wrote:
Estimates of global photosynthesis by NASA, the Intergovernmental Panel
on Climate Change and others are that roughly 50% occurs in the oceans
and 50% occurs on land. I have seen older textbooks with estimates
60/40 both ways so estimates vary. The current 50/50 estimates may
change as more accurate techniques to measure global photosynthesis are
employed.

http://www.nasa.gov/home/hqnews/2005...o_problem.html
http://www.newstarget.com/005139.html
http://www.noc.soton.ac.uk/JRD/SCHOO...phsynth01.html

The oceans are about twice the area of land but ocean photosynthesis is
often lower than on land as the color maps in the following NASA
website indicate:

http://earthobservatory.nasa.gov/Newsroom/NPP/npp.html

David R. Hershey

Hum... But doesn't the land trees use more oxygen than the bacterias and
algas (i'm not sure about the name of it in english)? Then wouldn't the
relation (oxygen produced)/(oxygen used) be greater in the ocean?