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The lakes and ponds are becoming covered with algae. In checking the lake at Mt. Pisgah State Park, I found a lot of duckweed floating on the surface of the water, giving the lake an uninvited appearance.
Our word algae comes from the Latin word alga, meaning seaweed. Algae, which are often referred to as either pond scum or pond moss, form a greenish mat on the water's surface. Although algae and scum are not the same, they are both commonly referred to as scum. The scum that forms on the bottom and sides of a pond becomes buoyant and floats to the surface due to the oxygen bubbles it has produced. This pond scum can quickly cover the surface of the water, giving the pond a dirty appearance.
Algae are plants, such as duckweed, watermeal, water hyacinth, water lettuce, milfoil, hydrillia and curly-leaf pondweed that grow on top of the water.
Although the green pond scum seen growing on the water does not look appealing, it is important for a healthy lake. Algae uses sunlight (through photosynthesis) to produce carbohydrates, which are eaten by zooplankton, such as water fleas. In turn, zooplankton are fed upon by small fish that are eaten by bigger fish and this continues on up the food chain. Algae are the base of the food chain and essential to life in both lakes and ponds. Not only is it a lake, with large fish, a fisherman's delight, wildlife and waterfowl also find refuge in the area of the lake.
The definition of the word scum is a film or layer of foul or extraneous matter that forms on the surface of a liquid. Someone committing a heinous act is often said to be the scum of the earth. Our word scum comes from the German word schaum, meaning foam. Algae come in all forms: the green slime appearing on rocks in a stream; the pea green soup seen on top of the water and the floating mats of green.
Algae come in many colors: red, brown, blue-green and green. There are the very small plants that grow on top of the water that are considered a form of algae. Duckweed is the main source of food for waterfowl, fish and several other animals that live in the water. There are nine species of duckweed that occur in North America, with common duckweed (Lemna minor) being the most common and most widespread. Another common alga is the watermeals.
Algae grow when conditions such as the following exist: adequate nutrients (mostly phosphorus with some nitrogen), light, pH and warm temperature so generally, phosphorus controls the amount of algae and the more nutrient-enriched a lake or pond becomes, the more algae in the water.
Duckweed and watermeal are the smallest flowering plants known. An individual plant consists of a single oval leaf (technically, a modified stem) that floats on the surface of still-moving ponds and lakes. Duckweed has two staminate flowers and one tiny pistillate flower in a pouch-like sac. It is believed that duckweed flowers are modified versions of the spadix of the skunk cabbage and Jack-in the pulpit plants.
There are those that believe the duckweed should be in the Arum family, along with the skunk cabbage and jack-in-the-pulpit. Although the small flowers of algae are cross pollinated by flies, mites, spiders and even bees, the duckweed can also be pollinated by the wind when two plants are blown together, jarring loose pollen onto the receptive stigma. The duckweed plants have roots, while watermeal plants do not.
Duckweed and other algae, such as watermeal, can completely cover the surface of a pond for an extended period of time and cause oxygen depletion, killing fish and blocking out the sunlight, which eliminates submerged plants.
Watermeal plants appear as tiny green seeds, each less than 1/16th of an inch in width. A handful of watermeal will feel gritty, being compared to rubbing cornmeal (or grits) between your fingers. Since duckweed is a favorite food of ducks, the plant is carried from one pond/lake to another by adhering to their feathers.
Although duckweed can be a nuisance to man, scientists have recently come to appreciate this fast growing plant. The duckweed helps to remove the excess amounts of phosphorus and nitrogen from agriculture runoff in waterways. The duckweed plant is then harvested to be used as food for livestock and as fertilizer. Researchers are using duckweed to make synthetic insulin.
Duckweed, being a plant, is immune to animal viruses that make the plant invaluable in creating new biomedicines.
Bill Bower is a retired Pennsylvania Game Commission Wildlife Officer. Read his blog and listen to his podcasts on the outdoors at www.onemaningreen.com.