Award: OCE-1356779

Viruses are very important in the oceans. When they kill their bacterial and phytoplankton hosts, the cellular content (carbon and nutrients) are released into the water in dissolved form instead of being used to feed other organisms in the food web. Although viruses are very abundant in the ocean, we know very little about them, and in many cases are unable to recognize who they might be infecting. Here, we focused on viruses infecting diatoms, a group of phytoplankton that are very important in the global carbon cycle. We examined diatom virus communities in the Pacific Northwest by sampling every month at 2 coastal and estuarine locations in Washington state (Gray?s Harbor and Penn Cove). We were able to isolate 41 new strains of pennate diatom Pseudo-nitzschia, which is capable of causing Harmful Algal Blooms, into culture. We tested viral communities from the same waters to see if they could infect the diatom cultures. The results varied quite a lot, with some cultures infected by many viral samples and others not infected at all. Some diatom strains that were very similar based on their DNA sequences were infected by different viral communities. This highlights the importance of the diversity of both the diatoms and their viruses in understanding and predicting these interactions. We also isolated a new virus capable of infecting Pseudo-nitzschia as well as other diatom genera. The ability for a single virus to infect such different species is unusual. The DNA sequence of this virus was also extremely unusual. It was made up of single-stranded DNA and was over 38,000 base pairs long. This is five times longer the majority of known single-stranded DNA viruses. The genes on this viral genome also looked different from those of known single-stranded DNA viruses. Instead the genes looked much more like those on double stranded DNA viruses. We think the ancestor of this virus may have been a double stranded virus. We looked for this virus in the North Pacific Ocean and found evidence that it was present and actively infecting the diatoms in these waters. Thus, our new virus may be very important in killing diatoms and affecting the fate of their carbon in the ocean. In total this project has contributed to the training of 16 early career scientists (1 post-doc, 3 graduate students, 8 undergraduate students and 4 high school students). The female post-doc has obtained a tenure track faculty position. Two graduate students (1M, 1F) received their PhDs and were both awarded nationally competitive fellowships to support their post-doctoral work elsewhere. A third female graduate student is still enrolled in the PhD program at UW. All 8 undergraduate students (5 F, 3M) received their bachelor's degree in a STEM field. 3 of these students are members of groups currently under-represented in STEM. Of the 8 undergraduate students, 2 (1F, 1 African-American M) are currently enrolled in graduate programs in the marine sciences, 2 (1F, 1M) are employed as research technicians in marine labs and 1 (F) is a middle school science teacher. The viral genome sequence and environmental virome sequences generated by this project have been deposited in GenBank. A project page and dataset pages have been created at BCO-DMO. https://www.bco-dmo.org/project/665012 Last Modified: 02/16/2019 Submitted by: Gabrielle Rocap