scholarly journals Differential Occupation of Available Coral Hosts by Coral-Dwelling Damselfish (Pomacentridae) on Australia’s Great Barrier Reef

Diversity ◽  
2019 ◽  
Vol 11 (11) ◽  
pp. 219
Author(s):  
Tory J Chase ◽  
Mia O Hoogenboom
Keyword(s):  
Great Barrier Reef ◽  
Coral Species ◽  
Habitat Type ◽  
Total Biomass ◽  
Barrier Reef ◽  
Reef Habitat ◽  
Large Spatial Scale ◽  
Stylophora Pistillata ◽  
Coral Colony ◽  
Seriatopora Hystrix

Associations between habitat-forming, branching scleractinian corals and damselfish have critical implications for the function and trophic dynamics of coral reef ecosystems. This study quantifies how different characteristics of reef habitat, and of coral morphology, determine whether fish occupy a coral colony. In situ surveys of aggregative damselfish–coral associations were conducted at 51 different sites distributed among 22 reefs spread along >1700 km of the Great Barrier Reef, to quantify interaction frequency over a large spatial scale. The prevalence of fish–coral associations between five damselfish (Chromis viridis, Dascyllus aruanus, Dascyllus reticulatus, Pomacentrus amboinensis and Pomacentrus moluccensis) and five coral species (Acropora spathulata, Acropora intermedia, Pocillopora damicornis, Seriatopora hystrix, and Stylophora pistillata) averaged ~30% across all corals, but ranged from <1% to 93% of small branching corals occupied at each site, depending on reef exposure levels and habitat. Surprisingly, coral cover was not correlated with coral occupancy, or total biomass of damselfish. Instead, the biomass of damselfish was two-fold greater on sheltered sites compared with exposed sites. Reef habitat type strongly governed these interactions with reef slope/base (25%) and shallow sand-patch habitats (38%) hosting a majority of aggregative damselfish-branching coral associations compared to reef flat (10%), crest (16%), and wall habitats (11%). Among the focal coral species, Seriatopora hystrix hosted the highest damselfish biomass (12.45 g per occupied colony) and Acropora intermedia the least (6.87 g per occupied colony). Analyses of local coral colony traits indicated that multiple factors governed colony usage, including spacing between colonies on the benthos, colony position, and colony branching patterns. Nevertheless, the morphological and habitat characteristics that determine whether or not a colony is occupied by fish varied among coral species. These findings illuminate the realized niche of one of the most important and abundant reef fish families and provide a context for understanding how fish–coral interactions influence coral population and community level processes.

scholarly journals Long-term shifts in the colony size structure of coral populations along the Great Barrier Reef

2020 ◽  
Vol 287 (1936) ◽  
pp. 20201432
Author(s):  
Andreas Dietzel ◽  
Michael Bode ◽  
Sean R. Connolly ◽  
Terry P. Hughes
Keyword(s):  
Great Barrier Reef ◽  
Colony Size ◽  
Size Structure ◽  
Coral Cover ◽  
Spatial Scales ◽  
Reproductive Capacity ◽  
Barrier Reef ◽  
Size Frequency Distribution ◽  
Coral Colony ◽  
Recovery Potential

The age or size structure of a population has a marked influence on its demography and reproductive capacity. While declines in coral cover are well documented, concomitant shifts in the size-frequency distribution of coral colonies are rarely measured at large spatial scales. Here, we document major shifts in the colony size structure of coral populations along the 2300 km length of the Great Barrier Reef relative to historical baselines (1995/1996). Coral colony abundances on reef crests and slopes have declined sharply across all colony size classes and in all coral taxa compared to historical baselines. Declines were particularly pronounced in the northern and central regions of the Great Barrier Reef, following mass coral bleaching in 2016 and 2017. The relative abundances of large colonies remained relatively stable, but this apparent stability masks steep declines in absolute abundance. The potential for recovery of older fecund corals is uncertain given the increasing frequency and intensity of disturbance events. The systematic decline in smaller colonies across regions, habitats and taxa, suggests that a decline in recruitment has further eroded the recovery potential and resilience of coral populations.

scholarly journals Asymmetric dispersal is a critical element of concordance between biophysical dispersal models and spatial genetic structure in Great Barrier Reef corals

2018 ◽  
Author(s):  
C Riginos ◽  
K Hock ◽  
AM Matias ◽  
PJ Mumby ◽  
MJH van Oppen ◽  
...  
Keyword(s):  
Gene Flow ◽  
Great Barrier Reef ◽  
Larval Dispersal ◽  
Coral Species ◽  
Spatial Genetic Structure ◽  
Critical Element ◽  
Barrier Reef ◽  
Long Distance ◽  
Biophysical Models ◽  
Asymmetric Dispersal

AbstractAimWidespread coral bleaching, crown-of-thorns seastar outbreaks, and tropical storms all threaten foundational coral species of the Great Barrier Reef, with impacts differing over time and space. Yet, dispersal via larval propagules could aid reef recovery by supplying new settlers and enabling the spread of adaptive variation among regions. Documenting and predicting spatial connections arising from planktonic larval dispersal in marine species, however, remains a formidable challenge.LocationThe Great Barrier Reef, AustraliaMethodsContemporary biophysical larval dispersal models were used to predict longdistance multigenerational connections for two common and foundational coral species (Acropora tenuisandAcropora millepora). Spatially extensive genetic surveys allowed us to infer signatures of asymmetric dispersal for these species and evaluate concordance against expectations from biophysical models using coalescent genetic simulations, directions of inferred gene flow, and spatial eigenvector modelling.ResultsAt long distances, biophysical models predicted a preponderance of north to south connections and genetic results matched these expectations: coalescent genetic simulations rejected an alternative scenario of historical isolation; the strongest signals of inferred gene flow were from north to south; and asymmetric eigenvectors derived from north to south connections in the biophysical models were significantly better predictors of spatial genetic patterns than eigenvectors derived from symmetric null spatial models.Main conclusionsResults are consistent with biophysical dispersal models yielding approximate summaries of past multigenerational gene flow conditioned upon directionality of connections. ForA. tenuisandA. millepora, northern and central reefs have been important sources to downstream southern reefs over the recent evolutionary past and should continue to provide southward gene flow. Endemic genetic diversity of southern reefs suggests substantial local recruitment and lack of long distance gene flow from south to north.

Occurrence of aggressive mechanisms during interactions between soft corals (Octocorallia : Alcyoniidae) and other corals on the Great Barrier Reef, Australia

1997 ◽  
Vol 48 (2) ◽  
pp. 129 ◽  
Author(s):  
J. K. Griffith
Keyword(s):  
Coral Reef ◽  
Great Barrier Reef ◽  
Soft Coral ◽  
Barrier Reef ◽  
Soft Corals ◽  
Acanthaster Planci ◽  
Coral Reef Community ◽  
Reef Community ◽  
Coral Colony ◽  
Factors Influencing

This study found that on two reefs of the Great Barrier Reef, Australia, most coral colonies within 10 cm of a soft coral colony were interacting to the detriment of one or both colonies. Soft corals were more likely to interact with neighbouring hard corals than with other soft corals. The relative infrequency of ties indicated that two coral colonies were rarely equal competitively. Allelopathy and simple overgrowth were the major aggressive mechanisms of alcyoniids. Soft corals tended to simply overgrow neighbouring hard corals but used allelochemicals more frequently when the neighbour was another soft coral. Other factors influencing the type of aggressive mechanism used included the size of the neighbouring colony. The importance of this to a coral reef community after events such as Acanthaster planci infestations is discussed.

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