*  Upper photo: Fill a Liquemin bottle  - as high as possible-
   whith cold water, * puncture the stopper by a hypodermic needle
* Press the stopper on the bottle without leaving an air bubble inside. * Remove the needle.
* Leave the bottle with water at a warm place.
* Observation (lower part of the photo): Small gas bubbles have appeared.
Explanation: Water cannot dissolve much air. If water gets warm the solubility decreases.
Organisms in fresh water and in salt water may suffer from a lack of air if water gets warm.