Public Beach Monitoring Program Bacteria and Microcystin

What is Monitored at the Beaches?

E. coli bacteria and harmful algae toxins, specifically microcystin, are monitored to give an indication of the quality of water at Nebraska swimming beaches.

E. coli bacteria are monitored to provide an “indirect” indication of potentially harmful (pathogenic) bacteria. While not all E. coli bacteria are considered a threat to human health, some bacteria strains are. The larger the population of E. coli bacteria measured, the greater are the odds of having harmful pathogenic bacteria. Using this rationale, the value of 235 colonies of E. coli bacteria per 100 ml of water is established as the upper limit for supporting full body contact recreation. Ingesting water with higher levels of E. coli bacteria may cause illness with most symptoms being exhibited within the intestinal tract. E. coli bacteria are primarily associated with animal and human waste. Animal sources of E. coli bacteria commonly enter our waters from livestock and wildlife wastes that runoff the landscape during significant rainfall events. Human sources of contamination can include improperly maintained septic systems and wastewater treatment facilities that discharge untreated wastewater.

Harmful algal toxins, including microcystin, are produced by certain types of Cyanobacteria, commonly referred to as blue-green algae or harmful algal blooms (HABs). Microcystin in the water can cause skin rashes, lesions, and blisters on people who have been swimming or wading. If algal toxins are swallowed they can cause headaches, nausea, muscle or stomach pain, diarrhea, or vomiting. Though rare, severe cases can include seizures, liver or respiratory failure, or even death. A microcystin level of 8 ppb is established as the criterion for full body contact recreational activities. While not all types of cyanobacteria are toxic, the greater the population of cyanobacteria, the greater is the chance of having a harmful algal bloom. In the absence of direct microcystin toxin measurements, one should recognize a severe harmful algal bloom and treat it with caution. Blue-green algae often have a “John Deere green” or “pea green soup” color, appear as thick green paint or oil floating on the surface of the water, and usually have a strong septic odor.

In situations where E. coli bacteria exceed counts of 235/100ml of water for a single sample, the water is considered at a higher risk for illness when used for full-body contact recreation. Lakes that exceed this level are specifically identified on the NDEE's website weekly, in the Environmental Alerts section. Unlike with dangerous levels of HABs, signs are not specifically posted and beaches are not closed for high bacteria levels. This is primarily because bacteria values change quickly while microcystin levels are more persistent and can remain for several weeks. This bacteria information, rather, is provided to allow the public to make their own decision on whether or not to use the lake. 

Guidance provided to assist the public in the decision making process includes:

• Assess the length of time from heavy rainfall to the time of use.
• Assess the condition of a lake and consider avoiding abnormally turbid waters.
• Consider chronic problems where bacteria levels are consistently high even in the absence of rainfall.
• Avoid activities which could result in a higher potential of swallowing lake water.
• When bacteria levels are high, shower after coming in contact with the water.
• Wash hands before eating if you have been in contact with lake water.

Lakes that repeatedly exceed the E. coli and microcystin water quality standard may be put on Nebraska’s Clean Water Act 303d list of impaired waters.

Why are there problems at some lakes and not others?

Biological communities such as algae are very complex systems and are affected by many variables. The HAB issue gets even more complicated as some species of blue-green algae sometimes produce toxins while at other times they do not. Research is being conducted worldwide to answer these questions. Additionally, NDEE is working with numerous collaborators to determine what factors are driving the growth of blue-green algae in Nebraska reservoirs and lakes. Certain conditions seem to consistently have significant effects.

The following conditions are often associated with harmful algae blooms:

• General weather of each year including the temperature, amount of sunlight and rainfall.
• Lake water levels. During drought years, problems seem to be more frequent.

The issue of HABs and its causes are quite complex, it is easier to understand by reducing the problem to simpler terms. In general, algae production is affected by temperature, sunlight and the nutrients of nitrogen and phosphorus. Higher temperature, sunlight, and excess nutrients result in greater blue-green algae production and therefore, a greater chance for HABs to become problematic. While temperature and sunlight are beyond our control, we can reduce the amount of nutrients reaching rivers, streams, and lakes. Any management practice that can be incorporated in a watershed that reduces these inputs into waters will reduce algae production and therefore the potential for HABs to occur.