Monday's high temperature topped 90, and with Tuesday's forecast threatening an even hotter afternoon, the Minnesota Pollution Control Agency is warning residents that the hot temperatures create an environment that is ripe for harmful algae growing in Minnesota lakes.
BEWARE BLUE-GREEN ALGAE
On Monday, the MPCA issued a bulletin reminding lake-goers that conditions are right for rapid growth of blue-green algae that can harm pets, livestock and people.
While most species of algae are harmless, blue-green algae can sicken people and animals to if ingested. In extreme cases, dogs and other animals have died following exposure.
"High rainfall, which has been common throughout much of Minnesota this spring, results in nutrient-rich runoff entering our lakes, fueling algae growth," MPCA lakes expert Steve Heiskary said. "While spring and early summer temperatures were cooler than normal, lake temperatures have warmed rapidly. Given these conditions, we are likely to see blue-green algae blooms on many of our lakes."
HARD TO IDENTIFY
There are many types of blue-green algae, and not all are toxic; however, the MPCA says there aren't any visual cues that indicate whether a blue-green algal bloom could be dangerous. Even so, Heiskary says it's best to avoid any algae that seems suspicious.
"You don't have to be an expert to recognize an algae bloom that might be harmful," Heiskary said. "If it looks bad and smells bad, don't take a chance. Stay out and keep children and pets away from the water until the bloom subsides."
Blooms of blue-green algae can look like pea soup, green paint or floating mats of scum. They are often accompanied by a bad odor and can be found across the state, particularly in warm, shallow lakes.
Since such sights aren't appealing for a summer swim, humans tend to steer clear and are rarely affected.
An animal that has ingested toxins from an algal bloom can show a variety of symptoms, including:
- Skin irritation
- Severe disorders involving the circulatory, nervous and digestive systems
- Severe skin lesions
In worst cases, the animal may suffer convulsions and die.
In humans, health effects can include irritation of skin, eyes and nasal passages, nausea and vomiting. Extreme cases can produce paralysis and respiratory failure.
There are not many preventative measures to combat blue-green algae, but weather changes -- like significant rainfall, wind shifts or cooler temperatures -- will disrupt growth.
In the long run, reducing the amount of phosphorus runoff can cut down the growth of algae. Some sources of phosphorus include pet waste, lawn clippings, yard debris and certain fertilizers. Most phosphorus-containing fertilizers are banned in Minnesota.
LAKE LEVELS ON THE RISE
Recent rains may help Lake Minnetonka ward off some algae growth.
The Minnehaha Creek Watershed District's most recent measurements taken on July 15 indicate Lake Minnetonka is at 930.13 feet above sea level. That's the highest it's been since June 2011, and just shy of the all-time-high of 930.52 feet recorded in September 2002.
Some bays have declared a "no wake" zone, but the water level must remain above 930 feet for eight consecutive days before the Lake Minnetonka Conservation District can declare high water. On July 12, the lake measured 929.72 feet, but early Saturday morning rainfall helped push the threshold.