States and municipalities across the country have spent billions of dollars to create an infrastructure to deliver safe drinking water to the public. Part of this money goes toward keeping reservoir water clean and non-toxic. Some forms of algae can create a challenge to water systems by producing toxins that can have unpleasant, and even serious, health effects. Other types of algae are benign and actually improve water quality.
Blue-green algae are unicellular photosynthetic organisms that can inhabit fresh and salty waters, as well as damp soil and rocks, everywhere on Earth. These organisms are not true algae but rather are a type of bacteria known as cyanobacteria. These little creatures can form blooms on the surfaces of bodies of water that earn them the nickname 'pond scum'. Blooms of blue-green algae can endanger drinking water by producing toxins that if ingested can cause illness and even death.
Some Good, Some Bad
Some cyanobacteria—those that don't produce toxins—can actually improve the quality of bodies of water by converting carbon dioxide into oxygen and by making nitrogen available to plants, a process called nitrogen fixation. These actions support the growth of plants and the animals that eat them. However, some cyanobacteria excrete poisons into the surrounding waters that can cause various symptoms if contacted or ingested. The types and amounts of these poisons, or cyanotoxins, produced depend on the species of cyanobacteria and the size of the bloom. When a bloom dies off, the decomposing algae attract non-photosynthetic organisms that can deplete oxygen from the water.
Effects of Cyanotoxins
The U.S. Environmental Protection Agency has identified numerous toxins produced by certain types of blue-green algae. Ingested cyanotoxins that attack the liver can create abdominal pain, vomiting, diarrhea, an inflamed and bleeding liver, pneumonia or kidney damage and might even promote tumor growth. Another set of cyanotoxins attacks the nervous system and can cause tingling, numbness, a burning sensation, drowsiness, incoherence, paralysis or death. Skin contact with cyanotoxins can cause irritation of the skin, eyes, throat, nose or respiratory tract.
True algae are single-celled plants that can form composite organisms, such as seaweed and kelp. Different species of algae can be green, red or brown. True algae can live in freshwater or marine environs and are generally less likely to produce toxins than are blue-green algae. However, certain varieties of true algae called dinoflagellates can form large masses known as red tides that can produce substantial quantities of toxins. Some dinoflagellates live in fresh drinking water and can poison fish and shellfish. Eating poisoned shellfish can be toxic or fatal to humans. Although algae in drinking water is generally harmless, it's best to be on the safe side—wash filtered-water pitchers, camping water containers and pet bowls with bleach, and keep them out of the sun.