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Planktonic AlgaePlanktonic algae float in the top layer of your pond's water. They are made up of tiny plants that make the water appear pale green to brown. The presence of this algae can cause an unpleasant odor in your pond. Planktonic algae can deplete your pond water of oxygen. Without oxygen, aquatic creatures in your pond may die. There also are some species of this algae that may be toxic to animals and humans.
Common planktonic genera include Anabaena, Chlorella, Pediastrum, Scenedesmus and Oocystis. Resistant AlgaeMany common algaes are controlled easily with algaecides, but resistant algae are those that are extremely difficult to control because they have protective mucilage that resists penetration from chemicals. Resistant algae may be one of two types: Lyngbya or pithophora.
Lyngbya algae species form green, black or gray clumps made up of thousands of cells that may be found on the bottom of the pond or floating along the surface. Pithophora is a dark green filamentous algae often referred to as horsehair algae. It grows in coarse, tangled clumps of filaments that resemble steel wool. Because of its high production of reproductive cells, pithophora algae grow prolifically on the bottom of ponds, and sometimes on the water’s surface.
An assortment of bird species in North America use their skills to capture and eat fish, with fish composing most or part of their diets. These fishing birds inhabit areas close to the ocean or inland locations in proximity to lakes, ponds, rivers and streams. Some of these birds capture their finned prey from above.
Toxic AlgaeToxic algae typically are blue-green bloom-forming species that can cause illness or death to pets, wildlife, plants and humans by producing poisonous substances from within the cells. Many unattended or poorly maintained ponds contain some of these toxic algae forms. After contact with these algae, whether through ingestion or contact, symptoms, such as rashes and headaches; stomach issues, such as nausea, vomiting and diarrhea; fever, body pains, and eye, nose and throat irritation can occur. Cultural ControlChemical algaecides can provide short-term control of most types of pond algae, but this is not an ideal long-term solution. Algae typically are bacteria, and are capable of rapid growth and reproduction, so the nutrients released on the death of treated algae may only result in more of the same species. Decaying algae also consume oxygen from the water, which is needed by valuable plants and aquatic creatures.
A better solution is to reduce the amount of phosphorus and nitrogen entering the pond. Leave a 25- to 50-foot wide buffer of undisturbed, grassy vegetation around the edge of the pond. Do not apply nutrients in the form of fertilizers or organic material to this buffer zone. Ponds without this buffer can erode, and sediments enter the pond carrying nutrients that algae can use to establish itself.