Limits...
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

Diagram illustrating the proposed mechanism of ridge formation derived from the branching Acropora model.The diagram shows a cross-section through two merging patch reefs after 50 iterations (the two uppermost patch reefs in Fig. 11C). Isochrons at 20 and 40 iterations show that the patch reefs were initially conical, and that the valley between them has accreted rapidly since the patch reefs merged. Rapid accretion is attributed to the tendency for colonies in valleys to remain in place and for colonies on reef slopes to collapse.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4499466&req=5

fig-15: Diagram illustrating the proposed mechanism of ridge formation derived from the branching Acropora model.The diagram shows a cross-section through two merging patch reefs after 50 iterations (the two uppermost patch reefs in Fig. 11C). Isochrons at 20 and 40 iterations show that the patch reefs were initially conical, and that the valley between them has accreted rapidly since the patch reefs merged. Rapid accretion is attributed to the tendency for colonies in valleys to remain in place and for colonies on reef slopes to collapse.

Mentions: The nodular reefs produced by the basic model appear straightforward and visually ‘correct’ as growth forms, because the individual patch reefs maintain their forms as they grow and merge. This straightforward morphology is indicative of pure in situ (in place) growth. Cellular reefs are more complex because the patch reefs transform as they merge, eventually becoming linked by a network of ridges. This transformation results from the high frequency of collapse in the branching Acropora model. However, it is not simply the frequency of collapse that produces ridges; more important is the distribution of collapse. Because the valleys between merging patch reefs are low points in the reef structure, coral colonies in the valleys are less likely to project above their neighbours than corals elsewhere. Consequently, they are relatively unrestricted by the collapse limit and are therefore more likely to remain in place as they grow, and less likely to collapse, than colonies elsewhere (Fig. 15). The retention of in-situ colonies transforms the V-shaped valleys into saddle-shaped ridges that grow to sea level, enclosing depressions (Figs. 11C and 11D, Fig. 11 Video). The subcircular shapes of the depressions arise through the same non-uniform distribution of collapse. Colonies in the re-entrant concavities of early-stage depressions are supported by neighbours and therefore tend to remain in place while those on projecting convexities tend to collapse. Over time this creates smooth rounded shapes, the ultimate smooth shape being a circle.


Self-generated morphology in lagoon reefs.

Blakeway D, Hamblin MG - PeerJ (2015)

Diagram illustrating the proposed mechanism of ridge formation derived from the branching Acropora model.The diagram shows a cross-section through two merging patch reefs after 50 iterations (the two uppermost patch reefs in Fig. 11C). Isochrons at 20 and 40 iterations show that the patch reefs were initially conical, and that the valley between them has accreted rapidly since the patch reefs merged. Rapid accretion is attributed to the tendency for colonies in valleys to remain in place and for colonies on reef slopes to collapse.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

fig-15: Diagram illustrating the proposed mechanism of ridge formation derived from the branching Acropora model.The diagram shows a cross-section through two merging patch reefs after 50 iterations (the two uppermost patch reefs in Fig. 11C). Isochrons at 20 and 40 iterations show that the patch reefs were initially conical, and that the valley between them has accreted rapidly since the patch reefs merged. Rapid accretion is attributed to the tendency for colonies in valleys to remain in place and for colonies on reef slopes to collapse.
Mentions: The nodular reefs produced by the basic model appear straightforward and visually ‘correct’ as growth forms, because the individual patch reefs maintain their forms as they grow and merge. This straightforward morphology is indicative of pure in situ (in place) growth. Cellular reefs are more complex because the patch reefs transform as they merge, eventually becoming linked by a network of ridges. This transformation results from the high frequency of collapse in the branching Acropora model. However, it is not simply the frequency of collapse that produces ridges; more important is the distribution of collapse. Because the valleys between merging patch reefs are low points in the reef structure, coral colonies in the valleys are less likely to project above their neighbours than corals elsewhere. Consequently, they are relatively unrestricted by the collapse limit and are therefore more likely to remain in place as they grow, and less likely to collapse, than colonies elsewhere (Fig. 15). The retention of in-situ colonies transforms the V-shaped valleys into saddle-shaped ridges that grow to sea level, enclosing depressions (Figs. 11C and 11D, Fig. 11 Video). The subcircular shapes of the depressions arise through the same non-uniform distribution of collapse. Colonies in the re-entrant concavities of early-stage depressions are supported by neighbours and therefore tend to remain in place while those on projecting convexities tend to collapse. Over time this creates smooth rounded shapes, the ultimate smooth shape being a circle.

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