Wilhelm, S.W., M.G. Weinbauer, D.R. Garza, K.M. Rodda, W.H. Jeffrey and C.A. Suttle. 1996. In situ light mediated destruction and repair of marine virus communities and isolates. Eos 76(3 suppl):OS208.

Viruses are ubiquitous members of aquatic systems and are important pathogens of marine bacteria and phytoplankton. Processes that regulate viruses thus may affect aquatic ecosystems, but these processes remain poorly understood. The decay of viral infectivity attributed to UV-B radiation was determined for natural cyanophage communities and clonal isolates of cyanophages and bacteriophages along a transect from oligotrophic to mesotrophic waters in the Gulf of Mexico. Decay rates of infectivity ranged from 0.4 to 0.9 h^-1 in surface waters at all stations, and correlated well with UV-B levels, DNA damage and depth. Particle destruction rates also decreased with increasing depth, although infective cyanophage abundances were relatively constant in the upper mixed layer. Differences in particle and infectivity loss rates integrated over depth indicate that the infectivity of 59% of the UV-B damaged cyanophages at the nearshore stations was restored by light-dependant host-mediated repair mechanisms. This study demonstrates that UV-B is a significant factor driving viral decay in marine systems, and that light-mediated repair is essential for the maintenance of steady state viral numbers in these systems. As the penetration of UV-B into the water column is different than that of the longer wavelengths required to activate DNA repair mechanisms, the optical quality of the water and mixing parameters may directly control the steady-state abundances of infective viral particles.