Hello, Adeyemi,

Four years ago, I taught an optional Marine Biology class at the University of Cyprus that was very well attended. I wanted to introduce the junior and senior Biology students to the incredible abundance of microorganisms, and sought supporting documentation for exactly such statements, as the one you are asking about.

The source I ended up using was a 2007 paper by Larry Pomeroy and colleagues in the Oceanography magazine. The article citation is:

Pomeroy, L.R., P.J. leB. Williams, F. Azam, and J.E. Hobbie. 2007. The microbial loop. Oceanography 20(2):28–33, http://dx.doi.org/10.5670/oceanog.2007.45.

And here is a link to the article on The Oceanography Society web-site, where you can download the paper:

http://www.tos.org/oceanography/archive/20-2_pomeroy.html

Make sure you check out Figures 1 and 2 on page 30. I think you will like them.

Best regards,

Angelos

Hello, Adeyemi,

Four years ago, I taught an optional Marine Biology class at the University of Cyprus that was very well attended. I wanted to introduce the junior and senior Biology students to the incredible abundance of microorganisms, and sought supporting documentation for exactly such statements, as the one you are asking about.

The source I ended up using was a 2007 paper by Larry Pomeroy and colleagues in the Oceanography magazine. The article citation is:

Pomeroy, L.R., P.J. leB. Williams, F. Azam, and J.E. Hobbie. 2007. The microbial loop. Oceanography 20(2):28–33, http://dx.doi.org/10.5670/oceanog.2007.45.

And here is a link to the article on The Oceanography Society web-site, where you can download the paper:

http://www.tos.org/oceanography/archive/20-2_pomeroy.html

Make sure you check out Figures 1 and 2 on page 30. I think you will like them.

Best regards,

Angelos

These might be of help:

Whitman, W.B. et al (1998) Prokaryotes: The unseen majority. PNAS June 9, 1998

vol. 95 no. 12        

http://www.pnas.org/content/95/12/6578

Partensky, F. et al. (1999) Prochlorococcus, a Marine Photosynthetic Prokaryote of Global Significance. Microbiol. Mol. Biol. Rev. March 1999 vol. 63 no. 1 106-127

http://mmbr.asm.org/content/63/1/106.full

You might also find relevant information about the diversity and significance of microbes in the ocean here:

Rusch DB, Halpern AL, Sutton G, Heidelberg KB, Williamson S, et al. (2007) The Sorcerer II Global Ocean Sampling Expedition: Northwest Atlantic through Eastern Tropical Pacific. PLoS Biol 5(3): e77. doi:10.1371/journal.pbio.0050077

http://journals.plos.org/plosbiology/article?id=10.1371/journal.pbio.0050077

There is a large batch of publications related to the mass balance models like ECOPATH. No one of them estimates biomass of microorganisms at 95%. The are several examples:

Bering Sea: phytoplankton - 11.0 (2.7% of total biomass), bacteria & protozoans - 20 t/sq. km (5.0%). Total biomass - 402.8 t/sq. km. Aydin K.Y., Lapko V.V., Radchenko V.I., Livingston P.A. A comparison of the eastern and western Bering Sea shelf and slope ecosystems through the use of mass-balance food web models. NOAA Technical Memorandum, NMFS-AFSC-130. 2002. 78 pp. 

Okhotsk Sea: phytoplankton - 40.25 (6.4% of total biomass), bacteria & protozoans - 11.3 t/sq. km (1.8%). Total biomass - 624.35 t/sq. km. Basic reference for protozoans and bacteria biomass: Sorokin, Y.I.; Sorokin, P.Y. Production in the Sea of Okhotsk. J. of Plankton Research. 21(2), 1999, pp. 201-230. 

North Sea: phytoplankton - 7.5 (1.3%), planktonic microflora - 3.037 (0.5%), benthic microflora - 0.065 (0.01%) t/sq. km. Total biomass - 573.7 t/sq. km. Mackinson S. 2001. Representing trophic interaction in the North Sea in the 1880s using the Ecopath mass-balance approach. In: Guénette S., Christensen V., Pauly D. (eds.). Fisheries Impacts on North Atlantic Ecosystems: Models and Analyses. Fisheries Centre Research Reports. 2001. Vol. 9. No. 4: 35-98.

Northern Humboldt Current Ecosystem under La Niña: phytoplankton (diatoms) - 53.416 (17.7%), protozoans (dino- and silicoflagellates) - 9.426 (3.1%), heterotrophic microzooplankton - 20.484 (6.8%) t/sq. km. Total biomass - 302.29 t/sq. km.

The same area under El Niño conditions: phytoplankton (diatoms) - 14.761 (6.7%), protozoans (dino- and silicoflagellates) - 17.328 (7.8%), microzooplankton - 6.572 (3.0%) t/sq. km. Total biomass - 221.65 t/sq. km. Tam J., Taylor M.H., Blaskovic V., Espinoza P., Ballón R.M., Díaz E., Wosnitza-Mendo C., Argüelles J., Purca S., Ayón P., Quipuzcoa L., Gutiérrez D., Goya E., Ochoa N., Wolff M. Trophic modeling of the Northern Humboldt Current Ecosystem, Part I: Comparing trophic linkages under La Niña and El Niño conditions // Progress in Oceanography. 2008. 79: 352–365. 

I feel that "95% of ocean biomass" is largely overstated to attract attention to importance of microflora in the oceanic food webs. 

@ Vladimir Radchenko,

If what you say is correct,then how does one explain the base of the ecological pyramid for the two base levels of primary producers & the first trophic level,which together constitutes the majority of ecological energy,numbers & biomass. 

Moreover the readings from the vast neritic zone needs to be taken into account, as the values therein are invariably more than in some of the oceanic zones.

Maybe you find what you are looking for in "Nature 415: 572-574 (2002)", or even in a text book "Kirchman, D.L.: Microbial ecology of the oceans; J. Wiley (2008)". There might be additional relevant references in these publications.

I doubt any paper will give you clear evidence because it is practically impossible to measure all the biomass in the ocean. What you can do is a back-of-an-envelop calculation to illustrate the relative biomass of different groups of organisms. Before you go further, you have to clearly define "microorganisms"--- is it just "bacteria" or is it all microscopic organisms that include viruses, prokaryotes and small eukaryotes? Once you have a clear definition, then:

1. Find out how many individuals of different types of organisms you expect to find in a parcel of water. For example, a good "average" number for marine bacteria is 10^5 to 10^6 cells per ml. You'll have to imagine a much larger parcel of water to find large animals.

2. Find out the "average" individual biomass of the organisms. The number is not constant but for this purpose you can use some average values from the literature.

3. Then calculate the total biomass contributed by the different groups, and you should be able to find out what percentage is accounted for by "microorganisms".

To one of the comments, the concept of "biomass pyramid" can be misleading because it does not account for turnover rate. Microorganisms can be very productive in the ocean but their populations also have a high turnover rate, giving an appearance of low standing stock.