Flow inside a coral colony measured using magnetic resonance velocimetry

Chang, Sandy; Elkins, Chris; Alley, Marcus T.; Eaton, John K.; Monismith, Stephen G.

doi:10.4319/lo.2009.54.5.1819

Cited by 42 publications

(66 citation statements)

References 22 publications

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“…For instance, if compensatory growth occurs on the flanks of the branches under low-flow conditions, then growth could be higher in injured compared to uninjured corals, and under these conditions the effects of temperature might be obscured by mass-transfer limitations. If flow enhances growth on the tips of branches through turbulence near the apices (Chang et al 2009), and low temperature at high flow accelerates growth because of the proximity of this temperature to the growth optimum , 1990, Edmunds 2005, when mass transfer limitation is less likely (Patterson 1992) then growth would be greatest in uninjured branches under high-flow, low-temperature conditions (Fig. 1).…”

Section: Discussionmentioning

confidence: 99%

Response of Pocillopora verrucosa to corallivory varies with environmental conditions

Lenihan

Edmunds²

2010

Mar. Ecol. Prog. Ser.

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) and fish predation (predators versus no predators), but not temperature, supported results of the microcosm experiment. Growth was greatest for corals in the high-flow, no predator treatment, and relatively high for injured corals in low flow. Together, these results suggest that P. verrucosa, a common branching coral, prioritizes overall growth over repair when injured by fish feeding, which differs from the outcome observed in a companion study in which juvenile colonies of massive Porites were subjected to similar injuries.

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Section: Discussionmentioning

confidence: 99%

Response of Pocillopora verrucosa to corallivory varies with environmental conditions

Lenihan

Edmunds²

2010

Mar. Ecol. Prog. Ser.

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“…Such dynamics are essential for understanding and monitoring heat-induced stress at reef- and colony-scale. To date, most studies of flow at the colony-scale have used laboratory and computational approaches with idealised geometries and/or flow conditions [6, 7, 41, 43–46]. Therefore, slight modifications in coral surface geometry, as well as thermal and flow properties, could result in variable surface temperatures of individual colonies.…”

Section: Introductionmentioning

confidence: 99%

The effect of allometric scaling in coral thermal microenvironments

et al. 2017

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A long-standing interest in marine science is in the degree to which environmental conditions of flow and irradiance, combined with optical, thermal and morphological characteristics of individual coral colonies, affects their sensitivity of thermal microenvironments and susceptibility to stress-induced bleaching within and/or among colonies. The physiological processes in Scleractinian corals tend to scale allometrically as a result of physical and geometric constraints on body size and shape. There is a direct relationship between scaling to thermal stress, thus, the relationship between allometric scaling and rates of heating and cooling in coral microenvironments is a subject of great interest. The primary aim of this study was to develop an approximation that predicts coral thermal microenvironments as a function of colony morphology (shape and size), light or irradiance, and flow velocity or regime. To do so, we provided intuitive interpretation of their energy budgets for both massive and branching colonies, and then quantified the heat-size exponent (b*) and allometric constant (m) using logarithmic linear regression. The data demonstrated a positive relationship between thermal rates and changes in irradiance, A/V ratio, and flow, with an interaction where turbulent regime had less influence on overall stress which may serve to ameliorate the effects of temperature rise compared to the laminar regime. These findings indicated that smaller corals have disproportionately higher stress, however they can reach thermal equilibrium quicker. Moreover, excellent agreements between the predicted and simulated microscale temperature values with no significant bias were observed for both the massive and branching colonies, indicating that the numerical approximation should be within the accuracy with which they could be measured. This study may assist in estimating the coral microscale temperature under known conditions of water flow and irradiance, in particular when examining the intra- and inter-colony variability found during periods of bleaching conditions.

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“…Such conditions occur on a daily basis on reefs where flow is dominated by tidal cycles (20,21) and in sheltered areas within lagoons or on leeward parts of the reef (18,22,23). Furthermore, ambient flow is significantly reduced within densely branched corals, where parts of the colony experience over 90% reduction in fluid flow compared with conditions outside the colony (18,23,24). At such places and times, mass transport enhancement due to ambient flow is restricted and may even jeopardize coral survival (17,25).…”

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confidence: 99%

Vortical ciliary flows actively enhance mass transport in reef corals

Shapiro

Fernández

Garren

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

179

167

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The exchange of nutrients and dissolved gasses between corals and their environment is a critical determinant of the growth of coral colonies and the productivity of coral reefs. To date, this exchange has been assumed to be limited by molecular diffusion through an unstirred boundary layer extending 1-2 mm from the coral surface, with corals relying solely on external flow to overcome this limitation. Here, we present direct microscopic evidence that, instead, corals can actively enhance mass transport through strong vortical flows driven by motile epidermal cilia covering their entire surface. Ciliary beating produces quasi-steady arrays of counterrotating vortices that vigorously stir a layer of water extending up to 2 mm from the coral surface. We show that, under low ambient flow velocities, these vortices, rather than molecular diffusion, control the exchange of nutrients and oxygen between the coral and its environment, enhancing mass transfer rates by up to 400%. This ability of corals to stir their boundary layer changes the way that we perceive the microenvironment of coral surfaces, revealing an active mechanism complementing the passive enhancement of transport by ambient flow. These findings extend our understanding of mass transport processes in reef corals and may shed new light on the evolutionary success of corals and coral reefs.coral microenvironment | coral reef evolution | diffusion boundary layer | microfluidics | biological fluid mechanics

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Flow inside a coral colony measured using magnetic resonance velocimetry

Cited by 42 publications

References 22 publications

Response of Pocillopora verrucosa to corallivory varies with environmental conditions

Response of Pocillopora verrucosa to corallivory varies with environmental conditions

The effect of allometric scaling in coral thermal microenvironments

Vortical ciliary flows actively enhance mass transport in reef corals

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