Masters Theses

Date of Award


Degree Type


Degree Name

Master of Science



Major Professor

Steven W. Wilhelm

Committee Members

Erik R. Zinser, Alison Buchan


Viruses are abundant in the world’s oceans and are thought to be important participants in marine biogeochemical cycling. Of these viruses, cyanophages are considered especially important because they infect and lyse cyanobacteria, which are some of the main primary producers in marine environments. Cyanophages are thought to influence the abundance and diversity of cyanobacterial populations and impart significant mortality, thereby affecting primary productivity and microbial community structure. Despite their ecological relevance, little is known about how environmental factors shape cyanophage abundance and diversity over large temporal and spatial scales. To address this gap in knowledge, seawater samples were collected during a research cruise transect from Honolulu, HI to San Diego, CA. The Myoviridae family of cyanophage was targeted for this study because of its perceived ecological dominance and the availability of molecular probes which can be used to measure their diversity and quantify abundance. The g20 gene (which codes for portal vertex protein in myoviruses) was targeted by an established primer set and used as a proxy for cyanomyophage abundance in qPCR assays. Initial analysis of quantification data has revealed significant correlations between cyanomyophage abundance and depth, dissolved inorganic carbon concentration, and total viral abundance. Total viral abundance was also significantly correlated with depth. The lack of trends between viral abundance and other environmental variables may have been due to the temporal offset in the phage-host relationship, which needs to be taken into consideration in future studies.

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