High viral abundance as a consequence of low viral decay in the Baltic Sea redoxcline

Abstract

Throughout the Baltic Sea redoxcline, virus production and the frequency of lytically-infected prokaryotic cells were estimated from parallel incubations of undiluted seawater and seawater that contained prokaryotes with substantially reduced numbers of viruses (virus dilution approach), effectively preventing viral reinfection during the incubation period. Undiluted seawater incubations resulted in much higher estimates of virus production (6–35×104 mL-1 h-1) and the frequency of infected cells (5–84%) than the virus dilution approach (virus production: 1–3×104 mL-1 h-1; frequency of infected cells: 1–11%). Viral production and the frequency of infected cells from both approaches, however, cannot be directly compared, as data obtained from undiluted incubations were biased by viral reinfection and other uncontrollable processes during the incubation period. High in situ viral abundance (1–2×107 mL-1) together with low virus production rates based on the virus dilution approach resulted in some of the longest viral turnover times (24–84 d) ever reported for the epipelagial. Throughout a wide range of environmental conditions, viral turnover time and burst size were negatively correlated. Given that viral decay estimated in ultra-filtered water was below the detection limit and the burst size was low (1–17), we conclude that prokaryotic viruses in the Baltic Sea redoxcline are investing most of their resources into stress defense (strong capsids) rather than proliferation (high burst size). In summary, the Baltic Sea redoxcline constitutes an environment where low virus production is found in combination with low viral decay, resulting in high viral abundance.

Mixing alters the lytic activity of viruses in the dark ocean

“…2004, Köstner et al. 2017). At the onset of the experiments and every 24 h, subsamples were taken to obtain fingerprints of the bacterial, archaeal, and viral community composition to detect possible changes in the host and corresponding virus community in response to the experimental treatments as follows.…”

“…2004, Köstner et al. 2017; Appendix S3). For that, viruses were removed by tangential‐flow filtration during set‐up of the experiments (see above).…”

“…2004, Köstner et al. 2017). These VP data were corrected for differences between prokaryotic abundance at the onset of the experiments and in situ prokaryotic abundance.…”

“…2004, Köstner et al. 2017). We also wanted to know whether potential changes in viral lytic activity as a consequence of mixing would affect the community composition of prokaryotes and viruses as detected by fingerprinting approaches.…”

A viral reckoning: viruses emerge as essential manipulators of global ecosystems

“…The major scientific questions highlighted in Story 3 (viral decay, contact rate and the continuum of viral infection strategies), are long-standing challenging topics. While the first conceptual frameworks were established 20-30 years ago (Heldal and Bratbak, 1991;Suttle and Chen, 1992;Murray and Jackson, 1992;Thingstad, 2000), new work and new discoveries are still being made around the same fundamental question today (Dell'Anno et al, 2015;Knowles et al, 2016;Weitz et al, 2017;Köstner et al, 2017). Most of the debate and controversy is rooted in the resolution at which we can observe these phenomenon in nature, i.e.…”