Muddy Sand Research Articles

Modern sedimentary facies, depositional environments, and major controlling processes on an arid siliciclastic coast, Al qahmah, SE Red Sea, Saudi Arabia

The facies and environments along the arid siliciclastic coast of Red Sea in Al Qahmah, Saudi Arabia are studied to establish a depositional model for interpretation of ancient rocks deposited in rift settings. Field and petrographic studies of 151 sediment samples in an area of 20 km2 define seven main facies types: beach, washover fan, tidal channel, dune, sabkha, delta, and wadi (seasonal stream). The wadi and delta facies are composed of poorly to moderately well-sorted, gravelly, medium-to-fine sands. Delta-front sands are redistributed by southward longshore currents to form a beach. Beach facies is composed of well-to-moderately sorted fine sands with minor gravels, which contain high concentrations of magnetite, ilmenite, garnet, pyroxene, amphibole, epidote, titanite, and apatite grains, indicating strong winnowing. Crabs and other burrowers destroy primary sedimentary structures and mix sediments in foreshore and backshore of the beaches. Wind and storm surge rework foreshore and backshore sediments to form washover fans. Sabkha facies occurs extensively in supratidal depressions behind beach, are flooded by rainstorms and spring tide, and capped by a 5-cm-thick crust composed of interlaminated halite, quartz, albite, minor gypsum and biotite, and rarely calcium carbonate. Halite occurs as thin sheets and gypsum as nodules with a chicken-wire structure. Clastic fraction in sabkha sediments ranges from coarse silt to coarse sand with moderate sorting, and is transported by currents and wind. Tidal inlets and tidal creeks assume abandoned wadis and are filled by muddy sand. Sand dunes and sand sheets are 1–7 m high and widely distributed due to variable wind directions. Fine-grained dune sands are moderately well sorted, whereas sheet sands are coarser and poorly sorted due to vegetation baffling. Most eolian sands are sourced from beach deposits. This suite of complex riverine, wave, tidal, wind, chemical, and biological processes form the facies mosaic along the arid Al Qahmah coast, which is strongly affected by climate-driven evaporation and wind action.

Komposisi Spesies dan Struktur Komunitas Moluska Bentik Teluk Jakarta

<strong>The Composition of Species and Structure of Benthic Mollusc of Jakarta Bay.</strong> The development and increasing of population in mainland may have negative impact on water and sediment quality in the Jakarta Bay as habitat of benthic molluscs. The study was conducted in June and September 2003. The aim of this study was to observe the species composition and diversity of benthic mollusc community in the Jakarta Bay. Samples were collected from 30 stations at 1 – 12 m depth using Smith McIntyre Grab with opening area was 0.05 m². A sieve with 0.5 mm in mesh size used for collecting benthic molluscs as well as for determining the profil of benthic substrates. Results of this study showed that the substrate in the study sites was characterized by muddy, muddy sand and sandy mud sediment. A total of 24 mollusc species were identified, which belong to 18 genera. Abundance of benthic molluscs ranged from 0.3 to 15779.7 individu/m<sup>2</sup> in June and from 0.3 to 820.3 individu/m<sup>2</sup> in September. Tellinidae was the highest species composition, and <em>Alveinus sp</em>. (Kelliellidae) was distributed widely in June and September. Most of the molluscs found in this study area were common species in Indonesia waters. The value of diversity index (H’) ranged from 0.03 to 0.95 and evenness index (J’) ranged from 0.05 to 0.69 in June and in September diversity index (H’) ranged from 0.01 to 1.08 and evenness index (J’) ranged from 0.01 to 1.00. These indexes showed that the diversity of benthic mollusc in Jakarta Bay were relatively low.

Stratigraphic position and sedimentary environment of Late Pleistocene deposits along the cliffed coast of the middle part of the Polish Baltic coast

The study was carried out in the wall of a cliff that formed as a result of erosional cutting in the western foreland of a moraine landform from the Pomeranian and Gardno phases (Upper Plenivistulian, Rowy–Ustka clifs; northern Poland). Individual lithostratigraphic units have been documented: glaciofluvial delta deposits, Poddąbie Till, lacustrine-glacial Wytowno Formation (consisting of three facies: deltaic, lower diamicton, and upper diamicton), lacustrine deposits of the Orzechowo Formation with a thick peat layer, and aeolian series at the cliff crest. The Wytowno Formation deposits include the following lithologies: medium-grained sands, fine-grained sands, muddy sands, muds, silty clays, clays, varved clays, fine-grained multi-fraction deposits, and tills (Debina Till). Very high inclination of the strata is the result of glaciodynamic deformation. The deposits were accumulated in a proglacial lake. They are characterized by mud and clay as well as sand and sand-muddy lithofacies. The vastness of the water body is evidenced by a considerable size of the delta, and by massive structures of the clay layers.

Are trawl marks a good indicator of trawling pressure in muddy sand fishing grounds?

The development of the vessel monitoring system (VMS) in the recent years has offered high-resolution data to map the distribution and intensity of fishing activities and contributed to enhancing the potential identification of fishing impacts. However, impacts could vary at very small scale and the resolution of VMS data might not be fine enough. Other proxy could be used, such as trawl marks visible on the seabed observed by underwater video or side-scan sonar to evaluate small-scale trawling effort. In the Bay of Biscay, an underwater video survey of the Nephrops norvegicus fishing ground was conducted and provided environmental characteristics such as depth and number of trawl marks at 152 transects. The relevance of observed trawl marks as a small-scale proxy of trawling effort was tested depending on the sediment type. The model showed a significant positive relation between density of marks and trawling effort for all sediments together but a different relation for each sediment type. Considering each sediment type separately, the unexpected high number of marks observed on sands could be linked with cohesive interactions between calcium carbonates particles while the low number of marks on fine lithoclastic muds could be due to sediment reworking and bioturbation. We conclude that the impact of trawling on the seabed varies with the type of sediments, hydrodynamic parameters, bioturbation and trawling intensity, leading to a very complex relationship. Trawl marks observed on video footage thus could be used as a proxy of trawling effort among the same type of sediment and not for fine lithoclastic muds.

Perbandingan Morfometrik dan Meristik Lamun Halophila ovalis di Perairan Pulau Serangan dan Tanjung Benoa, Bali

Halophila ovalis is a type of seagrass that has a round oval shape that can live in waters that have a muddy sand substrate. Morphometric and meristic are used to describe the waters where seagrass life seen from the morphology of leaves, rhizomes and roots. Morphometrics is a measure to determine the quantitative morphology of an organism structure and Meristik is a calculation to know the sum of a part of an organism.This research was conducted in December 2016-February 2017 with purposive sampling method at 10 observation station in Serangan Island and Tanjung Benoa. Data analyzed with descriptive analysis, Sturges criteria and Similarity Index of Morisita. Based on the results of leaf length study ranged from 9.4-51.3 mm, leaf width ranged from 6.7-19.8 mm, the number of leaf bones ranged from 10- 21 pairs, the length of the petiole ranges from 4.5 to 55.6 mm, the diameter of the petiole ranged from 0.03 - 1.4 mm, the length of rhizoma ranged from 6.2- 41.2 mm, diameter of rhizoma ranged from 0.04 -1.8 mm and root length ranged from 7.5-89 mm. By categorizing morfometrik-meristic seagrass H. ovalis, hence formed value of each research station gaze which will describe similarity between stations. In the similarity index of morisita, the research station in Serangan and Tanjung Benoa waters has similarity of morphometry - meristic very similar to 92.8% equality.

Deep sea habitats in the chemical warfare dumping areas of the Baltic Sea

The Baltic Sea is a severely disturbed marine ecosystem that has previously been used as a dumping ground for Chemical Warfare Agents (CW). The presence of unexploded underwater ordnance is an additional risk factor for offshore activities and an environmental risk for the natural resources of the sea. In this paper, the focus is on descriptions of the marine habitat based on the observations arising from studies linked to the CHEMSEA, MODUM and DAIMON projects. Investigated areas of Bornholm, Gotland and Gdańsk Deeps are similarly affected by the Baltic Sea eutrophication, however, at depths greater than 70m several differences in local hydrological regimes and pore-water heavy metal concentrations between those basins were observed. During the lifespan of presented studies, we were able to observe the effects of Major Baltic Inflow, that started in December 2014, on local biota and their habitats, especially in the Bornholm Deep area. Reappearance of several meiofauna taxa and one macrofauna specimen was observed approximately one year after this phenomenon, however it's ecological effects already disappeared in March 2017. According to our findings and to the EUNIS Habitat Classification, the three reviewed areas should be characterized as Deep Sea Muddy Sands, while the presence of suspicious bomb-like objects both beneath and on top of the sediments confirms their CW dumpsite status.

The structure and organisation of integral marine benthic communities in relation to sieve mesh size

Few studies consider meiofauna and macrofauna at the same time, even though both form parts of wider ecological networks, and fewer consider interactions between sample size, body size and spatial clustering. It has been suggested that the elements of the structure of the physical environment have fractal properties. If habitat complexity largely determines species diversity this leads to the prediction (for a single perfect fractal) that all organisms, regardless of size, will perceive the environment as equally complex and should have equivalent diversity and, as we move up the size spectrum, species composition should change in a regular and gradual fashion. This study examines the degree to which infaunal assemblage structure varies with mesh size, sample size and sample dispersion within two different areas of homogeneous intertidal sediment, a muddy sand and a coarse sand, in the Isles of Scilly, UK. In each area samples were extracted using a standard range of 5 mesh sizes (63, 125, 250, 500, 1000μm), with the sample areas and distances between samples scaled to the mesh size. All metazoans were identified to species level. Diversity and species composition did not show a gradual and even degree of change over the size range at either site. Instead, they showed a dramatic stepwise change between the 250μm and 500μm mesh size samples, being relatively constant in the <500μm and >500μm categories, with diversity higher in the former. Higher proportions of species in the <500μm categories showed evidence of spatial clustering than in the >500μm categories. This suggests a fractal structure within but not between the <500μm and >500μm body size categories, which apparently is not driven by differences in sediment structure. The biology of marine metazoan benthos does not scale continuously across the full range of taxa and body size as has been recently suggested, but may do so for individual taxa and restricted size ranges.

An autonomous, bottom-mounted sonar for measurement of mid-frequency reverberation

While bottom reverberation is typically dominant over surface reverberation at mid-frequencies in shallow water, sea surface roughness has a significant impact on transmission loss and hence on reverberation. Measurements of this effect can be difficult with a system deployed from a moving ship due to both the system motion and the constraints of operating the ship safely in the rough seas of interest. To overcome these difficulties, the Autonomous Reverberation Measurement System (ARMS) has been developed under an ONR-sponsored DURIP. This system is a benthic lander with a directional source and receive array mounted on a rotation stage. Powered by batteries and programmed prior to deployment, the system can measure reverberation from 2-6 kHz as a function of direction autonomously for up to 3 months. This system was deployed in the spring of 2017 as part of an experiment conducted off Geoje Island, Republic of Korea. During this experiment, the ARMS was deployed in 28 m of water and measured reverberation in a muddy sand environment with a range-dependent water depth that was punctuated with rock outcroppings on the seafloor. [Work supported by the U.S. Office of Naval Research.]

N2 production and fixation in deep-tier burrows of Squilla empusa in muddy sediments of Great Peconic Bay

Global marine N budgets often show deficits due to dominance of benthic N2 production relative to pelagic N2 fixation. Recent studies have argued that benthic N2 fixation in shallow water environments has been underestimated. In particular, N2 fixation associated with animal burrows may be significant as indicated by high rates of N2 fixation reported in muddy sands populated by the ghost shrimp, Neotrypaea californiensis (Bertics et al., 2010). We investigated whether N2 fixation occurs at higher rates in the burrow-walls of the deep-burrowing (~0.5–4m) mantis shrimp, Squilla empusa, compared to ambient, estuarine muds and measured seasonal in-situ N2 concentrations in burrow-water relative to bottom-water. Acetylene reduction assays showed lower N2 fixation in burrow-walls than in un-populated sediments, likely due to inhibitory effects of O2 on ethylene production. Dissolved N2 was higher in burrow-water than proximate bottom-water at all seasons, demonstrating a consistent balance of net N2 production relative to fixation in deep-tier biogenic structures.

Sebaran dan Struktur Komunitas Moluska di Pantai Mertasari Kota Denpasar, Provinsi Bali

The research objectives were to investigate the distribution and molluscs community structure in Mertasari beach, Denpasar-Bali. The research area was divided into 2 sites, the first site (I) has sandy substrate and second site (II) has muddy sand substrate. This research used quadrat transects systematic sampling method with 1x1 m2 quadrat. The data of the research were analyzed used Microsoft Excel. It was conducted from January to March 2017. The research result shows that the structure of molluscs in Mertasari Beach was support by 31 species richness of 25 species from gastropods and 6 species of bivalves. The density number of the molluscs was 124.5 ind/m2. The diversity index of the molluscs ranged from 2.29 to 2.58 were category as moderate diversity, the evenness index ranged 0.83 to 0.87 were category as high evenness, the dominance index ranged from 0.09-0.13 were category as low. the index number indicates that the ecological condition at Mertasari beach was in good condition so it is suitable to support the molluscs community livelihood. Which was supported by water quality value of dissolved oxygen at Mertasari beach ranged from 4-6.7 mg/l, pH waters ranged from 7.39-7.74, water temperature ranged from 25.9-29oC, water salinity ranged from 9-29 ppt. The distribution pattern of 31 species of molluscs were in groups (Id&gt;1).

Benthic Foraminifera from Shelf Sediments of the Bay of Bengal, Central East Coast, India

Benthic foraminiferal study, carried out in 23 surface sediment samples from different water depth, between 15 and 250 m in the Bay of Bengal, has led to the identification of 187 foraminiferal species. Principal Component and Cluster Analysis performed on 23 abundant species (> 5%) resulted in four different assemblages that correlate well with bathymetry, nature of sediment and other physicochemical parameters of the bottom water. The shallowest inner shelf assemblage (I) dominated by Amphistegina radiata, Asterorotalia pulchella, Elphidium crispum, Rotalidium annectens and Rotalinoides gaimardii, is characteristically found up to 30 m water depth on sandy sediment formed under high energy condition. The second shallower inner shelf assemblage (II) composed mainly of Ammonia beccarii, Cibicidoides wuellerstorfi, Hanzawaia concentrica, Quinqueloculina seminula, Rotalinoides compressiuscula and Textularia agglutinans is restricted to 30-80 m of water depth and sandy to slightly muddy sand sediments. The third middle shelf assemblage (III) which is confined to the 80–150 m of water depth and slightly muddy sand to muddy sand, includes Asterorotalia dentata, Cancris communis, Cassidulina laevigata, Lenticulina thalmani, Triloculina oblonga, Nonion costiferum, Quinqueloculina venusta and Uvigerina proboscidea. The fourth outer shelf assemblage (IV) consisting of Brizalina subspathulata, Globulimina notovata, and Uvigerina mediterranea exists from 150 to 250 m depth in the muddy sand and sandy mud with low dissolved oxygen in the bottom water. The high abundance of Amphistegina radiata at 0-30 m water depth and Ammonia beccarii at 30-80 m water depth represents low salinity and high energy conditions prevailing inner shelf region of the study area. The presence of Cancris, Cassidulina, and Lenticulina, which are found to be more associated with moderate dissolved oxygen condition, reflects the occurrence of suboxic environment in the middle shelf area. The deeper water sediment dominated by Brizalina, Globulimina, and Uvigerina indicates the oxygen depleted environments with low energy condition. The presence of relict forms in the sediments at 50, 80 and 100 m water depth in the study area denotes different sea stands suggesting past sea level changes. The principal component analysis of the abundant species with grain size and other physicochemical parameters of the bottom water reveal that the distribution of benthic foraminifera in this shelf region is chiefly controlled by the nature of sediments, bathymetry coupled with salinity, dissolved oxygen and hydrodynamic condition.

Rethinking Alternative Livelihood Projects for Women of the Pits: The Case of Atiwa

Abstract Artisanal Small Scale Mining with its environmental, social, economic, and health impacts, is replacing agriculture as the main economic activity in sub-Saharan Africa. Mining activities have therefore become an economic activity in the rural mining areas, as a quick way to escape poverty. This exploratory qualitative study examines the factors behind the prevalence of women in the pit business, washing muddy sand for particles of gold, in the Atiwa district of Ghana. However, not much is known about the impact of the pit work on the women’s wellbeing. The goal is to understand the lived experiences of the women and explore ways they could be assisted. Findings from the study indicate that poverty, lack of economic opportunities, and unattractive rural poverty alleviation strategies have contributed to the plight of these women. The women could benefit from asset-based interventions that could redirect their work to projects that would enhance their livelihoods.

Taxonomy, ecology and geographic distribution ofGallardoneris iberica(Polychaeta, Lumbrineridae) in southern Europe

The polychaeteGallardoneris ibericawas described in soft-bottom benthic habitats from the Atlantic Iberian Peninsula coasts in 2012. Since then, successive studies have found this species in Spain, Italy and Croatia. The present study is the first to reportG. ibericafor Greece and Cyprus (42 new records) confirming its wide geographic distribution on southern European coasts. Taxonomic accounts and ecological preferences based on a large survey and review of available literature are being presented. The species was frequently found in habitats characterized by infralittoral muddy sands with variable organic matter and ‘Moderate’ ecological quality status; nevertheless it was also recorded in coarser and finer sediments, circalittoral mixed sediments, phytal substrates and undisturbed sites. Its relative abundance per sample was always lower than 2%. A review of the available ecological and geographic data of the otherGallardonerisspecies and a worldwide taxonomic key toGallardonerisspecies are provided.

Seabed sediments (grain size) of Nordland VI, offshore north Norway

ABSTRACTThis paper presents a seabed sediments (grain size) map of the Nordland VI area (25,000 km2) off the Lofoten islands, north Norway. The map is based on multibeam echosounder data (bathymetry and backscatter), visual analysis of 215 video transects (each 700-m long), and visual and grain-size analysis of seabed sediment samples from 40 sampling stations acquired by grabs, boxcores and multicores. A total of 14 sediment classes were identified, with sediments varying in grain size from mud to boulders. Seabed types also include bedrock and bioclastic sediments from degrading cold-water coral reefs. The continental shelf is mostly characterised by coarse-grained sediments such as gravelly sand and sandy gravel, especially in till areas. In basins and glacial troughs, finer-grained sediments such as sandy mud and muddy sand dominate. The upper continental slope (300–600-m water depth) is characterised by coarse-grained sediments related to the influence of the strong north-east flowing Norwegian Atlantic Current. In deeper areas, finer-grained sediments are prominent. Below 1000-m depth, mostly mud and mud with sediment blocks occur.

The Characteristics of Hydrogeological Parameters of Unconsolidated Sediments in the Nakdong River Delta of Busan City, Korea

This study dealt with the characteristics and the interrelations of hydrogeological parameters such as hydraulic conductivity, dispersivity and effective porosity of unconsolidated sediments for providing the basic data necessary for the planning of the management and preservation of groundwater quality in the Nakdong River Delta of Busan City, Korea. Groundwater quality in this area has been deteriorated due to seawater intrusion, agricultural fertilizer and pesticide, industrial wastewater, and contaminated river water. The physical properties (grain size distribution, sediment type, sorting) and aquifer parameters (hydraulic conductivity, effective porosity, longitudinal dispersivity) were determined from grain size analysis, laboratory permeability test and column tracer test. Among 36 samples, there were 18 Sand (S), 7 Gravelly Sand (gS), 5 Silty Sand (zS), 5 Muddy Sand (mS), and 1 Sandy Silt (sZ). Hydraulic conductivity was determined through a falling head test, and ranged from <TEX>$9.2{\times}10^{-5}$</TEX> to <TEX>$2.9{\times}10^{-2}cm/sec$</TEX> (0.08 to 25.6 m/day). From breakthrough curves, dispersivity was calculated to be 0.35~3.92 cm. Also, effective porosity and average linear velocity were obtained through the column tracer test, and their values were 0.04~0.46 and 1.06E-04~6.49E-02 cm/sec, respectively. Statistical methods were used to understand the interrelations among aquifer parameters of hydraulic conductivity, effective porosity and dispersivity. The relation between dispersivity and hydraulic conductivity or effective porosity considered the sample length, because dispersivity was affected by experimental scale. The relations between dispersivity and hydraulic conductivity or effective porosity were all in inverse proportion for all long and short samples. The reason was because dispersivity was in inverse proportion to the groundwater velocity in case of steady hydrodynamic dispersion coefficient, and groundwater velocity was in proportion to the hydraulic conductivity or effective porosity. This study also elucidated that longitudinal dispersivity was dependent on the scale of column tracer test, and all hydrogeological parameters were low to high values due to the sand quantity of sediments. It is expected that the hydrogeological parameter data of sediments will be very useful for the planning of groundwater management and preservation in the Nakdong River Delta of Busan City, Korea.

Vulnerability of macronutrients to the concurrent effects of enhanced temperature and atmospheric pCO2 in representative shelf sea sediment habitats

Fundamental changes in seawater carbonate chemistry and sea surface temperatures associated with the ocean uptake of anthropogenic CO2 are accelerating, but investigations of the susceptibility of biogeochemical processes to the simultaneous occurrence of multiple components of climate change are uncommon. Here, we quantify how concurrent changes in enhanced temperature and atmospheric pCO2, coupled with an associated shift in macrofaunal community structure and behavior (sediment particle reworking and bioirrigation), modify net carbon and nutrient concentrations (NH4-N, NOx-N, PO4-P) in representative shelf sea sediment habitats (mud, sandy-mud, muddy-sand and sand) of the Celtic Sea. We show that net concentrations of organic carbon, nitrogen and phosphate are, irrespective of sediment type, largely unaffected by a simultaneous increase in temperature and atmospheric pCO2. However, our analyses also reveal that a reduction in macrofaunal species richness and total abundance occurs under future environmental conditions, varies across a gradient of cohesive to non-cohesive sediments, and negatively moderates biogeochemical processes, in particular nitrification. Our findings indicate that future environmental conditions are unlikely to have strong direct effects on biogeochemical processes but, particularly in muddy sands, the abundance, activity, composition and functional role of invertebrate communities are likely to be altered in ways that will be sufficient to regulate the function of the microbial community and the availability of nutrients in shelf sea waters.

Nearshore Influences of Upwelling, Waves, and Currents On A Tropical Carbonate Ramp: Holocene, Northwestern Yucatán Shelf, Mexico

Abstract: Many ancient carbonate strata represent deposition on gently dipping ramp systems, yet processes and patterns of carbonate accumulations of modern carbonate ramps are not as extensively studied as those on modern isolated platforms and rimmed shelves. To better understand controls on sediment accumulations of the shallowest parts of tropical carbonate ramp systems, this study investigates geomorphology, sediment, and organic-matter abundance on the nearshore areas of the Holocene ramp system on the northwestern Yucatan Shelf, Mexico. Currents generated by the day-to-day easterly trade winds, and larger waves caused by winter cold fronts, have the net effect of transporting sediment and upwelled nutrient-rich (occasionally in excess of 5 mg/m 3 , eutrophic to hypertrophic) and cooler (∼ 16–20°C) water southward. The upper shoreface includes shore-parallel belts of mollusk- and Halimeda -rich muddy sand to gravel. Longshore sediment transport along the coast forms barrier-island spits of molluscan coquina beach ridges which have prograded southward and westward. The islands in turn act as barriers to form protected lagoons that accumulate ubiquitous fine sediment. A broad supratidal to freshwater marsh landward of the lagoons includes dominantly fine-grained carbonate sediment. Across the area, mollusks are the primary sediment contributors, although Halimeda is locally ubiquitous offshore. Barnacles, benthic foraminifera, sponges, bryozoans, and serpulid worm tubes dominate the remainder of carbonate sediment producers, although echinoderms and planktonic forams are present as well. Corals are notably absent, as are peloids and ooids. Biosiliceous organisms (diatoms, sponge spicules, dinoflagellates) contribute up to 20% of sediment throughout the shoreface and lagoon, and the greater part of carbonate mud is calcitic. This assemblage, which includes many biota of the heterozoan association, is interpreted to be related to upwelled cool nutrient-rich water, although local freshwater springs may provide nutrients in the lagoons. The results of this study illustrate the roles of energy level, sea-surface temperature, upwelled nutrient-rich waters, and possibly freshwater mixing on the geomorphology, biota, and sedimentology of the nearshore parts of this Holocene ramp system. The insights provide an actualistic model for sedimentological character and depositional heterogeneity of shoreface regions of ancient carbonate ramps influenced by upwelling.

Rich shallow-water benthic ecosystem in Late Miocene East Antarctica (Fisher Bench Fm, Prince Charles Mountains)

Abstract A single shell of a pectenoid bivalve was found in the lower part of the Fisher Bench Formation (Fisher Massif, Prince Charles Mountains). In contrast to glacigenic sediments that form extensive outcrops in this area and are almost barren of foraminifera, small pieces of muddy sand attached to this shell contained a rich assemblage of calcareous and siliceous microfossils. The diatom assemblage associated with this shell was dominated by marine benthic forms with abundant Saeptifera, associated with subordinate marine neritic taxa, and Chaetoceros resting spores. Benthic foraminifera are very abundant but of low diversity, strongly dominated by Rosalina globularis with uniform chambers. It is the first Miocene foraminiferal assemblage reported from East Antarctica excluding the Ross Sea area. These new results confirm the early Late Miocene age of the shell that was dated by Sr isotope values in an earlier study, and suggest an initial phase of deposition in a shallow-water (possibly no > 10 m) marine, cold, and possibly oligotrophic environment. After initial burial in microfossil-bearing sediment that was weakly lithified, the shell was eroded and transported to be incorporated in fossil-poor glacigenic sediments. Since transport from a nearby location could have been facilitated by glacial and/or down-slope movements in this fjordal setting, the shell is considered para-autochthonous. Based on the Antarctic foraminiferal fossil records, it appears that through most of the Cenozoic, those parts of the Antarctic continental shelf that were deeper than a few tens of meters, with the exception of the Ross Sea area, were mostly unfavorable for development and/or preservation of calcareous microfossils.

Seasonal variation in coastal marine habitat use by the European shag: Insights from fine scale habitat selection modeling and diet

Studies of habitat selection by higher trophic level species are necessary for using top predator species as indicators of ecosystem functioning. However, contrary to terrestrial ecosystems, few habitat selection studies have been conducted at a fine scale for coastal marine top predator species, and fewer have coupled diet data with habitat selection modeling to highlight a link between prey selection and habitat use.The aim of this study was to characterize spatially and oceanographically, at a fine scale, the habitats used by the European Shag Phalacrocorax aristotelis in the Special Protection Area (SPA) of Houat-Hœdic in the Mor Braz Bay during its foraging activity. Habitat selection models were built using in situ observation data of foraging shags (transect sampling) and spatially explicit environmental data to characterize marine benthic habitats. Observations were first adjusted for detectability biases and shag abundance was subsequently spatialized. The influence of habitat variables on shag abundance was tested using Generalized Linear Models (GLMs). Diet data were finally confronted to habitat selection models.Results showed that European shags breeding in the Mor Braz Bay changed foraging habitats according to the season and to the different environmental and energetic constraints. The proportion of the main preys also varied seasonally. Rocky and coarse sand habitats were clearly preferred compared to fine or muddy sand habitats. Shags appeared to be more selective in their foraging habitats during the breeding period and the rearing of chicks, using essentially rocky areas close to the colony and consuming preferentially fish from the Labridae family and three other fish families in lower proportions. During the post-breeding period shags used a broader range of habitats and mainly consumed Gadidae. Thus, European shags seem to adjust their feeding strategy to minimize energetic costs, to avoid intra-specific competition and to maximize access to suitable habitats and preys.

Occurrence of jarosite within Quaternary coastal sabkha sediments in Kuwait, Arabian Gulf

X-ray diffractometer analysis and SEM investigation confirmed the occurrence of jarosite and alunogen minerals in the Quaternary siliciclastic sabkha sediments of northern Kuwait within the Bahrah oilfield area, Arabian Gulf. Jarosite is relatively abundant in a near-surface whitish sticky tidal muddy sand layer about 60 cm thick that overlies the ferruginous sandstone of the Oligo-Miocene Ghar Formation. Jarosite occurs as clusters of euhedral pseudo-cubes of about 1 μm in size and as agglomerated nanoglobules of 250 nm in size. A hypogenetic origin related to the reaction of sulfuric acid produced by the oxidation of H2S associated with hydrocarbon gas seepages with K and Fe leachates is suggested. The restricted occurrence of jarosite within near-surface sabkha sediments may be attributed to limited tidal inundation and prevalence of arid climatic conditions.