Silver Lake Algae - A Two-part Story. From the Silver Lake Water Quality Committee

Silver Lake is a part of a watershed and environment that is complex and contains many species and many layers of interdependent relationships. We are blessed to have a watershed that is classified as having Exceptional Value (EV) the highest rating in Pennsylvania. There is a long evolution of balance among species in a healthy lake environment.   That balance can be upset by a number of factors whose impact can be cumulative even if any one factor is small. We may be able to ameliorate some of the factors that have a negative impact on the quality of the lake water and aquatic life.

This story is about two of the organisms whose impact we have observed over the past several years: green algae and blue-green algae.  Understanding the distinction between these two organisms will help in our effort to protect our lake water quality.

The first part of this Silver Lake story deals with the Green Algae;

the second part turns to a group of organisms under the name of Blue-Green Algae.

We are living with these algal species and hopefully this article will serve as a basis for all of us Silver Lakers to better understand some of the relationships, interdependencies, benefits and risks involved in our lake environment.

Part One:  The Green Algae

One branch of the tree of life includes plants, which we commonly think of as the grasses, bushes, flowers, and trees among many other forms.

The Green Algae is closely related to green plants; their cells contain a nucleus and chloroplasts that have the components necessary to undergo photosynthesis.

In Silver Lake there are many forms of naturally occurring Green Algae which use sunlight to grow and reproduce.  With excess nutrients, such as nitrates and phosphorus, the Green Algae population can over grow and effect water clarity.

The Green Algae are near the bottom of the food chain and are food for many very small animals, including zooplankton such as Daphnia.  Daphnia are filter feeders whose food is usually made up of planktonic algae of which Green Algae is a major component.  Daphnia in a healthy lake help control the amount of planktonic Green Algae and keep the population in balance.  

At Silver Lake, sometime in the last twenty years, we had an incident that caused the Green Algae and Daphnia relationship to tip out of balance.   A Saltwater bait fish, Alewife, were introduced into the waters of Silver Lake. Alewife breed in fresh water and love to eat Daphnia.  Over a number of breeding seasons, the alewife flourished, and as a consequence the Daphnia population plummeted.   With a lower number of Daphnia and an increase in nutrients, the Green Algae were left to grow out of control and the lake water clarity suffered.  Green algae are typically non-toxic

Led by action from the Silver Lake community and Water Quality Committee, Brown trout have been stocked in the lake which helps to reduce (not eliminate) the alewife population.   The lake is getting back into balance between the Daphnia and the Green Algae, and our water clarity has markedly improved.

Thank you to the many families who have contributed to the trout stocking and Catch & Release program.

Part Two: The Blue-Green Algae

The second part of the story of Silver Lake involves Cyanobacteria, which is also called Blue-Green Algae. It,  is more closely related to bacteria than to green plants.  Cyanobacteria do not have a cell nucleus, can fix nitrogen, and can move up and down in the water using air-sac vacuoles.

Blue-green algae thrives in warm water that has excess nutrients (especially phosphorus) and can grow and reproduce into large mats (blooms) of various colors that can be seen at the surface.   The blue-green algae can grow fast and out-compete the green algae.

The trout stocking does not help reduce cyanobacteria, which have a very different life cycle than green algae,

Sometimes the Cyanobacteria (blue-green algae) produce toxins that can harm fish, pets, and humans.

The best defense against Cyanobacteria (blue green) algae blooms is to keep excess nutrients out of the lake.    Once excess nutrients are in the lake, an annual cycle can develop involving nutrients, sediments, motile cyanobacteria, and temperature.

Over the last few years, there have been multiple incidents of blue-green algal blooms in Silver Lake, some of which have shown some toxicity.

The Silver Lake Association is actively doing inlet and lake water testing.  In August 2022, the Association purchased and installed some technology in the form of ‘Eutrosorb’ bags/booms that are designed to absorb phosphorus from flowing inlet water.  They are unobtrusive black bags in the two main inlets on the north ends of the lake. Testing will be done to monitor effectiveness of the booms at removing nutrients from the inlet water before it gets into Silver Lake.

Here is a link to additional information on Harmful Algae Blooms  (HABs) in Pennsylvania:

https://www.dep.pa.gov/OurCommonWealth/pages/Article.aspx?post=44

If the Eutrosorb bags reduce the amount of phosphorus entering the lake from the inlets, we hope to see a reduction in the number and extent of blue-algae blooms. We need to understand, however, that there are other sources of phosphorus that can tip the balance. We all need to be aware and to treat the Exceptional Value (EV) Silver Lake environment with care, keeping septic systems working properly and pumped out regularly, planting shoreline buffers of native plants to help absorb nutrients, not letting ash from fires get into the lake,  keeping fertilizer use on lawns and plants to a minimum and keeping fertilizers and manure runoff away from the lake, and doing what we can to manage drainage and runoff from our roads and properties to minimize their carrying silt and all that goes with it from entering the lake without passing through buffers.