For your second breath, thank plankton Featured
notes: For more on the contribution of phytoplankton, see "Source of half the worlds' oxygen gets little credit.", National Geographic. Of course, in addition to adding oxygen, they take up CO2 from the atmosphere.
Special thanks to Brian Ettling, for bringing this idea to my attention.
source: inspired by Marlene Cimons, National Science Foundation, in A Center to Study Oceans and Climatee, US News & World Report,
image source: Coccolithophores, a common type of phytoplankton, via BBC
May 28, 2012