The Microbial Loop
Lawrence R. PomeroyODUM School of Ecology , University of Georgia
The Ocean’s Food Web, A Changing Paradigm1974
Methodical Limitations
• AODC developed in the mid to late 1970’s
• DAPI 1980’s
• Bacterial production (rudimentary) 1980’s
Bacterialconcentrations
beforeepiflourescent
microscopy
Bacterialconcentrations after
epiflourescentmicroscopy
Coined the term “Microbial Loop”
Important for the recycling of organic matter and nutrients above the thermocline
Something else?1988 Prochlorococcus was discovered
Very small autotroph (Cyanobacteria, uses chlorophyll b)
Present in high abundance in the ocean, especially in oligotrophicareas
Why is this important• Base of the food web
• Hetertrophic and autotrophic bacteria are asignificant percentage of the total biomass of theocean
Pomeroy et al 2007
Why is this important• Base of the food web• Hetertrophic and autotrophic bacteria are a significant percentage of
the total biomass of the ocean
• Carbon cycling– ½ of global primary production occurs in the
ocean• How is this carbon used and how does it move
through the system?
Works Cited• Azam, F. 1993. Bacteria-Organic Matter Coupling and Its Significance for Oceanic Carbon Cycling.
Microbial Ecology. 28: 167-179.• Azam, F. 1998. Microbial Control of Oceanic Carbon Flux: The Plot Thickens. Science, New
Series.280.5364:694-696• Azam, F. 2007. Microbial structuring of marine ecosystems. Nature Reviews.,5:782-793• Azam, F., Fenchel, T., Field, J.G., Gary, J.S., Meyer-Reil, L.A., and Thingstad, F. 1983. The
Ecological Role of Water-Column: Microbes in the Sea. Mar. Ecol. Prog. Ser., 10:257-263.• Caron, D.A. 1994. Inorganic Nutrients, Bacteria, and the Microbial Loop. Microbial Ecology.28:
295-298• Pomeroy, L.R.1974. The Ocean’s Food Web, A Changing Paradigm. BioScience, 24.9:499-504.• Pomeroy, L.R., Williams, Peter J, Azam, Farooq, and Hobbie John E. 2007. Oceanography,
20.2:28-33.
Why is this important• Base of the food web, hetertrophic and autotrophic bacteria are a
significant percentage of the total biomass of the ocean• Carbon cycling
– Eutrophic systems microbial community acts as a sink fororganic C (respired as CO2)
– Oligotrophic system microbial community acts as a direct linkbetween trophic levels
Why is this important• Base of the food web, hetertrophic and autotrophic bacteria are a
significant percentage of the total biomass of the ocean• Carbon cycling
– Eutrophic systems microbial community acts as a sink fororganic C (respired as CO2)
– Oligotrophic system microbial community acts as a direct linkbetween trophic levels