Thermodynamics and hydrodynamics in an atoll reef system and their influence on coral cover

Rogers, Justin S.; Monismith, Stephen G.; Koweek, David A.; Torres, Walter I.; Dunbar, Robert B.

doi:10.1002/lno.10365

Cited by 32 publications

(41 citation statements)

References 63 publications

(112 reference statements)

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“…Palmyra reef span a similar range of z o , 2.2-5.5 cm (Rogers et al 2016). For the two studies over Moorea's back reef (Rosman and Hench 2011;Monismith et al 2013), the inferred z o exceeds 20 cm.…”

mentioning

confidence: 82%

Coral Reef Drag Coefficients – Water Depth Dependence

Lentz

Davis

Churchill

et al. 2017

Journal of Physical Oceanography

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A major challenge in modeling the circulation over coral reefs is uncertainty in the drag coefficient because existing estimates span two orders of magnitude. Current and pressure measurements from five coral reefs are used to estimate drag coefficients based on depth-average flow, assuming a balance between the cross-reef pressure gradient and the bottom stress. At two sites wind stress is a significant term in the cross-reef momentum balance and is included in estimating the drag coefficient. For the five coral reef sites and a previous laboratory study, estimated drag coefficients increase as the water depth decreases consistent with open channel flow theory. For example, for a typical coral reef hydrodynamic roughness of 5 cm, observational estimates, and the theory indicate that the drag coefficient decreases from 0.4 in 20 cm of water to 0.005 in 10 m of water. Synthesis of results from the new field observations with estimates from previous field and laboratory studies indicate that coral reef drag coefficients range from 0.2 to 0.005 and hydrodynamic roughnesses generally range from 2 to 8 cm. While coral reef drag coefficients depend on factors such as physical roughness and surface waves, a substantial fraction of the scatter in estimates of coral reef drag coefficients is due to variations in water depth.

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mentioning

confidence: 82%

Coral Reef Drag Coefficients – Water Depth Dependence

Lentz

Davis

Churchill

et al. 2017

Journal of Physical Oceanography

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“…The physical environment on reefs is inherently variable over time and space . Fundamentally, this variability and the differential responses it can initiate in physiology is partially driving which corals bleach and where …”

Section: Biophysical Factors Influencing Bleaching Heterogeneitymentioning

confidence: 99%

“…Water movement is enhanced by wave‐driven, oscillatory flows on reefs, with the degree of enhancement depending on the morphology of reef structure and wave energy . The complex three dimensionality of reef environments also creates a wide range of microhabitat flow regimes resulting in the formation of turbulent eddies that create fluctuations in flow superimposed on the mean conditions experienced by a reef . The spatial variability in rates of mass transfer over shallow water reefs contributes to flow‐related variability in bleaching responses of corals on spatial scales of 0.1 – 100 m (Box ) through the physiological effects of flow on different cellular processes.…”

Section: Flow Conditions Have Direct Effects On the Physiology Of Cormentioning

confidence: 99%

“…Water flow conditions over reefs are able to modulate metabolic functioning at the cellular level on the exchange of gases and metabolites and the effect the thermal environment corals may be exposed to, at spatial extents that scale from the cell to the reef itself . Understanding the impact of water flow at different levels of ecological scale is necessary in understanding the heterogeneity of bleaching responses observed on reefs.…”

Section: Introductionmentioning

confidence: 99%

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Seeking Resistance in Coral Reef Ecosystems: The Interplay of Biophysical Factors and Bleaching Resistance under a Changing Climate

et al. 2019

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If we are to ensure the persistence of species in an increasingly warm world, of interest is the identification of drivers that affect the ability of an organism to resist thermal stress. Underpinning any organism's capacity for resistance is a complex interplay between biological and physical factors occurring over multiple scales. Tropical coral reefs are a unique system, in that their function is dependent upon the maintenance of a coral-algal symbiosis that is directly disrupted by increases in water temperature. A number of physical factors have been identified as affecting the biological responses of the coral organism under broadscale thermal anomalies. One such factor is water flow, which is capable of modulating both organismal metabolic functioning and thermal environments. Understanding the physiological and hydrodynamic drivers of organism response to thermal stress improves predictive capabilities and informs targeted management responses, thereby increasing the resilience of reefs into the future.

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“…These values are typical of the rough reef crests such as the one we studied in Ofu, (Fig. 1B) (Rogers et al 2018), as well as similar reefs (Rosman and Hench 2011;Rogers et al 2016). In order to investigate the effect of variable depth on drag, we binned the time series by water depth to determine how the drag effects changed with depth.…”

Section: Assessmentmentioning

confidence: 85%

Instrumentation for direct measurements of wave‐driven flow over a fringing reef crest

Hefner

Rogers

Maticka

et al. 2019

Limnology & Ocean Methods

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Shallow dynamic flows are very important processes in environmental systems, yet they are notoriously difficult to measure. For example, on coral reefs, shallow flows over the reef crest typically range from 0 to 1 m depth and velocity up to 1–2 m s−1 including oscillatory motion of waves. To directly measure depth and velocity in this challenging environment, we retrofitted a vertical acoustic Doppler current profiler (ADCP, Teledyne, RDI) designed for streams into a new shallow water acoustic Doppler current profiler system (SW‐ADCP) to expand memory and power limitations and allow for deployment in wave‐dominated environments. We captured variations in shallow reef crest depth and flow over a period of 3 weeks in the reef/lagoon system of Ofu Island, American Samoa. The new SW‐ADCPs recorded water depth and three‐dimensional velocity in 3 cm bins every 3 s. We then used velocity profiles to estimate volumetric flow and drag coefficients and verified these estimates using boundary layer theory. We observe that the mean velocity profile is well approximated by a log‐layer formulation with z0 of 3.5 cm, despite the shallow depths, strong flows, and breaking waves. Our observations validated the use of SW‐ADCPs as a tool for measuring flows in shallow (0.1–1 m), dynamic coastal marine environments.

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Thermodynamics and hydrodynamics in an atoll reef system and their influence on coral cover

Cited by 32 publications

References 63 publications

Coral Reef Drag Coefficients – Water Depth Dependence

Coral Reef Drag Coefficients – Water Depth Dependence

Seeking Resistance in Coral Reef Ecosystems: The Interplay of Biophysical Factors and Bleaching Resistance under a Changing Climate

Instrumentation for direct measurements of wave‐driven flow over a fringing reef crest

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