Acoustic tracking of a large predatory marine gastropod, Charonia tritonis, on the Great Barrier Reef

Crown-of-thorns starfish Acanthaster planci (COTS) outbreaks are a major cause of coral cover loss on the Great Barrier Reef (GBR), with manual culling having only localised success. The endangered giant triton snail Charonia tritonis is a natural predator of COTS, although aquarium and field observations indicate the intensity of direct predation may be inadequate to significantly mediate outbreaks. However, their mere presence can elicit a chemically induced sensory behavioural response which may suppress COTS populations when in non-outbreak status. While there is increasing knowledge of the sensory biology of both species, little is known regarding giant triton snail numbers on the GBR or about how they move and occupy space, making it difficult to determine their true zone of influence and thus their capacity to disrupt COTS behaviour. We used passive acoustic telemetry to establish short-term activity space and movement patterns of giant triton snails on the GBR. Individuals were tracked for up to 41 d, were observed to travel 234.24 m d-1, with a mean total cumulative distance travelled at night (1923.19 m) nearly double that observed during the day (1014.84 m). These distances encompass those reported for COTS (10.3 m d-1) and align with COTS nocturnal behaviour. Space utilisation distributions (UDs) revealed a mean (±SD) home range of 1179.40 ± 659.40 m2 (95% UD) and a core area of 195.68 ± 141.31 m2 (50% UD). Revealing the short-term movement patterns of this natural COTS predator within a reef environment advances knowledge of its spatial ecology and will provide information for its future conservation and for COTS management efforts.

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

10.1101/114173 ◽

2017 ◽

Cited By ~ 4

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.

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

Proceedings of The Royal Society B Biological Sciences ◽

10.1098/rspb.2020.1432 ◽

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.

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

Diversity ◽

10.3390/d11060085 ◽

2019 ◽

Vol 11 (6) ◽

pp. 85 ◽

Cited By ~ 1

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.

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Assessing loss of coral cover on the Great Barrier Reef: A response to Hughes et al. (2011)

Coral Reefs ◽

10.1007/s00338-011-0794-7 ◽

2011 ◽

Vol 30 (3) ◽

Cited By ~ 23

Author(s):

H. Sweatman ◽

C. Syms

Keyword(s):

Great Barrier Reef ◽

Coral Cover ◽

Barrier Reef

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Short-term movement patterns and diet of small dasyurid marsupials in semiarid Australia

Australian Mammalogy ◽

10.1071/am10052 ◽

2012 ◽

Vol 34 (1) ◽

pp. 49 ◽

Cited By ~ 9

Author(s):

Lisa Warnecke ◽

Gerhard Körtner ◽

Chris J. Burwell ◽

James M. Turner ◽

Fritz Geiser

Keyword(s):

Spatial Ecology ◽

Arid Zone ◽

Activity Patterns ◽

Movement Patterns ◽

Small Scale ◽

Radio Tracking ◽

Short Term ◽

Resting Sites ◽

Sminthopsis Crassicaudata ◽

Radio Transmitters

Since little information is available on the spatial ecology of small arid-zone marsupials, we used radio-tracking to investigate the small-scale activity patterns of three dasyurid species in semiarid Australia. Sminthopsis crassicaudata, Planigale gilesi and S. macroura were equipped with miniature radio-transmitters to monitor choice of resting sites and daily movements. Resting sites were located within an area of 1.27 ± 0.36 ha, 0.12 ± 0.02 ha and 3.60 ± 0.95 ha, respectively and individuals returned to previously used resting sites regularly. We also analysed scat samples of S. crassicaudata and P. gilesi, and identified Araneae, Hymenoptera and Orthoptera as the major prey taxa for both species. Our study presents the first radio-tracking-based information on movements for these species in semiarid habitat, which indicates that, over a period of several weeks, resting sites are situated within small and defined areas.

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Closing the gap: mixed stock analysis of three foraging populations of green turtles (Chelonia mydas) on the Great Barrier Reef

PeerJ ◽

10.7717/peerj.5651 ◽

2018 ◽

Vol 6 ◽

pp. e5651

Author(s):

Karina Jones ◽

Michael Jensen ◽

Graham Burgess ◽

Johanna Leonhardt ◽

Lynne van Herwerden ◽

...

Keyword(s):

Great Barrier Reef ◽

Spatial Ecology ◽

New Caledonia ◽

Relative Proportion ◽

Chelonia Mydas ◽

Barrier Reef ◽

Green Turtles ◽

Mixed Stock Analysis ◽

Stock Analysis ◽

Mixed Stock

A solid understanding of the spatial ecology of green turtles (Chelonia mydas) is fundamental to their effective conservation. Yet this species, like many marine migratory species, is challenging to monitor and manage because they utilise a variety of habitats that span wide spatio-temporal scales. To further elucidate the connectivity between green turtle rookeries and foraging populations, we sequenced the mtDNA control region of 278 turtles across three foraging sites from the northern Great Barrier Reef (GBR) spanning more than 330 km: Cockle Bay, Green Island and Low Isles. This was performed with a newly developed assay, which targets a longer fragment of mtDNA than previous studies. We used a mixed stock analysis (MSA), which utilises genetic data to estimate the relative proportion of genetically distinct breeding populations found at a given foraging ground. Haplotype and nucleotide diversity was also assessed. A total of 35 haplotypes were identified across all sites, 13 of which had not been found previously in any rookery. The MSA showed that the northern GBR (nGBR), Coral Sea (CS), southern GBR (sGBR) and New Caledonia (NC) stocks supplied the bulk of the turtles at all three sites, with small contributions from other rookeries in the region. Stock contribution shifted gradually from north to south, although sGBR/CS stock dominated at all three sites. The major change in composition occured between Cockle Bay and Low Isles. Our findings, together with other recent studies in this field, show that stock composition shifts with latitude as a natural progression along a coastal gradient. This phenomenon is likely to be the result of ocean currents influencing both post-hatchling dispersal and subsequent juvenile recruitment to diverse coastal foraging sites.

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High survival following bleaching highlights the resilience of a highly disturbed region of the Great Barrier Reef

10.1101/2021.10.18.464880 ◽

2021 ◽

Author(s):

Cathie A Page ◽

Christine Giuliano ◽

Line K Bay ◽

Carly J Randall

Keyword(s):

Great Barrier Reef ◽

Coral Cover ◽

Heat Exposure ◽

High Survival ◽

Barrier Reef ◽

Recovery Potential ◽

Coral Communities ◽

Degree Heating Weeks ◽

High Turbidity ◽

Exposure Metrics

Natural bleaching events provide an opportunity to examine how local scale environmental variation influences bleaching severity and recovery. During the 2020 marine heatwave, we documented widespread and severe coral bleaching (75 – 98% of coral cover) throughout the Keppel Islands in the Southern inshore Great Barrier Reef. Acropora, Pocillopora and Porites were the most severely affected genera, while Montipora was comparatively less susceptible. Site-specific heat-exposure metrics were not correlated with Acropora bleaching severity, but recovery was faster at sites that experienced lower heat exposure. Despite severe bleaching and exposure to accumulated heat that often results in coral mortality (degree heating weeks ~ 4 – 8), cover remained stable. Approximately 94% of fate-tracked Acropora millepora colonies survived, perhaps owing to reduced irradiance stress from high turbidity, heterotrophic feeding, and large tidal flows that can increase mass transfer. Severe bleaching followed by rapid recovery, and the continuing dominance of Acropora populations in the Keppel Islands is indicative of high resilience. These coral communities have survived an 0.8 °C increase in average temperatures over the last 150 years. However, recovery following the 2020 bleaching was driven by the easing of thermal stress, which may challenge their recovery potential under further warming.

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Rates of decline and recovery of coral cover on reefs impacted by, recovering from and unaffected by crown-of-thorns starfish Acanthaster planci:a regional perspective of the Great Barrier Reef

Marine Ecology Progress Series ◽

10.3354/meps196179 ◽

2000 ◽

Vol 196 ◽

pp. 179-186 ◽

Cited By ~ 34

Author(s):

MJ Lourey ◽

DAJ Ryan ◽

IR Miller

Keyword(s):

Great Barrier Reef ◽

Coral Cover ◽

Barrier Reef ◽

Regional Perspective

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

10.21203/rs.3.rs-299051/v1 ◽

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 .

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