Introduction
A bloom doesn’t always arrive with a neat, predictable timeline. One week the water looks normal, the next you get green streaks along the downwind shore, then the surface turns into a patchwork. If that shift continues on to become large scale algal blooms, it’s no longer just a cosmetic issue, it’s an operational issue that requires careful management. For operators, large scale algal blooms demand a different level of monitoring, planning, and response than small, short-lived events.
In its overview of harmful algal blooms, NOAA explains that blooms occur when algae grow rapidly and accumulate. In lakes and reservoirs, the same drivers repeat: warmth, calm days, and nutrients arriving faster than the basin can absorb them. Below, we map the drivers to what you can measure, and what you can do.
Why stagnant waters turn to green
Stagnation changes the rules. With weak mixing, buoyant organisms can sit near the surface where sunlight is strongest. That top layer warms and stays stable. Add a nutrient pulse from runoff and you have a clean algae bloom example that can spread quickly and escalate into large scale algal blooms under stable conditions.
The EPA links rapid bloom growth to nutrient pollution, especially nitrogen and phosphorus. In reservoirs, layering can make the surface behave like a separate “mini lake”. Prevention upstream, before nutrients enter the basin, often gives the best return.
How does algae act as a pollution indicator?
Algae react fast, and that speed is useful. Pigments can rise after a storm, or during a calm heat spell; either way, algae acts as a pollution indicator. It tells you where pressure is building, and when a lake is staying stable long enough for buoyant organisms to keep winning the light game.
A practical monitoring set is simple: chlorophyll and phycocyanin for growth signals, temperature for stratification risk, dissolved oxygen for stress. Add wind data and you can often predict where biomass will collect next.
USGS notes that harmful blooms can affect people, pets, livestock, and wildlife; their HAB science updates highlight why detection and monitoring matter.
Effects of large scale algal blooms in reservoirs and lakes
Algal bloom effects are not limited to surface color. Dense growth shades submerged vegetation, shifts food webs, and increases organic material. When that material breaks down, microbes consume oxygen; overnight dips can stress fish and invertebrates in sheltered coves.
What is the role of oxygen in water quality?
EPA explains the chain reaction: nutrient-driven blooms consume oxygen and can make survival impossible for aquatic life. Oxygen is also a planning metric: if oxygen keeps dropping at night while pigments rise, expect wider impacts.
For public guidance, the CDC advises avoiding discolored or scummy water and following local advisories. If it looks suspicious, keep people and pets out, and investigate.
Effects of algal blooms on drinking water
Many reservoirs supply raw water. During blooms, operators often see higher organic load and more taste and odor pressure, even before toxins are confirmed. That is why lake decisions, especially in summer, can ripple downstream.
How long does algae bloom last?
How long does algae bloom last depends on what the weather does next. Wind and cooler temperatures can disperse a bloom in days. Calm and heat can keep it active for weeks, particularly when the surface layer stays stable.
Treat duration as measurable. Link pigments, temperature, and oxygen to local bloom history. If pigments climb and night oxygen dips deepen, you are not looking at a short event anymore.
Easy installation and lower costs with ultrasound technology
A lake plan fails when it is too complex to run. Installation should be straightforward; operations should be repeatable; results should show up in data. Ultrasonic algae control supports that workflow because it is deployed in the basin and paired with continuous monitoring.
LG Sonic’s technology overview explains how monitoring and targeted frequencies work together to interrupt buoyancy regulation. Practically, teams can watch pigment trends, respond earlier, and keep programs aligned with what the lake is doing this week.
How do you stop algae from growing in a lake?
Stopping growth requires two timelines. First, Prevention reduces how often blooms ignite: limit nutrient inputs, slow runoff, and manage inflows so nutrients do not arrive in sudden pulses. Second, in-lake actions reduce severity when conditions still align.
A remedy to remove algae at reservoir scale starts with continuous measurement. Sensors track pigments, temperature, pH, and oxygen, so teams can respond when risk rises. LG Sonic combines monitoring with ultrasonic algae control: sound waves interfere with buoyancy regulation, helping keep algae from concentrating at the surface.
Used consistently, the remedy to remove algae becomes part of routine lake management and supports Prevention by shortening bloom windows and making trends visible.
Large Scale Algae Reduction: Cases
Johnstown, Colorado
In Johnstown’s case study, summer conditions would tip Town Lake toward cyanobacteria, and the knock-on effect was taste-and-odor pressure that operators then had to chase. So the town made a practical move in 2022: put two MPC-Buoy systems on Town Lake and stop relying on occasional snapshots. Continuous monitoring became the baseline, so shifts in the lake could be seen as they happened, not after the fact.
Findings and results: The case study reports a late-season shift in the numbers that matter for customer perception: geosmin and MIB dropped significantly toward the end of the 2025 season, and staff also noted less floating algae during that period. John Ferguson, the water superintendent, captured it in plain language: “I feel like we are finally seeing a positive change in Town lake this year, based off of Geosmin/MIB results throughout 2025.” It reads like what it is, a field confirmation that the trend finally moved in the right direction.
Windsor Lake, Colorado
Windsor Lake in Windsor, Colorado, is public-facing water, meaning the bloom story is never just “ecology”, it becomes access, closures, and community frustration. The town responded in 2023 with a lake-wide setup: four MPC-Buoys distributed across the basin, each feeding continuous data from chlorophyll, phycocyanin, dissolved oxygen, pH, and temperature. In other words: not one sensor, not one location, but a fuller picture of what the lake was doing, day to day.
Findings and results: The case study reports a sharp change in bloom intensity indicators: chlorophyll-a moved from about 60–70 µg/L down to below 10 µg/L within weeks, which aligns with clearer water and improved transparency. Then comes the outcome residents actually care about: in 2025 the lake stayed open all year with zero algae-related closures, reported as a first for Windsor Lake. Data and lived experience matching up, that is the point; numbers on a chart, and a shoreline that stays open.
FAQ for teams and stakeholders
Algae bloom example: A shoreline slick after a warm, calm week is a common algae bloom example, and it usually means risk is rising.
How long does algae bloom last: How long does algae bloom last varies by basin; track pigments, weather, and mixing to estimate it locally.
Algal bloom effects: Algal bloom effects include clarity loss and oxygen stress; early monitoring reduces the worst impacts.
Toxic algae blooms: Toxic algae blooms require clear advisories and early action, especially where pets and swimmers frequent shorelines.
Prevention and a remedy to remove algae: Prevention reduces frequency, and a remedy to remove algae reduces severity when conditions still align.
Conclusion
Large scale blooms are driven by familiar factors: nutrients, heat, and calm conditions. Pair Prevention upstream with monitoring in the basin, then apply a remedy to remove algae where it fits the site. Over time, that combination limits algal bloom effects and lowers the chance that toxic algae blooms dominate the season.