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Quantifying the Diversity and Activity of Microbes Catalyzing Particle Decomposition in Open Ocean

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Title:Quantifying the Diversity and Activity of Microbes Catalyzing Particle Decomposition in Open Ocean
Authors:Kyi, Eint M.
Contributors:Oceanography (department)
Date Issued:May 2018
Publisher:University of Hawaiʻi at Mānoa
Abstract:Sinking particles are a primary mechanism for transport of material and energy from the upper
ocean to the deep sea, and hence they are a key component of the ocean’s biological carbon
pump. These particles are frequently colonized by microorganisms that catalyze their
decomposition. In this thesis, I conducted a series of experiments aimed at quantifying
microbial productivity (including both filter size-fractionated rates of bacterial production and
inorganic carbon fixation) associated with sinking particles at Station ALOHA (22° 45’N, 158°
00’W) in the North Pacific Subtropical Gyre (NPSG). In addition, I examined the composition of
microorganisms associated with various filter size-fractions from these experiments based on
amplifying and sequencing 16S ribosomal (rRNA) genes. Results from these experiments
revealed that the addition of particles significantly increased rates of bacterial production
across all filter size fractions (except in the 2-20 μm filter fraction during April, 2017 (HOT 292),
relative to unamended controls. In contrast, rates of carbon fixation generally did not increase
significantly in any of the filter size fractions, aside from 0.2-2 μm filter size fraction from March
2017 (KOK 1703-2) and 2-20 μm filter size fractions from 3 single experiments conducted in
August, 2016 (HOT 286), and March, 2017 (KOK 1703-1, KOK 1703-2) at 175 m. Sequencing of
amplified 16S rRNA genes revealed that both treatment and filter size fractions independently
had significant effects on the bacterial taxonomic composition. In particular, the composition of
microorganisms associated with the smallest filter size fraction (0.2 μm) in the unamended
controls were typically dominated by members of the Thaumarchaea, Alphaproteobacteria,
Actinobacteria, and Cyanobacteria, while the larger filter fractions (2 μm and 20 μm) in the
controls were generally dominated by members of the Planctomycetes, Flavobacteria,
Bacteroidetes, and Gammaproteobacteria. In the particle-enriched treatments, the
composition of 16S rRNA genes in the 0.2 μm filter size fraction were similar to this filter
fraction in the unamended controls. However, the larger filter size fractions were enriched in
members of the Alphaproteobacteria, Gammaproteobacteria, and Bacteroidetes. In general,
particle-enriched treatments were observed to be dominated by heterotrophic copiotrophs,
further evidenced by the significant increase in bacterial production rates.
Description:M.S. Thesis. University of Hawaiʻi at Mānoa 2018.
Rights:All UHM dissertations and theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission from the copyright owner.
Appears in Collections: M.S. - Oceanography

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