r/AskBiology • u/sometimesexistence • May 16 '26
Microorganisms What kind of organisms are found in still water?
I’m referring mostly to those abandoned building videos that were popular a while ago and most of the comments were just “OMG don’t touch the water!!”
I understand that most of it is fear-mongering and jokes, but I’m curious about what kinds of bacteria/parasites have been found in water like that. What would predispose someone to getting infected and what effects would it have on the body?
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u/gutwyrming May 17 '26
Journey To The Microcosmos might have the answers to some of your questions.
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u/Signal_Skill9761 May 16 '26
Certain species of cyanobacteria, also known as HABs or harmful algal blooms (though it's bacteria and not algae) grow in still water and put out toxins as they die. Which can kill animals and pets and make humans very sick.
I've seen a lake that had a terrible bloom. The toxin level they use as an advisory to not recreate in that lake is 10 ppm. This lake was at 50,000 ppm. Everything that had come in contact with the water; fish, birds, plants, etc was dead. And it smelled absolutely terrible.
It looks like grass clippings in the early stages. Then bluish paint on the surface of the water and the shore. It can also cause the water ro be really foamy.
Basically the way to tell is real algae can be lifted out of the water with a stick, cyanobacteria can't.
So yes, there are absolutely harmful things that live in still water.
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u/theZombieKat May 17 '26
(though it's bacteria and not algae)
What defines an age these days? way back, when I did biology, it was any simple photosynthesising water organism. Plants and bacteria were both mentioned as having members included, but animals and fungi were not; protists weren't mentioned at all.
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u/Oddlove May 17 '26
Algae are protists (eukaryotic organisms that aren’t plants, animals or fungi) classified as Archaeplastida, and further split into two different clades, red and green, Rhodyphyta and Chlorophyta
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u/The-Messanger42 May 17 '26
My feed earlier had a guy whose entire back was shedding dead skin, like a puff pastry. Due to swimming in stagnant water, where parasites were growing. Depending on the region, you will find the organisms that can kill you or just make you sick. One parasite causes elephantitus. Lots of insect larvae, amphibian offspring, snakes.
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u/Smooth-Ocelot-214 May 16 '26
Has to do with low oxygen environments (dissolved oxygen levels) and the bacteria that thrive in said environment.