The readers of Hopatcong Lake Regional News have been asking the question. “What’s Happening to our Lake, with all of this scum on the surface?" So, we investigated the issue and here is what we know. The good news is this should be a short-term issue!
As always, with any lake issues we’ve turned to the most knowledgeable person within our region. “Donna Holly” with the Lake Hopatcong Foundation, as to what is happening and why.
Lake Hopatcong suffering from Blue-Green Algae
It seems that the higher than normal warmer water temperatures and several other factors have combined to create the issue that we are seeing on the lake today. The good news is this is normal and should be only a temporary issue.
Donna provided the following information on Blue-Green Algae from Rutgers Cooperative Extension Fact Sheet FS1216.
What is it?
Blue-green algae are common primitive microorganisms that resemble algae, but are uniquely classified with bacteria. Blue-green algae are actually cyanobacteria, microscopic organisms that use sunlight to photosynthesize and produce their own food, but lack a cell nucleus or membrane-bound organelles like true algae.
“Cyan” means blue and cyanobacteria get their name from the blueish pigment phycocyanin. They also contain chlorophyll a similar to plants, and use both pigments to capture light for photosynthesis (Crayton, 2004). Cyanobacteria occur naturally in freshwater worldwide and can be found in oceans, ponds, lakes, streams, and moist soil.
What Causes a Blue-Green Algae “Bloom”?
Blue-green algae are a normal part of a healthy aquatic environment, but the population can “explode” in response to certain environmental conditions. High concentrations of blue-green algae can form “blooms” within just a few days.
There are three main factors that have shown to increase the likelihood of a cyanobacteria bloom on a body of water. First, since cyanobacteria are photosynthetic, they need direct access to sunlight for significant growth. More light and corresponding warmer water temperatures have been associated with increased growth. Second, nutrient enrichment, particularly nitrogen and phosphorous, is essential for a bloom in waters with a pH range of 6–9. Lastly, poor water circulation can facilitate growth of cyanobacteria. With mild winds or currents, large cyanobacteria colonies will accumulate on the leeward shore and expand rapidly as water becomes stagnant. Under these conditions a body of water can become very turbid with green, blue-green, or a reddish-brown color, the appearance of a thin oily looking film resembling paint, or a thick floating scum on the surface.
Three genera of cyanobacteria account for the vast majority of blooms; Microcystis, Anabaena, and Aphanizomenon. A bloom can consist of one or a mix of two or more genera of cyanobacteria.
Cyanobacteria cannot maintain this abnormally high bloom population for long and will rapidly die and disappear after one or two weeks. If conditions remain favorable, another bloom can quickly replace the previous one. Successive blooms may overlap so that it appears as if one continuous bloom occurs for up to several months.
As long as nutrients remain in excess, cyanobacteria can grow until some other factor such as light or temperature limits their growth. Increased nutrients enter the water body as runoff from either point or nonpoint sources. Nutrient sources can include storm water and agricultural runoff, runoff from fertilized lawns or recreation fields, sediments from soil erosion, improperly functioning septic systems, as well as from natural sources such as leaves, plant residues, and woody material.
Impacts of Blue-Green Algae
Some of the negative impacts of a cyanobacteria bloom include:
- Spoiling water quality, producing odors or scum
- Making recreational areas unpleasant or unusable
- Dense blooms can block sunlight which can kill other plants or animals in the water.
- When not photosynthesizing to produce oxygen, cyanobacteria still need to respire. This along with decomposition from large bloom die-offs uses large amounts of oxygen and can negatively lower the balance in the ecosystem to the point of causing fish “kills.”
- They can release potential toxins harmful to humans, pets, and livestock.
Potential Toxins Associated with Blue-Green Algae
Some, but not all cyanobacteria can produce toxins. Even blooms that contain known toxin-producing species may not produce toxins at detectable levels. It is not known what triggers toxin production in the cyanobacteria. These toxins are produced inside the cells and stay there as long as the cells are alive. When the cyanobacteria cells die and break down, the toxins are released into the water. Toxin concentrations may vary dramatically and are not evenly distributed. Potential toxins include nerve toxins, anatoxins, and liver toxins called microcystins. It is not possible to tell if the cyanobacteria present in the water body are producing toxins without laboratory tests. These toxins have been known to kill cattle, dogs, and other animals that drink infested waters. Because of this, waters that show signs of cyanobacteria should be treated with caution.
While rare, humans and animals that come in contact with cyanobacteria toxins may result in health problems that include:
- Skin rashes, hives and blisters
- Irritation of the eyes, nose and throat; possible breathing problems
- Abdominal pain, diarrhea and vomiting
To protect yourself and your pets:
- Don’t swallow water from any waterway.
- Don’t swim or wade into areas that might have evidence of cyanobacteria.
- If you swim in or come in contact with water that might have a bloom, wash thoroughly with fresh water as soon as possible.
- Don’t let pets or livestock drink or enter water where cyanobacteria are present.
- If pets or livestock enter the water, rinse them off immediately. Do not let them lick algae/water off their fur.
- Don’t irrigate lawns with water that looks scummy or smells bad.
Prevention/Control of Blue-Green Algae
While there are some short-term treatment options for controlling cyanobacteria, the long-term solution involves finding ways to reduce phosphorous and nitrogen inputs at their source, before they can runoff into a water body. Since nutrients come from a variety of sources, it is often difficult to pinpoint an exact cause.
Some management practices to include:
- Reduce excessive application of fertilizer on lawns; use soil tests to determine fertilization needs.
- Grow lawn species that require less input of nitrogen and phosphorus fertilizers such as fine fescues or turf-type tall fescue cultivars that have been shown to grow under low input of fertilizer and water.
- Properly maintain septic tanks and fields.
- Clean up pet waste and isolate livestock from water bodies.
- Establish natural planting buffers adjacent to the water body. Rather than mowing to the edge, create a buffer strip of tall grasses and native plants, and maintain vegetation along the water banks to filter runoff and prevent soil erosion.
- As tree leaves and grass clippings break down, they are a source of nitrogen and phosphorous. Though beneficial if mulched into turf or composted and incorporated into soil, leaves and grass clippings should be raked from the water’s edge and from curbs and gutters to prevent them from being washed into waterways.
- Keep trees or establish new trees along the water’s edge to help shade and cool surface water.
- Reduce the amount of area in pavement or other impervious surface to control runoff directly into a water body.
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