When do algae blooms occur

If you or your pet go into water where there may be a bloom, wash off with fresh water immediately afterwards. We can't eliminate blue-green algae from a lake -- they are an inherent part of the overall algal community.

What we really want to do is control their overall intensity and the frequency of the blooms. Since we can't control the water temperature, the best thing we can do is to reduce the amount of nutrients getting into the lake. This can best be accomplished by reducing the amount of phosphorus and nitrogen from man-made sources such as lawn fertilizer, and runoff from cities, cultivated fields, feedlots, and a myriad of other sources.

Though a reduction of nuisance algal blooms will not be immediate, it is the best long-term solution to minimizing the frequency and intensity of algal blooms. Counties, cities, and other local government entities may consider closing swimming beaches or posting advisories when harmful algae blooms are known or suspected in local bodies of water.

The MPCA has developed guidance and recommendations for local officials dealing with public health issues related to blue-green algae.

Learn more on the Harmful algae blooms: Water recreation advisories page. Skip to main content. Water How's the water? The state of water The state of lakes Blue-green algae and harmful algal blooms Summertime in Minnesota: When in doubt, best keep out!

What are blue-green algae? What do blue-green algal blooms look like? A couple of easy tests can tell you if the green stuff you're seeing in your body of water is likely to be blue-green algae: Simple, no-cost tests for blue-green algae wq-swm What are harmful algal blooms?

When do harmful algal blooms occur? Where are harmful algal blooms found? What are the possible health effects? Levels of risk The activities that put you in contact with the water — and the amount of time you spend on them — will affect your exposure to algae toxins. Activities Level of exposure to algae toxins Drinking incidental or intentional Highest Swimming, diving, water skiing, windsurfing, tubing, paddle boarding High Canoeing, kayaking, sailing, personal watercraft Moderate Fishing, boating, fish consumption Low How can I reduce my risks from harmful algae blooms?

During water recreation Avoid or minimize recreating in waters that appear to have a blue-green algae bloom; if you do come in contact with algae-laden water, wash with fresh water afterwards.

Blue-green algae in sources of drinking water Avoid using untreated lake or river water for drinking, cooking, and brushing teeth, especially for infants and small children. Eating fish from algae-laden waters Toxins from algae can accumulate in the entrails guts of fish and occasionally in the muscle fillet of fish. Can animals be affected? This can cause marine algae to invade freshwater ecosystems. In the southwestern and south central United States, toxic marine algae have been killing fish in freshwater lakes since Algae need carbon dioxide to survive.

Higher levels of carbon dioxide in the air and water can lead to rapid growth of algae, especially toxic blue-green algae that can float to the surface of the water. Climate change might affect rainfall patterns, leading to alternating periods of drought and intense storms.

This can cause more nutrient runoff into waterbodies, feeding more algal blooms. Scientists predict that sea level could rise up to one meter by the year This would create more shallow and stable coastal water, conditions that are perfect for the growth of algae. Coastal upwelling is the process by which winds push surface water offshore and deep water moves towards the coast, bringing nutrients from the ocean floor to the surface.

HABs occur both naturally in the environment and as a result of human activities, but the latter are vastly increasing the frequency, prevalence, and toxicity of HABs. The following are some of the main freshwater algal bloom causes:. Nutrients like nitrogen and phosphorus, essential to plant growth, are a natural part of underwater ecosystems.

But when they run off urban and rural surfaces and flow into a river, lake, pond, or reservoir in excess—a phenomenon known as nutrient pollution —they act like fertilizer and promote the growth of algae and bacteria. Most excess nutrients enter waterways via agricultural runoff particularly from animal manure and chemical fertilizers that get washed from farms by rain , leaked waste from animal feedlots , stormwater runoff from urban and suburban areas, and discharges from wastewater treatment facilities.

According to the U. Warm water gives cyanobacteria a competitive advantage. These bacteria grow faster than more benign algae in higher temperatures , and once a bloom forms, a feedback loop can be triggered: As blooms grow thicker, the dark surfaces of the algae mats absorb more sunlight , which leads to warmer water and more algal growth.

Slow-moving or stagnant water can also become thermally stratified, meaning that a layer of warm water, which favors algal blooms, floats on top of cooler water. Factors that contribute to decreased water flow, or ponding, include drought, water extraction for irrigation or drinking, and the alteration of natural waterways via dams, canals, and other man-made infrastructure.

Climate change is both increasing the frequency and duration of droughts in many parts of the country and intensifying extreme storms. Periods of drought interspersed with strong precipitation increase runoff from agricultural lands, lawns, and other sources, leading to higher nitrogen levels in rivers—and therefore harmful algal blooms.

Burning fossil fuels, deforestation, and land development are increasing the amount of carbon dioxide in the atmosphere. This fuels harmful algal blooms because cyanobacteria can feed on the carbon dioxide not only present at the surface of a water body but also dissolved in the water.

And when algae die and sink to the bottom of a freshwater body, they decompose and release carbon that was once sequestered, providing more fuel for cyanobacteria growth. Climate change and more severe droughts also modify the flow regime in freshwater bodies and can increase competition for ever-scarcer freshwater supplies. Reduced flows in waterways means the remaining water will be warmer and more stagnant, creating conditions ripe for algal blooms.

People can be exposed to HAB toxins by swallowing or swimming in affected waters, eating poisoned fish or shellfish even when food is cooked, algal toxins remain , or inhaling airborne droplets of affected water. Depending on the level of exposure and the type of algal toxin, health consequences may range from mild to severe to, in extreme cases, fatal. A recent paper published in the journal Toxins found 63 dog deaths associated with HABs in 13 states.

There are three classes of cyanotoxins , and each type has different effects:. The cyanotoxins most frequently reported in freshwater ecosystems are the liver-damaging toxins microcystins and cylindrospermopsin. It is estimated that some 30 million to 48 million Americans get their drinking water from lakes and reservoirs that could be periodically contaminated by algal toxins.

Inadequate treatment can compromise water quality and threaten public health, and disrupt or even shut down treatment plants. When cyanotoxin levels exceed EPA health advisory levels for tap water, people are at risk of various adverse health effects, from gastrointestinal issues to liver and kidney damage.

HABs cause lakes, reservoirs, and rivers to become unsightly and at times dangerous, reducing tourism, recreation, commercial fishing, and property values and increasing water quality monitoring, management, and treatment costs. Even single bloom events can be crushing for local economies. The toxins released from a HAB can cause large-scale fish kills commonly seen as a result of golden algal blooms and work their way up the food web , impacting mammals, birds, and other wildlife that feed on grasses, shellfish, or fish tainted with toxins.

Texas recently experienced a major fish kill that devastated Lake Texoma, a reservoir on the Oklahoma-Texas border. Approximately , fish died in just three days due to a golden algae bloom. This was not the first time the lake was hit with this type of bloom. Also known as hypoxic zones, dead zones are typically a result of eutrophication, which is what happens when a waterway becomes overly polluted with nutrients.

When algae and bacteria in an algal bloom die, the decomposition process uses up most of the surrounding oxygen, causing other organisms in an affected water body to suffocate and die or be forced to relocate to survive. According to the EPA, more than 16 6 dead zo nes have been reported nationwide.