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Open Access Publications from the University of California

Scholarly Works (2 results)

  • Thesis
  • Peer Reviewed
UC Santa Barbara Electronic Theses and Dissertations (2024)

Macroalgae attract a diverse array of microorganisms to their surfaces by exuding nutrient-rich organic matter, which leads to microbial colonization and biofilm formation. These microbes play a variety of crucial roles in maintaining the overall health of the ecosystem. To fully understand these beneficial interactions and uncover additional, less apparent microbial functions, it is imperative to study the genetic composition of these microorganisms and explore their metabolic potential.

My research delves into these metabolic capabilities by studying the microbes that live on, in, and around a photosynthetic macroalga known as Sargassum. While many Sargassum species are benthic, two species, S. natans and S. fluitans, are holopelagic, meaning they float freely in the open ocean without attaching to any substrates. These species are typically found in the nutrient-poor subtropical waters of the North Atlantic Ocean, especially the Sargasso Sea. Since 2011, however, Sargassum’s range and abundance have expanded significantly beyond the subtropical North Atlantic into the tropical Atlantic waters. Various environmental factors have contributed to the recurring blooms of Sargassum, which can span from West Africa to the Gulf of Mexico.

By examining the genetic profiles of the microbes associated with Sargassum, I aim to understand their roles in (1) iron acquisition via siderophores and (2) the remineralization of phosphonates. Siderophores are iron-chelating molecules and phosphonates are an important phosphorus (P) source in P-limited systems such as the Sargasso Sea. Both of these nutrients are essential for Sargassum to perform photosynthesis. Using amplicon and metagenomic data, we identified complete and partial gene clusters that Sargassum’s microbial symbionts leveraged to biosynthesize siderophores like amphibactins, ferrioxamines, and ferrichromes. We also detected genes involved in several phosphonate degradation pathways in free-living bacteria found inside and outside Sargassum communities of Sargasso Sea. By revealing these genetic capabilities, our research seeks to add another piece to the puzzle that explains the success and persistence of Sargassum in the oligotrophic conditions of the Sargasso Sea and beyond.

    Cover page: Unraveling the Metabolic Potential of Pelagic Sargassum-Associated Microbes: Insights into siderophore production, biosynthesis, and phosphonate degradation
    • Article
    • Peer Reviewed
    UC Riverside Previously Published Works (2019)
    Ecological interactions between aquatic plants and sediment communities can shape the structure and function of natural systems. Currently, we do not fully understand how seagrass habitat degradation impacts the biodiversity of belowground sediment communities. Here, we evaluated indirect effects of disturbance of seagrass meadows on meiobenthic community composition, with a five-month in situ experiment in a tropical seagrass meadow. Disturbance was created by reducing light availability (two levels of shading), and by mimicking grazing events (two levels) to assess impacts on meiobenthic diversity using high-throughput sequencing of 18S rRNA amplicons. Both shading and simulated grazing had an effect on meiobenthic community structure, mediated by seagrass-associated biotic drivers and sediment abiotic variables. Additionally, shading substantially altered the trophic structure of the nematode community. Our findings show that degradation of seagrass meadows can alter benthic community structure in coastal areas with potential impacts to ecosystem functions mediated by meiobenthos in marine sediments.
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