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Wisconsin Natural Resources magazine

Wisconsin Natural Resources magazine

Volunteers at Milwaukee's Bradford Beach clean up accumulated <i>Cladophora</i>. © Milwaukee County Health Department
Volunteers at Milwaukee's Bradford Beach clean up accumulated Cladophora.

© Milwaukee County Health Department

June 2005

Algae that's
bad news for the nose

Conditions remain right for periodic outbreaks of stinky algae along the Lake Michigan coast.

Shaili Pfeiffer


Other algae are more dangerous
Nuisance all over the Great Lakes
Learning more about the lake
Dealing with Cladophora outbreaks

Last summer the air along many coastal communities up and down Lake Michigan reeked with a septic-like odor, but the smells and accompanying windrows of green, slimy plants were not caused by sewage overflows. The culprit was algae, Cladophora, which have been washing up on Lake Michigan beaches in copious amounts for the last four to five summers, just as they did some 25 years ago. Cladophora outbreaks could well wash up on Lake Michigan beaches again this year.

Cladophora grow attached to rocks on the lake bottom. A survey of the nearshore last summer found Cladophora completely covered every available rock surface with a forest of algae up to six inches long. Cladophora beds were growing more than 30 feet down! When storms whip up the winds and blow inland, the algae break off from the bottom and wash ashore or pile up in the shallow waves near the beach. The decaying algae give off putrid odors that certainly make a visit to the beach an unpleasant, stinky experience.

Winds may make the beach awash in green after a storm and a few days later another storm with strong winds from the west can carry the algae right back out into the lake. Later in the summer, particularly in August, the algae tend to slough off the rocks and wash ashore more consistently. With warmer temperatures and a steady source of algae, the odors are often worst in late summer.

"The algae may be only part of the problem," says DNR researcher Paul Garrison. Some of the really bad smells may come from decomposing critters, like mussels that are carried ashore tangled in the mass of vegetation. These decomposing little animals can smell even worse than the algae, just as we've all observed when cleaning out a refrigerator – the smells of rotting meats and other proteins are usually stronger than the odors from decomposing fruits and vegetables, Garrison explained.

Other algae are more dangerous

Cladophora are a family of green algae and are different from the blue-green algae that can produce toxins. The blue-green algae have sickened or killed humans and animals that come into contact with them. Green algae don't produce toxins. "But it is still important to think about practicing good hygiene, such as washing off, if you come in contact with Cladophora because they are a good host for bacteria," says Julie Kinzelman, microbiologist with the Racine Health Department. Kinzelman also explains how Cladophora may play a role in harboring E. coli that lead to beach closures. "Because other organisms wash up with the algae onto shore, gulls are attracted to the algae mats. This in turn results in more gull feces on the beaches that can lead to beach closure. We've studied how to manage our beaches to reduce the potential for algae accumulation thatcontribute to high bacteria concentrations. We've learned it's important to avoid grinding algae into the sand where they can serve as a food source for bacteria in the sand. Good beach management techniques can improve swimming water quality. Beach goers can help too by refraining from feeding waterfowl at the beach."

Nuisance all over the Great Lakes

Cladophora are a significant nuisance in portions of all of the Great Lakes where there is suitable rocky substrate with the exception of Lake Superior. Lake Superior water temperatures are too cold for the algae to grow in abundance. On Lake Michigan, the algae problems are confined to the western shore that is very rocky. In contrast, the eastern shore along the state of Michigan has a sand bottom and the algae aren't a nuisance there.

Cladophora outbreaks were last a problem in Lake Michigan back in the 1960s and early '70s. Those outbreaks were linked to industrial and municipal discharges of wastes that contained a lot of phosphorus. The worst Cladophora outbreaks happened near areas where these pipelines drained into the lake. One positive outcome of those old outbreaks was they created public awareness, pressure and spurred action to help pass the Clean Water Act. As a result significant federal grant money was invested in improving sewage treatment plants nationwide to stem problems from industrial and municipal wastewater pipelines. Also there was a successful push to reduce phosphorus in laundry detergent.

Lake Michigan phosphorus concentration dropped significantly and the Cladophora went away, but the Great Lakes levels were also very low in the 1960s (lowest on record was 1964). At the same time phosphorus concentrations dropped, the lake levels rose, light didn't reach the lake bottom in as many areas and the Cladophora were no longer the nuisance they had been. This is a classic example of how many variables can affect the Great Lakes and makes it difficult to understand how the different factors are interconnected and affect the ecosystem.

Why are the algae a problem again now? The short answer is we don't know definitively – Lake Michigan is a big system that is constantly changing. The answer probably lies somewhere in an interconnection among conditions that vary such as the amount of available light, available nutrients, low lake levels, water temperature, and wind directions. Zebra mussels, recent invaders to Lake Michigan since 1991, may have a big role by increasing water clarity and recirculating nutrients.

Phosphorus recycling – Open water phosphorus concentrations have decreased substantially in Lake Michigan since the 1960s and '70s and currently meet phosphorus standards. The researchers haven't observed any sharp increases that would account for a large Cladophora rise. However, nearshore phosphorus concentrations haven't been regularly monitored, so we don't know for sure how they've changed. On the other hand, zebra mussels are amazingly efficient filter feeders and the bottom of the nearshore of Lake Michigan is covered with these powerhouses. They may be capturing phosphorus that typically would have moved into the open lake and be excreting it in the nearshore area where Cladophora grow. Some phosphorus still runs off the land from urban stormwater and agricultural fields. We do know that fertilizer sales across the U.S are also increasing. All of those nutrients only add to the growth of algae in Lake Michigan.

Wisconsin lake topography or hydrology – The Wisconsin side of Lake Michigan has many areas that are rocky and have cobbles rather than fine sand. Cladophora need a hard surface to attach to, so if there is lots of light and food, there are plenty of surfaces for these algae to proliferate on the Wisconsin shores along the lake.

Light penetrationCladophora need a certain amount of light to grow well. Since they need to attach to the lake bottom, algae growth is limited by how deep sunlight can penetrate. This is another environmental condition that the zebra mussels have modified. Given their amazing filtering capacity, the mussels have made Lake Michigan water clearer. Last summer up and down the lake we could see the bottom of the lake at 30 feet deep.

Lower water levels now – Water levels in the Great Lakes fluctuate depending on precipitation and evaporation. In the last few years Great Lakes water levels have been at their lowest levels since the 1960s. Consequently there may be more light penetration in the nearshore shelf area of Lake Michigan than in many years. With the wet weather last spring, water levels started to rise. If this rise continues it may get too deep in the nearshore area for Cladophora to grow in abundance and these outbreaks may decrease.

Rising temperatures – Could global warming be a factor too? Maybe. Water temperatures in the nearshore area of Lake Michigan have risen about 2 C in the last 25 years and these algae grow better with increasing water temperatures.

Wind shifts – Wind patterns on Lake Michigan show that the prevailing winds more often are coming from the east rather than the west. East winds will blow the algae onto shore rather than washing them out into the open lake.

Learning more about the lake

Several teams of investigators are searching for causes of the Cladophora outbreaks. The partners include the Wisconsin Department of Natural Resources, the UW-Milwaukee WATER Institute, Centerville Cares – a citizen group from the Manitowoc area – and community health officials.

The DNR research team, supported by funding from Wisconsin's Coastal Management program and the National Oceanic and Atmospheric Administration undertook several studies last summer.

The shoreline along Lake Michigan from the Illinois border north to the tip of Door County was extensively sampled during June and again in September last year. Sample sites were selected at 16-mile intervals north along the coast. At each site, the researchers collected samples and made observations from the nearshore area in six feet of water and farther offshore in 30 feet of water. In the deeper water, water samples were taken both at the surface and on the bottom. Researchers measured water clarity, nutrient concentration of the water, and did physical inspections of algae growth and zebra mussel populations.

Test results show that phosphorus levels near shore remain low compared to inland lakes and streams, but are well within the range that algae need to grow. Nearshore phosphorus concentrations also dropped significantly north of Manitowoc County, yet algal growth was as much of a problem on some Door County beaches as it was farther south.

Health departments and volunteers who are already monitoring coastal beaches for signs of bacteria are now also recording how much algae they find washed up on their beaches. This information is especially useful because the beach monitors collect samples and test water quality at their beaches at least weekly and often more frequently. From these beachfront observations we found that Bradford and McKinley beaches in Milwaukee and the beach at Newport State Park in Door County had the greatest number of days last summer where nuisance quantities of algae washed on shore.

Work plans to monitor for Cladophora outbreaks this summer will include repeating sampling in about half of the sampling sites from last year and adding new locations. Among the new sites, researchers will search for Cladophora along the Green Bay side of the Door Peninsula. The first sampling time has been changed to late April to observe Cladophora growth and lake nutrient concentrations at the beginning of the growing season. This sampling will be repeated in August when the algae start to slough off the bottom. DNR researchers are working in close collaboration with researchers at the UW-Milwaukee WATER Institute and of course, the partnership with health departments to monitor beaches for both bacterial and algae buildup will continue.

Dealing with Cladophora outbreaks

"Even if we can't stop or predict when and where Cladophora may drift ashore, we're learning how the algae grow and move in Lake Michigan," Garrison says. "We can allay public fears about the algae and make the best of cleaning them up, where feasible," he says.

"Cladophora don't necessarily wash up on the beach next to areas where the algae grow. Sometimes the ropey algae slough off the bottom, drift and blow ashore quite a distance from the areas where they form. Unfortunately some community beaches appear to be hotspots for nuisance algae accumulation due to Lake Michigan nearshore currents. It's a complicated picture and certainly frustrating for anyone dealing with the problem to not have a quick solution on hand," says Garrison.

Communities all along Lake Michigan are struggling to keep up with algae accumulation. Some communities rake up algae from the water onto land and collect amassed algae with beach groomers to keep windrows from building up on their beaches. Where there is heavy accumulation, some communities have used backhoes and frontend loaders to collect the algae. Chemical treatments aren't effective in such big lake areas.

The one factor currently under human control that contributes to a long term solution is to keep taking actions to reduce phosphorus runoff. "We don't know how the current way that phosphorus circulates is affecting nuisance algae. But we do know that reducing phosphorus to Lake Michigan is a good thing," says Chuck Ledin, director of the DNR's Office of Great Lakes. "Unfortunately reducing phosphorus today may be more challenging than upgrading sewage treatment plants because we need to change people's habits. Everyone needs to be aware that their actions can contribute to the Cladophora problem. We need to find ways to prevent any uses of phosphorus, big or small, that can result in a discharge to the lake. In the short term this will keep the problem from getting worse. In the long term we'll reduce what phosphorus is available in the lake. This is an endeavor we should start and continue."

We have a naturally-occurring alga that has recently resurfaced. It's clearly a stinky nuisance on Lake Michigan beaches and there is no reason to expect it to go away any time soon. Reducing fertilizer use, maintaining septic systems, keeping animal waste out of water ways and storm drains, preventing soil erosion on farms and construction sites, planting buffers along waterways, and keeping leaves and grass clippings out of the streets are just a few of the ways that we can all reduce phosphorus runoff over the long run to help keep the problem from getting worse, Ledin said.

Shaili Pfeiffer is a water resources specialist coordinating the Cladophora response for the Department of Natural Resources.