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    Dynamics of heterotrophic bacterioplankton in costal ecosystems of the central Red Sea

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    Name:
    Luis Ribeiro da Silva Dissertation.pdf
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    Description:
    Luis Ribeiro da Silva Dissertation
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    Type
    Dissertation
    Authors
    Silva, Luis cc
    Advisors
    Moran, Xose Anxelu G. cc
    Committee members
    Duarte, Carlos M. cc
    Daffonchio, Daniele cc
    Gasol, Josep
    Program
    Marine Science
    KAUST Department
    Biological and Environmental Science and Engineering (BESE) Division
    Date
    2020-03
    Permanent link to this record
    http://hdl.handle.net/10754/661943
    
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    Abstract
    Heterotrophic bacterioplankton dynamics have seldom been assessed in the Red Sea, an exceptionally warm oligotrophic basin, which could be used as a model for the future ocean. To understand the function of heterotrophic bacteria in biogeochemical cycles and the flows of matter and energy to higher trophic levels, it is peremptory to understand how bacterial growth is controlled. Bottom-up (resources availability), top-down (mortality by predators and viruses) and temperature are the main hypotheses of control of bacterial activity and stocks. This dissertation aims to assess the spatial-temporal variability of heterotrophic bacteria and their interactions with diverse sources of dissolved organic matter (DOM) through the observed effects on bacterial growth rates and productivity in coastal environments of the central Red Sea. To that end we conducted a total of 66 shortterm incubations (4-6 days) concurrently with the whole microbial community and predator-free (by filtration) in various shallow ecosystems characterized by different dominant sources of DOM. Frequent sampling combined flow cytometry and biogeochemical analysis allowed us to measure bacterial standing stocks, including the carrying capacity (maximum abundances), growth rates, characterize DOM concentrations and lability, assess bacterial DOM consumption rates and biomass production and ultimately quantify bacterial growth efficiencies. Our findings suggest that although bacteria seemed to thrive in nutrient-sufficient waters, the central coastal Red Sea is characterized by unusually low bacterial standing stocks (4.05 ± 0.31 x105 cells ml-1), probably controlled by protistan grazing. At the same time, bacterioplankton showed high potential to grow (0.35-1.75 d-1, reaching 4.16 d-1 when dilution and pre-filtration were performed). Even though the highest specific growth rates were observed during the warmer periods, we did not find any consistent relationship with temperature. While temperature seemed not to constrain bacterial specific growth rates, we observed a tight link between bacterial growth and resource availability in terms of both quantity and quality. Overall, by surveying one of the warmest marine regions on Earth, this dissertation provides detailed insights into heterotrophic bacterioplankton dynamics and how bottomup, top-down and temperature regulate them in tropical waters, a vast geographical extension of the world oceans that had remained strongly undersampled to date.
    Citation
    Silva, L. (2020). Dynamics of heterotrophic bacterioplankton in costal ecosystems of the central Red Sea. KAUST Research Repository. https://doi.org/10.25781/KAUST-1L6TV
    DOI
    10.25781/KAUST-1L6TV
    ae974a485f413a2113503eed53cd6c53
    10.25781/KAUST-1L6TV
    Scopus Count
    Collections
    Biological and Environmental Science and Engineering (BESE) Division; Marine Science Program; PhD Dissertations

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