University of Tennessee, Knoxville TRACE: Tennessee Research and Creative Exchange Masters Theses Graduate School 5-2005 Virus Dynamics in High-Nutrient, Low-Chlorophyll Marine Surface Waters Julie Linda Higgins University of Tennessee, Knoxville Follow this and additional works at: https://trace.tennessee.edu/utk_gradthes Part of the Microbiology Commons Recommended Citation Higgins, Julie Linda, "Virus Dynamics in High-Nutrient, Low-Chlorophyll Marine Surface Waters. " Master's Thesis, University of Tennessee, 2005. https://trace.tennessee.edu/utk_gradthes/4548 This Thesis is brought to you for free and open access by the Graduate School at TRACE: Tennessee Research and Creative Exchange. It has been accepted for inclusion in Masters Theses by an authorized administrator of TRACE: Tennessee Research and Creative Exchange. For more information, please contact [email protected]. To the Graduate Council: I am submitting herewith a thesis written by Julie Linda Higgins entitled "Virus Dynamics in High-Nutrient, Low-Chlorophyll Marine Surface Waters." I have examined the final electronic copy of this thesis for form and content and recommend that it be accepted in partial fulfillment of the requirements for the degree of Master of Science, with a major in Microbiology. Steven W. Wilhelm, Major Professor We have read this thesis and recommend its acceptance: John R. Dunlap, Robert N. Moore Accepted for the Council: Carolyn R. Hodges Vice Provost and Dean of the Graduate School (Original signatures are on file with official studentecor r ds.) To the Graduate Council: I am submitting herewith a thesis written by Julie Linda Higgins entitled "Virus Dynamics in High-Nutrient, Low-Chlorophyll Marine Surface Waters." I have examined the final paper copy of this thesis for form and content and recommend that it be accepted in partial fulfillment of the requirements for the degreeof Master of Science, with a major in Microbiology. We have read this thesis Acceptance£ r the Council: VIRUS DYNAMICS IN HIGH-NUTRIENT, LOW-CHLOROPHYLL MARINE SURFACEWATERS A Thesis Presented for the Master of Science Degree The University of Tennessee, Knoxville Julie Linda Higgins May2005 DEDICATION This thesis is dedicated to my biggest fans: my parents,Andrew and Linda Higgins who always told me that I could be anything I wanted to be; and my sister, JenniferAnsley Black and brother, Scott Higgins, my best friendsand role models, for their continued love, support and inspiration. 11 ACKNOWLEDGEMENTS I wish to thankall of those people who made this achievement possible. I would like to thankmy advisor, Dr, Wilhelm, forgiving me the guidanceand putting forththe effortto help me become familiarwith the manyfacets in which this thesis is involved and forpresenting me with the opportunitiesto see thingsthat I would have otherwise never experienced. I wish to thankDr. Dunlap forhis assistance with the transmission electron microscope andhis patience during the learningprocess. I would also like to thankDr. Moore forhis time andfeedback while serving on my committee. It is appropriate to also acknowledge the members of the Wilhelm lab: Johanna Rinta-Kantoand Dr. Cecile Mioni for their help with the statistics forthis project; Dr. Melanie Eldridge, Leo Poorvin,andDr. Andy Ouellette fortheir support, guidance,and friendship;Dr. Rinuhi Li, JanetRowe, andLynn Neal forteaching me Japaneseand Lynn Neal forher help while in Japan;Andy Kenst fordwelling as much as I do; Casey Rentz, Matt Smith, andMatt Stedmanfor their help with this project; Matt Carberryfor his help with thisproject andfor being the best house-sitter in history; and finally,Amanda Dean, forher unconditionalsupport, friendship,and patience, and for listening to each storyas if it were the firsttime she'd heardit, even if it was the fifth. I miss you, Pooks ! I wish to acknowledge the captains andcrew of the HakuhoMaru and Tangaroa, andthe chief scientists ofFeCycle and SEEDS II, Dr. PhilBoyd and Dr. Atsushi Tsuda, respectively. I would also like to thankAimee Hodge forher friendshipand support during this process. I wish to thankRick Biddle forhelping me to keep my head on andalways lll reminding me to laugh. Lastly, I would like to thank my family whose encouragement made this work possible, andmy friends,Lilly and Lyle. lV ABSTRACT Iron (Fe) limitationof primaryproductivity in high-nutrient,low-chlorophyll (HNLC)regions is relatively well-studied. Iron fertilizationexperiments as well as bottle incubations have been used to study changesin phytoplankton community biomass and diversity, changes in bacterial growthrates, etc. However, viral activity has been largely ignored in these studies. Viral activity was monitoredduring an iron budget study (FeCycle) in theHNLC waters of the SouthernOcean southwest of New Zealand as well as during a mesoscacle iron fertilizationin the subarctic Pacific(SEEDS II). The goal of these studies was to evaluate the role of viruses in the lysis of bacterial cells and the subsequent regeneration of iron and otherkey nutrients. Two methods, a transmission electronmicroscopy (TEM) approach anda dilution assay, were used to measureviral production in each study andcomparisons were made as to the appropriateness of each. From thesestudies, it appearsthat the viral community indirectly responds to changes in trophicproduction as observed by changes in virus abundanceand production, while burstsize and frequency of infection remain constant. These results suggest that there is a decrease in thelength of lytic cycle afterproductivity is stimulated. Virus-induced lysis was foundto regenerate up to 70 pM Fe in the SouthernOcean, andnearly 200 pM Fe in the subarcticPacific. While thereis little doubt as to the usefulnessof TEM and its importancein determininglytic burst sizes in naturalpopulations, the observations in this study suggest that there are problems associated with inferences concerningcommunity mortality fromsuch observations,especially duringperiods of trophic change. V TABLE OF CONTENTS BACKGROUND ................................................................................................................ 1 1. The Microbial Food Web ............................................................................................ 2 2. Viruses in Marine Systems ......................................................................................... 4 3. The Iron Hypothesis .................................................................................................... 8 4. Iron Fertiliza.tionExperiments .................................................................................. 11 PART ONE: AN ESTIMATION OF VIRAL DYNAMICS IN AN SF6-LABELED HNLCPATCH .................................................................................................................. 16 1. Introduction............................................................................................................... 1 7 2. Materials and Methods .............................................................................................. 18 2.1 Study site andsampling ...................................................................................... 18 2.2 Phytoplankton, bacterial, and viral abundance................................................... 18 2.3 Determinationof estimated burst size and the frequencyof visibly infectedcells ................................................................................................................................... 20 2.4 Calculating the frequencyof infected cells and viral-mediated bacterial mortality ......................................................................................................................... · ......... 20 2.5 Bacterial and viral production and virus-induced mortality rate estimates ........ 21 3. Results ....................................................................................................................... 24 3.1 Bacterial andviral abundance and production .................................................... 24 3.2 Chlorophyll a, dissolved iron and iron regeneration ........................................... 24 3.3 VMB, burst size other nutrient regeneration....................................................... 26 4. Discussion ................................................................................................................. 28 4.1 Increase in chlorophyll a, dissolved iron, and viral activity (by dilution approach)................................................................................................................... 28 4.2 VMB, burst size and nutrient remobiliza.tion...................................................... 31 5. PartI Conclusions ..................................................................................................... 34 PART TWO: A MESOSCALEIRON FERTILIZATION IN THE SUBARCTIC PACIFIC OCEAN AND ITS EFFECTS ON VIRAL ACTIVITY .................................. 35 1. Introduction............................................................................................................... 36 2. Materials an.dMethods .............................................................................................. 38 2.1 Study site and sampling...................................................................................... 3 8 2.2 Phytoplankton,bacterial and viral abundance, and bacterial production ........... 38 2.3 Additional viral parametersand tests for significance........................................ 40 3. Results ......................................................................................................................