Graduate Thesis Or Dissertation

 

Hydrogen isotopic composition of C₃₇ alkenones and the ecology and physiology of coccolithophores Public Deposited

Downloadable Content

Download PDF
https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/3197xr35c

Descriptions

Attribute NameValues
Creator
Abstract
  • A three-part study was conducted into the impact of physiological and ecological variables on the net isotopic fractionation of hydrogen, α[subscript K₃₇], expressed in C₃₇ alkenones. First, alkenone-producer production, abundance, and export were characterized in the summertime Gulf of California and Eastern Tropical North Pacific using compound-specific, labeled in situ incubations. It was found that these organisms routinely exhibited maximum production rates at depths associated with subsurface chlorophyll features and the nitracline, as opposed to the N-depleted surface, and that the relative contribution of coccolithophore productivity to overall productivity was decoupled from nutrient conditions. Our observations suggest that, in sufficiently well-stratified settings, a coccolithophore-favorable 'mid-to-low nutrient' niche may be absent. Second, results from a culture study were compared to samples from the initial field campaign in order to more firmly establish the physiological controls on the δD of alkenones. Nutrient-limitation experiments in culture, combined with previously published data, show that net fractionation between the growth medium and alkenones (α[subscript K₃₇]) increases rapidly with increasing cellular alkenone content and production rate, and, by extension, growth phase. To explain these results, a mechanism is proposed in which changing NADPH sources result in isotopically-depleted lipids at both high growth rates and in stationary phase growth. Comparison of these results to the field samples suggests that, in the water column, this dynamic (a relationship α[subscript K₃₇] and growth rate) drives correlations between α[subscript K₃₇] and both cell abundance and the carbon-fractionation term εp. Lastly, the chemical and isotopic composition of alkenones was measured in sediment samples along a transect of the North-American Pacific margin from ~42°N to the tip of Baja California. It was found that both core-top and LGM intervals expressed a strong relationship between the temperature proxy U₃₇[superscript K'] and estimated α[subscript K₃₇]. If covariation between U₃₇[superscript K'] and estimated α[subscript K₃₇] is robust in settings such as these, then paired analysis of U₃₇[superscript K'] and alkenone δD may enable paleoceanographic estimates water δD. In light of the results of the second study, it is proposed that this relationship derives from a control of temperature on cellular division rate on sedimentary time scales. Deviations from this relationship were tentatively interpreted as indicative of export from locations where alkenone producers are/are not subjected to nutrient deprivation before sedimentation. Overall, the results of this three-part study suggest A) that coccolithophore-derived inorganic carbon export may serve as a weaker positive feedback on atmospheric CO₂, in the future, than previously suggested; B) that α[subscript K₃₇] may lend valuable context to studies of alkenone-producer ecology, and C) that alkenone δD may prove a better than expected hydrologic proxy in marine settings and/or a coccolithophore-specific growth rate proxy.
License
Resource Type
Date Available
Date Copyright
Date Issued
Degree Level
Degree Name
Degree Field
Degree Grantor
Commencement Year
Advisor
Committee Member
Academic Affiliation
Non-Academic Affiliation
Keyword
Subject
Rights Statement
Peer Reviewed
Language
Replaces
Additional Information
  • description.provenance : Approved for entry into archive by Julie Kurtz(julie.kurtz@oregonstate.edu) on 2014-10-22T17:06:14Z (GMT) No. of bitstreams: 2 license_rdf: 1223 bytes, checksum: d127a3413712d6c6e962d5d436c463fc (MD5) WolhoweMatthewD2014.pdf: 5439938 bytes, checksum: d30f40640207a535044731eec3de7f57 (MD5)
  • description.provenance : Submitted by Matthew Wolhowe (wolhowem@onid.orst.edu) on 2014-10-08T20:34:01Z No. of bitstreams: 2 license_rdf: 1223 bytes, checksum: d127a3413712d6c6e962d5d436c463fc (MD5) WolhoweMatthewD2014.pdf: 5439938 bytes, checksum: d30f40640207a535044731eec3de7f57 (MD5)
  • description.provenance : Made available in DSpace on 2014-10-22T20:54:19Z (GMT). No. of bitstreams: 2 license_rdf: 1223 bytes, checksum: d127a3413712d6c6e962d5d436c463fc (MD5) WolhoweMatthewD2014.pdf: 5439938 bytes, checksum: d30f40640207a535044731eec3de7f57 (MD5) Previous issue date: 2014-09-05
  • description.provenance : Approved for entry into archive by Laura Wilson(laura.wilson@oregonstate.edu) on 2014-10-22T20:54:19Z (GMT) No. of bitstreams: 2 license_rdf: 1223 bytes, checksum: d127a3413712d6c6e962d5d436c463fc (MD5) WolhoweMatthewD2014.pdf: 5439938 bytes, checksum: d30f40640207a535044731eec3de7f57 (MD5)

Relationships

Parents:

This work has no parents.

Items