Foam on the water: Is it harmful or harmless?

October 03, 2024| Education, Environment

By: Fred S. Lubnow, Ph.D., Princeton Hydro, LLC

Sometimes foam is seen in near-shore areas or in the streams and wetlands that flow into Lake Hopatcong.  Frequently, people assume such foam is due to the discharge of detergents or other pollutants. However, foam can be the result of natural processes in the environment and/or human-related discharges. 

It should first be noted that people and pets should avoid direct contact with any foam since the material can concentrate microbial (bacteria/viruses) and chemical pollutants.

Two conditions must exist for the formation of foam in an aquatic setting. First, the water must contain a substance that can produce the foam. This substance can be natural, such as organic matter or decaying plant material, or it can be human-made chemicals. Second, there must be some type of mechanical action that introduces air into the substance to create the foam. Any turbulent action, such as wind, currents, water cascading over dams or waterfalls, or heavy rainfall can contribute to the production of foam.  Surface water foam tends to be more common in the spring due to increased runoff and in the fall due to increased decomposition.

Natural foams will develop where there is abundant decomposing plant material. The foam may look white at first, but it will usually turn tan or brownish in color and may have an earthy or organic odor. Again, this is a natural process and the brownish color of the water in the Jefferson Canal section of the lake is due to plant/woody decomposition, releasing tannins into the water.

In contrast, human-produced foams can be the result of spills, discharges, or runoff that is contaminated with cleaning agents, detergents, nutrients, firefighting foams, oils, de-icing products, or other chemical contaminants. Such foams will tend to be only white in color and will either have no odor or may smell pleasant. It is also possible that the foam is being generated from both natural and human-produced sources.

In conclusion, if you spot foam on the water, avoid touching it. If you're unsure whether it's naturally occurring or due to chemical pollutants, take a photo, record the location along with the date and time, and report it to the New Jersey Department of Environmental Protection. Non-emergency environmental concerns can be submitted via the WARN NJDEP app (available on  iTunes and Google Play), while environmental emergencies should be reported immediately by calling 1-877-WARNDEP (1-877-927-6337). Additionally, keep the Lake Hopatcong Foundation informed by emailing info@lakehopatcongfoundation.org or calling 973-663-2500.
 

Examples of Lake Foam

Upper left photo by Orion 2 on Flickr