Dynamics of the benthic boundary layer and seafloor contributions to oxygen depletion on the Oregon inner shelf

TitleDynamics of the benthic boundary layer and seafloor contributions to oxygen depletion on the Oregon inner shelf
Publication TypeJournal Article
Year of Publication2014
AuthorsMcCann-Grosvenor, K, Reimers, CE, Sanders, RD
JournalContinental Shelf Research
Type of ArticleJournal Article
KeywordsBenthic boundary layer, Eddy correlation, Hypoxia, Oregon shelf, Oxygen consumption, Permeable sediments

1. Introduction
2. Material and methods
3. Results
4. Discussion
Appendix A. Supplementary materials
Figures (11)
Fig. 1. Bathymetric and multibeam backscatter map of study site (prepared by C
Fig. 2. Digital images of seafloor taken by BOXER camera system in (A) September 2009…
Fig. 3. Stacked measurements of (A) chlorophyll-α and phaeophytin-α contents and (B)…
Fig. 4. Sediment formation factor (FF) and O2 microprofiles measured in situ
Fig. 5. EC time-series data from April 2009 with date and local time along the top…
Fig. 6. EC time-series data from June 2009
Tables (3)
Table 1
Table 2
Table 3
Extras (1)
Supplementary material
Continental Shelf Research
Volume 84, 1 August 2014, Pages 93-106
Continental Shelf Research
Research papers
Dynamics of the benthic boundary layer and seafloor contributions to oxygen depletion on the Oregon inner shelf
Author links open overlay panelKristinaMcCann-GrosvenorClare E.ReimersRhea D.Sanders
https://doi.org/10.1016/j.csr.2014.05.010Get rights and content

Eddy correlation O2 fluxes were measured in 2009 at a 30 m site off Newport, OR.

High flux contributions occurred at times at the frequencies of surface waves.

The rate of change of O2 concentration was negatively correlated with fluxes.

The benthic O2 flux was primarily into the bed (−18±3 mmol m−2 d−1).

Inner shelf benthic O2 fluxes were 2–5 times greater than fluxes on the mid-shelf.

Measurement of in situ O2 consumption and production within permeable sediments, such as those found over the Oregon–Washington inner shelf, has traditionally been done using methods that isolate the sediments from the dynamic influences of currents and wave motions. Modified from atmospheric research, the non-invasive eddy correlation technique can be used to characterize benthic boundary layer dynamics and measure O2 flux across the sediment–water interface without excluding the natural hydrodynamic flow. In 2009, eddy correlation measurements were made in 5 discrete months with varying conditions at a 30 m site off Yaquina Head, Newport, OR. The O2 flux was found to be primarily into the bed (−18±3 mmol m−2 d−1; mean±SE, n=137 15-min bursts) but was sensitive to non-steady state changes in O2 concentrations caused by the differential advection of water masses with variable mean O2 concentrations. Important contributions to O2 eddy fluxes at surface wave frequencies were seen in eddy correlation cospectra and these are interpreted as being indicative of consumption enhanced by advective transport of O2 into the bed. The sediments were deposits of fine sand with permeabilities of 1.3–4.7×10−11 m2 and wave-generated ripples. Sediment pigment and organic carbon concentrations were low (chlorophyll-α: 0.02–0.45 μg g−1, phaeophytin-α: 0.38–1.38 μg g−1 and organic carbon: 0.05–0.39% dry wt in discrete depth intervals from cores collected between March and October), but it was evident that during the summer fresh pigments were trapped in the sand and rapidly mixed over the uppermost 0–13 cm. From these results it is inferred that physical forcing associated largely with waves and currents may accentuate the role of sediment-covered inner shelf habitats as a regional O2 sink compared to the middle shelf. In effect, the action of waves and currents in the benthic boundary layer enables aerobic respiration that counterbalances the oxygenation of the water column by primary production and mixing in the surface layer.


Coastal Endurance