The concept of the microbial loop first began in 1926 by Vernadskii, who studied heterotrophic and phototrophic microbial metabolism; and understood that these systems represented a major part of total metabolism in the oceans (Pomeroy, 1988). Older techniques that scientists used for enumerating marine bacteria were by plate counts, serial dilutions and phase-contrast microscopy. These numbers represented about 10% of actual numbers and are no longer used (Azam et al, 1983). Scientists were unable to completely understand the microbial loop until recently when ultrafiltration techniques, applied electronic microscope techniques; and genomic techniques were developed to quantify biomass in oceans to study the bacteria and microorganisms that are important in oceanic processes. It was by these techniques, that a study in 1983 by Azam et al, discovered the trend that with an increase in bacterial numbers and biomass there is an increase in primary productivity. This was one of the key findings that led scientists to understand the microbial loop.
The microbial loop is the most critical process in the marine food web, because it increases the efficiency of the system by making dissolved organic matter available to other organisms in the food web. It provides the matter and energy for the rest of the system and keeps the energy flowing. These in turn have implications on very important resources such as productivity of fisheries or how much carbon is able to reach the ocean floor. In this paper, research was done to see why and how the microbial loop is such an important process in the oceans. Also discussed in this paper, are what the loop consists of, how it operates, the matter and energy that cycles through the loop, as well as how it fits into the ocean system and interacts with other elements of marine productivity.
Microbes are the tiny particles in the ocean that cannot be seen with the naked eye. They include viruses, bacteria, phytoplankton, and microzooplankton. Picoplankton are plankton cells in the ocean that are less than 2 μm. They account for 60% of primary production in the North Atlantic and 80-90% of primary production in oligotrophic waters (Anderson, 2001). In one liter of ocean water there is a billion microbes, including bacteria, viruses, and protists (Pomeroy, 2007). Without these critical microbes, the ocean would be much less hospitable to other organisms. The microbial loop acts as the bottom portion of the food web and represents the pathway that organic carbon follows in the oceanic system (Anderson, 2001). The microbial loop channels energy and carbon via bacteria to protozoa, then to larger zooplankton, then to fishes and cetaceans, through a complex system (Pomeroy et al, 2007). The microbial loop involves many interacting processes and ecological relationships, including commensalism, competition and predation (Azam, 1986).
To begin the cycle of the microbial loop, the bacteria consume organic...