What could happen if Oxygen were to disappear for 5 Seconds?

I Don't know if the answers provided below are 100% accurate, but it sure makes one start to think about the SERIOUS IMPLICATIONS of loss of the Phytoplankton populations in the world oceans on the Global O2 cycles? 

BETTER START THOSE BREATHING EXERCISES NOW!

What Would Happen if Oxygen Were to Disappear for Five Seconds?
This question originally appeared on Quora.

Answer by Andrew Cote, science junkie:

A few things ...

• Everyone at the beach would get sunburns. Ozone is molecular oxygen and blocks the majority of UV light. Without it, we are toast.
• The daytime sky would get darker. With fewer particles in the atmosphere to scatter blue light, the sky would get a bit less blue and a bit more black.
• Every internal combustion engine would stall. This means that every airplane taking off from a runway would likely crash to the ground, while planes in flight could glide for some time.
• All pieces of untreated metal would instantly spot-weld to one another. This is one of the more interesting side effects. The reason metals don't weld on contact is they are coated in a layer of oxidation. In vacuum conditions, metal welds without any intermediate liquid phase (Cold welding).
• Everyone's inner ear would explode. As mentioned, we would lose about 21 percent of the air pressure in an instant, equivalent to being teleported to the top of the high Andes (elevation, about 2,000 meters).
• Every building made out of concrete would turn to dust. Oxygen is an important binder in concrete structures (really, the CO2 is), and without it, the compounds do not hold their rigidity.
• Every living cell would explode in a haze of hydrogen gas. Water is one third oxygen; without it, the hydrogen turns into gaseous state and expands in volume.
• The oceans would evaporate and bleed into space. As oxygen disappears from the oceans' water, the hydrogen component becomes an unbound free gas. Hydrogen gas, being the lightest, will rise to the upper troposphere and slowly bleed into space through Atmospheric escape.
• Everything above ground would immediately go into free fall. As oxygen makes up about 45 percent of the Earth's crust and mantle, there is suddenly a lot less "stuff" beneath your feet to hold everything up.

To sum, it wouldn't be pretty.
More questions on Atmospheric Science:
www.slate.com/blogs/quora/2013/03/19/what_would_happen_if_oxygen_were_to_disappear_for_5_seconds.html