Patterns of zonation of assemblages of the Lutjanidae, Lethrinidae and Serranidae (Epinephelinae) within and among mid-shelf and outer-shelf reefs in the central Great Barrier Reef

1997 ◽  
Vol 48 (2) ◽  
pp. 119 ◽  
Author(s):  
Stephen J. Newman ◽  
David McB. Williams ◽  
Garry R. Russ
Keyword(s):  
Great Barrier Reef ◽  
Central Region ◽  
Spatial Scales ◽  
Outer Shelf ◽  
Barrier Reef ◽  
Fishing Pressure ◽  
Back Reef ◽  
Outer Continental Shelf ◽  
Spatial Differences ◽  
Reef Zones

Visual censuses were used to quantify the distribution and abundance of the Lutjanidae, Lethrinidae and Serranidae in three reef zones (windward reef slope, lagoon, back reef) of three reefs on the mid shelf and three reefs on the outer continental shelf in the central region of the Great Barrier Reef. Significant spatial variability was identified in the abundances of many species between locations (outer-shelf and mid-shelf communities), between reefs (high-abundance v. low-abundance reefs), and within reefs (characteristic communities within zones on individual reefs). Species of the Lutjanidae, Lethrinidae and Serranidae were found to occur in assemblages that were characteristic of major zones (windward reef slopes, lagoons and leeward back reefs), this pattern being consistent within and among shelf locations. Care will need to be taken in determining the appropriate spatial scales of sampling in any future experiments (e.g. manipulations of fishing pressure) to ensure that the effects of smaller-scale spatial differences are not confounded when larger-scale comparisons are made.

Water circulation around Britomart Reef, Great Barrier Reef, during July 1979

1980 ◽  
Vol 31 (4) ◽  
pp. 415 ◽  
Author(s):  
E Wolanski ◽  
M Jones
Keyword(s):  
Great Barrier Reef ◽  
Sea Level ◽  
Central Region ◽  
Reef Flat ◽  
Water Circulation ◽  
Barrier Reef ◽  
Trade Winds ◽  
Sea Breezes ◽  
Coral Sea ◽  
Sea Level Oscillations

Weather and currents at eight sites were measured and drogue trajectories obtained in July 1979 at Britomart Reef, a middle reef located at 18�16'S.,146� 38'E. in the central region of the Great Barrier Reef province. The longest current records (3 weeks) were obtained at two sites in passes between the Coral Sea and the Great Barrier Reef Lagoon where westerly currents modulated by tides were observed. Analysis of residuals also showed the importance of wind-driven secondary circulation. Non-tidal sea-level oscillations were very small. Shorter current records (1-10 days) at six sites in the lagoon and on the reef flat showed a predominant northerly flow, also modulated by tides and wind. A residual anticlockwise water circulation existed in the lagoon where flushing was controlled more by winds than by tides. The rise in sea level over the reef flat as a result of waves breaking was negligible. Temperature differences between air and water accounted for the cooling of the water column during the expedition. Constant south-east trade winds were experienced at the reef, while on land the wind was weaker. more variable, and often dominated by land-sea breezes.

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.

Population structure and trophic composition of the free-living nematodes inhabiting carbonate sands of Davies Reef, Great Barrier Reef, Australia

1986 ◽  
Vol 37 (5) ◽  
pp. 609 ◽  
Author(s):  
DM Alongi
Keyword(s):  
Population Structure ◽  
Great Barrier Reef ◽  
Reef Flat ◽  
Detrended Correspondence Analysis ◽  
Reef Crest ◽  
Barrier Reef ◽  
Back Wall ◽  
Free Living ◽  
Shallow Lagoon ◽  
Reef Zones

Population structure and trophic composition of free-living nematodes from carbonate sands within different functional zones (reef crest, reef flat and lagoon) of Davies Reef in the Great Barrier Reef were examined. At the reef crest (station C) and at a shallow lagoon area unprotected by the back wall of the reef flat (station G), sediments were subjected to intense wave action and supported significantly (P < 0.05) lower mean nematode densities (<60 individuals per 10 cm2) than sands within the other reef zones (100-400 individuals per 10 cm2). Mean nematode densities and numerical species richness were highest (P < 0.05) in a shallow lagoon habitat protected from hydrodynamic- induced disturbances by the back wall of the reef flat (station H). Differences in population densities among the reef zones were not related to water depth or sediment granulometry. Species diversity was low within the reef, with only six species present in deep lagoon sands co-inhabited by actively bioturbating ghost shrimps (Callianassa spp.). Normal classification, nodal analysis and detrended correspondence analysis indicated that faunal groups were distinct among the different reefal zones. Very coarse to medium sands at the reef crest and across the reef flat were inhabited primarily by omnivorous and epistrate-feeding nematodes. Most nematodes within the very fine to fine sands of the lagoon were non-selective or selective deposit feeders. Nematode community structure from the reef crest to the shallow lagoon appears to be determined primarily by sediment granulometry as controlled by reef hydrodynamics, whereas in the deep lagoon nematode communities are negatively affected by the presence of thalassinid ghost shrimps.

Benthic community composition influences within-habitat variation in macroalgal browsing on the Great Barrier Reef

2010 ◽  
Vol 61 (9) ◽  
pp. 999 ◽  
Author(s):  
C. Cvitanovic ◽  
A. S. Hoey
Keyword(s):  
Coral Reefs ◽  
Great Barrier Reef ◽  
Benthic Community ◽  
Spatial Scales ◽  
Structural Complexity ◽  
Barrier Reef ◽  
Removal Rates ◽  
Ecological Processes ◽  
Habitat Variation ◽  
Benthic Composition

The removal of macroalgae by herbivores is fundamental to the long-term persistence of coral reefs. Variation in macroalgal browsing has been documented across a range of spatial scales on coral reefs; however, few studies have examined the factors that influence within-habitat rates of herbivory. The aim of the present study was to quantify herbivory on two species of Sargassum across three bays on an inshore island in the central Great Barrier Reef (GBR), and to determine whether these removal rates were related to the benthic composition or herbivorous fish communities. Removal rates of Sargassum differed significantly among bays, with removal rates in the southern bay (66.9–83.0% per 3 h) being approximately double that of the two other bays (29.2–38.5% per 3 h). The removal rates displayed a direct relationship with the benthic community structure, in particular the cover of macroalgae and live plate corals. Although it is difficult to determine whether these relationships are related to the availability of food resources or the structural complexity of the substratum, they highlight the potential influence of benthic composition on ecological processes. Quantifying and understanding the drivers of herbivory across a range of spatial scales is essential to the future management of coral reefs.

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.

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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