Graduate Thesis Or Dissertation

 

Eddy correlation benthic O₂ exchange rates and characterizations of sediment properties from the central Oregon shelf at 30 meters Public Deposited

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/mw22v994b

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  • Rates of benthic O₂ exchange are important measurements for determining organic matter remineralization, and can shed light on factors driving biogeochemical processes in coastal environments. Measurement of in situ O₂ consumption and production within permeable sediments, such as those found over ~43% of the Oregon-Washington shelf, has traditionally been done using methods that underestimate the flux for environments affected by waves. Modified from atmospheric research, the non-invasive eddy correlation technique can measure O₂ flux across the sediment-water interface without disturbing the natural hydrodynamic flow. In 2009, eddy correlation measurements were made at discrete times over a 7-month period at a 30 m site off Yaquina Head, Newport, OR. The results of this newly developed method are evaluated here, together with properties of sediment cores taken at the study site. O₂ flux was found to be primarily into the bed (-6.2 to -30.7 mmol m⁻² d⁻¹) and was enhanced during periods of higher bottom water O2 concentration. Contributions to O₂ flux were seen in eddy correlation cospectra at surface wave frequencies and dependent on wave height. The sediments were fine sands with permeabilities of 1.3-4.7 x 10⁻¹¹ m². Sediment pigment and organic carbon concentrations were low (chlorophyll-α : 0.03-0.45 μg g⁻¹, phaeophytin-α: 0.6-1.4 μg g-1 and organic carbon: 0.07-0.11 wt %), indicating high rates of organic matter export and/or remineralization. From these results it is inferred that physical forcing and changes in bottom water properties affect the inner shelf sedimentary environment more than seasonal cycles in primary production.
  • Keywords: Chemical oceanography, oxygen flux, remineralization, Oregon shelf, biogeochemical, oxygen exchange, organic matter, eddy correlation, permeable sediments
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