Written by Industry Expert, Shannon Junior, Aquatic Ecologist and Territory Leader
Have you ever noticed a clear, scummy, or iridescent film on the surface of a pond or lake? This phenomenon, known as a “biofilm,” is often mistaken for an algae bloom or oil spill, and can be quite alarming to our clients when it shows up in their waterbodies. However, surface biofilms are not caused by either algae or hydrocarbons – they are actually produced by bacteria in the presence of large amounts of decaying plant or animal life. And although they can be quite widespread on ponds throughout the year, very little research has been done on the causes and treatments of biofilms. Most of the information in academic literature or on the internet is focused on substrate biofilms, or on small-scale occurrences such as in fish tanks and water storage tanks. However, Aquafix, a leading wastewater biotechnology firm that partners with SOLitude Lake Management on many aquatic projects, is in the early stages of a comprehensive biofilm study.
Biofilms form on the surface of the water when algae or metazoan (animal) life dies at a rate faster than the naturally occurring bacteria are able to degrade it. The films can be classified as either dead algae scums or dead protozoan scums, and they become worse during the summer months when water temperatures exceed 76° F. The effect of precipitation on biofilms is inconsistent – they can be worse in times of very little or excessive rainfall, and this seems to very geographically. Biofilms also seem to be worse in waterbodies with low pH. In general, biofilms are a sign that a pond has poor water quality and is out of balance.
It can be very difficult to gain control of biofilm issues when they develop. Biofilms can be extremely elusive, and may show up in the afternoon when the pond was clear in the morning, and then may dissipate again overnight. Raising the pH of the water by the addition of soda ash or lime may provide good control of biofilms, and there are a few beneficial bacteria and enzyme products that may be effective. However, repeated applications of algaecides and herbicides are not effective and tend to make the problem worse. Unfortunately, control of biofilm is not something that is part of a typical annual contract or management program, as it is widely sporadic and there is no cookie cutter method for resolving the issue. Each time this problem presents itself, a comprehensive evaluation of water quality and chemistry will be required to develop a site specific prescription to resolve.
Are you still wondering how to tell if the scum on your pond is an oil slick, algae bloom, or biofilm? A quick test to see if the scum is caused by a hydrocarbon-based oil is to grab a stick and poke it into the film. An oil slick will swirl back on itself in the wake of the stick, whereas a biofilm will fracture into small pieces that remain separated. We would also recommend the collection of a water sample for examination under a microscope to identify the different species of algae and protozoans present in the water, as well as to measure the baseline water chemistry parameters. Once we have some basic information, the SOLitude team of biologists and ecologists can help you develop a site-specific water quality improvement program to remediate whatever is ailing your waterbody.
Contact the experts at 888-480-LAKE (5253) for all of your lake, pond and fisheries management needs.
Shannon Junior is an Aquatic Ecologist and Territory Leader with SOLitude Lake Management. SOLitude Lake Management is committed to providing full service lake and pond management services that improve water quality, preserve natural resources, and reduce our environmental footprint. Lake, pond and fisheries management services, consulting, and aquatic products are available nationwide. Learn more about SOLitude Lake Management and purchase products at www.solitudelakemanagement.com.