Factors influencing viral degradation in aquatic system

Over the past decade, viruses have been recognized to be the numerically dominant component of plankton in most marine and freshwater environments, with abundances between 104 and more than 108 particles per ml. Own studies and diverse investigations concerning viral dynamics revealed that rapid increases and decreases in pelagic and benthic viral numbers occur on a diurnal basis. Degradation of viruses has a number of ecologically relevant consequences: e.g. it reduces viral-mediated mortality of bacterio-, phyto- and zooplankton, it increases the DNA / RNA pool which is qualitatively important for the ecosystem with respect to nitrogen and phosphorus, it shifts the processes of genetic recombination within the microbial compartment from transduction towards transformation, it increases the concentration of peptides and amino acid, and it can lead to changes in the microbial diversity. Consequently, viral degradation plays a critical role in the balance of the microbial food webs and in the flow of genetic information within the prokaryote compartment. Knowing the environmental factors which lead to the viral destruction of viral is therefore critical to elucidating the role(s) of viruses in aquatic systems. Yet, many factors have been claimed to influence viral persistence, e.g. solar radiation, temperature, pH of the suspending medium, the presence of organic matter and sediment particles, soluble chemicals such as salts, heavy metals, predation by e.g. nanoflagellates, and the activity of enzymes and other metabolites. However, most studies have focused on the loss of infectivity of enteroviruses or of coliphages used as indicators of enteroviral pollution. From the point of view of a system ecologist, however, information on the total degradation of viral particles is more attractive than the loss of infectivity because of the numerous ecologically relevant consequences described above. The aim of the present study is to investigate the effect of abiotic and biotic parameters on viral degradation which were neglected until now and recalculate the role of viral dynamics within the microbial compartment of the water column and the sediment of aquatic systems. The use of the entire virioplankton from natural waters rather than single virus isolates is an important distinction differentiating our study from those of others, considering the recent interest in the role of viruses in aquatic ecosystems.

Over the past decade, viruses have been recognized to be the numerically dominant component of plankton in most marine and freshwater environments, with abundances between 104 and more than 108 particles per ml. Own studies and diverse investigations concerning viral dynamics revealed that rapid increases and decreases in pelagic and benthic viral numbers occur on a diurnal basis. Degradation of viruses has a number of ecologically relevant consequences: e.g. it reduces viral-mediated mortality of bacterio-, phyto- and zooplankton, it increases the DNA / RNA pool which is qualitatively important for the ecosystem with respect to nitrogen and phosphorus, it shifts the processes of genetic recombination within the microbial compartment from transduction towards transformation, it increases the concentration of peptides and amino acid, and it can lead to changes in the microbial diversity. Consequently, viral degradation plays a critical role in the balance of the microbial food webs and in the flow of genetic information within the prokaryote compartment. Knowing the environmental factors which lead to the viral destruction of viral is therefore critical to elucidating the role(s) of viruses in aquatic systems. Yet, many factors have been claimed to influence viral persistence, e.g. solar radiation, temperature, pH of the suspending medium, the presence of organic matter and sediment particles, soluble chemicals such as salts, heavy metals, predation by e.g. nanoflagellates, and the activity of enzymes and other metabolites. However, most studies have focused on the loss of infectivity of enteroviruses or of coliphages used as indicators of enteroviral pollution. From the point of view of a system ecologist, however, information on the total degradation of viral particles is more attractive than the loss of infectivity because of the numerous ecologically relevant consequences described above. The aim of the present study is to investigate the effect of abiotic and biotic parameters on viral degradation which were neglected until now and recalculate the role of viral dynamics within the microbial compartment of the water column and the sediment of aquatic systems. The use of the entire virioplankton from natural waters rather than single virus isolates is an important distinction differentiating our study from those of others, considering the recent interest in the role of viruses in aquatic ecosystems.