Marine viruses smulate carbon flux to lower and higher trophic levels

Sheri A. Floge1, Jesica D. Waller2, David M. Fields3 and Mahew B. Sullivan4 1 Wake Forest University, 2Maine Department of Marine Resources, 3Bigelow Laboratory for Ocean Sciences, 4The Ohio State University

BACKGROUND RESULTS CONCLUSIONS

• Phytoplankton play crical roles in 1. VIRUSES ENHANCE C and N FLUX TO ZOOPLANKTON • Marine viruses enhance C transfer from biogeochemical cycles, including picophytoplankton to higher trophic

transforming atmospheric CO2 into levels (copepods). 12 6 ) 13 13 - Virus parculate maer that eventually sinks 4 Copepod C Copepod C • Marine viruses also smulate DOC 4 + Virus to the deep ocean (the biological carbon 8 2 release and bacterial growth (C transfer C (x10

pump). 13 0 4 to lower trophic levels). δ Normalized • The fate of carbon (C) within the oceans Δ -2 In both a culture-based • Picophytoplankton viruses smulate 0 -4 is controlled by individual interacons in simplified plankton food web zooplankton feeding and fecal pellet a highly complex and interconnected and a natural community,

) 15 60 15 formaon, thereby potenally facilitang marine food web. 4 50 Copepod N Copepod N addion of viruses infecng 40 picophytoplankton leads to C export to the deep sea. 40 • Independent analyses of global datasets N (x10 30 increased C and N flux from 15 20 picophytoplankton to copepods. δ revealed a strong posive link between Normalized 20 Δ viruses and C flux to the deep ocean1, 2. 10 0 0 • Mechanisms underlying virus-enhanced 0 12 24 36 48 0 12 24 36 48 FUTURE DIRECTIONS C transfer to parculate organic maer Time (h) Time (h) (POM) are unknown. Culture experiment Field experiment Intact, virus-infected cells release a range of dissolved organic substances, including chemoaractants, but lile is known about Carnivores 2. VIRUSES ENHANCE COPEPOD FECAL PELLET PRODUCTION Phytoplankton Grazers the composion and impact of viral-derived A. tonsa fecal pellet organic compounds on microbial interacon and the mixotroph Fecal pellet production Viruses P-D-OM Ochromonas sp. dynamics. 0.8 - Virus -1 h Acara tonsa fecal pellet -1 + Virus Current work includes use of: Heterotrophic bacteria CO2 producon was >2x higher in • Microfluidics to quanfy the the presence of viruses infecng 0.4 the picophytoplankton chemotacc response of various Pellets animal 3 Ostreococcus tauri. marine microbes to dissolved organic Food web demonstrang the “viral shunt” . 100 μm 0.0 maer (DOM) released from intact, Viral shunt paradigm. Viruses enhance C and 0-12 h 12-24 h virus-infected picophytoplankton. nutrient recycling and reduce upward trophic transfer and export of carbon • Chip-based microbial food webs to 3. VIRUSES FACILITATE GROWTH OF BACTERIA AND characterize viral impacts on micron- HETEROTROPHIC PROTISTS scale predator-prey interacons.

)

7 Viruses Bacteria 8 ) 30 5 • Untargeted stable isotope enabled (x10 -1 OBJECTIVES 6 (x10 20 - Virus -1 mass spectrometry to idenfy novel + Virus Quanfy viral impacts on trophic transfer of 4 10 viral-derived chemoaractants. Cells mL

Particles mL 2 0 carbon (C) and nitrogen (N) using a We observed viral-smulated formaon of 13 ) 2.0 Synechococcus ) Heterotrophic protists Field experiments revealed that

combinaon of stable isotope labeling ( C, 4 2 aggregates >500 μm. 15 20 <20 µm enrichment of a natural virus community N), fluorescence acvated cell sorng 1.8 (x10 OCB Summer (x10 Workshop 2019 -1 -1 resulted in reduced Synechococcus 10 • Quanfying viral impacts on marine (FACS) and isotope rao mass spectrometry 1.6 growth, increased bacterial growth, and (IRMS) in a mock plankton community and increased growth of heterotrophic prosts aggregate formaon is essenal to Cells mL 1.4 Cells mL 0 a coastal ocean ecosystem. 0 12 24 36 48 0 12 24 36 48 feeding upon Synechococcus. understanding C export. Time (h) Time (h)

METHODS:

1. SIMPLIFIED MARINE PLANKTON FOOD WEB 2. COASTAL ATLANTIC OCEAN FIELD EXPERIMENT 13 - 15 - H CO3 , NO3

1 mm 13 • The picophytoplankton, Ostreococcus tauri, (RCC4221) was grown with C-labeled sodium Field site Sampling site: high tide 15 bicarbonate and N-labeled sodium nitrate for 48 h. 13 15 100 µm C, N Whole seawater (60 L) • The cells were then washed and resuspended in stable-isotope free seawater, enabling us to 36 h Incubate in situ 36 h Meso- trace the flow of C and N from the picophytoplankton to other members of the plankton zooplankton community. Fecal Isolate labeled phytoplankton pellets • One treatment contained the lyc virus OtV5, that infects only the Ostreococcus tauri Micro- via serial filtraon and FACS picophytoplankton; one treatment contained no OtV5. zooplankton DOC • Five biological replicates per treatment. 13C-labeled

natural phytoplankton • Other model organisms added: the nanoautotroph Isochrysis galbana (CCMP1323), the • Field experiments conducted in July 2016, Boothbay, Maine, during a Synechococcus bloom. Mixotroph mixotroph Ochromonas sp. (CCMP1391), the microzooplankton Oxyrrhis marina (CCMP3375), 13 15 <28 μm + viral • Whole seawater was incubated in situ for 36 h with NaH CO3 and Na NO3 and the calenoid copepod Acara tonsa. concentrate • 13C, 15N-labeled phytoplankton <28 nm were isolated via fluorescence acvated cell sorng Nano- • 4 4 Bacteria Heterotrophic bacteria in the model community were derived from the copepods and non- (FACS) and re-mixed at in situ concentraons with a natural plankton assemblage <210 μm. autotroph 1 µm axenic plankton cultures. biological biological • One treatment received 40% more viruses (isolated and concentrated from field site). 13 13 replicates replicates 13 Lytic algal • Samples were collected at 0, 6, 12, 24, 48 h for virus and organism abundance, C-DIC, C- NaH CO3 13 15 13 15 • Both treatments received adult, female Acara tonsa, isolated from field site, as the apex 15 Pico- virus DOC, C-POC, N-PON, and copepod C and N. Na NO3 predator in the food web. phytoplankton autotroph phytoplankton • Samples were collected at 0, 6, 12, 24, 48 h for virus and organism abundance, 13C-DIC, 13C- + zooplankton + zooplankton Arrows represent possible Eight orders of magnitude difference in organism DOC, 13C-POC, 15N-PON, and copepod 13C and 15N. + ambient viruses + 40% more viruses C flux pathways C content and volume from boom to top of food web (No virus enrichment) (With viral enrichment)

ACKNOWLEDGEMENTS REFERENCES This work was supported by Naonal Science Foundaon Biological Oceanography (award #1829905), the A. O. Beckman Foundaon 1. Guidi et al. 2016. Plankton networks driving carbon export in the oligotrophic ocean. Nature 532: 465-473. (Postdoctoral Fellowship Program), and the Gordon and Bey Moore Foundaon (GBMF #3790, 3305). We also thank Bigelow 2. Brum et al. 2015. Paerns and ecological drivers of ocean viral communies. Science 348: 1261498. 3. Wilhelm, S. W., and C. A. Sule. 1999. Viruses and nutrient cycles in the sea. Bioscience 49: 781-788. Analycal Services and the J. J. MacIsaac Center for Aquac Cytometry for facilies support.