Rafael Almeida wrote in
:

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/feb/HQ_05042
_bio_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?

That ratio might be greater, but remember that the ocean is a
nutrient poor environment. Low levels of Iron especially limit
growth. That accounts for the lower levels of photosynthesis in the
oceans.

Sean