Project: Driving marine biogeochemical cycles through phytoplankton host-virus interactions
Marine phytoplankton contribute over 50 percent of the total primary productivity on Earth, making them an important component of the global carbon cycle. Diatoms, eukaryotic phytoplankton that contribute 40 percent of the marine primary productivity, are unique in their obligate requirement for silicon for cell wall formation and growth. As the largest group of siliceous organisms in the ocean, diatoms represent the critical link between the carbon and silicon cycles. Thus, identifying and understanding the factors that regulate diatom growth and mortality is crucial for assessing how these ecologically dominant organisms influence community productivity, biological pump efficiency, and silicon biogeochemistry. Viral infection and subsequent host demise has been shown to significantly impact other phytoplankton groups, but the role that diatom-infecting viruses play in regulating diatom populations is completely unknown. Historically thought to be immune to infection due to the physical protection afforded by their silica cell wall, the identification, isolation and cultivation of diatom host-virus model systems has opened the door for detailed mechanistic studies. Specifically, I plan to combine laboratory-based studies with analysis of targeted field samples of natural diatom populations to determine the effect that viral infection has on both silica production (i.e., cell wall formation) and silica remineralization (the process by which silica returns to a dissolved, bioavailable form). As the most abundant entity in the ocean, viruses play a critical role in shaping microbial ecosystems and driving global biogeochemical cycles. Drawing upon tools from the fields of molecular and cell biology, viral ecology, biogeochemistry and microbial oceanography, this research will explore how viruses impact one of the most globally important and ecologically dominant organisms in the modern ocean.