mi·​cro·​cys·​tin | \ ˌmī-krə-ˈsi-stin How to pronounce microcystin (audio) \

Definition of microcystin

: any of various toxins that are produced by freshwater cyanobacteria (genus Microcystis, especially M. aeruginosa), have hepatotoxic effects in animals including humans, and may occur in large quantities and contaminate water supplies during algal blooms (see bloom entry 2 sense 1d) … two water samples from a Toledo treatment plant tested positive for microcystin, a toxin possibly caused by an algae bloom in Lake Erie. Residents were told not to drink, or even boil, the water tainted with microcystin, which can cause nausea and impair liver function.— Lauren Raab When cyanobacteria die, they release microcystin, and scientists have found that remaining cyanobacteria respond to the molecule by making more of their own.— Carl Zimmer

Examples of microcystin in a Sentence

Recent Examples on the Web

Algae doesn’t always pose a health or environmental risk, but cyanobacteria can produce a toxin called microcystin that, if consumed, can damage the liver and irritate the skin, eyes and throat, according to the U.S. Environmental Protection Agency. Maya Sweedler, WSJ, "Florida Fights Giant Algal Bloom in Lake Okeechobee," 16 July 2018 As the weather warmed, the bloom grew and developed toxins — specifically, the cyanotoxins known as cylindrospermopsin and microcystin. Everton Bailey Jr., OregonLive.com, "1 dead, several injured in 3-car crash near Woodburn," 7 June 2018 On Friday, results from June 25, the latest posted, showed microcystins only at two locations, in Moore Haven and LaBelle, and at much lower levels. Jenny Staletovich, miamiherald, "Massive and toxic algae bloom threatens Florida coasts with another lost summer," 29 June 2018 The toxins, called microcystins, can cause liver damage among other adverse health effects in humans. National Geographic, "250,000 Football Fields of Green Algae Now Cover Lake Erie," 3 Oct. 2017 These blooms can produce a toxin called microcystin, which causes a number of health effects in humans, ranging from rashes and diarrhea to liver damage. Emily Matchar, Smithsonian, "Underwater Robot Labs Monitor Toxins," 10 Aug. 2017

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'microcystin.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

See More

First Known Use of microcystin

1965, in the meaning defined above

History and Etymology for microcystin

New Latin Microcystis, a species of cyanobacteria (from micro- micro- + Greek kýstis "pouch, bladder") + -in entry 1 — more at cyst

Keep scrolling for more

Learn More about microcystin

Statistics for microcystin

Look-up Popularity

Time Traveler for microcystin

The first known use of microcystin was in 1965

See more words from the same year

Comments on microcystin

What made you want to look up microcystin? Please tell us where you read or heard it (including the quote, if possible).


having a desire to acquire more things

Get Word of the Day daily email!

Test Your Vocabulary

Words for Summer: A Quiz

  • a closeup of a sunflower
  • Which of the following words means “of or relating to summer”?
How Strong Is Your Vocabulary?

Test your vocabulary with our 10-question quiz!


Test Your Knowledge - and learn some interesting things along the way.

Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!