How to Get Rid of Blue-Green Algae in Lakes?
Eliminating blue-green algae, also known as cyanobacteria, from lakes requires a multifaceted approach that addresses the root causes of their proliferation, focusing on nutrient reduction and improved water quality. Effective solutions include managing nutrient runoff from surrounding land, using algaecides responsibly, implementing bio-manipulation strategies, and in some cases, physically removing the algae.
Understanding the Problem: Blue-Green Algae Blooms
Blue-green algae blooms, scientifically known as cyanobacteria blooms, are a significant environmental and public health concern impacting lakes globally. These blooms are not technically algae, but rather photosynthetic bacteria. They can rapidly multiply in nutrient-rich waters, often creating unsightly surface scums, discoloring the water, and producing toxins harmful to humans, animals, and aquatic ecosystems. The proliferation of cyanobacteria is often indicative of a broader imbalance within the lake’s ecosystem.
Why are Blue-Green Algae Blooms a Problem?
- Toxicity: Some species of cyanobacteria produce toxins known as cyanotoxins, such as microcystins, anatoxins, and cylindrospermopsins. These toxins can cause skin irritation, gastrointestinal distress, liver damage, and neurological problems in humans and animals upon exposure through drinking water, recreational activities, or even inhalation.
- Oxygen Depletion: When large blooms die and decompose, the process consumes significant amounts of oxygen from the water, leading to hypoxia or anoxia. This lack of oxygen can kill fish and other aquatic organisms, disrupting the lake’s food web and overall health.
- Aesthetic Degradation: Blooms can make lakes unattractive for recreation, impacting tourism and property values. The foul odors and unsightly scums associated with these blooms can significantly detract from the enjoyment of the water body.
- Ecological Imbalance: Excessive algae growth can shade out other aquatic plants, further reducing biodiversity and altering the lake’s ecosystem.
Strategies for Blue-Green Algae Control
Effectively controlling blue-green algae requires a combination of preventive and remedial measures. The specific approach will depend on the unique characteristics of the lake, the severity of the bloom, and the available resources.
1. Nutrient Management: Addressing the Root Cause
The primary driver of blue-green algae blooms is often excessive nutrient loading, particularly phosphorus and nitrogen. Reducing nutrient inputs is crucial for long-term control.
- Watershed Management: Implement best management practices (BMPs) in the surrounding watershed to reduce nutrient runoff from agricultural lands, urban areas, and septic systems. This includes practices like cover cropping, reduced fertilizer use, stormwater management, and proper septic system maintenance.
- Point Source Control: Regulate and treat wastewater discharges from industrial and municipal sources to minimize nutrient releases into the lake.
- Internal Nutrient Loading Reduction: Address internal nutrient loading by reducing sediment release. Techniques like phosphorus inactivation using alum can bind phosphorus in the sediment, preventing its release into the water column. Dredging can also remove nutrient-rich sediments, but it’s an expensive and disruptive process.
2. Chemical Control: Algaecides
Algaecides, such as copper sulfate and hydrogen peroxide-based products, can be used to kill blue-green algae. However, algaecides should be used with caution and as a short-term solution due to potential impacts on non-target organisms and the risk of releasing toxins from the algae cells upon lysis (cell rupture).
- Targeted Application: Use algaecides selectively and in accordance with label instructions to minimize impacts on other aquatic life.
- Professional Application: Algaecide applications should be performed by trained professionals who understand the potential risks and benefits.
- Monitoring: Monitor water quality closely after algaecide applications to assess effectiveness and identify any adverse effects.
3. Biological Control: Biomanipulation
Biomanipulation involves manipulating the food web to favor organisms that graze on algae.
- Zooplankton Enhancement: Increase the population of zooplankton (small aquatic animals that feed on algae) by reducing the population of fish that prey on them. This can be achieved through selective fish removal or stocking piscivorous (fish-eating) fish.
- Aquatic Plant Restoration: Re-establishing native aquatic plants can compete with algae for nutrients and provide habitat for zooplankton.
4. Physical Removal: Harvesting and Aeration
- Algae Harvesting: Removing algae mechanically through harvesting can reduce the biomass and nutrient load in the lake. This is most effective for surface blooms and is often used in conjunction with other control methods.
- Aeration: Increasing oxygen levels in the water can inhibit the growth of some cyanobacteria species and promote the growth of beneficial bacteria that decompose organic matter. This is typically done through the use of aerators or diffusers. However, aeration can also have unintended consequences, such as destratification, which can release nutrients from the sediments.
Frequently Asked Questions (FAQs)
1. What exactly are blue-green algae and why are they called that?
Blue-green algae, properly known as cyanobacteria, are a type of bacteria that photosynthesize, meaning they use sunlight to create energy. They are called “blue-green” because many species have a bluish-green pigment, although they can also appear red, brown, or even purple. The “algae” part is a misnomer as they are bacteria, not eukaryotic algae.
2. How can I tell if my lake has blue-green algae?
Visually, blue-green algae blooms often appear as a pea-soup like scum on the surface of the water. They can also look like paint spills or mats of algae floating on the surface. Suspect blooms should be avoided and reported to local authorities for testing.
3. Are all blue-green algae blooms toxic?
No, not all blue-green algae blooms produce toxins. However, it is impossible to tell by sight whether a bloom is toxic or not. Therefore, it’s essential to avoid contact with any suspected bloom.
4. What are the health risks associated with exposure to cyanotoxins?
Exposure to cyanotoxins can cause a range of health problems, including skin irritation, nausea, vomiting, diarrhea, liver damage, and neurological effects. Children and pets are particularly vulnerable.
5. What can I do to protect myself and my family from blue-green algae blooms?
Avoid swimming, boating, or other recreational activities in areas with visible algae blooms. Keep pets away from the water. Do not drink untreated water from lakes with potential blooms. If you experience any symptoms after contact with a suspected bloom, seek medical attention.
6. How can I reduce nutrient runoff from my property?
Use fertilizers sparingly and avoid applying them before heavy rain. Maintain septic systems properly. Plant native vegetation along shorelines to filter runoff. Reduce impervious surfaces like concrete and asphalt.
7. Is there a natural way to get rid of blue-green algae?
Biomanipulation, specifically increasing the populations of zooplankton, can be considered a “natural” method, although it involves deliberate manipulation of the ecosystem. Restoring native aquatic plants also contributes to a healthier, more balanced lake ecosystem.
8. How effective are algaecides in controlling blue-green algae?
Algaecides can be effective in the short term, but they do not address the underlying causes of the bloom. They can also release toxins from the algae cells into the water, potentially increasing the risk of exposure.
9. What is phosphorus inactivation and how does it work?
Phosphorus inactivation involves adding a chemical, such as aluminum sulfate (alum), to the lake to bind with phosphorus in the sediment. This prevents the phosphorus from being released into the water column and fueling algae growth.
10. How long does it take to get rid of blue-green algae in a lake?
There’s no simple answer. It depends on the severity of the problem, the size of the lake, and the effectiveness of the control measures implemented. Significant improvements may take months or even years. Long-term management requires a sustained effort to reduce nutrient inputs.
11. Can dredging help to get rid of blue-green algae?
Dredging removes nutrient-rich sediments from the bottom of the lake, which can reduce internal nutrient loading. However, it’s an expensive and disruptive process and should be carefully considered in light of its potential impacts on the ecosystem. It can also release nutrients into the water column during the process.
12. What are the regulations regarding blue-green algae control?
Regulations vary depending on the location. Contact your local environmental agency or water management district for information on specific regulations regarding algaecide use, nutrient management, and other control measures. They can provide guidance and resources to help you manage blue-green algae in your lake.
By understanding the causes of blue-green algae blooms and implementing a comprehensive management strategy, we can work towards restoring the health and beauty of our lakes for future generations.