In situ production and decay of marine viruses




Garza, Delfino Randy

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Viruses which cause lysis of Synechococcus spp. were present in the western Gulf of Mexico and may be responsible for <1% to 8% of Synechococcus mortality throughout the year in the mixed layer. Solar-mediated decay rates of infectivity at the air/water interface of natural cyanophage communities ranged from undetectable to 0.335 h⁻¹, with the highest rate generally occurring during the summer. Decay rates of cyanophage isolates (SPWM-1 & SPWM-3) were similar in the spring and winter but were up to 2X greater than those of the natural community. These results indicate that natural cyanophage communities are more tolerant in summer to damage by solar radiation than cyanophage isolates. Moreover, decay rates of cyanophage infectivity were similar whether in the presence or absence of host cells, indicating that detectable cyanophage production did not occur during in situ incubations. The decay rates of virus isolates and natural cyanophage communities were examined in parallel incubations at several times during the year. Results from theses experiments showed that isolates predict decay rates of the natural communities during the winter. However, during the summer, isolates overestimated the decay rates of natural communities by as much as two-fold, indicating that surrogate viruses do not predict the decay processes of natural communities at all times