Microbial loop developments

This chapter has reviewed several key aspects of the marine microbial loop that have become clearer in the past 20 years. Many of the developments in our understanding have come about thanks to novel molecular techniques and advances in microscopy. While conceptualised models of the microbial loop have changed dramatically since first conceived (Ducklow, 1983 le and WiUiams, 1981 Pomeroy,... 

The focus of this review has been on the history and state-of-the-art of N-cycle models. One can legitimately ask how relevant these models are given recent advances in our understanding of the factors that control primary production and particulate matter export in the ocean. Fifteen to twenty years ago, when the Fasham et al. (1990) model was stiU under development, the potential importance of iron limitation was only beginning to be appreciated. The emphasis at that time was on N limitation, the intricacies of the food web and the potential importance of bacteria and the microbial loop. We now know that iron limits phytoplankton growth over... 

There are a few other kinds of industrial plants. An air-lift tower fermenter was developed by ICI for the production of single-cell protein from methanol which employs an external loop for heat removal. Trickle beds for the treatment of waste waters employ packing structures or packing elements of 4-6 cm dia and porosities above 50%. Microbial films are formed on the packing that react with the organic substrate and the air as the liquid flows down and the air up. 

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