As temperatures drop and sunlight lessens, the algae stops growing. That is when it is likely to break off of what it’s clinging to, float to shore with the currents, and eventually rot in the warm sun.

Can you smell that smell? It’s that smell that creeps up on you as you turn down Lincoln Memorial Drive, and approach Lake Michigan.

Milwaukeeans can’t help but notice the stench emanating from the shore, but they often incorrectly pinpoint the source. Believe it or not, it has little to do with raw sewage being dumped in the lake.

It’s the rotting algae called cladophora that causes the insult to your nostrils.

Cladophora is a branching, green algae found naturally along the coastline of most of the Great Lakes, according to Great Lakes Water Institute’s website, and it tends to get worse in the fall.

It is thought that the smell is not only the algae, but also bits and pieces of other invertebrates, like mussels, which the algae grow on, said Erica Young, assistant professor in the Biological Sciences department at UWM.

Cladophora has grown all summer long. As temperatures drop and sunlight lessens, the algae stops growing. That is when it is likely to break off of what it’s clinging to, float to shore with the currents, and eventually rot in the warm sun.

Then, to add to the mess, birds come to feed on the debris and leave behind their own droppings. All these processes add up to a big stink along the lake.

The algae blooms not only lead to unattractive and repulsive smelling beaches, but can also result in reduced quality of drinking water and decreased property values.

“It has been a big problem, a big management problem. It affects a lot of people, and it’s not just aesthetic. There are health problems from the bacteria involved. There are economic problems as well. The algae plug up electric plants when lake water is used for condensing purposes. When filtering systems back up, plants get shut down, losing tens to thousands of dollars a day,” said Harvey Bootsma, a specialist in freshwater lakes at the Great Lakes WATER Institute at the University of Wisconsin–Milwaukee.

Fertilizer and sewage entering the water through runoff and combined sewage overflow is another possible cause for the explosion of cladophora in the lake, but it does not seem to be as responsible as the mussels.

Young doesn’t think that the fertilizer could be responsible for all the algae present in the water.

“During the summer there is naturally little phosphorous in the lake. The sun soaks up what phosphorous there is. The fertilizer in the water may have a slight influence, which has been measured. Studies show that 25 percent of the algae in the water could be supported by phosphorous alone. The rest is supported by cycles that occur in the lake, which the mussels have to do with,” Young said.

Phosphorous is a sticky substance that naturally adheres to the limestone that is found on the lake bed. If there was no phosphorous in the water, then the amount found on the rocks would detach from the rock and enter the water. Eventually levels of phosphorous would lower, but it would take a lot of time to see any affect.

“I’m not saying that we shouldn’t stop phosphorous input into the lake,” said Young. “But the effects won’t happen as quickly as many people would like to see.”

The Great Lakes WATER Institute has been working on the current cladophora problem for the past five years. The scientists found that there are three things affecting the cladophora growth- light, temperature and the concentration of phosphorous in the water.

“We know light is the problem here. We can’t control the light or temperature, so we have to push phosphorous levels even lower,” said Bootsma, “It’s comparable to tending to a garden. Plants need light and nutrients to survive. The cladophora has plenty of light, so we are taking away the nutrients, the phosphorous.”

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