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23
with Saprospiraceae (22 ASVs) and the Flavobacteriaceae
(18 ASVs) being the most diverse families. Alphaproteo-bacteria
included 44 ASVs, which were largely made
up by the Rhodobacteraceae (21 ASVs). Of the 15 Gam-maproteobacteria
comprising >1%, ten were in the genus
Alteromonas. Three ASVs were placed into Gammapro-teobacteria;
however, SILVA was only able to identify two
of them to class. The other ASV was placed into the family
Oligoflexaceae. Other groups crossing the 1% threshold
were the Planctomycetes (three ASVs), Verrucomictrobia
(two ASVs), and the Actinobacteria (one ASV).
We did not detect differences in community composi-tion
between constant vs. fluctuating treatments at broad
taxonomic levels in the spring experiment (Fig. 4b), but
did for Alphaproteobacteria and Cyanobacteria in the
fall (p < 0.05). The summer experiment demonstrated
much greater variation between the constant temperature
and fluctuating treatments. For example, summer-derived
communities demonstrated a decrease in the relative
abundance of Alphaproteobacteria recovered sequences
(p < 0.05) in the future-fluctuating treatment as compared
to both present-constant and present-fluctuating
treatments. These were mostly made up of copiotrophic
heterotrophs in the Hyphomonadaceae and Rhodobacter-aceae
(Table S4), and there was also an increase in the
relative abundance of Planctomycetes (p < 0.05) sequen-ces
in the future-fluctuating treatment. The shift in the
Planctomycetes was from an increase in a single ASV
(ASV20), which when BLASTed most closely matched
Candidatus Brocadiales fulgida, a known anammox
bacteria [62]. Gammaproteobacteria also decreased in
relative abundance (p < 0.05) during the summer experi-ment
in the present-fluctuating treatment relative to the
present-day constant treatment. The largest change came
Fig. 3 Ordination of a principle
coordinate analysis (PCoA)
using Euclidean distance
calculated on 16s rRNA gene
amplicon data from a spring,
b summer, and c fall. Listed
p values are the result of a
permutational ANOVA
Fig. 2 Community growth rates determined as changes in particulate
organic carbon (POC, a–c), and the diatom-specific growth measured
with changing BSI (d–f), both measured over 2 days at the end of
14 days of growth. g−i depict BSi to POC ratios as an indicator of the
relative abundance of diatoms in each treatment. Statistical sig-nificance
between two treatments (p < 0.05) is shown with a star. p
values for nearly significant treatments (p < 0.1) are shown with their
respective brackets, and error bars represent standard deviation
J. D. Kling et al.
Object Description
| Title | Thermal diversity within marine phytoplankton communities |
| Author | Kling, Joshua David |
| Author email | Joshuakl@usc.edu;Joshuakl@berkeley.edu |
| Degree | Doctor of Philosophy |
| Document type | Dissertation |
| Degree program | Biology (Marine Biology and Biological Oceanography) |
| School | College of Letters, Arts and Sciences |
| Date defended/completed | 2020-08-11 |
| Date submitted | 2020-08-11 |
| Date approved | 2020-08-11 |
| Restricted until | 2020-08-11 |
| Date published | 2020-08-11 |
| Advisor (committee chair) | Hutchins, David |
| Advisor (committee member) |
Levine, Naomi Heidelberg, John Ehrenreich, Ian |
| Abstract | Marine photosynthetic carbon fixation in the sunlit upper reaches of the ocean is almost entirely carried out by chlorophyll-containing, single-celled microorganisms, and is responsible for half of the net primary production on the planet. Because of this connection to the marine carbon cycle, it is essential to assess the responses of marine phytoplankton to global change. However, this work is challenged by the dazzling diversity of both eukaryotic and prokaryotic lineages which coexist in complex phytoplankton assemblages. My dissertation contributes to this effort by investigating how the diversity of phytoplankton influences their resilience to rising temperatures. In my first study, I used natural California coastal communities collected across three seasons to show that the phytoplankton assemblage as a whole was able to maintain growth well above typical temperature ranges. However, either steady or fluctuating temperatures exceeding the maximum threshold recorded in a decade-long observational dataset caused drastic rearrangements in the phytoplankton community, including the appearance of novel dominant species. My dissertation work also highlights that there are still unrecognized but environmentally-important taxa with bizarre and unexpected life histories and thermal responses, even in the most well-studied environments. In my second study, I characterized a recently isolated nanoplanktonic diatom from the Narragansett Bay Time Series that occupies a distinct low-light, low-temperature niche. This isolate demonstrated an unusual sensitivity to light, whereby its ability to respond to what should be favorable increases in temperature is constrained by light intensity. Six years of amplicon sequencing data from the time series site suggest that this diatom is a temperate wintertime/early spring specialist, and will likely not fare well in a warmer and more stratified future ocean. In addition to expanding knowledge of functional diversity at the species level, my work also examines the potential of intra-specific diversity to house hidden adaptations to rising temperatures. Natural microbial populations are composed of distinct individual strains, whose relative abilities to contribute to the success of the whole population in a changing environment have not been well-studied. In my third study, I compared the thermal responses of 11 strains of the marine unicellular cyanobacterium Synechococcus simultaneously isolated from a single estuarine water sample to explore this cryptic intra-specific diversity. Surprisingly, these nearly genetically-identical strains showed distinct low and high temperature phenotypes. This study indicates that strain-level variation could be a key yet understudied element in the responses of phytoplankton to global change. Together, these studies highlight that the diversity of marine phytoplankton at the species and individual level includes both functional variability and redundancy relative to temperature. We can expect community composition to change over time in a warming ocean, reflecting the increasing abundance of preadapted groups or individual strains; however, wherever there are winners there are also losers. Besides providing new insights into the contribution of diversity to climate resilience, this dissertation also highlights the need to expand our knowledge of functional thermal traits, especially for typically under-studied pico- and nanoplankton which are often only known from sequence data. |
| Keyword | thermal response; phytoplankton; community ecology |
| Language | English |
| Part of collection | University of Southern California dissertations and theses |
| Publisher (of the original version) | University of Southern California |
| Place of publication (of the original version) | Los Angeles, California |
| Publisher (of the digital version) | University of Southern California. Libraries |
| Provenance | Electronically uploaded by the author |
| Type | texts |
| Legacy record ID | usctheses-m |
| Contributing entity | University of Southern California |
| Rights | Kling, Joshua David |
| Physical access | The author retains rights to his/her dissertation, thesis or other graduate work according to U.S. copyright law. Electronic access is being provided by the USC Libraries in agreement with the author, as the original true and official version of the work, but does not grant the reader permission to use the work if the desired use is covered by copyright. It is the author, as rights holder, who must provide use permission if such use is covered by copyright. The original signature page accompanying the original submission of the work to the USC Libraries is retained by the USC Libraries and a copy of it may be obtained by authorized requesters contacting the repository e-mail address given. |
| Repository name | University of Southern California Digital Library |
| Repository address | USC Digital Library, University of Southern California, University Park Campus MC 7002, 106 University Village, Los Angeles, California 90089-7002, USA |
| Repository email | cisadmin@lib.usc.edu |
| Filename | etd-KlingJoshu-8915.pdf |
| Archival file | Volume13/etd-KlingJoshu-8915.pdf |
Description
| Title | Page 28 |
| Full text | 23 with Saprospiraceae (22 ASVs) and the Flavobacteriaceae (18 ASVs) being the most diverse families. Alphaproteo-bacteria included 44 ASVs, which were largely made up by the Rhodobacteraceae (21 ASVs). Of the 15 Gam-maproteobacteria comprising >1%, ten were in the genus Alteromonas. Three ASVs were placed into Gammapro-teobacteria; however, SILVA was only able to identify two of them to class. The other ASV was placed into the family Oligoflexaceae. Other groups crossing the 1% threshold were the Planctomycetes (three ASVs), Verrucomictrobia (two ASVs), and the Actinobacteria (one ASV). We did not detect differences in community composi-tion between constant vs. fluctuating treatments at broad taxonomic levels in the spring experiment (Fig. 4b), but did for Alphaproteobacteria and Cyanobacteria in the fall (p < 0.05). The summer experiment demonstrated much greater variation between the constant temperature and fluctuating treatments. For example, summer-derived communities demonstrated a decrease in the relative abundance of Alphaproteobacteria recovered sequences (p < 0.05) in the future-fluctuating treatment as compared to both present-constant and present-fluctuating treatments. These were mostly made up of copiotrophic heterotrophs in the Hyphomonadaceae and Rhodobacter-aceae (Table S4), and there was also an increase in the relative abundance of Planctomycetes (p < 0.05) sequen-ces in the future-fluctuating treatment. The shift in the Planctomycetes was from an increase in a single ASV (ASV20), which when BLASTed most closely matched Candidatus Brocadiales fulgida, a known anammox bacteria [62]. Gammaproteobacteria also decreased in relative abundance (p < 0.05) during the summer experi-ment in the present-fluctuating treatment relative to the present-day constant treatment. The largest change came Fig. 3 Ordination of a principle coordinate analysis (PCoA) using Euclidean distance calculated on 16s rRNA gene amplicon data from a spring, b summer, and c fall. Listed p values are the result of a permutational ANOVA Fig. 2 Community growth rates determined as changes in particulate organic carbon (POC, a–c), and the diatom-specific growth measured with changing BSI (d–f), both measured over 2 days at the end of 14 days of growth. g−i depict BSi to POC ratios as an indicator of the relative abundance of diatoms in each treatment. Statistical sig-nificance between two treatments (p < 0.05) is shown with a star. p values for nearly significant treatments (p < 0.1) are shown with their respective brackets, and error bars represent standard deviation J. D. Kling et al. |
