Temporal dynamics of natural communities of marine algal viruses and eukaryotes

The composition of algal virus communities in relation to temperature, salinity, chlorophyll a (chl a) concentration and eukaryotic community composition was monitored at a single location for 14 mo. Changes in algal virus and eukaryote communities were determined using polymerase chain reaction (PCR) and denaturing gradient gel electrophoresis (DGGE) to generate genetic fingerprints. Sequence analysis of bands extracted from denaturing gradient gels revealed the presence of at least 5 distinct viruses as well as temporally dynamic and diverse communities of eukaryotes that included taxa from the viridiplantae, fungi and metazoa. Comparison of algal virus fingerprints with environmental conditions revealed that, at certain times, changes in algal virus community composition were coincident with changes in tide height, salinity or chl a concentration. However, algal virus community changes were not often coupled to eukaryote community changes. The lack of coincidence between changes in virus and eukaryote communities can be explained by the presence of organisms that were not hosts of the detected viruses. It is likely that the uncoupling of 18S and AVS fingerprints was due to succession among non-host eukaryotes. Although algal virus fingerprint patterns were stable throughout most of the study, stable eukaryote fingerprint patterns were observed only during the winter months. Furthermore, specific taxa of algal viruses persisted in fluctuating physical and biological environments. We concluded that the constant production of, and mortality from, some taxa of algal viruses provide further evidence that algal viruses affect phytoplankton community structure and dynamics.