Reading Marine Biology, I realised I had been errornous for the most part of my subadult life. I had always thought (what I had been taught) that oceans, due to their large size, contribute most to the primary production on the planet.
I now believe this is not the case. While oceans may be vast, compared to minute earth patches, there are some short falls. First, photosynthetic organisms in water are not as dense on land (meaning chl is not spread over 100% (or more) of the available surface). This means that they use about 7% of PAR (photosynthetically available radiation), compared to 31% on land. Moving on the the next point, a fairly reach upper meter of agricultural soil has about 0,5% nitrogen. This is sufficient to grow about 50kg of dry organic matter. As a second point, ocean waters are, compared to land, fairly poor in nitrogen (as NH4+, NO3 or NO2) - about 0,00005%/m3, which is enough to grow about 5 g of dry organic matter. While oceans are deep, there are limitations light penetrating wise. Not all light passes down to the ocean floor. There is a term used compensation depth where just enough light is available to put photosynthesis and respiration into an equillibrium. This of course varies from organism to organism, and is effected by numerous other factors, such as turbidity, season, atmospheric conditions, water mixing… Due to all these factors, mass photosynthesis is confined within about 3,5 m from surface.
Bringing out final numbers, plants on land produce about 56,5 × 1015 grams, while oceans produce about 48,5 × 1015 of carbon. As we can see, numbers are, despite vast difference in land/water ratio, very close. I don’t know what has been included in the model and what not (such as deserts and poor non-agricultural land). The answer probably lies in two pages of references at the end of the chapter. An article in Nature from 1998, volumne 281 on pages 237-240, Primary production of the biosphere: Integrating terrestrial and oceanic components.
While searching for viable reference on this at the bibliography section at the end of Chapter two, I came across a duplicated reference. I noticed this because I read about bacterial rhodopsin (protorhodopsin) and subsequently did a few searches online. As I was reading through the references, I noticed that the same article was attributed to two authors. Here are the two references:
Spudich, J. et. al. 2000. Bacterial rhodopsin: Evidence for a new type of phototrophy in the sea. Science 289: 1902-1906
Beja, O. et. al. 2000. Bacterial rhodopsin: Evidence for a new type of phototrophy in the sea. Science 289: 1902-1906
I’ll email the editor and see what’s up with this.