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Pond Sludge

Muck or organic sediment is found in most water bodies. Muck’s impact can be visual and non-visual and come with health concerns that should not be overlooked.

The most obvious indicator of muck is felt when entering the water. Muck is the mushy slop that your feet sink in to in the lake. Along with the mushy feeling, muck has another noticeable characteristic; Muck releases hydrogen sulfide gas which gives off a sulfur or, more commonly known, rotten egg smell.

What causes pond muck?

The words muck and sludge can be used interchangeably to describe the decayed waste that accumulates at the bottom of a pond or lake.

Observe your surroundings. Are there trees near the water’s edge, shoreline vegetation, or weeds growing within the lake? Are there run-off or drainage areas, streams feeding the lake? What kinds of inhabitants are in or around the water; fish, frogs, birds (especially geese, ducks, swans), wildlife, or farm animals? Every single one of these mentioned add organic material to a lake.

Muck Contributors:

  • Dead pond weeds
  • Fallen leaves
  • Fish waste
  • Dead algae
  • Waterfowl waste
  • Grass clippings
  • Waste from cattle using the pond
  • Fish food

Muck accumulates from decaying materials such as leaves, pine needles, aquatic plants, and algae. Some of these materials are carried into lakes from streams or run-off drainage. Additional contributors to muck are aquatic life, visiting waterfowl, wildlife or livestock. Muck build up can concentrate in areas over-run by weeds and algae, near shorelines, as well as shallow or stagnant regions of a lake. Areas where leaves fall in from nearby trees are also prone to have higher waste accumulation. Depending on the type of pond weed, decomposition time could range from six to eighteen months. The plant is completely broken down at the end of decomposition and appears as a brown/ black build-up settled at the bottom of the pond or lake.

Organic sediment can be difficult to quantify without taking samples and send for laboratory testing. The amount of organic matter present in a soil sample, whether 20% or 80%, will still have major impacts on a lake ecosystem over time. Sediment sample testing can also reveal the volume of usable phosphate and nitrate within sediment. These nutrients can slowly release back into the water column, affecting aquatic life and overall health. Quantifying these nutrients allows lake owners or managers to develop a more precise nutrient management plan.

Muck Degrades Your Pond Health

Sludge creates serious side effects! As it builds year after year pond depth shrinks. Muck is literally filling in the pond.While this gradual process is taking place, some more noticeable problems arise.

Indicators that pond muck is impacting a pond:

  • Algae blooms
  • Low water visibility
  • Foul odors

Other less noticeable impacts include:

  • Nutrient level spike
  • Drop in fish growth rate
  • Lower fish production levels
  • Increase in biological oxygen demand
  • Drop in dissolved oxygen levels

Muck can have serious and long-lasting negative impacts. The most noticeable visual effects of muck are reduced clarity, water discoloration, and increased algae blooms. Less visible consequences include deterioration of water quality over time and changes to total fish populations. In severe cases, muck build up can lead to harmful algae blooms, extended E. coli presence and fish kills.

Impacts to water clarity

Muck reduces clarity in a number of ways. Water circulation, wave action, boat motors, or swimming can disturb organic material, resulting in muck particles being suspended in the water column. Bottom feeding fish like carp and catfish constantly churn bottom sediment while searching for food, causing a decrease in water clarity. Suspended muck particles give water a murky appearance.

An influx of nutrients in water that release from muck can trigger a planktonic algae bloom. This microscopic algae gives water a murky green appearance. When phosphate levels released from muck reach high enough levels, water can even appear a milky gray color.

Increased Algae Growth

In addition to cloudy water, muck can lead to increased filamentous algae or string algae growth. This type of algae bloom creates unsightly green surface scum/mats. Ponds and lakes can also experience planktonic algae blooms caused by an influx of nutrients being released into the water from the bottom sediment; this algae bloom gives the water a murky green appearance. Filamentous algae begins growth in the bottom sediment due to its rich nutrient content. Blooms become more visible as they float to the surface. When algae blooms reach the surface, they are in the later part of their life. The life cycle of filamentous algae spans 30 to 60 days. New algae is constantly regenerating and cycling into water. Dying algae drops to the bottom, breaks down into muck, and creating a vicious cycle.

Water Quality Impacts From Muck

Muck can have damaging impacts to water quality. Muck can release nutrients like nitrate and phosphate and heavy metals such as manganese and iron into the water. Additionally, muck increases biological oxygen demand (BOD) which can lead to hypoxia (depleted oxygen in a water body). Often overlooked as a contributing factor, muck releases large volumes of phosphorus found in lake water water. While there are many ways that phosphorus enters the water column from sediment, one way is through a chemical reaction that occurs in low oxygen or anoxic zones. Additional ways phosphorus is released from muck include increased bacterial activity during warm weather and when there is a drastic pH shift in the water. When bacteria populations become more active, they decompose organic waste and consume oxygen faster, triggering phosphorus to release from the sediment. Changes to pH can be caused when weeds and algae perform photosynthesis. During photosynthesis, water with little buffering capacity can notice dramatic climbs in pH levels. Since photosynthesis occurs the most during times of direct light, such as 2 pm, the pH can read up to 9, while the same location can read 6.5 at 6 am because of less photosynthesis taking place at night. Phosphorus can release from the muck in conditions with a high pH.

Nitrogen in multiple forms, ammonium and nitrate, also accumulate in sediment and can be released back into water. This is readily used by plants and algae as food.

Heavy metals like manganese and iron can be found in muck as well. The concentration of these metals increases under anoxic conditions. Waters polluted with high metal concentrations impact the growth and reproduction of fish.

Biological oxygen demand increases as organic sediment build up. BOD is the amount of oxygen necessary for organic sediment to be consumed by bacteria. All aquatic life and vegetation impact BOD. Sediments add stress to an aquatic environment which can 2 result in many of the previously stated issues. The influx of nutrients in particular produce even greater environmental impacts.

E.coli Survival in Muck

Escherichia coli (E. Coli) comes from warm blooded animals and humans. When E. coli enters a mucky environment, it has the ability to survive and, in some cases, even thrive due to the lack of oxygen and high nutrient levels. A study done by Robert L. Tate from the University of Florida compared the survival rate of E. coli in sandy soils and muck. Over a period of 8 days, the number of E. coli cells in the sandy solid were 2.6 x 105 compared to E. coli cells in muck were 6.7 x 105. E. coli survival rates were 3 times greater in the muck than in sandy soil. Additional research was done by Tate and compared the impact of aerobic versus anaerobic conditions (presence or lack of oxygen). Tate concluded that the growth rates of E. coli cells in anaerobic conditions (lacking oxygen) far exceeded the growth rates of cells in aerobic conditions (presence of oxygen) (Tate 1). These studies proved that E. coli not only can survive for extended periods of time in muck, but their cells are also capable of growth in these conditions. Muck presents E. coli with the ideal living environment. In normal conditions, this waste would cycle out of the water; however, muck prevents that and provides a habitat where it can survive and even thrive. This makes bodies of water with large accumulations of muck very dangerous for recreational users as they are at risk for contracting illnesses from potentially contaminated water.

Muck Improves Conditions for Cyanobacteria to Thrive

A growing concern for many pond and lake owners is cyanobacteria also referred to as harmful algae blooms or HABs. Cyanobacteria are single-celled organisms that produce many toxins capable of harming humans, pets, wildlife and fish. Cyanobacteria rely on the same nutrients that cause algae blooms to form. Although normal algae blooms are not directly harmful to fish or wildlife, cyanobacteria can easily out-compete them and lead to serious consequences for the water's inhabitants. If the correct nutrients are present, cyanobacteria will continue to reproduce and harm the aquatic ecosystem. They thrive in calm or stagnant water. Once in a water body, it is difficult to eliminate cyanobacteria cells.

Cyanobacteria cells are capable of producing toxins known as cyanotoxins. These toxins include endotoxins, neurotoxins, and hepatoxins. Effects of exposure include skin irritation(endotoxin), abdominal pain(endotoxin), headache(endotoxin), vomiting(endotoxin), diarrhea(endotoxin), respiratory disease(neurotoxin), paralysis (neurotoxin), liver failure(hepatoxin)and even death. Exposure to cyanotoxins can occur from swimming in infested areas, ingesting contaminated water, and inhaling toxins when near or around affected waters. It is important to note that even boiling water infected with cyanobacteria will not kill cyanotoxins.

While blue-green algae blooms are the most noticeable form of cyanobacteria bloom, benthic blooms (bottom sediment dwelling) often go undetected. Benthic cyanobacteria blooms are just as harmful as the more noticeable blooms. These blooms can be found in shallow shoreline areas where sunlight can reach the muck or soils. Light availability plays a key role in the growth of benthic cyanobacteria. Wildlife and pet illness and even death incidents caused by benthic cyanobacteria blooms have continued to climb in recent years.[Read about dog poisoning from HABs here] Harmful algae blooms as a whole are quickly becoming the largest widespread water quality concern of our generation.

Cyanobacteria directly correlates with organic sediment buildup due to its need for nutrients to survive. While nutrient loading is commonly associated with run-off or drainage, internal loading of nutrients from muck is the greater concern in many cases. Phosphorus loading in particular is linked to organic sediment. There are multiple ways that phosphorus bound within muck is making its way into the water column. Fish species like catfish and carp that inhabit bottom areas can cause phosphorus to release from sediment when searching for food. The disturbance of the ground while seeking insects, vegetation and algae causes phosphorus to release. Wave action in shallow muck infested areas can also cause phosphorus to release. While these are easy explanations, the more complex and most common source of P loading happens during summer months when water becomes stratified.

Stratification is the separation of water layers that occurs from differentiating water temperatures. Colder water will sink to the bottom of the pond due to higher density, while warmer water will remain close to the surface. When stratification occurs, there is no mixing of these layers, which leads to oxygen depletion in the greater depths due to reduced surface contact. This phenomenon allows for an increase in the diffusion of phosphorus and iron into the water column. The increase in phosphorus levels in the lake results in an increase in nutrient concentrations that can cause algal blooms and other water quality issues.

While there are many treatments for muck, prevention is the most efficient and cost-effective control method.

Managing lake sediment reverses lake aging. Think of muck management as the anti-aging cream for your lake. While muck reduction can be quickly achieved with dredging, it often comes with a hefty price tag and disruption to aquatic life. If you calculated the volume of muck in your lake, take the cubic footage of muck and multiply that by $5.50(rough estimate). For a 1 acre pond (43,560 square feet) with 6 inches of muck, the estimated cost of dredging is $119,790. These estimations can vary depending on the location and severity of the muck accumulation in your pond, but they provide a baseline for the cost of dredging.

Simplified and cost effective options include muck reduction pellets and aeration. Muck reducing pellets consist of beneficial bacteria and enzymes. The specialized formula in muck pellets consume waste naturally, but at a faster rate than bacteria that is presently living within the lake. You may ask how aeration plays a role in muck reduction. Aeration that produces adequate dissolved oxygen can break down muck. Oxygen presence at the organic material layer also reduces the release of nutrients and heavy metals into the water. In addition, circulation in muck-rich areas reduce ideal habitat for cyanobacteria and E. coli.

How to clean muck from bottom of pond

Shoreline scraping and complete pond dredging are the fastest options for pond bottom cleaning. It's important to know where the muck layer ends and the pond soil begins. Operate equipment with caution while removing material. Digging too deep can break the pond's seal, leaving you with a clean pond that doesn't hold water.

Muck takes time to dry. If sludge isn't being hauled away in containers, there needs to be enough area to stock pile material as it comes from the pond. Muck generally doesn't stack higher than 2 feet high unless it's contained. For example, if you have a 10,000 square foot pond that has a foot of muck, you will need an area of at least 5,000 square feet to place the removed sludge. If that same pond has 2 feet of muck, then you will need an area of 10,000 square feet for waste material to dry.

Alternatively, Muck Remover pellets can be utilized to consume organic waste. This solution is slower than dredging, but is far less expensive. Treating the pond with muck pellets (good bacteria) is safe for fish and wildlife. We forgot to mention that point about will lose the majority of your fish when the pond is drained. Muck Remover provides a safer solution that keeps your pond ecosystem intact while cleaning the bottom.

While lake sediment can severely impact the water quality, habitability of aquatic life, and safety of users, that doesn’t have to be the end of the story. Restoration can occur without major destruction to natural aquatic habitat or major financial burden of dredging or draining and scraping the lake bottom. Improving oxygen levels through aeration and targeting muck with beneficial bacteria restores and maintains aquatic habitats and recreational uses for generations to come.

References: Tate, Robert L. “Cultural and Environmental Factors Affecting the Longevity of Escherichia Coli in HistosolsR.” Journals.Asm.Org, aem.35.5.925-929.1978. Accessed 26 May 2023.

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