# How does air get into kelp air bladders?

**URL:** <https://boards.straightdope.com/t/how-does-air-get-into-kelp-air-bladders/718868>\
**Category:** Factual Questions\
**Created:** [April 30, 2015, 3:30am UTC](https://boards.straightdope.com/t/how-does-air-get-into-kelp-air-bladders/718868 "2015-04-30T03:30:27Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![CC](https://avatars.discourse-cdn.com/v4/letter/c/f1d935/32.png) [@CC](https://boards.straightdope.com/u/CC)\
**Post date:** [April 30, 2015, 3:30am UTC](https://boards.straightdope.com/t/how-does-air-get-into-kelp-air-bladders/718868/1 "2015-04-30T03:30:27Z")

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These structures form underneath the surface of the water. They’re called air bladders and maybe they do have air in them, but if the gas is air, where did it come from? Or, if it’s some other gas, where did that gas come from? Do the cells that line these bladders extract gasses from the water? Is it O2 resulting from photosynthesis? PURE Oxygen? How do these little structures form underwater with pockets of gas inside them? Where’s the gas come from?

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**Author:** ![naita](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/naita/32/5862_2.png) [@naita](https://boards.straightdope.com/u/naita)\
**Post date:** [April 30, 2015, 5:48am UTC](https://boards.straightdope.com/t/how-does-air-get-into-kelp-air-bladders/718868/2 "2015-04-30T05:48:24Z")

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They’re plants and, as you say, photosynthesis produces excess oxygen, plants also produce carbon dioxide when it’s dark. My WAG is that the surrounding cells expirate into the bladders.

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**Author:** ![eburacum45](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/eburacum45/32/8690_2.png) [@eburacum45](https://boards.straightdope.com/u/eburacum45)\
**Post date:** [April 30, 2015, 7:52am UTC](https://boards.straightdope.com/t/how-does-air-get-into-kelp-air-bladders/718868/3 "2015-04-30T07:52:00Z")

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This seems to be a partial answer;

> **[Algae](https://books.google.co.uk/books?id=uazMBQAAQBAJ&pg=PA101&dq=gas%2Bpneumatocyst&hl=en&sa=X&ei=AdxBVcmFK8faaLeIgNAI&ved=0CDYQ6AEwAw#v=onepage&q=gas%20pneumatocyst&f=false)**
>
> A single-source reference on the biology of algae, Algae: Anatomy, Biochemistry, and Biotechnology, Second Edition examines the most important taxa and structures for freshwater, marine, and terrestrial forms of algae. Its comprehensive coverage goes...

> [@](#):
>
> Oxygen and nitrogen, in roughly the same proportion as in air, form the bulk of the gas, but there are also small, variable amounts of CO2 and CO. Oxygen and CO2 derive partly from metabolic activities in the cells of the pneumatocyst wall, and diurnal changes in the composition and pressure of pneumatocysts have been shown. However equilibriation takes place between the surrounding water (or air). This is the source of nitrogen, and also the major source of O2 and CO2

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Carbon monoxide appears to be a minor metabolic product.

In other words air passes from the water into the bladder through the walls of the structure. I’m still not quite clear how these pneumatocysts are inflated against water pressure; maybe it is the mechanical strength of the bladder that prevents collapse. But there must be an active process going on, or the gases would pass out of the cyst just as readily as they pass in, and the cyst would deflate.

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**Author:** ![johnpost](https://avatars.discourse-cdn.com/v4/letter/j/f17d59/32.png) [@johnpost](https://boards.straightdope.com/u/johnpost)\
**Post date:** [April 30, 2015, 2:00pm UTC](https://boards.straightdope.com/t/how-does-air-get-into-kelp-air-bladders/718868/4 "2015-04-30T14:00:50Z")

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could be puffer fish making shade.