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dc.contributor.advisorMoran, Xose Anxelu G.
dc.contributor.authorSabbagh, Eman I.
dc.date.accessioned2018-10-14T08:41:29Z
dc.date.available2019-10-14T00:00:00Z
dc.date.issued2018-09
dc.identifier.citationSabbagh, E. I. (2018). Weekly variation of viruses and heterotrophic nanoflagellates and their potential impact on bacterioplankton in a Red Sea shallow ecosystem. KAUST Research Repository. https://doi.org/10.25781/KAUST-1P3FO
dc.identifier.doi10.25781/KAUST-1P3FO
dc.identifier.urihttp://hdl.handle.net/10754/629129
dc.description.abstractHeterotrophic bacterioplankton plays a pivotal role in marine food webs and biogeochemical cycling. However, their temporal dynamics and underlying factors are still poorly understood in many regions, including the tropical waters of the Red Sea. The main goal of the MS project was to describe the seasonality and assess the impact of top-down controls (viruses and heterotrophic nanoflagellates) in parallel to bottom-up controls (substrate availability) on coastal bacterioplankton on a weekly basis. To that end, we monitored the abundance of the different planktonic groups by flow cytometry together with a set of environmental variables including temperature, salinity, dissolved organic carbon (DOC) and nitrogen (DON) and chlorophyll a concentration. We analyzed a weekly dataset collected over 2017 at the surface water of KAUST Harbor. The abundance of heterotrophic bacteria ranged from 1.55 to 4.97 x 105 cells ml-1, with that of autotrophic bacteria 4 to 14 fold less on average and presents 1 x 104 to 1.19x105 cells ml-1, while viruses ranged from 1.30 x 106 to 1.59 x 107 particles ml-1, and heterotrophic nanoflagellates (HNF) ranged from 8.62 x 10 to 1.63 x 103 cells ml-1. We distinguished between five groups of heterotrophic bacteria depending on the relative nucleic acid content, membrane state and cell-specific metabolic activity, two groups of Synechococcus, as well as three groups of viruses based on relative nucleic acid content. We found unexpected inverse relationship between viruses and HNFs. Based on a strong negative correlation, the results suggest that viruses controlled heterotrophic bacteria during summer until early winter period. HNFs showed a selective grazing behavior based their apparent preference to prey on both high (HNA) and low nucleic acid bacteria (LNA). Our results demonstrates that top-down control are key agents of heterotrophic bacterioplankton mortality and more important than bottom-up control in governing heterotrophic bacterioplankton abundances in the coastal tropical waters of the Red Sea.
dc.language.isoen
dc.subjectHeterotro phic bacteria
dc.subjectviruses
dc.subjectHeterotrophic Nanoflagellates
dc.subjectWeekly variation
dc.subjectNutrients
dc.titleWeekly variation of viruses and heterotrophic nanoflagellates and their potential impact on bacterioplankton in a Red Sea shallow ecosystem
dc.typeThesis
dc.contributor.departmentBiological and Environmental Science and Engineering (BESE) Division
dc.rights.embargodate2019-10-14
thesis.degree.grantorKing Abdullah University of Science and Technology
dc.contributor.committeememberVoolstra, Christian R.
dc.contributor.committeememberDaffonchio, Daniele
thesis.degree.disciplineBioscience
thesis.degree.nameMaster of Science
dc.rights.accessrightsAt the time of archiving, the student author of this thesis opted to temporarily restrict access to it. The full text of this thesis became available to the public after the expiration of the embargo on 2019-10-14.
refterms.dateFOA2019-10-14T00:00:00Z


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