Microbial loop components

The inefficiency of microbial heterotrophy does have a side benefit as it enhances nutrient remineralization rates. This serves to increase the availability of inorganic nitrogen and phosphorus for the photoautotrophs. The multiple roles of bacteria in the marine food web were shown in Figure 23.2, with the component of the food web controlled by the algal herbivores depicted on the left side and the microbial loop on the right. The viral shunt acts on both pathways. 

FIGURE 2 Rooted universal phylogenetic tree highlighting major components of the microbial loop. CFB indicates the Cytophaga-Flavobacter-Bacteriodes lineage. (Adapted from Woese, 1994). 

FIGURE 1 Detrital structure and primary fluxes of dissolved organic carbon in lake ecosystems with the food-web structure of predominantly pelagic components (box) that reflects the importance of the microbiota, the microbial loop, and physical processes by which most other organic matter inputs are metabolized heterotrophically or degraded by physical processes. DOM denotes dissolved organic matter, with labile (LDOM) and recalcitrant (RDOM) components POM denotes particulate organic matter. 

The purpose of this chapter is to emphasise the role of the microbial loop in the oceanic nitrogen cycle. It begins by briefly introducing classical concepts of microbial loop function, then shifts to the increase in our knowledge that has occurred in the past three decades. It then introduces the components of the microbial loop that... 

The removal and residence time of colloidal substances from sea water would depend upon either their degradation to soluble components or their aggregation to form sinking macroparticles. The results of Wells and Goldberg support the concept of a continuous flow of material between the colloidal, particulate, and dissolved states by aggregation. The microbial loop maybe less important as a direct sink for colloidal organic carbon. 

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