Natural and unnatural elements lead to excess pond scum

Eastern’s three ponds – Upper or McGraw Lake, Lower Lake, and Willow Lake – are typically picturesque. Photographers and painters travel miles to capture their beauty. However, the ponds sometimes seem a little more unhealthy than usual and a green film appears along their surfaces. Students have frequently wondered what causes this.

The green film is made up of different types of algae, duckweed and native aquatic plants. “These plants have the ability to be the most aggressive and fast-growing plant species in the ponds and quickly respond to the opportunity to grow, presented by the abundance of dissolved nutrients in the water,” said John Munro, adjunct instructor and applied ecologist.

According to Executive Director of Campus Services Carl Altomare, the algae explosion is part of a natural progression. Under certain circumstances, an imbalance can occur, causing extreme growth in some populations and a decrease in others. 

“The exotic fish population, fertilizer put on lawns to make them look nice and green and the many unpleasant gifts left by geese and ducks have provided perfect conditions for an algae explosion,” Altomare said.

An overload of nutrients and sunlight cause plants to grow at a rapid rate. “You can’t get rid of (the algae) by just skimming it off,” Munro said. “The key to removal is to reduce, remove or isolate the source of the nutrients.” The Eastern staff has to try and cope with the algae with limited resources. 

Furthermore, the ponds sometimes have a pungent odor about them. “The mud stinks when disturbed,” Munro said. 

Munroe and Altomare explained that the maintenance of the ponds is quite complicated, especially when exotic or foreign plants and fish find their way into the ponds. A few years ago, McGraw Lake had some restoration work done to it. 

“The water quality is the best of the three,” Munro said. “It has little or no algae on it.” 

Unfortunately, less than a year after the restoration, about 500 goldfish were illegally released into the pond. The goldfish are exotic and bad for the pond, so Eastern got a permit from the Pennsylvania Fish and Boat Commission to get rid of the invasive species. 

According to Munro, there are plenty of natural inhabitants of the pond. “The pond has bluegills, bass, some macro invertebrates, mallard ducks, painted turtles, snapping turtles, green heron, great blue heron, Canada geese, and other species, ” he said.