs. Nitrogen and phosphorus are prime nutrients contributing to algal growth, with phosphorus limiting nutrients in nearly all freshwater systems.
Warmer Waters - Warmer surface water temperatures enhance algal growth. We usually see the heaviest growth or blooms in mid to late summer. As climate change affects average temperatures, we expect to see both more intense and longer-lasting algal growth. In addition, increased periods of drought and stagnation will further exacerbate the problem in some water bodies. This trend has been seen in waters throughout the southeastern U.S. and the Great Lakes.
The combination of higher temperatures and climbing nutrient loads in many N.C. water bodies means that algal blooms will continue to increase.
How can you spot HABs?
HABs most often happen in stagnant or slow-moving water. They turn the water solid green or neon green. As a result, the water loses that clear, clean water look.
HABs sometimes grow on the bottom of the lake or pond and form a thick mat of green or blackish growth on the water's surface in very stagnant water. This mat will be disturbed and float down current if the water is moving.
Fish kills may result after a HAB due to the reduction in dissolved oxygen.
HABs may only last a few days, so testing them is difficult.
It's important to note that the water may still have toxins present even after the bloom is gone. Once it has been confirmed that the presence of cyanobacteria and cyanotoxins is gone, it’s safe to go into the water.
Normal Day (Clean Water - Left) and HABs Day (Green Water - Right) I Moss Lake, Kings Mountain, NC/Broad Riverkeeper
Where do HABs happen?
Heavy algal growth is often noted in farm ponds where runoff from surrounding pasture or feeding areas is allowed to drain directly into the pond. This results in a thick green mat that may entirely cover small ponds.
In larger water bodies where there may be more water flow, heavy algal growth may be dispersed and result in blooms without forming a visible mat on the surface. The water is solid green to neon green. HABs may occur in areas with fertilizer runoff from farms and yards and high nutrient (phosphorus and nitrogen) levels.
What to do if you see a HAB?
Stay away! Keep away from the water if it looks like a HAB. Coming in contact with the water, eating fish from that water source and letting your pets drink from the water can be very harmful.
Report! Report the HAB to the state system NC Division of Water Resources Citizen Report Form and your local riverkeeper.
Take Action! Become a Clean Water Warrior to get advocacy alerts and demand better regulations to prevent and manage HABs.
Why are HABs dangerous?
These blooms pose threats to people, pets, wildlife and our economy.
PEOPLE - HABs pose threats to humans when we come in contact with cyanotoxin-contaminated water or eat contaminated food. According to the EPA, human exposure to elevated levels of cyanotoxins can impact the kidneys, liver and neurological system. According to the Centers for Disease Control and Prevention, depending on the particular cyanotoxin, symptoms may range from skin, eyes, nose and throat irritation, to headaches and abdominal pains, to more serious neurological or respiratory system impacts.
Perhaps the most significant risk posed by HABs is community drinking water supplies. This would result in expensive treatment costs and potential negative health effects, and related health care costs.
PETS - Pets that have come into contact with toxic algae or ingested water contaminated with cyanotoxins may also experience adverse health impacts. Two dogs died near Wilmington, NC, in 2019. Several other pets have been killed across the county due to high concentrations of cyanotoxins in bodies of water caused by HABs. Exposure can cause health impacts that include too much salivation, general weakness, staggered walking and difficulty breathing. In some severe cases, animals exposed to toxic algae may die within hours or days of exposure.
WILDLIFE - Even without the production of toxins, HABs can potentially cause catastrophic impacts on an ecosystem. For example, HABs may keep sunlight from reaching deeper into the water. As a result, they may remove dissolved oxygen from the water as they decompose, leading to hypoxia or reduced dissolved oxygen levels, potentially harming fish and plant life.
TOURISM - HABs can also have significant negative impacts on local economies. Health and swim advisories resulting from HABs directly affect recreational uses and limit related economic activity. In addition, HABs may reduce property values if the problem is not addressed and becomes dangerous. Waterfront property on lakes and rivers is often a major source of local property tax revenues, which will decline with reductions in property values. In cases where HABs impact aquatic ecosystems, fisheries may suffer, limiting commercial and recreational fishing opportunities.
What can you do?
The issue of HABs is beyond the impact of individual actions. There are bigger causes in place that create the biggest impact. But every effort is needed to curb HABs.
Advocate for better agricultural runoff controls and regulations on large-scale, industrial animal operations.
Report any HABs you see to increase scientific data and frequency counts. Report the HAB to the state system and your local riverkeeper.
Join our Clean Water Warrior list to get advocacy alerts to get better regulations to prevent and manage HABs.
What can our government do?
The state of North Carolina does not have the proper testing requirements in place. We do not have an ambient water quality standard for cyanobacteria or related cyanotoxins.
The U.S. Environmental Protection Agency (EPA) has recommended:
Water quality criteria for two of the most common cyanotoxins, microcystins and cylindrospermopsin.² In addition to the concentration levels, these recommendations also take into consideration the duration and frequency of the blooms to assess threats to public health in recreational waters. But these recommendations are not enforceable in our state, absent adoption by N.C. Environmental Management Commission.
Health-advisory levels to protect drinking water supplies3, and the World Health Organization has set a preliminary guideline of 1ug/L microcystin-LR in drinking water,4 these recommendations are not enforceable absent state rulemaking.
Our state legislators have not created rules or enforcement of these two standards leaving our communities vulnerable to HABs.
Despite the absence of regulation, the N.C. Department of Environmental Quality (DEQ) tracks algal blooms. Click here to report a HAB.
Policy Recommendations
To address ongoing concerns about the proliferation of HABs in North Carolina's rivers and lakes, state and federal elected officials and agencies should pursue the following policies:
Sampling of cyanobacteria and cyanotoxins where indicated due to past occurrences, taking into account species of cyanobacteria, density, size, and toxicity levels.
Establish waterbody-specific chlorophyll-a standards as an indicator of excess nutrients and potential HAB occurrences in High Rock Lake.
N.C. Environmental Management Commission should adopt the 2019 EPA-recommended cyanotoxin ambient water-quality criteria for recreational use.
Establish statewide water-quality standards for nutrients (nitrogen and phosphorus) and develop management strategies tied to watershed-wide reductions in nonpoint and point source nutrient pollution.
Improve communications between state departments and local agencies in defining and responding to HABs and increase funding for NCDEQ (including regional offices), NC DHHS, and county health departments to monitor, sample, and assess HABs and cyanotoxins, and notify the public with swim advisories when needed.
Increase funding for implementing agricultural best management practices, stormwater management, and stream restoration.
More research and development on the fate and transport of cyanotoxins produced by HABs and their correlation with hypoxia and low dissolved oxygen.
Download these flyers and spread the word about HABs.
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Stay Out of the Green Water
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Stay Out of Green Water
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Green Water is Dangerous for Dogs!
