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Observations of spatial flow patterns at the coral colony scale on a shallow reef flat

Publication ,  Journal Article
Hench, JL; Rosman, JH
Published in: Journal of Geophysical Research: Oceans
March 1, 2013

Although small-scale spatial flow variability can affect both larger-scale circulation patterns and biological processes on coral reefs, there are few direct measurements of spatial flow patterns across horizontal scales <100 m. Here flow patterns on a shallow reef flat were measured at scales from a single colony to several adjacent colonies using an array of acoustic Doppler velocimeters on a diver-operated traverse. We observed recirculation zones immediately behind colonies, reduced currents and elevated dissipation rates in turbulent wakes up to 2 colony diameters downstream and enhanced Reynolds stresses in shear layers around wake peripheries. Flow acceleration zones were observed above and between colonies. Coherent flow structures varied with incident flow speeds; recirculation zones were stronger and wakes were more turbulent in faster flows. Low-frequency (<0.03 Hz) flow variations, for which water excursions were large compared with the colony diameters (Keulegan-Carpenter number, KC >1), had similarspatial patterns to wakes, while higher-frequency variations (0.05-0.1 Hz, KC<1) had no observable spatial structure. On the reef flat, both drag and inertial forces exerted by coral colonies could have significant effects on flow, but within different frequency ranges; drag dominates for low-frequency flow variations and inertial forces dominate for higher frequency variations, including the wave band. Our scaling analyses suggest that spatial flow patterns at colony and patch scales could have important implications or both physical and biological processes at larger reef scales through their effects on forces exerted on the flow, turbulent mixing, and dispersion. © 2013. American Geophysical Union. All Rights Reserved.

Duke Scholars

Published In

Journal of Geophysical Research: Oceans

DOI

EISSN

2169-9291

Publication Date

March 1, 2013

Volume

118

Issue

3

Start / End Page

1142 / 1156

Related Subject Headings

  • 3709 Physical geography and environmental geoscience
  • 3708 Oceanography
  • 3706 Geophysics
  • 0406 Physical Geography and Environmental Geoscience
  • 0405 Oceanography
  • 0404 Geophysics
 

Citation

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Hench, J. L., & Rosman, J. H. (2013). Observations of spatial flow patterns at the coral colony scale on a shallow reef flat. Journal of Geophysical Research: Oceans, 118(3), 1142–1156. https://doi.org/10.1002/jgrc.20105
Hench, J. L., and J. H. Rosman. “Observations of spatial flow patterns at the coral colony scale on a shallow reef flat.” Journal of Geophysical Research: Oceans 118, no. 3 (March 1, 2013): 1142–56. https://doi.org/10.1002/jgrc.20105.
Hench JL, Rosman JH. Observations of spatial flow patterns at the coral colony scale on a shallow reef flat. Journal of Geophysical Research: Oceans. 2013 Mar 1;118(3):1142–56.
Hench, J. L., and J. H. Rosman. “Observations of spatial flow patterns at the coral colony scale on a shallow reef flat.” Journal of Geophysical Research: Oceans, vol. 118, no. 3, Mar. 2013, pp. 1142–56. Scopus, doi:10.1002/jgrc.20105.
Hench JL, Rosman JH. Observations of spatial flow patterns at the coral colony scale on a shallow reef flat. Journal of Geophysical Research: Oceans. 2013 Mar 1;118(3):1142–1156.

Published In

Journal of Geophysical Research: Oceans

DOI

EISSN

2169-9291

Publication Date

March 1, 2013

Volume

118

Issue

3

Start / End Page

1142 / 1156

Related Subject Headings

  • 3709 Physical geography and environmental geoscience
  • 3708 Oceanography
  • 3706 Geophysics
  • 0406 Physical Geography and Environmental Geoscience
  • 0405 Oceanography
  • 0404 Geophysics