BEMIDJI - People fertilize their lawns to keep their grass green, but what they may not know is that the fertilizer can run off into lakes, feeding the growth of blue-green algae, which can cause harm to animals.
"(Algae) is pretty common this time of year," said Bob Ekstrom, the Aquatic Habitat Specialist for the Minnesota Department of Resources' Bemidji Area Fishery office. "What it is is the reflection of excess nutrients in the system."
Ekstrom said algae is in virtually every body of water at all times, but it goes through a "bloom" - an extensive growth period that can cause a lake to change to a bluish green color because of the density of the plant.
The bloom period is natural, occurring in the peak of summer when the days are long, the sun is at a high angle and the nutrients for plant growth are easily accessible for the algae to feed off of.
"All of those things are constant across the landscape except for the nutrient inflow," Ekstrom said. "When you have more human activity you typically have far more nutrients coming into the system, which causes lakes to turn those bright greenish colors."
In addition to turning the lake's color to various shades of green, algae can cause problems to fish and other animals.
According to the DNR website, Plankton Algae, commonly called blue-green algae, can release toxic materials that can poison animals. When in full bloom, the algae resemble pea soup, with jelly-like masses forming along the shoreline.
Dan Olson of the Minnesota Pollution Control Agency's Detroit Lakes' office said reports of blue-green algae in the Beltrami County area started coming in a couple weeks ago. He said the MPCA was not able to confirm if the reports were blue-green algae but the extended period of warm temperatures, extended sunny and calm days are all ideal for blue-green algae growth.
"What we're suggesting people do is if they encounter conditions where the water looks really bad and smells really bad, our advice is to stay out of that area of the lake," Olson said.
Olson said that in extreme cases it is easy to identify a blue-green algae outbreak because of the thick bluish green color and the water having a thickness of latex paint. He said people are likely to stay away from the water if it looks this bad, but pets may not be as concerned.
If seen, it is recommended that pet owners keep their animals away from the tainted water, which has been known to kill dogs that swim in it.
If pets have contact with blue-green algae, the University of Minnesota Extension Regional office recommends washing the dog immediately and not letting them lick the algae off their fur. The Extension Office issued a news release this week warning people of the dangers of blue-green algae.
Ekstrom could not speak to the algae's effects on animals, but he said that an over abundance of any type of algae can cause problems for fish.
"The consequence is that when these plants become really abundant and they start to die, they will decompose, which consumes oxygen, reducing the oxygen available for fish creating the conditions for a fish kill," Ekstrom said.
He said that when this happens, fish that need cold water to survive, which include whitefish, eelpout and white suckers, are forced to go into warmer water towards the surface where oxygen is more accessible.
The warmer water stresses the fish and can lead to death. Ekstrom said fish like bass, bluegills, and sunfish are more resilient in the north and are able to survive in the warm water.
Ekstrom said major fish kills do not happen very often because the unique set of circumstances required. The weather has to be hot and dry and the water has to be calm, eliminating the mixture of the water with the fresh oxygen. He said that though this summer has been hot, the wind may be enough to prevent a major kill.
"Fortunately we have had wind," Ekstrom said. "The wind is enough to kind of keep things just teetering on the edge. What would really push us over is if we had a stretch of a week or two of not necessarily glass calm days, but very light winds.
"That would be the final straw that would break the camel's back and we would likely see pretty a pretty major fish kill."
According to an article from the Extension Office's water resources division, the main nutrient feeding algae growth is phosphorus, a natural nutrient found in lakes. However, the amount of phosphorus naturally in the lakes is not enough to support large algae blooms; it is the additional phosphorus added through fertilizing that causes the bloom. According to the article, one pound of phosphorus can promote the growth of 500 pounds of algae.
Ekstrom said people who live on the shoreline can minimize the influx of phosphorus and other nutrients that feed the algae by limiting fertilizers and creating a buffer along the shoreline to trap nutrients on the upland, preventing it from entering the water.
The blame, however, is not limited to those who live directly on the lake, he said. People that live in the surrounding neighborhoods feed the algae through the runoff from their yards, which gets passed through the storm drains.
The Extension Office recommends people who live along the shoreline do the following to reduce phosphorus from their property:
- Dispose of leaves and clippings away from the lake.
- Maintain septic system properly
- Use water-bars or berms to redirect storm water from running into the lake.
"The reality is everything all of us do ends up in the water somewhere," Ekstrom said.
Olson said that the blue-green algae season can last throughout the summer months and into the early fall if the weather remains warm.
If people see a potential blue-green algae outbreak, they can contact the MPCA at (218)-846-8108.