Virus-to-prokaryote ratio in spring waters along a gradient of natural radioactivity

Although a strong link between viruses and prokaryotes is commonly known to exist in aquatic systems, few studies have investigated their relationship in spring waters. In the French Massif Central, certain springs are known to exhibit varying levels of naturally occurring radioactivity. Therefore, the aim of this study was to examine the standing stock of viruses together with prokaryotes and determine the potential environmental factors influencing them in springs characterized by contrasted radioactivity gradient. Among the investigated 15 spring habitats, flow cytometry analyses indicated that both viral (VA) and prokaryotic abundances (PA) varied by an order of magnitude accompanied by virus-to-prokaryote ratio ranging between 8 and 144.2. Significant differences in VA was evident among springs where low abundances (mean +/- SD: 21.3 +/- 7.0 x 10(7) VLP l(-1)) corresponded to high (mean +/- SD: 1911 +/- 814.0 nGy h(-1)) gamma (gamma) dose radiation (Rn-222) and vice versa. Adverse effect of water radioactivity (Rn-222) on VA could perhaps corroborate our hypothesis of drastic effect of ionizing radiations on viruses, which might explain for lack of significant relationship between PA and VA. In such a scenario of prevailing low VA, the adopted phage life strategies could define their existence in these specialized ecosystems.

Automated summary

While the link between viruses and prokaryotes in aquatic systems is well-known, there is limited research on this relationship in spring waters. This study examined the abundance of viruses and prokaryotes and identified the environmental factors affecting them in springs with varying levels of naturally occurring radioactivity. The results showed significant differences in viral abundances among springs, with low abundances corresponding to high gamma radiation dose and vice versa. The findings suggest a possible adverse effect of water radioactivity on viruses, explaining the lack of significant relationship between prokaryotic and viral abundances.