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Aquatic Microbial Ecology

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AME 11:79-90 (1996)  -  doi:10.3354/ame011079

Cycling of marine dissolved organic matter. II. A model analysis

Blackburn N, Zweifel UL, Hagström Å

Nutrient pathways within the microbial food web were analysed using a mechanistic model based on a multi-stage flow-through experimental system. Good agreement with measured values reflected the model's ability to function on 3 different orders of magnitude with respect to turnover time. Important observations made from the experimental system included the production of viruses, the presence of dead bacterial cells (ghosts), and the production of detritus. This led to the concept that the bacterial community forms a continuum from live uninfected cells through infected cells, dead cells, degraded cells (detritus) and ends in dissolved organic matter. Enzymatic degradation of dissolved organic matter was balanced by its release during cell lysis caused by viruses, predation by flagellates, and degradation of detritus. This formed 3 closed loops in the model for nutrient recycling. Simulations predicted that phosphorus recycling occurred via nucleic acids released during cell lysis caused by viruses and that nitrogen was recycled via proteins released as a combined result of cell lysis caused by viruses, predation by flagellates, and degradation of detritus. This implies that for natural ecosystems, the availability of nitrogen, phosphorus, and carbon species for bacterial growth can be dominated by internal recycling, depending on the molecular species in question and the turnover time. Different nutrients are made available by different processes of recycling which potentially occur on different time scales.

Dissolved organic matter recycling · Microbial food web dynamics · Nutrient recycling · Computer simulation · Bacteria · Virus · Heterotrophic nanoflagellates · Bacterial ghosts

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