Name: Claudia Weihe

Email: cweihe@uci.edu

Author: Claudia Weihe, Jessica L. Clasen, Aayah Fatayerji, China Hanson, Yazeed Ibrahim, and Jennifer B.H. Martiny

Author affiliation: University of California, Irvine, Dept. of Ecology & Evolutionary Biology

Abstract title: Enumerating the abundance of cyanophages infecting Synechococcus along the south

Absstract:

Cyanophages are thought to contribute to a significant fraction of cyanobacterial mortality in marine environments, although this contribution appears to vary over time and space. In part, this variation may be due to variability in cyanophage abundance. Little is known about the factors that regulate cyanophage distribution and dynamics, however. To study these dynamics in coastal waters, we estimated the abundance of cyanophage capable of infecting marine Synechococcus along the southern California coast on a monthly basis from October 2007 to March 2009. To determine cyanophage abundance, we performed Most Probable Number (MPN) assays using four different Synechococcus strains (WH7803, WH 8101, WH 8012 and WH 8018) on seawater samples from a single location. In addition, we compared cyanophage abundance capable of infecting host strain WH7803 at three different coastal locations. Finally, we tested whether various aspects of our MPN method affected the abundance estimates. We found that cyanophage abundance was highest during the summer months (June-August) and lowest in the spring (March-May). As reported in other studies, Synechococcus WH7803 showed the highest sensitivity to infection over all months. We also observed spatial differences in cyanophage abundance at the 3 sampling locations. The number of cyanophages infecting WH7803 was higher at the 2 coastal sites (sampling in the surf) than at the site within a protected bay. Moreover, one of the coastal sites had consistently higher abundance than the other coastal site only 30 km away. Finally, several minor changes in our assay methods (well size, incubation time before assaying, and placement of the control wells) increased the consistency of the MPN assay across multiple observers. Overall, our results reveal that the abundance of coastal cyanophages is highly dynamic both temporally and spatially. Further study is needed to test whether environmental factors such as temperature, salinity, pH and currents explain this variation in cyanophage abundance.