0.37-0.65 Gigaton carbon/year
||Danovaro R, Dell'Anno A, Corinaldesi C, Magagnini M, Noble R, Tamburini C, Weinbauer M. Major viral impact on the functioning of benthic deep-sea ecosystems. Nature. 2008 Aug 28 454(7208):1084-7.PubMed ID18756250
||Researchers collected a data set of 232 deep-sea sediment samples and measured the impact of viruses on deep-sea benthic prokaryotes and biogeochemical cycles. Their data cover latitudes from 79° N to 34° S, and all depths from 165 m to 5,571 m (sampling location and details on the data set is provided in Supplementary Table 1 and Fig. 1), and include deep-sea sites spanning a wide range of bottom-water temperatures and trophic conditions. Measurements of viral and prokaryotic abundance and production were carried out synoptically on the same samples and by using the same protocols for the entire data set, thus ensuring methodological consistency. Viral and prokaryotic abundances in deep-sea sediments were determined by epifluorescence microscopy using highly sensitive fluorochromes. For the determination of viral production, two different procedures were applied and compared. The first is based on a dilution technique of samples with virus-free sea water, and allows the determination of viral production on the basis of the increase in viral number over time. The second is based on the use of 3H-thymidine, and allows the determination of viral production through the assessment of the incorporation rates of radiolabelled substrates into viral genomes.
||Researchers estimated the impact of viruses on benthic prokaryotic production, calculating the number of prokaryotes killed as the ratio between viral production and prokaryotic burst size. Using the mean burst size of the time course experiments (burst size of 45) they calculated that viruses are responsible for the abatement of 80% of the total prokaryotic heterotrophic production in global deep-sea sediments. The release of labile organic material from killed prokaryotic cells has important implications for carbon cycling and nutrient regeneration on a global scale. They estimate that the viral shunt, on a global scale, can release from approx 0.37 Gt C yr-1 (the most conservative estimate on the basis of the highest value of burst size) to 0.63 Gt C/yr (if a burst size of 45 is used). Therefore, the carbon released by viral lysis of prokaryotic biomass (the viral shunt) is an essential source of labile organic compounds to deep-sea ecosystems. The lysis of prokaryotes and their conversion into detritus limits prokaryotic consumption by higher trophic levels but provides nutrients for other prokaryotes.