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Self-generated morphology in lagoon reefs.

Blakeway D, Hamblin MG - PeerJ (2015)

Bottom Line: In these situations reef morphology can be considered a phenotype of the predominant reef building organism.The capacity to infer coral type from reef morphology can potentially be used to identify and map specific coral habitat in remotely sensed images.More generally, identifying ecological mechanisms underlying other examples of self-generated reef morphology can potentially improve our understanding of present-day reef ecology, because any ecological process capable of shaping a reef will almost invariably be an important process in real time on the living reef.

View Article: PubMed Central - HTML - PubMed

Affiliation: School of Earth and Environment, University of Western Australia , Crawley , Western Australia, Australia.

ABSTRACT
The three-dimensional form of a coral reef develops through interactions and feedbacks between its constituent organisms and their environment. Reef morphology therefore contains a potential wealth of ecological information, accessible if the relationships between morphology and ecology can be decoded. Traditionally, reef morphology has been attributed to external controls such as substrate topography or hydrodynamic influences. Little is known about inherent reef morphology in the absence of external control. Here we use reef growth simulations, based on observations in the cellular reefs of Western Australia's Houtman Abrolhos Islands, to show that reef morphology is fundamentally determined by the mechanical behaviour of the reef-building organisms themselves-specifically their tendency to either remain in place or to collapse. Reef-building organisms that tend to remain in place, such as massive and encrusting corals or coralline algae, produce nodular reefs, whereas those that tend to collapse, such as branching Acropora, produce cellular reefs. The purest reef growth forms arise in sheltered lagoons dominated by a single type of reef builder, as in the branching Acropora-dominated lagoons of the Abrolhos. In these situations reef morphology can be considered a phenotype of the predominant reef building organism. The capacity to infer coral type from reef morphology can potentially be used to identify and map specific coral habitat in remotely sensed images. More generally, identifying ecological mechanisms underlying other examples of self-generated reef morphology can potentially improve our understanding of present-day reef ecology, because any ecological process capable of shaping a reef will almost invariably be an important process in real time on the living reef.

No MeSH data available.


Related in: MedlinePlus

Cross-section through a hypothetical model reef.Upward-pointing arrows indicate vertical growth directions, horizontal and diagonal arrows indicate neighbour growth directions.
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fig-7: Cross-section through a hypothetical model reef.Upward-pointing arrows indicate vertical growth directions, horizontal and diagonal arrows indicate neighbour growth directions.

Mentions: Growth from the initial coral recruits is effected by assigning two growth probabilities to each cell in the array in each iteration: a vertical probability representing the likelihood of the cell growing upward itself and a neighbour probability representing the likelihood of the cell being overgrown by a neighbouring coral (Fig. 7). The vertical probability of vacant seafloor cells is zero, and the vertical probability of coral-filled cells is random. The neighbour probability of each cell is the product of a random number between zero and one and a ‘neighbour value’ that depends on the state of the eight surrounding cells. Cells with no shallower neighbours are assigned a neighbour value of zero; otherwise, the cell’s neighbour value rises incrementally for each shallower neighbour. If a cell becomes surrounded by shallower neighbours, it is guaranteed to be overgrown. Otherwise, growth is determined by comparing the cell’s vertical and neighbour probabilities against two random numbers between zero and one. If either or both probabilities exceed their respective random numbers, the cell grows by one metre when the array is updated prior to the next iteration. Vertical accretion is halted at sea level but lateral accretion continues. The time represented by each iteration is arbitrary but we consider it to be 100 years, giving a mean vertical reef accretion rate of 7 mm/yr (the theoretical maximum rate of 10 mm/yr is not achieved because corals do not grow in every iteration).


Self-generated morphology in lagoon reefs.

Blakeway D, Hamblin MG - PeerJ (2015)

Cross-section through a hypothetical model reef.Upward-pointing arrows indicate vertical growth directions, horizontal and diagonal arrows indicate neighbour growth directions.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4499466&req=5

fig-7: Cross-section through a hypothetical model reef.Upward-pointing arrows indicate vertical growth directions, horizontal and diagonal arrows indicate neighbour growth directions.
Mentions: Growth from the initial coral recruits is effected by assigning two growth probabilities to each cell in the array in each iteration: a vertical probability representing the likelihood of the cell growing upward itself and a neighbour probability representing the likelihood of the cell being overgrown by a neighbouring coral (Fig. 7). The vertical probability of vacant seafloor cells is zero, and the vertical probability of coral-filled cells is random. The neighbour probability of each cell is the product of a random number between zero and one and a ‘neighbour value’ that depends on the state of the eight surrounding cells. Cells with no shallower neighbours are assigned a neighbour value of zero; otherwise, the cell’s neighbour value rises incrementally for each shallower neighbour. If a cell becomes surrounded by shallower neighbours, it is guaranteed to be overgrown. Otherwise, growth is determined by comparing the cell’s vertical and neighbour probabilities against two random numbers between zero and one. If either or both probabilities exceed their respective random numbers, the cell grows by one metre when the array is updated prior to the next iteration. Vertical accretion is halted at sea level but lateral accretion continues. The time represented by each iteration is arbitrary but we consider it to be 100 years, giving a mean vertical reef accretion rate of 7 mm/yr (the theoretical maximum rate of 10 mm/yr is not achieved because corals do not grow in every iteration).

Bottom Line: In these situations reef morphology can be considered a phenotype of the predominant reef building organism.The capacity to infer coral type from reef morphology can potentially be used to identify and map specific coral habitat in remotely sensed images.More generally, identifying ecological mechanisms underlying other examples of self-generated reef morphology can potentially improve our understanding of present-day reef ecology, because any ecological process capable of shaping a reef will almost invariably be an important process in real time on the living reef.

View Article: PubMed Central - HTML - PubMed

Affiliation: School of Earth and Environment, University of Western Australia , Crawley , Western Australia, Australia.

ABSTRACT
The three-dimensional form of a coral reef develops through interactions and feedbacks between its constituent organisms and their environment. Reef morphology therefore contains a potential wealth of ecological information, accessible if the relationships between morphology and ecology can be decoded. Traditionally, reef morphology has been attributed to external controls such as substrate topography or hydrodynamic influences. Little is known about inherent reef morphology in the absence of external control. Here we use reef growth simulations, based on observations in the cellular reefs of Western Australia's Houtman Abrolhos Islands, to show that reef morphology is fundamentally determined by the mechanical behaviour of the reef-building organisms themselves-specifically their tendency to either remain in place or to collapse. Reef-building organisms that tend to remain in place, such as massive and encrusting corals or coralline algae, produce nodular reefs, whereas those that tend to collapse, such as branching Acropora, produce cellular reefs. The purest reef growth forms arise in sheltered lagoons dominated by a single type of reef builder, as in the branching Acropora-dominated lagoons of the Abrolhos. In these situations reef morphology can be considered a phenotype of the predominant reef building organism. The capacity to infer coral type from reef morphology can potentially be used to identify and map specific coral habitat in remotely sensed images. More generally, identifying ecological mechanisms underlying other examples of self-generated reef morphology can potentially improve our understanding of present-day reef ecology, because any ecological process capable of shaping a reef will almost invariably be an important process in real time on the living reef.

No MeSH data available.


Related in: MedlinePlus