Reef Province Research Articles

Trace metals in corals from the Great Barrier Reef

Various octocorallian and scleractinian corals from within the Great Barrier Reef Province were analysed for zinc, copper, cadmium, nickel and lead by atomic absorption spectroscopy. Of the two coral groups, the octocorals accumulated significantly greater amounts of all detectable metals. The soft coral, Sarcophyton sp., revealed distinct inter-locational differences for zinc, copper and cadmium. The potential of this genus for monitoring trace metal pollution in tropical reef waters is briefly discussed.

Trace metals in surface water from the Great Barrier Reef

Filtered (0.45 μm), unacidified, surface seawater samples, collected at 3-monthly intervals for 9 months from three locations within the Great Barrier Reef Province, were analysed for zinc, copper, nickel, cadmium and lead by atomic absorption spectroscopy (air/acetylene flame) following Chelex-100 (ammonium form) extraction. Mean levels of each metal ranged from 0.03–0.35; 0.11–0.24; 0.06–0.16; <0.01–0.06; all less than 0.06 μg l −1 respectively. Significant interlocational differences were observed for copper and nickel and clear temporal trends were identified for copper (location-dependent) and cadmium.

Étude paléontologique du genre Sabinia (Rudiste à canaux)des récifs du Campanien de Tunisie

Campanian rudist reefs of Central Tunisia are rich in pallial-canal rudists, belonging to the genus Sabinia. The Djebel Serraguia layer shows well-preserved samples allowing to make a detailed paleontologic study. A new sub species of a previously observed species from the Maastrichtian of Yugoslavia and Turkey is described. Identified for the first time on the african margins, this new taxon gives interesting data concerning systematic and evolution of the genus Sabinia, as well as the relationships between reef provinces during the Upper Senonian. The biosedimentologic role of Sabinia within tunisian reefs is pointed out.

Post‐glacial seismic stratigraphy, central Great Barrier Reef, Australia

ABSTRACTA regional programme of continuous seismic (boomer) profiling in the central Great Barrier Reef Province has identified a widespread shallow seismic discontinuity (reflector A) which is interpreted as the pre‐Holocene surface.Nine seismic facies units are distinguished primarily on the basis of the seismic records, but also with the aid of additional criteria such as location and surface sediment types. Two units underlie reflector A and are pre‐Holocene. These units are interpreted as: (a) Permo‐Carboniferous bedrock, and (b) Pleistocene/? Tertiary sediments, consisting of both shelf‐wide terrigenous units, and carbonate mounds and platforms under present reefs. Seven units are post‐glacial and overlie reflector A. These units are interpreted as: (c) fluvial/estuarine channel fill, (d) relict delta‐front deposits, (e) relict transgressive veneer, (f) coastal coarse and (g) fine deposits, (h) modern reef and (i) reef talus.In general post‐glacial sediment cover is very thin and in many places on the mid‐shelf the pre‐Holocene units crop out. Substantial post‐glacial accumulations are limited to protected coastal embayments and to offshore reef masses.

Tumor formations in scleractinian corals

A highly localized incidence of skeletal malformations (tumors) in the scleractinian coralsPlatygyra pini andP. sinensis on an inshore fringing reef at Cockle Bay, Magnetic Island within the Great Barrier Reef province is reported. These tumors are typified by a localized area of increased growth rate resulting in roughly circular protuberances extending up to 4.5 cm above the colony's surface. In both species, similar proportions of their populations carried tumors (24.1 % inP. pini and 18.7 % inP. sinensis). Larger colonies (>80 cm in diameter) are at least 7 times more likely to possess tumors than smaller colonies (<40 cm in diameter). X-radiographs of the skeletal malformations indicate a point of origin, presumably from a single budded polyp with subsequent, localized, accelerated growth. The mean radial growth rate of the tumorous area was 29 % greater than that of the surrounding normal regions. In contrast to the normal tissue, the tumorous tissue exhibited proliferation of cells, atrophied gastrodermal cells and mesenterial filaments which were larger and disordered in structure. The environmental conditions at Cockle Bay are relatively extreme with high turbidity, periodic exposure of the reef flat, abrupt changes in salinity during the wet season and mechanical damage to corals caused by unpredictable cyclonic storms. It is suggested that a combination of environmental stresses coupled with an injury inflicted on the corals are possible stimuli that initiate the development of these abnormal growth through either bacterial attack or the development of an aberrant polyp during tissue repair.

Halimeda biomass, growth rates and sediment generation on reefs in the central great barrier reef province

The average biomass ofHalimeda per m2 of solid substratum increased progressively on a series of reefs situated at increasing distances from the shore in the central Great Barrier Reef. There was none on a reef close inshore, increasing to nearly 500 g m−2 total biomass (≃90% calcium carbonate) on an oceanic atoll system in the Coral Sea. The biomass measured contained 13 species ofHalimeda but was dominated by only two species,H. copiosa andH. opuntia, except on the atoll whereH. minima was dominant. Three sand-dwelling species were also present but did not occur anywhere in substantial quantities. Growth rates of the dominant species were measured bv tagging individual branch tips. A mean value of 0.16 segments d−1 was recorded but 41% of the branch tips did not grow any new segments whilst only 1% grew more than one per day. The number of branch tips per unit biomass was very constant and has been used in conjunction with growth rates and biomass to calculate productivity rates, and thence sedimentation, in the lagoon of one of the reefs. Biomass doubling time of 15 d and production of 6.9 g dry wt m−2 d−1 are considerably higher than previously reported values forHalimeda vegetation and there was little seasonal change detected over a whole year. Those values indicate annual accretion of 184.9 g m−2 year−1 ofHalimeda segment debris over the entire lagoon floor (5.9 km2) of Davies Reef, equivalent to 0.13 mm year−1 due toHalimeda alone, or 1 m every 1,892 years when other contributions to that sediment are taken into account.

Nemerteans of the Great Barrier Reef: 6. Enopla Hoplonemertea (Polystilifera: Reptantia)

Two new genera and species of reptantic polystiliferous hoplonemerteans from the Great Barrier Reef province of Australia are described and illustrated. Urichonemertes pilorhynchus gen. et sp. nov. and Xenonemertes rhamphocephalus gen. et sp. nov. are both placed in the family Drepanophoridae (Polystilifera: Eureptantia: Aequifurcata).

Nemerteans of the Great Barrier Reef: 5. Enopla Hoplonemertea (Monostilifera)

Three new species of monostiliferous hoplonemerteans from the Great Barrier Reef province of Australia are described and illustrated. These are, with their families indicated in parentheses, Poseidonemertes bothwellae sp. nov. (Amphiporidae), Nemertes hermaphroditicus sp. nov. (Emplectonematidae) and Pantinonemertes mooreae sp. nov. (Prosorhochmidae).

Positive relief over buried post-glacial channels, Great Barrier Reef Province, Australia

Continuous seismic profiling on the continental shelf, central Great Barrier Reef Province, Australia, has delineated a major sub-bottom reflector interpreted as the pre-Holocene surface. Channels eroded in this surface are infilled and overfilled by post-glacial sediments. Filling is ascribed to estuarine backfilling during sea-level rise followed by deposition of delta front deposits. In many cases these fills create positive relief over buried channels. Hence modern shelf morphology may not be an accurate guide to the positions of Pleistocene channels across the shelf.

Regional Variation in Shade-Dwelling Coral Assemblages of the Great Barrier Reef Province

Research on shade-dwelling scleractinian corals involved the study of more than 120 caves, tunnels, and shaded overhangs from various reef types within the Great Barrier Reef Province. Study was concentrated in the Lizard lsland region (14c15 S), with comparative work in the central (19 S) and especially the southern (23 S) sectors of the province. Numerical classification was used to analyse patterns of distribution and association within these shade-dwelling assemblages. Analysis confirmed the existence of definite regional differences in the shade-dwelling coral fauna, with caves in the southern part of the Barrier Reef having a generally impoverished scleractinian fauna compared with that found in more northerly areas. Observations of other shade-dwelling biota suggest that at higher latitudes, certain algal groups are more successful than corals in cryptic habitats, with the algae tending to exclude their scleractinian competitors. This suggestion is borne out by records from the southwest Indian Ocean. These and other studies indicate that while there are some basic similarities between the cryptic biota from many reef regions, generalizations about the structure of the shadedwelling communities should not be made from studies within a limited area.

Nemerteans of the Great Barrier Reef: 4. Anopla Heteronemertea (Valenciniidae)

A new valenciniid heteronemertean, Valencinina albula, gen. et sp. nov. from the Great Barrier Reef province of Australia, is described and illustrated. This is the first record of a valenciniid from Australasian waters.

Nemerteans of the Great Barrier Reef: 3. Anopla Heteronemertea (Lineidae)

Nine species of lineid heteronemerteans are recorded from the Great Barrier Reef province of Australia. Six of these are new species, including four new genera, and are fully described and illustrated. These are Aetheorhynchus actites gen. et sp. nov., Bennettiainsularis gen. et sp. nov., Cerebratulus magnetkus sp. nov., Colemania albulus gen. et sp. nov., Micrura tridacnae sp. nov. and Quasilineus pulcherrimus gen. ct sp. nov. Lineus tricuspidatus (Quoy & Gaimard) is re-established, illustrated and described. Gorgonorhynchus repens Dakin & Fordham and Parborlasia hutchingsi Gibson have been fully described elsewhere, but a full list of known locations is provided.

Annual temperature cycle in Cleveland Bay, Great Barrier Reef province

Weekly temperature measurements have been taken over a 55-month period at a 10 m deep station in Cleveland Bay. Temperature at the surface ranged from 19.3 to 30.9�C with a mean monthly minimum of 20.9�C in July and a mean monthly maximum of 29.0�C in January. The water-temperature curve lagged behind the 0900 h air-temperature curve by an average of 10 days. Differences between the present data and other published temperature data for Great Barrier Reef waters are discussed.

Mid-Holocene high sea levels along the coastal plain of the Great Barrier Reef Province: A discussion

Belperio (1979) has suggested that lack of evidence for higher relative Holocene sea levels in the coastal plain of North Queensland negates previously presented research. Lack of evidence in particular areas is here suggested as insufficient argument and the features and radiometric dates which lead to the conclusion that higher relative sea levels have existed are reviewed in the light of Belperio's comments. In particular Belperio's claim for uniform Holocene stability in eastern Australia is challenged in the light of recently reported 6 m of uplift in the last 6000 years in the Broad Sound area.

Structural Interpretation of Buried Silurian Reefs in Southwestern Indiana: ABSTRACT

End_Page 1283------------------------------Two or more generations of buried Silurian reefs are present in southwestern Indiana. Possibly all the larger reefs grew until Devonian time. Some may have attained thicknesses greater than those of any other group of Silurian reefs. Strata topping the reefs range from Middle or Late Silurian to Middle Devonian in age. Deep drilling is sparse in southwestern Indiana, and limited geophysical surveys are mostly confidential. Interpretation of the reef province then relies heavily on evaluation of structural deformation (broad sense) of the rocks both encasing and overlying these and other Silurian reefs and of the reefs-proper and their flanks. The amounts of suprareef drape in strata as young as Pennsylvanian are related to reef thickness, kind of reef, erosion of reef and postreef rocks, height above reef, and counterproductive subreef sagging. Both suprareef draping and subreef sagging are expectable for any given reef. Long-continued diagenesis, even to the present time, was the most significant cause of such structural deformation; subreef soft-sediment deformation penecontemporaneous with reef growth also was a factor. Differential compaction between reef and contemporaneously deposited interreef rocks was the most important diagenetic process. Differential compaction in rocks far above the reefs, acting in concert with lithologic and thickness differences brought about by continued growth of drape structure, had a min r role. Differential solution and recrystallization could have contributed especially to subreef sagging. These interpretations temper some ideas that localized tectonic uplifts influenced both reef siting and suprareef draping and that early cementation resulted in structural stabilization of substrate, reef, and reef flank penecontemporaneous with growth. The ranges in geologic circumstances that apply--in setting, reef genesis and abortion, erosion or nonerosion and burial of reefs, and postreef attainment of structural clues to reef recognition--suggest that southwestern Indiana has a reef-related reservoir potential that applies differentially within the reef province. The differential extends to the reefs themselves and to individual formations draped over the reefs. This province, surely, is inadequately explored for hydrocarbon potential in sub-Mississippian rocks. End_of_Article - Last_Page 1284------------

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

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.

Nemerteans of the Great Barrier Reef: 2. Anopla Heteronemertea (Baseodiscidae)

Nine species of lineid heteronemerteans are recorded from the Great Barrier Reef province of Australia. Six of these are new species, including four new genera, and are fully described and illustrated. These are Aetheorhynchus actitesgen. et sp. nov., Bennettiainsularisgen. et sp. nov., Cerebratulus magnetkus sp. nov., Colemania albulus gen. et sp. nov., Mkrura tridacnae sp. nov. and Quasilineus pulcherrimus gen. ct sp. nov. Lineus tricuspidatus (Quoy & Gaimard) is re-established, illustrated and described. Gorgonorhynchus repens Dakin & Fordham and Parborlasia hutchingsi Gibson have been fully described elsewhere, but a full list of known locations is provided.

Negative evidence for a mid-Holocene high sea level along the coastal plain of the Great Barrier Reef Province

New data are presented from the north Queensland coastal plain which indicate that present Holocene sea level was reached about 6000 years B.P. and has not deviated significantly since then. Together with negative geomorphic evidence for higher sea levels along the coastal plain, this implies that previous reports of evidence for higher stands may have resulted from misinterpretation of field evidence. Close agreement with sealevel data from central Queensland and New South Wales indicates that eastern Australia has followed a common relative sea-level history and has been an area of relative tectonic stability.

Nemerteans of the Great Barrier Reef: 1. Anopla Palaeonemertea

Two new palaeonemerteans, Carinoma patriciaesp. nov., and Hubrechtella queenslandicasp. nov., from the Great Barrier Reef province of Australia, are described and illustrated. The systematic relationships of these nemerteans are discussed and emended diagnoses are given for the genera Carinoma (Carinomidae) and Hubrechtella (Hubrechtidae).

Copepod swarms: Attributes and role in coral reef ecosystems

Monospecific aggregations of copepods were observed and sampled from eleven coral reefs, two sea grass habitats, and several marine lakes in the Central and Northern Great Barrier Reef Provinces of Australia and in Palau, Western Caroline Islands. Acartia australis, Acartia bispinosa, Oithona oculata, and Centropages orsinii regularly occurred at swarm densities of from 500,000·m−3 (A. australis) to 1,500,000·m−3(O. oculata). During the day copepods swarmed over white sand on the lagoon side of windward reefs, adjacent to or downstream from isolated coral outcrops, with size of swarm dependent on size and shape of the nearby coral head. Swarms 1–2 m in diameter were common; they occasionally exceeded 30 m3. Seasonally these large swarms coalesced and carpeted the lagoon floor with copepods. In Palau O. oculata also swarmed near the surface in a continuous linear band in the solution notch that undercuts the limestone islands. Acartia bispinosa swarmed at the surface in open water in the marine lakes of Palau and over sea grass beds in the lagoon at low water. Swarming probably serves several adaptive functions, but protection from predators appears of major importance. Visual behavior and orientation to surrounding objects maintained swarm integrity, as did mechanical winnowing by currents. At night, swarms dispersed throughout the water column and swarming species sometimes dominated the nocturnal plankton within the reef lagoon. Previous investigations of coral reef zooplankton have not sampled swarming copepods properly and prior estimates of food available to the reef community must be re‐evaluated.