Note on the sediments and hydrology of the Gulf of Carpentaria, Australia

1994 ◽  
Vol 45 (3) ◽  
pp. 283 ◽  
Author(s):  
IF Somers ◽  
BG Long
Keyword(s):  
Grain Size ◽  
Tidal Mixing ◽  
Clear Trend ◽  
Sediment Grain Size ◽  
Commercial Fish ◽  
North West ◽  
Fish Resources ◽  
The North ◽  
Sediment Types ◽  
Torres Strait

The Gulf of Carpentaria is a large embayment less than 70 m deep on Australia's remote northern coastline. This paper, which describes aspects of its hydrology and variation in sediment types, is part of a larger study of the size and distribution of commercial fish resources of the gulf. Much of the data on the hydrology and sediments were collected during a gulf-wide survey in November and December 1990. Waters in the central part of the gulf were found to be vertically stratified, with bottom temperatures just below 25°C and surface temperatures around 30°C. The waters to the north of the gulf remained well mixed, presumably because of greater tidal mixing through the Torres Strait. In contrast to water temperature, salinity was relatively uniform throughout the water column: between 35 and 36. In depths below 20 m, there was a clear trend in sediment grain size, from sediments of >80% >63 pm (sandy) in the south-eastern gulf to sediments of > 80% < 63�m (muddy) in the north-west. A second muddy zone was also evident in the coastal zone (<20 m) in sheltered embayments or adjacent to rivers.

Sedimentary provinces, and associated bedforms and benthos on the Scott Reef-Rowley Shoals platform off north-west Australia

1988 ◽  
Vol 39 (2) ◽  
pp. 133 ◽  
Author(s):  
RJ McLoughlin ◽  
TLO Davis ◽  
TJ Ward
Keyword(s):  
Grain Size ◽  
Carbonate Content ◽  
Sediment Type ◽  
Sediment Grain Size ◽  
North West ◽  
Significant Relationships ◽  
Sediment Types ◽  
Sea Bed ◽  
Mean Grain Size ◽  
High Carbonate

The distribution of sediment types on the Scott Reef-Rowley Shoals platform, a marginal plateau adjoining the continental shelf of north-west Australia, has been investigated. Sediments in this region are predominately muds, with a high carbonate content. Sands, which are scarce, are mainly composed of both benthic and pelagic skeletal remains, with any gravel-sized material consisting of relict molluscan debris and, occasionally, relict coralline material. Correlation of sediment type with sea-bed characteristics as determined from photographs of the bottom at the same site showed significant relationships between mean grain size, and degree of sediment rippling and benthic activity. Similar correlations were found for the skewness measure of the analysis of sediment grain-size frequency. It is concluded that sediment type bears strong relationships with benthic activity and bedform morphology. Correlations between sediment provinces and the distribution of Australian scampi (Metanephrops sp.), a relatively new fishery in the region, are discussed.

Sedimentary provinces of the fishing grounds of the North West Shelf of Australia: Grain-size frequency analysis of surficial sediments

1985 ◽  
Vol 36 (5) ◽  
pp. 671 ◽  
Author(s):  
RJ McLoughlin ◽  
PC Young
Keyword(s):  
Grain Size ◽  
Frequency Analysis ◽  
Fine Sand ◽  
Carbonate Content ◽  
North West ◽  
North East ◽  
The North ◽  
Size Frequency ◽  
Sediment Types ◽  
Shelf Slope

As part of a multidisciplinary study of the continental shelf of north-west Australia, 354 sediment samples were taken to describe the distribution of sedimentary provinces contained within the region. A grain-size frequency analysis and subsequent classification have revealed six principal sediment types roughly corresponding to an east-west and inshore-offshore distribution. The study area is characterized by coarse skeletal detritus in the south-west, with a transition to a significant accretionary carbonate component in the form of oolites, pellets and infilled biogenic particles in the north-east. Superimposed on this pattern is a decrease in grain size from shallow to deeper waters, culminating in carbonate muds on the shelf slope. Carbonate content of sediments is uniformly high, ranging from 60 to 100% of the total weight of all samples. Non-carbonate material is principally clay; however, small quantities (less than 1%) of fine sand-size angular quartz are present.

scholarly journals Remote sensing of underwater vegetation using single-beam acoustics

2009 ◽  
Vol 67 (3) ◽  
pp. 594-605 ◽  
Author(s):  
Victor Quintino ◽  
Rosa Freitas ◽  
Renato Mamede ◽  
Fernando Ricardo ◽  
Ana Maria Rodrigues ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Grain Size ◽  
Algal Biomass ◽  
Sediment Grain Size ◽  
Coastal System ◽  
Single Beam ◽  
Acoustic Data ◽  
Sediment Types ◽  
Caulerpa Prolifera ◽  
Sandy Sediments

Abstract Quintino, V., Freitas, R., Mamede, R., Ricardo, F., Rodrigues, A. M., Mota, J., Pérez-Ruzafa, Á., and Marcos, C. 2010. Remote sensing of underwater vegetation using single-beam acoustics. – ICES Journal of Marine Science, 67: 594–605. A single-beam, acoustic, ground-discrimination system (QTC VIEW, Series V) was used to study the distribution of underwater macrophytes in a shallow-water coastal system, employing frequencies of 50 and 200 kHz. The study was conducted in Mar Menor, SE Spain, where the expansion of Caulerpa prolifera has contributed to the silting up of the superficial sediments. A direct relationship was identified between algal biomass and sediment-fines content. Acoustic information on sediment grain size and data on algal biomass were obtained in muddy and sandy sediments, including vegetated and non-vegetated seabed. Non-vegetated muddy areas were created by diving and handpicking the algae. The multivariate acoustic data were analysed under the null hypotheses that there were no acoustic differences between bare seabeds with contrasting superficial sediment types or among low, medium, and high algal-biomass areas, having in mind that grain size can act as a confounding factor. Both null hypotheses were rejected, and the results showed that 200 kHz was better than 50 kHz in distinguishing cover levels of algal biomass. The relationship between the 200-kHz acoustic data and algal biomass suggests utility in modelling the latter using the former.

scholarly journals Comparative organic geochemistry of Indian margin (Arabian Sea) sediments: estuary to continental slope

2014 ◽  
Vol 11 (2) ◽  
pp. 3387-3422 ◽  
Author(s):  
G. Cowie ◽  
S. Mowbray ◽  
S. Kurian ◽  
A. Sarkar ◽  
C. White ◽  
...  
Keyword(s):  
Grain Size ◽  
Continental Slope ◽  
Arabian Sea ◽  
Organic Geochemistry ◽  
Strong Relationship ◽  
Sediment Grain Size ◽  
Organic C ◽  
Oxygen Exposure ◽  
The North ◽  
Upper Slope

Abstract. Surface sediments from sites across the Indian margin of the Arabian Sea were analysed for their carbon and nitrogen compositions (elemental and stable isotopic), grain size distributions and biochemical indices of organic matter (OM) source and/or degradation state. Site locations ranged from the estuaries of the Mandovi and Zuari rivers to depths of ~ 2000 m on the continental slope, thus spanning nearshore muds and sands on the shelf and both the semi-permanent oxygen minimum zone (OMZ) on the upper slope (~ 200–1300 m) and the seasonal hypoxic zone that impinges on the shelf. Source indices showed mixed marine and terrigenous OM within the estuaries, and overwhelming predominance (80%+) of marine OM on the shelf and slope. Thus, riverine OM is heavily diluted by autochthonous marine OM and/or is efficiently remineralised within or immediately offshore of the estuaries. Any terrigenous OM that is exported appears to be retained in nearshore muds; lignin phenols indicate that the small terrigenous OM content of slope sediments is of different origin, potentially from rivers to the north. Organic C contents of surface shelf and slope sediments varied from < 0.5 wt % in relict shelf sands to over 7 wt % at slope sites within the OMZ, decreasing to ≤ 1 wt % at 2000 m. Major variability (~ 5 wt %) was found at slope sites within the OMZ of similar depth and near-identical bottom-water oxygen concentration. A strong relationship between organic C and sediment grain size was seen for sediments within the OMZ, but lower C loadings were found for sites on the shelf and below the OMZ. Diagenetic indices confirmed that lower C content below the OMZ is associated with greater extent of OM degradation, but that C-poor shelf sediments are not consistently more degraded than those within the OMZ. Together, the results indicate that OM enrichment on the upper slope can be explained by physical controls (winnowing and/or dilution) on the shelf and progressive OM degradation with increasing oxygen exposure below the OMZ. Reduced oxygen exposure may contribute to OM enrichment at some sites within the OMZ, but hydrodynamic processes are the overriding control on sediment OM distribution.

Distribution and transport pathways of Panulirus ornatus (Fabricius, 1776) and Panulirus spp. larvae in the Coral Sea, Australia

2001 ◽  
Vol 52 (8) ◽  
pp. 1175 ◽  
Author(s):  
Darren M. Dennis ◽  
C. Roland Pitcher ◽  
Timothy D. Skewes
Keyword(s):  
Ocean Currents ◽  
Boundary Current ◽  
Transport Pathways ◽  
North West ◽  
The North ◽  
Coral Sea ◽  
Breeding Grounds ◽  
Equatorial Current ◽  
Torres Strait ◽  
Phyllosoma Larvae

Distribution of phyllosoma larvae and pueruli of the rock lobster Panulirus ornatus and other Panulirus species was surveyed in the north-west Coral Sea in May 1997 and compared to ocean currents. Distribution of P. ornatus larvae revealed the sources of recruits to the Torres Strait lobster fishery. Phyllosomas and pueruli of P. ornatus dominated the Panulirus spp. plankton-trawl catch. Surviving pueruli were transferred to an aquarium to await confirmation of their identity. Pregilled P. ornatus phyllosomas were most abundant approximately 300 km east of the northern Great Barrier Reef (GBR) and near the confluence of the South Equatorial Current and Coral Sea Gyre. Gilled phyllosomas were also common there but most numerous adjacent to the GBR. Pueruli were most abundant adjacent to the GBR well south of Torres Strait. The distribution of P. ornatus phyllosomas and pueruli in relation to the ocean currents supported the hypothesis that phyllosomas are transported from the Gulf of Papua breeding grounds by the Hiri boundary current into the Coral Sea Gyre and then by surface onshore currents onto the Queensland coast and into Torres Strait. Distributions of larvae of other Panulirus species and the synaxid Palinurellus wieneckii differed from those of P. ornatus.

scholarly journals A synthetic map of the north-west European Shelf sedimentary environment for applications in marine science

2018 ◽  
Vol 10 (1) ◽  
pp. 109-130 ◽  
Author(s):  
Robert J. Wilson ◽  
Douglas C. Speirs ◽  
Alessandro Sabatino ◽  
Michael R. Heath
Keyword(s):  
Grain Size ◽  
North Sea ◽  
Sedimentary Environment ◽  
Marine Policy ◽  
Seabed Sediment ◽  
North West ◽  
The North ◽  
Wide Range ◽  
The North Sea ◽  
West European

Abstract. Seabed sediment mapping is important for a wide range of marine policy, planning and scientific issues, and there has been considerable national and international investment around the world in the collation and synthesis of sediment datasets. However, in Europe at least, much of this effort has been directed towards seabed classification and mapping of discrete habitats. Scientific users often have to resort to reverse engineering these classifications to recover continuous variables, such as mud content and median grain size, that are required for many ecological and biophysical studies. Here we present a new set of 0.125∘ by 0.125∘ resolution synthetic maps of continuous properties of the north-west European sedimentary environment, extending from the Bay of Biscay to the northern limits of the North Sea and the Faroe Islands. The maps are a blend of gridded survey data, statistically modelled values based on distributions of bed shear stress due to tidal currents and waves, and bathymetric properties. Recent work has shown that statistical models can predict sediment composition in British waters and the North Sea with high accuracy, and here we extend this to the entire shelf and to the mapping of other key seabed parameters. The maps include percentage compositions of mud, sand and gravel; porosity and permeability; median grain size of the whole sediment and of the sand and the gravel fractions; carbon and nitrogen content of sediments; percentage of seabed area covered by rock; mean and maximum depth-averaged tidal velocity and wave orbital velocity at the seabed; and mean monthly natural disturbance rates. A number of applications for these maps exist, including species distribution modelling and the more accurate representation of sea-floor biogeochemistry in ecosystem models. The data products are available from https://doi.org/10.15129/1e27b806-1eae-494d-83b5-a5f4792c46fc.

scholarly journals JENIS DAN SEBARAN SEDIMEN DI PERAIRAN PAPELA DAN SEKITARNYA, ROTE-NDAO, NUSA TENGGARA TIMUR

2016 ◽  
Vol 13 (3) ◽  
pp. 153
Author(s):  
Deny Setiady ◽  
Udaya Kamiludin ◽  
Nienu Yayu Gerhaneu
Keyword(s):  
Grain Size ◽  
Water Area ◽  
Silty Sand ◽  
Grain Size Analysis ◽  
Size Analysis ◽  
Sediment Grain Size ◽  
Sediment Distribution ◽  
The North ◽  
Sandy Silt ◽  
Seafloor Sediments

Daerah Penelitian terletak di perairan Papela dan sekitarnya yang merupakan bagian dari Selat Rote yang secara administratif merupakan wilayah dari Kabupaten Rote-Ndao, Provinsi Nusa Tenggara Timur. Di daerah penelitian pada 40 lokasi telah dilakukan pengambilan sedimen dasar laut dengan pemercontoh comot, deskripsi megaskopis dan analisis besar butir. Penelitian bertujuan untuk mengetahui jenis sedimen, sebaran sedimen dan lingkungan pengendapannya. Berdasarkan hasil analisis besar butir nomenklatur sedimen di daerah penelitian dijumpai 4 jenis sedimen yaitu: kerikil, pasir, pasir lanauan, lanau pasiran dan lanau. Sebaran kerikil terdapat di dua tempat, yaitu di utara dan selatan tepian daerah penelitian.Sebaran pasir mencapai kurang lebih 30 % dari luas perairan penelitian, pasir lanauan menutupi kurang 5 % dari luas perairan penelitian, lanau pasiran mempunyai sebaran kurang lebih 30 % dari luas perairan daerah penelitian dan sebaran lanau terdapat di muka muara sungai bagian dalam Teluk Papela dengan tutupan kurang lebih 5 % dari luas perairan penelitian.Kata kunci Sedimen permukaan dasar laut, analisis besar butir, sebaran sedimen, perairan Papela The study area is located in Papela waters area and that is part of the Rote Strait, administratively is a region of Rote-Ndao regency, East Nusa Tenggara Province. The method of research conducted is sampling seafloor sediments, megaskopis description and analysis of the grain size. The study area is located in Papela waters area and that is part of the Rote Strait, administratively is a region of Rote-Ndao regency, East Nusa Tenggara Province. The method of research conducted is sampling seafloor sediments, megaskopis description and analysis of the grain size. The purpose of research is the grain size analysis of seabed surface sediment to determine the type of sediment, sediment distribution and depositional environment. Based on nomenklature sediment grain size analysis result in the study area was found four types of sediments , there are: gravelly, sand, silty sand, sandy silt and silt Distribution of gravel found in two places, namely on the north and south banks of the study area. Distribution of sand reaches approximately 30% of the water area of research, silty sand covering approximately 5% of the water area of research, sandy silt has spread approximately 30% of the total water area of research and distribution of silt contained in the inner face of the Gulf estuaries Papela with cover approximately 5% of the water area of research. Keywords: Surficial sediment, grain size analysis, sediment distribution, Papela Waters

SEM and TEM observations of sperm development in the testis of the freshwater fish Oreochromis mossambicus

1990 ◽  
Vol 48 (3) ◽  
pp. 58-59
Author(s):  
Daryl A. Cornish ◽  
George L. Smit
Keyword(s):  
Morphological Characteristics ◽  
Oreochromis Mossambicus ◽  
Breeding Cycle ◽  
Limited Information ◽  
North West ◽  
The North ◽  
Sem And Tem ◽  
Sperm Development ◽  
Ultrastructural Characteristics ◽  
The University

Oreochromis mossambicus is currently receiving much attention as a candidater species for aquaculture programs within Southern Africa. This has stimulated interest in its breeding cycle as well as the morphological characteristics of the gonads. Limited information is available on SEM and TEM observations of the male gonads. It is known that the testis of O. mossambicus is a paired, intra-abdominal structure of the lobular type, although further details of its characteristics are not known. Current investigations have shown that spermatids reach full maturity some two months after the female becomes gravid. Throughout the year, the testes contain spermatids at various stages of development although spermiogenesis appears to be maximal during November when spawning occurs. This paper describes the morphological and ultrastructural characteristics of the testes and spermatids.Specimens of this fish were collected at Syferkuil Dam, 8 km north- west of the University of the North over a twelve month period, sacrificed and the testes excised.

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