Treatments to Prevent Algal Blooms in Lakes and Reservoirs

Introduction to Algal Blooms

Algae are aquatic, plant-like organisms. From single-celled phytoplankton floating in the water to massive seaweeds (macroalgae) affixed to the ocean floor, they include a wide range of basic forms. Algae can be found living in rivers, lakes, ponds, seas, and even snow. They are an important part of any lake ecosystem. In any water body, the algae concentration can affect the entire ecological balance. Algal blooms in lakes and reservoirs are often caused by nutrient pollution and environmental changes, disrupting the natural balance and degrading water quality. Additionally, algae that grow rapidly and in excess end up suffocating other aquatic organisms. While not all algal blooms are harmful, certain types especially those involving blue-green algae (cyanobacteria) can pose serious risks to aquatic ecosystems, water quality, and public health. These harmful algal blooms (HABs) are becoming more common in freshwater systems and coastal waters worldwide, driven by excess nutrients, higher water temperatures, and changes in land use.

What Causes Algal Blooms?

Stagnant water, high temperatures, and excessive nutrients stimulate blue-green algae growth. Environmental changes, such as shifts in weather patterns or nutrient inputs, can increase the risk of harmful algal bloom formation. In summer, when the water warms up, algae can grow and spread really fast. Water reservoirs often lack circulation, therefore the water is stagnant. Abundant nutrients, especially nitrogen and phosphorus, help algae over-compete other water organisms, forming massive blooms. These conditions can lead to the proliferation of harmful algae, which may result in a harmful algal bloom.

Why Do We Need To Understand Algal Blooms?

Algae, including green algae, golden algae, and filamentous algae, are essential for aquatic life, forming the base of the food web and producing oxygen through photosynthesis. However, when nutrient-rich water often resulting from nutrient pollution such as nitrogen and phosphorus runoff fuels excessive algae growth, the balance is disrupted.  Harmful algal blooms in lakes and reservoirs can turn water bodies into green, soupy masses, deplete oxygen, and release dangerous algal toxins that threaten fish, other aquatic organisms, and even human health. Understanding the causes and consequences of algae blooms is crucial for protecting our lakes, reservoirs, and drinking water supplies. The water turns green, tastes moldy, smells bad, and can be dangerous for consumption. Eventually, this triggers freshwater deficiency, massive death of fish and other aquatic life. Severe algal blooms can create dead zones, where low oxygen levels make it impossible for aquatic life to survive. Restoring the balance of an ecosystem requires monitoring and control of algal growth.

Types of Algae

• Planktonic, single-celled, microscopic algae. They can float in water freely or form colonies. They can turn water green, yellow, brown or red;
• Filamentous algae, single-celled algae forming long hair like mats;
• Macrophytes, resemble real plants, appearing to have stems and leaves. Algal blooms can block sunlight and reduce oxygen, leading to the decline of underwater plants that are vital for aquatic ecosystems.

Preventing nutrient contamination in water doesn’t completely solve the issue. Growth, decay, gravity, and eutrophication will continue the internal phosphorus cycle in reservoirs, lakes, and other bodies of water. Plus, human activities such as agriculture accelerate eutrophication. This, in turn, further releases nutrients stored in the sediment. Concerningly, this can lead to irreversible, long-term damage in the ecosystem. Freshwater blooms can have significant economic and environmental impacts, including loss of tourism and property value. A long term solution to algal blooms in lakes and reservoirs involves reducing nutrient inputs and restoring ecological balance through sustainable technology without harming aquatic life.

Planktonic (microscopic algae) and filamentous under the microscope

How to Prevent Algal Blooms?

To prevent algal blooms and serious environmental, health, and health impacts, you must predict and control the proliferation of algae. Sustainable algae management practices aim to reduce the inflow of nutrients in water bodies. Long-term success requires changes in policies and human activities. Therefore, it can take several years to significantly improve water quality. Freshwater HABs, particularly those caused by cyanobacteria, are a major concern in lakes and reservoirs. Real-time water quality monitoring helps prevent algae problems. Monitoring key parameters; chlorophyll-a, phycocyanin, temperature, DO, pH, and turbidity allows you to see trends and forecast harmful blooms. This monitoring is especially important for detecting cyanobacteria blooms, which can produce dangerous toxins.

Dangers of Algal Blooms

Excessive cyanobacteria and green algae in water bodies can deteriorate water quality. Blue green algae bloom events can make water unsafe for recreation and pose serious health risks. These organisms can release potent toxins that often lead to massive fish and animal die-offs. They can also impact humans, causing illness, paralysis, liver cancer, or even death. Anyone exposed to contaminated water should rinse off with fresh water as soon as possible. Contaminated water can endanger the entire water supply, as these toxins and metabolites dissolve in water, escaping the conventional treatment. Harmful algae, especially cyanobacteria blooms, are responsible for producing these dangerous substances.

Different Solutions for Algal Blooms

Controlling the spread of cyanobacteria has become a pressing global challenge, especially for lakes/reservoirs and larger ponds. Effective management of freshwater blooms is essential to protect water quality and ecosystem health. Common methods to prevent algal blooms include aeration, chemical/biological additives, or ultrasonic technology. Although there are plenty of treatment solutions on the market, they all have their cons. For example, algaecides offer quick results but damage the entire water ecosystem. Improper chemical control can also contribute to the formation of dead zones in lakes and reservoirs. Other methods, such as aeration, are quite expensive. To address these challenges, it is important to implement a long term solution focused on nutrient reduction, particularly phosphorus and nitrogen, to sustainably minimize the frequency and intensity of harmful algae blooms.

Ultrasonic Algae Control

Ultrasound refers to sound waves with frequencies above 22 kHz. At specific frequencies, ultrasound can control algae growth. Cyanobacteria use gas vesicles for buoyancy and depth regulation. During the day, algae can be found in the top layer, where they perform photosynthesis. The carbon dioxide and dissolved nutrients help them produce oxygen and polysaccharides. At night, cyanobacterial cells empty their vacuoles and sink to the bottom where they use oxygen and nutrients to produce biomass. Ultrasonic technologies create a sound layer in the upper water layer, affecting algae’s buoyancy. Algae cells drown all the way to the bottom where they are deprived of sunlight. Without light, they eventually die off and decompose with the help of bacteria. However, to guarantee that the ultrasonic treatment will be effective, it’s critical to use specific ultrasonic programs. This is selected based on the current algae species and water characteristics. It’s also important to keep adjusting the frequencies of the ultrasound. The reason for this is that algae can adapt to various treatments and weather conditions, so adjusting the frequencies can lead to effective algae treatment.

Advantages: Controlling algae with ultrasound is a well-known method that’s been used for decades. It’s a proven effective solution for green and blue-green algae species. Also, what make it truly great is that it’s environmentally friendly; it’s safe for the aquatic life and for the ecosystem. Plus, ultrasound can be used for small, as well as medium and large water bodies. This method is also safe for underwater plants, preserving essential habitat for aquatic life. Combined with real-time water quality monitoring, this method allows for accurate prediction and prevention of harmful blooms.

Disadvantages: Must cover the entire surface of the lake. Each spatial spot must be treated to achieve full efficiency.

Chemical control

Water treatment often involves using chemical additives to control nutrient levels and suppress algal growth. Compounds like alum (aluminum sulfate) and lanthanum-based products are used to precipitate or sequester ionized orthophosphates, reducing phosphorus availability, a key nutrient driving algal blooms. To directly target algae, aquatic herbicides known as algaecides are applied. These typically include copper-based compounds, such as copper sulfate or chelated copper formulations, as well as organic algaecides.

Advantages: Effective if the entire surface is treated.

Disadvantages: Algaecides are expensive and need frequent dosing. They must be used with care, and even then they can cause algal cell rupture. This triggers the release of toxins into the water. Chemical treatments can sometimes promote the proliferation of harmful algae, increasing the risk of harmful algal blooms. Rapid decay of a harmful algal bloom can release large amounts of toxins, contaminating the water with algal toxins. This is dangerous for fish and plants. Algaecides can have significant long-term negative effects on a lake’s ecological balance. They aren’t suitable for large water surfaces.

Aeration

It’s crucial to maintain healthy levels of dissolved oxygen in waterbodies. Oxygen helps break down decaying vegetation and other nutrients in water. Microorganisms help break down the silt at the bottom. Aerobic and anaerobic bacteria both contribute to decomposition. Aerobic decomposition requires continuous oxygen supply. It intensifies when dissolved oxygen concentrations approach saturation levels. The primary result of aerobic bacteria decomposition is carbon dioxide. Anaerobic decomposition is slower. The end products are organic compounds like alcohols and foul-smelling organic acids.

Advantages: Aeration is an environmentally-friendly technique that rejuvenates water bodies. It increases the oxygen level in water. Aeration systems can help avoid chemicals and create a healthy ecosystem. It is particularly beneficial for maintaining fresh water quality waterbodies, helping to prevent harmful algal blooms in lakes and reservoirs, protecting overall aquatic health.

Disadvantages: Aeration systems offer a proactive way to enhance water quality, although expensive with routine maintenance that helps to maximize their long-term effectiveness. While not designed to directly eliminate algae, aeration plays a key role in restoring ecological balance by improving oxygen levels and reducing excess nutrients, making it an excellent partner to other sustainable treatment solutions.

Mixing

Mixing circulates water to achieve destratification in reservoirs. The process involves mixing water to eliminate stratified layers. The Epilimnion and metalimnion layers are usually circulated to control the algae. The aim is to clear the surface water from iron, manganese, and anoxic odors that usually occur in the hypolimnion. This created less favorable conditions for algal growth in certain layers.

Advantages: Artificial circulation causes less environmental damage chemicals. It’s generally more effective in deep reservoirs (mean depth >15 m).

Disadvantages: Circulating water requires high system maintenance due to wear and tear. Such systems have fluctuating results on blooms. The effect on total cyanobacteria levels is controversial. Mixing may have variable effects on freshwater HABs, particularly those caused by cyanobacteria blooms, which can produce toxins and pose risks to humans, animals, and aquatic ecosystems. In lakes, mixing often affects only surface layers close to destratifiers. In large systems, mixing sediments can actually increase the available nutrients. This triggers further algae growth in the short-term.

Reporting and Response

Timely reporting and effective response are critical in managing harmful algal blooms and minimizing their impact on aquatic life, water quality, and public health. If you notice signs of an algae bloom, such as water that looks like pea soup, has a blue-green tint, emits a strong odor, or is accompanied by dead fish or other wildlife, it’s important to act quickly. Avoid contact with the water, keep pets and livestock away, and do not use the water for drinking, fishing, or recreation until it has been deemed safe. Report suspected harmful blooms to your local environmental or public health authorities, who can initiate water testing to determine toxin levels and identify the type of algae present. Authorities may issue public advisories, close affected water bodies, and provide guidance on safe water use. Early detection and rapid response help prevent harmful blooms from spreading, protect aquatic animals and other wildlife, and safeguard water supplies for communities. Public awareness and cooperation are essential in preventing exposure to contaminated water and supporting efforts to manage and prevent harmful algal blooms.

Local Government Role

Local governments play a vital role in monitoring, managing, and preventing harmful algal blooms in lakes and reservoirs. They are responsible for regular water quality assessments, using advanced monitoring systems to detect changes in algae growth, nutrient levels, and water temperature. By enforcing regulations that limit nutrient pollution from sources like agricultural runoff, pet waste, and wastewater discharge, local authorities help reduce the risk of nutrient-rich water fueling harmful blooms. In addition to regulatory measures, local governments often collaborate with environmental agencies, researchers, and community groups to implement long-term solutions. These may include restoring native plants and underwater vegetation, promoting sustainable land use practices, and investing in aeration systems or other technologies to improve water circulation and oxygen levels. Public education campaigns raise awareness about the dangers of harmful blooms and encourage responsible behaviors, such as proper disposal of fertilizers and pet waste. By taking a proactive approach, local governments help protect natural resources, maintain property values, and support the health of aquatic ecosystems and local economies.

Conclusion

Algal blooms in lakes and reservoirs are a growing threat around the world, impacting aquatic life, water quality, and human health. While algae are a natural part of aquatic ecosystems, excess nutrients, stagnant water, and higher temperatures can trigger dangerous blooms that produce toxins and disrupt vital ecosystems. Preventing harmful algal blooms requires a combination of real-time monitoring, responsible nutrient management, and innovative treatment solutions.

Everyone has a role to play from individuals reducing nutrient runoff to local governments enforcing regulations and investing in long-term solutions. By working together to monitor water bodies, report suspected blooms, and support sustainable practices, we can protect our lakes, reservoirs, and drinking water supplies for future generations. Ongoing vigilance and collaboration are essential to prevent harmful algal blooms and preserve the health of our aquatic environments.