scholarly journals Cross-Shelf Variation in Coral Community Response to Disturbance on the Great Barrier Reef

Diversity ◽  
2019 ◽  
Vol 11 (3) ◽  
pp. 38 ◽  
Author(s):  
Camille Mellin ◽  
Angus Thompson ◽  
Michelle J. Jonker ◽  
Michael J. Emslie
Keyword(s):  
Great Barrier Reef ◽  
Community Composition ◽  
Community Dynamics ◽  
Coral Cover ◽  
Light Attenuation ◽  
Coral Community ◽  
Community Response ◽  
Outer Shelf ◽  
Barrier Reef ◽  
Chronic Stressors

Changes in coral reef health and status are commonly reported using hard coral cover, however such changes may also lead to substantial shifts in coral community composition. Here we assess the extent to which coral communities departed from their pre-disturbance composition following disturbance (disassembly), and reassembled during recovery (reassembly) along an environmental gradient across the continental shelf on Australia’s Great Barrier Reef. We show that for similar differences in coral cover, both disassembly and reassembly were greater on inshore reefs than mid- or outer-shelf reefs. This pattern was mostly explained by spatial variation in the pre-disturbance community composition, of which 28% was associated with chronic stressors related to water quality (e.g., light attenuation, concentrations of suspended sediments and chlorophyll). Tropical cyclones exacerbated the magnitude of community disassembly, but did not vary significantly among shelf positions. On the outer shelf, the main indicator taxa (tabulate Acropora) were mostly responsible for community dissimilarity, whereas contribution to dissimilarity was distributed across many taxa on the inner shelf. Our results highlight that community dynamics are not well captured by aggregated indices such as coral cover alone, and that the response of ecological communities to disturbance depends on their composition and exposure to chronic stressors.

scholarly journals Cross-Shelf Variation Among Juvenile and Adult Coral Assemblages on Australia’s Great Barrier Reef

Diversity ◽  
2019 ◽  
Vol 11 (6) ◽  
pp. 85 ◽  
Author(s):  
Michelle J. Jonker ◽  
Angus A. Thompson ◽  
Patricia Menéndez ◽  
Kate Osborne
Keyword(s):  
Great Barrier Reef ◽  
Coral Cover ◽  
Synergistic Effects ◽  
Outer Shelf ◽  
Lower Latitude ◽  
Barrier Reef ◽  
Hard Coral ◽  
Coral Abundance ◽  
The Status ◽  
Community Types

Coral reefs are under increasing pressure from a variety of stressors, highlighting the need for information about the status of coral reef communities including the distribution, abundance and composition of juvenile and adult coral assemblages. This information is currently limited for the Great Barrier Reef (GBR) and is necessary for understanding the impacts of disturbances and the system’s potential for recovery. This study reports juvenile and adult hard coral abundance and composition from 122 reefs on the GBR during a period of limited acute disturbance. The data represent baseline observations for juvenile hard coral assemblages spanning the longitudinal cross-shelf gradient of the GBR and 12 degrees of latitude and augment reported distribution of adult coral assemblages over the same scale with inclusion of additional reefs. Juvenile and adult coral assemblages reflected broad differences imposed by the gradient of environmental conditions across the GBR. The mean density of juvenile hard corals was lower in the inshore reefs (5.51 m2) than at either the mid-shelf (11.8 m2) or outer shelf reefs (11.2 m2). The composition of juvenile and adult coral assemblages covaried overall, although there were different relationships between these two life stages across the continental shelf and among community types. Dissimilarity between juvenile and adult coral assemblages was greater on inshore and outer shelf reefs than on reefs in the mid-shelf, although, there were differences in community types both within these shelf positions and those that spanned mid- and outer shelf reefs. Dissimilarity was greatest for Inshore branching Acropora and high for Southern Acropora communities, although very high coral cover and very low juvenile densities at these reefs precluded interpretation beyond the clear competitive dominance of Acropora on those reefs. Dissimilarity was also high between juvenile and adult coral assemblages of Turbid inshore communities suggesting water quality pressures, along with synergistic effects of other stressors, pose ongoing selective pressures beyond the juvenile stage. Conversely, relatively low dissimilarity between juvenile and adult coral assemblages on mid-shelf and lower latitude outer shelf reefs suggests pressures beyond those influencing settlement and early post-settlement survival were having less influence on the composition of adult coral assemblages.

scholarly journals U-Th dating reveals regional-scale decline of branching Acropora corals on the Great Barrier Reef over the past century

2017 ◽  
Vol 114 (39) ◽  
pp. 10350-10355 ◽  
Author(s):  
Tara R. Clark ◽  
George Roff ◽  
Jian-xin Zhao ◽  
Yue-xing Feng ◽  
Terence J. Done ◽  
...  
Keyword(s):  
Great Barrier Reef ◽  
Coral Cover ◽  
Regional Scale ◽  
Coral Community ◽  
Past Century ◽  
Barrier Reef ◽  
The Past ◽  
Hard Coral Cover ◽  
Term Monitoring

Hard coral cover on the Great Barrier Reef (GBR) is on a trajectory of decline. However, little is known about past coral mortality before the advent of long-term monitoring (circa 1980s). Using paleoecological analysis and high-precision uranium-thorium (U-Th) dating, we reveal an extensive loss of branching Acropora corals and changes in coral community structure in the Palm Islands region of the central GBR over the past century. In 2008, dead coral assemblages were dominated by large, branching Acropora and living coral assemblages by genera typically found in turbid inshore environments. The timing of Acropora mortality was found to be occasionally synchronous among reefs and frequently linked to discrete disturbance events, occurring in the 1920s to 1960s and again in the 1980s to 1990s. Surveys conducted in 2014 revealed low Acropora cover (<5%) across all sites, with very little evidence of change for up to 60 y at some sites. Collectively, our results suggest a loss of resilience of this formerly dominant key framework builder at a regional scale, with recovery severely lagging behind predictions. Our study implies that the management of these reefs may be predicated on a shifted baseline.

scholarly journals Cumulative impacts across Australia’s Great Barrier Reef: A mechanistic evaluation

2020 ◽  
Author(s):  
Yves-Marie Bozec ◽  
Karlo Hock ◽  
Robert A. B. Mason ◽  
Mark E. Baird ◽  
Carolina Castro-Sanguino ◽  
...  
Keyword(s):  
Water Quality ◽  
Life History ◽  
Great Barrier Reef ◽  
Community Dynamics ◽  
Multiple Stressors ◽  
Coral Cover ◽  
Environmental Data ◽  
Environmental Drivers ◽  
Barrier Reef ◽  
Cumulative Impacts

ABSTRACTCumulative impacts assessments on marine ecosystems have been hindered by the difficulty of collecting environmental data and identifying drivers of community dynamics beyond local scales. On coral reefs, an additional challenge is to disentangle the relative influence of multiple drivers that operate at different stages of coral ontogeny. We integrated coral life history, population dynamics and spatially-explicit environmental drivers to assess the relative and cumulative impacts of multiple stressors across 2,300 km of the world’s largest coral reef ecosystem, Australia’s Great Barrier Reef (GBR). Using literature data, we characterized relationships between coral life history processes (reproduction, larval dispersal, recruitment, growth and mortality) and environmental variables. We then simulated coral demographics and stressor impacts at the organism (coral colony) level on >3,800 individual reefs linked by larval connectivity, and exposed to temporally- and spatially-realistic regimes of acute (crown-of-thorns starfish outbreaks, cyclones and mass coral bleaching) and chronic (water quality) stressors. Model simulations produced a credible reconstruction of recent (2008–2020) coral trajectories consistent with monitoring observations, while estimating the impacts of each stressor at reef and regional scales. Overall, corals declined by one third across the GBR, from an average ∼29% to ∼19% hard coral cover. By 2020, less than 20% of the GBR had coral cover higher than 30%. Global annual rates of coral mortality were driven by bleaching (48%) ahead of cyclones (41%) and starfish predation (11%). Beyond the reconstructed status and trends, the model enabled the emergence of complex interactions that compound the effects of multiple stressors while promoting a mechanistic understanding of coral cover dynamics. Drivers of coral cover growth were identified; notably, water quality (suspended sediments) was estimated to delay recovery for at least 25% of inshore reefs. Standardized rates of coral loss and recovery allowed the integration of all cumulative impacts to determine the equilibrium cover for each reef. This metric, combined with maps of impacts, recovery potential, water quality thresholds and reef state metrics, facilitates strategic spatial planning and resilience-based management across the GBR.

scholarly journals Benthic meiofaunal community response to the cascading effects of herbivory within an algal halo system of the Great Barrier Reef

PLoS ONE ◽  
2018 ◽  
Vol 13 (3) ◽  
pp. e0193932 ◽  
Author(s):  
Quinn R. Ollivier ◽  
Edward Hammill ◽  
David J. Booth ◽  
Elizabeth M. P. Madin ◽  
Charles Hinchliffe ◽  
...  
Keyword(s):  
Great Barrier Reef ◽  
Community Response ◽  
Barrier Reef ◽  
Cascading Effects ◽  
Meiofaunal Community

scholarly journals Potential for rapid genetic adaptation to warming in a Great Barrier Reef coral

2017 ◽  
Author(s):  
Mikhail V. Matz ◽  
Eric A. Treml ◽  
Galina V. Aglyamova ◽  
Madeleine J. H. van Oppen ◽  
Line K. Bay
Keyword(s):  
Genetic Variation ◽  
Great Barrier Reef ◽  
Coral Cover ◽  
Reef Coral ◽  
Biophysical Model ◽  
Detectable Effect ◽  
Genetic Adaptation ◽  
Barrier Reef ◽  
Biophysical Modeling ◽  
Adaptive Genetic Variation

AbstractCan genetic adaptation in reef-building corals keep pace with the current rate of sea surface warming? Here we combine population genomic, biophysical modeling, and evolutionary simulations to predict future adaptation of the common coralAcropora milleporaon the Great Barrier Reef. Loss of coral cover in recent decades did not yet have detectable effect on genetic diversity in our species. Genomic analysis of migration patterns closely matched the biophysical model of larval dispersal in favoring the spread of existing heat-tolerant alleles from lower to higher latitudes. Given these conditions we find that standing genetic variation could be sufficient to fuel rapid adaptation ofA. milleporato warming for the next 100-200 years, although random thermal anomalies would drive increasingly severe mortality episodes. However, this adaptation will inevitably cease unless the warming is slowed down, since no realistic mutation rate could replenish adaptive genetic variation fast enough.

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.

Diversity, abundance, and distribution of reef sharks on outer-shelf reefs of the Great Barrier Reef, Australia

2014 ◽  
Vol 161 (12) ◽  
pp. 2847-2855 ◽  
Author(s):  
Justin R. Rizzari ◽  
Ashley J. Frisch ◽  
Katalin A. Magnenat
Keyword(s):  
Great Barrier Reef ◽  
Outer Shelf ◽  
Barrier Reef ◽  
Reef Sharks ◽  
Abundance And Distribution
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