Abstract
The growth of scleractinian corals is strongly influenced by the effect of water motion. Corals are known to have a high level of phenotypic variation and exhibit a diverse range of growth forms, which often contain a high level of geometric complexity. Due to their complex shape, simulation models represent an important option to complement experimental studies of growth and flow. In this work, we analyzed the impact of flow on coral's morphology by an accretive growth model coupled with advection-diffusion equations. We performed simulations under no-flow and uni-directional flow setup with the Reynolds number constant. The relevant importance of diffusion to advection was investigated by varying the diffusion coefficient, rather than the flow speed in Péclet number. The flow and transport equations were coupled and solved using COMSOL Multiphysics. We then compared the simulated morphologies with a series of Computed Tomography (CT) scans of scleractinian corals Pocillopora verrucosa exposed to various flow conditions in the in situ controlled flume setup. As a result, we found a similar trend associated with the increasing Péclet for both simulated forms and in situ corals; that is uni-directional current tends to facilitate asymmetrical growth response resulting in colonies with branches predominantly developed in the upstream direction. A closer look at the morphological traits yielded an interesting property about colony symmetry and plasticity induced by uni-directional flow. Both simulated and in situ corals exhibit a tendency where the degree of symmetry decreases and compactification increases in conjunction with the augmented Péclet thus indicates the significant importance of hydrodynamics.
Highlights
Some corals are known to have a high degree of morphological plasticity along different environmental conditions [1,2,3]
There is a long standing discussion if this process in which colonies develop symmetrical colonies is controlled by genes or by the environment. We address this question for the scleractinian coral Pocillopora verrucosa
We first have acquired coral colonies from a controlled in-situ flow experiment where the coral was growing under uni-directional flow conditions
Summary
Some corals are known to have a high degree of morphological plasticity along different environmental conditions [1,2,3]. Light and water motion are the main environmental factors related to morphological variations of a coral colony [2]. In a low energy environment, sparely spacing branching structures allow flow to penetrate deeper inside the colony as opposed to densely compacted branching. Reidenbach et al [16] estimated mass transfer in unidirectional and oscillatory flows of three coral species - Stylophora pistillata, Pocillopora verrucosa and Pocillopora compressa. Mass transfer rate was shown to be a function of the physical flow characteristic and the morphology of branching structure. Mass transfer rate of sparsely branched corals was observed to be larger for increasing flow velocity. At a higher frequency oscillatory flow, the compactness in branch spacing greatly enhance mass transfer rate through the inner structure of the branches
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
