Does algae need sunlight

[richierich]

Random question here. I've read on this forum conflicting statements. I've seen people say algae needs sunlight to grow. However, based on reading some posts I'm not sure if that's true. Here are some examples.

1) I've read people saying they just bought a house and the pool has been covered for 2 years but it's a swamp
2) Why does it matter if you open your pool when the water temp is below 60? If you have a solid cover on it with no sunlight algae can't grow right? Even if your chlorine level is zero, theoretically there should be no algae. However I've read people saying they closed their pool clear but opened in June and there was algae....


Thanks

 

[Texas Splash]

Here's a great discussion on that very issue: Does Algae like sun or not?.

- - - Updated - - -

Remember, chlorine will eventually get consumed (cover or not) which is why some posts speak of swamps after opening. Colder water makes it harder for organics to grow. Proper closing is critical to opening to clear water. Follow the tips on the Pool School - Closing an In Ground Pool and you will do fine.

 

[JamesW]

Point #1: The pool might have been covered/closed with algae already in the pool.
Point #2: As long as there is 100% sun blockage, algae shouldn't be able to grow. However, many safety covers allow some light to get through.

 

[richierich]

Yeah I follow all that and close and open clear. THanks. It was just more of a weird question that popped into my head. I still think that algae can grow in complete darkness with zero chlorine. I have a friend that closed last year in September with clear water. They likely had low chlorine. Then opened in late June and the pool had algae. I saw the cover it was complete darkness in the pool. So I think algae can grow without sun?

 

[JamesW]

Algae needs light for photosynthesis. In complete darkness, algae shouldn't be able to grow.

 

[duraleigh]

Photosynthesis is the process by which organisms use sunlight to produce sugars for energy. Plants, algae and cyanobacteria all conduct oxygenic photosynthesis. That means they require carbon dioxide, water, and sunlight (solar energy is collected by chlorophyll A)

Yep, Algae requires SOME light.

 

[Poolzzz]

Does that mean there are no known cases of algae in solar panels, plumbing, or filters?

 

[JamesW]

Algae can grow in sunlight and then get into the system.

Bacteria can also get in the system.

 

[Poolzzz]

Algae can grow in sunlight and then get into the system.

But then the algae dies, right?

 

[JamesW]

Doing some research, it seems that some genetically modified algae can grow in darkness if they can eat glucose. But, that's only specific algae and you would need glucose in the water.

I don't know how fast algae dies in complete darkness. It needs light to grow, but it might be able to survive for an extended time if it goes into some sort of hibernation.

Maybe a microbiologist would know the specifics.

 

[Poolzzz]

I don't know how fast algae dies in complete darkness... it might be able to survive for an extended time if it goes into some sort of hibernation.

Probably true.

Some species survived on the outside of the Space Station in space for 16 months. Others are known to survive under the polar ice cap in darkness for months at a time. And certain micro algae can survive in deep ocean without light or oxygen.

But there's limited biomass production in those cases.

If something similar happens in our solar panels etc I doubt we'd ever notice.