Analysis of Pond Water in Ridgefield Lakes

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By Elizabeth Rogers, and Florence Mercurio - Ridgefield Girl Scout Troop 50075

For our Silver Awards, a project where small groups are put in charge of improving part of their community, our small Girl Scout troop decided to investigate two bodies of water that are frequently used by the public: Woodcock Pond and Fox Hill Lake.

Throughout the summer, averaging about once a week, we tested the lakes’ dissolved oxygen and pH levels. The dissolved oxygen levels decreased throughout the year at both locations.

Throughout the testing process, the dissolved oxygen content in Fox Hill Lake dropped dramatically. According to the U.S. Geological Survey, a healthy lake should have around 8-12 mg/L of dissolved oxygen, and anything below 2 mg/L can be classified as hypoxic, which means that a lake is lacking oxygen to a deadly extent. Most of these ‘Dead Zones’ are due to fertilizer runoffs from surrounding neighborhoods. All fertilizers, even all-natural ones, contain extreme amounts of nitrogen and phosphorus to enhance plant growth. Unfortunately, these elements also work on aquatic plants, including algae, so that when fertilizer ends up in the water, algae growth increases to a dangerous level. These surface plants block out the majority of the sunlight, preventing underwater plants from getting the light they need to produce oxygen through photosynthesis, lowering the oxygen content of the lake.

Woodcock Pond borders Woodcock Nature Center, a wildlife preserve with year-round programs, including a summer camp, that focuses on understanding nature and the environment. Summer Campers use the pond for canoeing and catching turtles and frogs for observation before releasing them. Some summers it is more difficult for the campers to paddle due to increased plant growth. This is suspected to be caused by fertilizer runoff from the houses around the lake. In satellite photos from a few years ago, there were huge swaths of algae blooms from specific houses (see above photo). 

We suspect the dissolved oxygen of the bodies of water we tested were at an average level of around 6 mg/L, low enough that fish and other aquatic creatures are at risk. We believe that the decrease in dissolved oxygen levels is because of large amounts of fertilizer runoff from nearby homes. This may lead to the formation of dead zones and algae blooms, endangering native species, including fish, turtles, frogs, and water snakes, as well as people.

In a meeting with Sarah Breznen, the Director of Education at Woodcock Nature Center, we talked about the fertilizer and algae in the lake, and how it has affected the land and animals. She said that the lake’s algae level has fluctuated during the twelve years she has worked at Woodcock Nature Center, but that it has been doing better in the past few years. However, there was a bad summer over 5 years ago, when dead fish were floating on the surface. The counselors had to start pulling out lake plants to prevent the oxygen from getting even lower than it already was. Since then, the pond has improved. 

She recommends that homeowners who use any sort of fertilizer rethink how their lawn is laid out, specifically the amount and type of fertilizer used, as well as how often it is applied. When asked what she would say to people who use large amounts of fertilizer, she responded with, “I would tell them to stop. People are adding fertilizer to get their grass to grow, but I think that it’s a bigger philosophy about yards in general… you drive around, and you see these houses with nothing but green grass, and those yards are not habitats. Those yards are a dead zone.” Grass is a plant that has shallow roots, so it is prone to drought and turning brown, needing a lot of effort to keep it alive and green. The fertilizers and pesticides homeowners apply to keep it green eventually run off into the ponds, rivers and streams.  She suggests that homeowners work toward changing their backyards into a garden with native plants, which are hosts for butterflies, bees, and birds. Lawn grass does not support caterpillars or bug species that are important food sources for higher up the food web. 

To sum up our research, fertilizers can have a deadly effect on the wildlife around them. If people don’t start to take action for the living organisms that they are endangering, it could have a devastating impact on the lakes and oceans of the world, one that is not easily remedied. The people who take action in the world are the ones who want to change this planet for the better. Instead of large green lawns, try making a garden with native plants, to reduce the amount of fertilizer being used.  Educate your friends and family and work to reduce the fertilizer used on lawns, and together we can change the world!