08 Apr

Duckweed (lemna minor) and Watermeal (wolfia) are invasive free-floating plants that can quickly cover the surface of a pond or small lake often blowing toward the downwind side.  In addition to making a pond or lake unsightly and not very appealing for swimming, thick growths of these plants can prevent sunlight from reaching the deeper parts of the water body. Thus reducing the ability of sub-surface plants to photosynthesize and produce oxygen, which in turn may reduce the levels of dissolved oxygen below the acceptable levels required for a healthy fish population.

Duckweed plants are about 1/8th to a 1/4 of an inch in width, so they are not very large. They are generally round in outline, with a single root hanging from each small plant.

Watermeal is the smallest flowering plant in existence and is much smaller than Duckweed. Watermeal plants look like tiny green seeds, which are less than 1/16th of an inch in diameter.  A handful of watermeal will feel gritty, like you are rubbing cornmeal or small seeds between your fingers.

Since these plants require a lot of nutrients (nitrogen and phosphorus) to grow, they are typically found in ponds and lakes where deciduous trees drop leaves into the water and/or where drainage from on-lot septic systems, animal feed lots or other nutrient-rich watersheds exist. Testing water sources for nutrients often identify the primary source.

Both Duckweed and Watermeal tend to disappear from the pond surface in late fall and reappear in the spring.  In the spring and summer, the plants are photosynthesizing. This process produces food, which is stored as starch, and oxygen, which becomes trapped in the plant body and provides buoyancy. In the fall, the accumulated starch makes the plants heavier, and as photosynthesis slows down and less oxygen is produced, the plants lose buoyancy. They sink to the sediments where they overwinter, relying on stored starch for energy. In the spring, the plants start photosynthesizing again and the accumulated oxygen causes them to rise to the surface.

Given enough nutrients, duckweed and watermeal can reproduce by budding prolifically to cover an entire pond within a few weeks after coming to the surface.

Lochness Pond & Lake Dye in ether blue or black can be utilized to retard the sun’s ray’s ability to penetrate the water-body reducing the plant’s ability to photosynthesize. Dye is not recommended for fast flowing or quick turnover bodies of water. It is however suitable for use in sewage lagoons and shallow or muddy lakes and ponds.

Chemicals can be used to kill duckweed and watermeal and can be effective in clearing the pond or lake surface. However, as the chemicals kill the plants and the plants decay the process utilizes oxygen.  On the bottom, this reduction of oxygen releases additional nutrients to the already nutrient rich water-body. Thus oxygen levels are reduced and nutrient levels are increased.  This process may then lead to fish kills and/or additional algae and weed growth.

To develop a long term water quality plan to effectively control duckweed, watermeal and other invasive weeds and algae, nutrient levels must be reduced and controlled. As a part of this process both a watershed and water-body plan are essential.  Just as in the human body, it is important to control the nutrients that go into the body as well as how you process them for maximum health.  The process in a water-body is very similar, and not surprisingly oxygen is a key component.

Oxygen is the most important constituent of lake or pond health.  Oxygen is an essential element for all aquatic organisms that breathe.  Therefore, there is a direct relationship between the oxygen concentrations and exchanges occurring in a lake or pond, and the physiological status of aquatic organisms.

Without oxygen at the bottom of a pond or lake, anaerobic bacteria (those that live without oxygen) produce an acid environment.  These acids not only increase acidity, but also cause a massive release of phosphorus and nitrogen, two major fertilizers, from the organic sediment into the water column of the pond or lake.  These fertilizers feed duckweed and watermeal increasing their quantity and density.

These same anaerobes put toxic gases into the water including hydrogen sulfide (that rotten egg smell), ammonia and methane that kill beneficial bacteria and insects that would feed on the bottom organic sediment and biodegrade it into carbon dioxide, water and a tiny amount of inorganic ash.  This ash is beneficial in reducing acidity.

Lack of oxygen can cause fish kills or prevent fish from feeding on benthic (bottom feeding) insects.

Without oxygen at the bottom at all times, beneficial bacteria and insects cannot biodegrade the organic sediment.  Large accumulations of organic sediment follow.

The CLEAN-FLO Process of Water and Lake Restoration provides a custom solution for providing aeration in your water-body from bottom to top.

With the availability of oxygen, a specific combination of beneficial bacteria and enzymes are recommended to control duckweed and watermeal:

LAKE CLEAR:  a proprietary blend of bacteria and enzymes to control and reduce ammonia and nitrite in water.

C-FLO – a proprietary formulation of beneficial microorganisms that feed on organic sediment (muck).