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 Great Barrier Reef Degradation, Sea Surface Temperatures, and Atmospheric CO2 Levels Collectively Exhibit a Stochastic Process with Memory

2021 ◽  
Author(s):  
Allan Elnar ◽  
Christianlly Cena ◽  
Christopher Casenas Bernido ◽  
M. Victoria Carpio-Bernido
Keyword(s):  
Stochastic Process ◽  
Great Barrier Reef ◽  
Coral Cover ◽  
Sea Surface ◽  
Atmospheric Co2 ◽  
Sea Surface Temperatures ◽  
Barrier Reef ◽  
Hard Coral ◽  
Co2 Levels ◽  
Hard Coral Cover

Abstract Quantifying ecological memory could be done at several levels from the rate of physiological changes in an ecosystem all the way down to responses at the genetic level. One way of unlocking the information encoded in a collective environmental memory is to examine the recorded time-series data generated by different components of an ecosystem. In this paper, we probe into the case of the Great Barrier Reef (GBR) which is threatened by elevated sea surface temperatures (SST) and ocean acidification attributed to rising atmospheric CO 2 levels. Specifically, we investigate the interrelated dynamics between the degradation of the GBR, SST, and rising atmospheric CO 2 levels, by considering three datasets: (a) the mean percentage hard coral cover of the GBR from the archives of the Australian Institute of Marine Science; (b) SST close to the GBR from the National Oceanic and Atmospheric Administration; and (c) the Keeling curve for atmospheric CO 2 levels measured by the Mauna Loa Observatory. We show that fluctuating observables in these datasets have the same memory behavior described by a non-Markovian stochastic process. All three datasets show a good match between empirical and analytical mean square deviation. An explicit analytical form for the corresponding probability density function is obtained which obeys a modified diffusion equation with a time dependent diffusion coefficient. This study provides a new perspective on the similarities of and interaction between the GBR’s declining hard coral cover, SST, and rising atmospheric CO2 levels by putting all three systems into one unified framework indexed by a memory parameter μ and a characteristic frequency ν . The short-time dynamics of CO2 levels and SST fall in the superdiffusive regime, while the GBR exhibits hyperballistic fluctuation in percent coral cover with the highest values for μ and ν .

Population Explosions ofAcanthaster planciand Associated Destruction of the Hard-coral Cover of Reefs of the Great Barrier Reef, Australia

1975 ◽  
Vol 2 (4) ◽  
pp. 247-256 ◽  
Author(s):  
Robert Endean ◽  
William Stablum
Keyword(s):  
Great Barrier Reef ◽  
Coral Cover ◽  
Pacific Region ◽  
Barrier Reef ◽  
Hard Coral ◽  
Acanthaster Planci ◽  
West Pacific ◽  
Significant Percentage ◽  
Hard Coral Cover ◽  
Principal Region

Population explosions of the Crown-of-thorns Starfish,Acanthaster planci, first reported on reefs of the Great Barrier Reef in the Cairns region near lat. 17° S during the early 1960s, have since spread to numerous other reefs. The spread has been predominantly southwards, the principal region of infestation currently lying between lat. 19° S and lat. 19°20' S. South of this region, scattered infestations of reefs have recently been reported. Available data indicate that most reefs in the middle third of the Great Barrier Reef were infested during the last decade, and it is postulated that most reefs in the southernmost third will be infested during the next decade.The bulk of the hard-coral cover of most of the inner platform reefs infested, and a lower but significant percentage of the hard-coral cover of the outer platform reefs affected by the infestations, have been devastated. Recovery of devastated reefs is in progress but is slow.TheA. planciinfestations appear to the authors to be man-induced, and it is suggested that international action be taken to assess the magnitude of theA. planciproblem and to coordinate possible control activities in the Indo-West Pacific region.

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 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

scholarly journals Cross-shelf distribution patterns of tropical juvenile cephalopods sampled with light-traps

1995 ◽  
Vol 46 (4) ◽  
pp. 707 ◽  
Author(s):  
NA Moltschaniwskyj ◽  
PJ Doherty
Keyword(s):  
Great Barrier Reef ◽  
Distribution Patterns ◽  
Present Knowledge ◽  
Outer Shelf ◽  
Barrier Reef ◽  
Light Traps ◽  
Coral Sea ◽  
Reef Environments ◽  
High Concentrations ◽  
Abundant Genus

This paper describes the cephalopod genera caught with light-traps at different locations and depths in the waters of the central Great Barrier Reef (GBR). Multiple stations were sampled in four locations: (I) the coastal GBR Lagoon, (2) inter-reef passages (Magnetic and Palm), (3) near-reef environments (Keeper, Helix, Faraday and Myrmidon) ranging from mid- to outer-shelf locations, and (4) the Coral Sea. A total of 13 cephalopod genera was caught from monthly cruises conducted from October to January of 1990-91 and 1991-92. Octopus, the most abundant juvenile cephalopod, was present in relatively high numbers at all shelf locations; few were caught in the Coral Sea. Photololigo, the most abundant squid, was rarely caught outside the GBR Lagoon. In contrast, Sthenoteuthis, the second most abundant squid, was caught at all locations. Deep samples from most locations were dominated by Octopus. Abralia was found only near the bottom of the GBR Lagoon; in contrast, Euprymna, the fourth most abundant genus, was collected only at the surface. Cephalopod communities from the GBR Lagoon had higher abundances of Octopus, Photololigo and Abralia compared with communities from the three other areas. Reef passages and reef locations shared similar communities, with the squid component dominated by Sthenoteuthis. Very low numbers of cephalopods were caught in the Coral Sea by light attraction. High concentrations of cephalopods detected in the middle of the GBR Lagoon are consistent with present knowledge about oceanographic processes over this shelf.

scholarly journals Flushing time of solutes and pollutants in the central Great Barrier Reef lagoon, Australia

2007 ◽  
Vol 58 (8) ◽  
pp. 778 ◽  
Author(s):  
Yonghong Wang ◽  
Peter V. Ridd ◽  
Mal L. Heron ◽  
Thomas C. Stieglitz ◽  
Alan R. Orpin
Keyword(s):  
Diffusion Coefficient ◽  
Great Barrier Reef ◽  
Diffusion Model ◽  
Outer Shelf ◽  
Barrier Reef ◽  
Flushing Time ◽  
Reef Lagoon ◽  
Exchange Processes ◽  
Offshore Reef ◽  
Outer Half

The flushing time of the central Great Barrier Reef lagoon was determined by using salinity as a tracer and developing both an exchange model and a diffusion model of the shelf exchange processes. Modelling suggests that the cross-shelf diffusion coefficient is approximately constant for the outer half of the lagoon but decays rapidly closer to the coast. The typical outer-shelf diffusion coefficient is ~1400 m2 s–1, dropping to less than 100 m2 s–1 close to the coast. Flushing times are around 40 days for water close to the coast and 14 days for water in the offshore reef matrix.

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