Résumé
Virucidal properties of sunlight and temperature have been identified for a long time. However, it is less well established if virioplankton communities are evenly susceptible or geographically adapted to these environmental factors. Transplant experiments were conducted between a tropical (Senegal) and temperate (France) site to examine the effect of natural daylight conditions and temperature on the persistence of free viruses in water. Fresh- and seawater viruses from both countries were simultaneously subjected to 12 h of full sunlight and dark exposure under their native and "transplanted" latitudes. Consistently, viruses decayed much faster when incubated abroad, regardless of origin (latitude and/or water type). However, viral losses, in most cases, were not significantly different between sunlight exposed and dark samples, implying that ambient radiation does not exert strong negative effects on virioplankton particles. Rather, temperature clearly emerged as the principal determinant of viral survival in all samples. This suggests that viruses, under local temperature, can adapt through an evolutionary process to survive for longer periods of time thus increasing their chances to encounter their hosts.