Microbial Loop
The microbial loop is a trophic pathway in the marine microbial food web. The term, microbial loop is coined by Azam et al. (1983) to describe the role of microbes playing in the marine ecosystem carbon and nutrients cycles where dissolved organic carbon (DOC) is returned to higher trophic levels via the incorporation into bacterial biomass, and also coupled with the classic food chain formed by phytoplankton-zooplankton-nekton.
At the end of phytoplankton bloom, when the algae enter a senescent stage, there is an accumulation of phytodetritus and an increased release of dissolved metabolites. It is particularly at this time that the bacteria can utilize these energy sources to multiply and produce a sharp pulse (or bloom) that follows the phytoplankton bloom. The same relationship between phytoplankton and bacteria influences the vertical distribution of bacterioplankton. Maximum numbers of bacteria generally occur at the pycnocline, where phytodetritus accumulates by sinking from the overlying euphotic zone. There, decomposition by bacteria contributes to the formation of oxygen minimum layers in stable waters.
Read more about this topic: Pycnocline