With blue-green algae expected to reach "bloom" densities on some Wisconsin lakes and ponds starting later this month, water quality officials are beginning another season in a multi-year study to better understand the algae and when it produces toxins that may pose a threat to people and pets.


They also are encouraging people planning to swim or boat on Wisconsin waters to take some common sense steps to recognize when lake conditions are not safe for swimming.


"Blue-green algae are a normal part of many aquatic ecosystems in Wisconsin that have been here for millions of years," says Bob Masnado, who leads the Department of Natural Resources water quality standards section. "Excessive nutrients have made the problem worse on some waters over the past few decades, and that requires all of us to use common sense when we choose to recreate in Wisconsin waters."


Blue-green algae, also known as cyanobacteria, are an ancient and ubiquitous group of photosynthesizing bacteria that make up a portion of the tiny floating microscopic plants that form the bottom of the aquatic food chain. They can produce a variety of toxins that can affect human and animal nervous systems, kidneys and skin. Last year, Lake Kegonsa and Crystal Lake in Dane County, and Tainter and Menomin Lakes in Dunn County were closed to swimming because of high levels of blue-green algae. Ponds near Lake Kegonsa also had high blue-green algae levels that were associated with dogs developing seizure symptoms.


Blue-green algae are typically present in low numbers in water bodies with low nutrients, but partly because they are not readily eaten by other aquatic creatures, they may increase to "bloom" densities in water bodies with high nutrient levels when water temperatures rise. Waters in the southern two-thirds of Wisconsin tend to have higher nutrient levels, both naturally and as a result of agricultural and urban runoff, Masnado says.


For the third year in a row, DNR staff are sampling lakes statewide to screen for blue-green algae and other algae that may pose a health threat, and to better learn whether there is a correlation between the density of blue-green cells and the presence of toxins, says Elisabeth Harrahy, a DNR water quality specialist coordinating the study.


"Not all blue-green algae produce toxins and even those that can, don't produce them all the time," she says.


Under the study, DNR water quality specialists will sample a total of up to five lakes in each geographic region of the state periodically throughout the summer. Some additional sampling will be done in southern Wisconsin on ponds -- natural and man-made -- that are accessible to the public, according to Dick Lathrop, a DNR researcher involved in the study.


The state Laboratory of Hygiene will be screening the water samples for blooms of different species of blue-green algae. A subset will be selected for more detailed analyses to quantify the volume and the presence of toxins, Lathrop says.


Information from the study will help agency scientists understand what species of blue-green algae produce toxins, where these toxin producing blue-green algae are most likely found, and when during the summer the algae tend to dominate and produce toxins, Lathrop says. Study results will be shared with public health agencies.


DNR tests conducted last summer on a number of waters in southern Wisconsin showed that densities of the blue-green algae were very high in some waters. In addition, blue-green algal toxins were detected at some of these locations during periods of the summer, Harrahy says.


"Typically, the waters where we're finding these blooms are in the southern two-thirds of the state and in ponds that were designed as storm water detention basins," she says. Such detention basins are not intended for recreation and shouldn't be used as such because they collect stormwater runoff and pollutants including fertilizers, pesticides, and other substances the rain can pick up.


Regardless of where you swim or boat, Harrahy says, the key is to avoid coming into contact with water with heavy, visible concentrations of blue-green algae. That goes for water-skiers and users of personal watercraft, as well as swimmers.


"Any time you see a pea green layer on top of the water, don't come into contact with that water, or let your children or your pets contact that water," Harrahy says. "It's safest to assume that if that scum layer's there, assume toxins are present."


In addition to avoiding contact with scum layers, large mats or other visible blooms of blue green algae, these common sense steps can help you stay safe on Wisconsin waters.


Avoid using personal watercraft, windsurfers, or water skis over mats of blue-green algae.


Don't swallow lake or river water. Don't use it for drinking, cleaning food or washing camping gear, and don't boil contaminated water, as this may release toxins from blue-green algae.


Shower after swimming.


Wash off your pet's coat to prevent the pet from ingesting pathogens or blue-green algae while it cleans itself.


Help prevent contaminants from entering Wisconsin's recreational waters: dispose of litter in containers, do not feed the birds by swimming areas, avoid using excess fertilizers on yards and don't dump anything down storm drains.


More information on blue-green algae can be found on the DNR Web site.


FOR MORE INFORMATION CONTACT: Bob Masnado, DNR - (608) 267-7662 or Elisabeth Harrahy, blue-green algae (608) 264-6260; Mark Werner, DHFS - (608) 266-7480