Mixture Of Seawater Research Articles

Growth of Harmful Phytoplankton, Heterosigma akashiwo, in the Mixture of Surface and Deep Seawater

Growth of Harmful Phytoplankton, Heterosigma akashiwo, in the Mixture of Surface and Deep Seawater

Water masses in the Humboldt Current System: Properties, distribution, and the nitrate deficit as a chemical water mass tracer for Equatorial Subsurface Water off Chile

Three sections are used to analyze the physical and chemical characteristics of the water masses in the eastern South Pacific and their distributions. Oceanographic data were taken from the SCORPIO (May–June 1967), PIQUERO (May–June 1969), and KRILL (June 1974) cruises. Vertical sections of temperature, salinity, σθ, dissolved oxygen, nitrate, nitrite, phosphate, and silicate were used to analyze the water column structure. Five water masses were identified in the zone through T–S diagrams: Subantarctic Water, Subtropical Water, Equatorial Subsurface Water, Antarctic Intermediate Water, and Pacific Deep Water. Their proportions in the sea water mixture are calculated using the mixing triangle method. Vertical sections were used to describe the geographical distributions of the water mass cores in the upper 1500 m. Several characteristic oceanographic features in the study area were analyzed: the shallow salinity minimum displacement towards the equator, the equatorial subsurface salinity maximum associated with a dissolved oxygen minimum zone and a high nutrient content displacement towards the south, and the equatorward intermediate Antarctic salinity minimum associated with a dissolved oxygen maximum. The nitrate deficit generated in the denitrification area off Peru and northern Chile is proposed as a conservative chemical tracer for the Equatorial Subsurface Waters off the coast of Chile, south of 25°S.

Ethanol fermentation withKluyveromyces marxianusfrom Jerusalem artichoke grown in salina and irrigated with a mixture of seawater and freshwater

To study fuel ethanol fermentation with Kluyveromyces marxianus ATCC8554 from Jerusalem artichoke (Helianthus tuberosus) grown in salina and irrigated with a mixture of seawater and freshwater. The growth and ethanol fermentation of K. marxianus ATCC8554 were studied using inulin as substrate. The activity of inulinase, which attributes to the hydrolysis of inulin, the main carbohydrate in Jerusalem artichoke, was monitored. The optimum temperatures were 38 degrees C for growth and inulinase production, and 35 degrees C for ethanol fermentation. Aeration was not necessary for ethanol fermentation with the K. marxianus from inulin. Then, the fresh Jerusalem artichoke tubers grown in salina and irrigated with 25% and 50% seawater were further examined for ethanol fermentation with the K. marxianus, and a higher ethanol yield was achieved for the Jerusalem artichoke tuber irrigated with 25% seawater. Furthermore, the dry meal of the Jerusalem artichoke tubers irrigated with 25% seawater was examined for ethanol fermentation at three solid concentrations of 200, 225 and 250 g l(-1), and the highest ethanol yield of 0.467, or 91.5% of the theoretical value of 0.511, was achieved for the slurry with a solid concentration of 200 g l(-1). Halophilic Jerusalem artichoke can be used for fuel ethanol production. Halophilic Jerusalem artichoke, not competing with grain crops for arable land, is a sustainable feedstock for fuel ethanol production.

Formation of replacement dolomite in the Latemar carbonate buildup, Dolomites, northern Italy: Part 2. Origin of the dolomitizing fluid and the amount and duration of fluid flow

Replacement dolomite in the Latemar carbonate buildup developed when limestone was infiltrated by reactive fluid. Minor-element, trace-element, and oxygen and carbon isotope compositions of dolomite and precursor limestone constrain the origin of the fluid and fundamental aspects of the flow. Inferred salinity (similar to seawater); temperature (45°–85°C); ⁸⁷Sr/⁸⁶Sr (0.7076–0.7079); Ca/Mg (<1.4); and Fe, Mn, and Zn content of the dolomitizing fluid are consistent with a fluid similar to modern diffuse effluent. Modern diffuse effluent itself is approximately a mixture of seawater with up to ∼25 percent high-temperature mid-ocean ridge hydrothermal vent fluid. Time-integrated fluid flux was in the range (2–4) · 10⁶ mol fluid/cm² rock or (4–7) · 10⁷ cm³ fluid/cm²rock. Estimation of time-integrated flux leads to an internally consistent framework for the appropriate interpretation of the oxygen, strontium, and carbon isotope compositions of replacement dolomite. The oxygen and strontium isotope compositions reflect equilibration with dolomitizing fluid and provide a chemical fingerprint of the fluid. The carbon isotope composition of dolomite, however, was simply inherited directly from the precursor limestone in nearly all cases. A quantitative evaluation of the minor- and trace-element budget of dolomitization verifies that a fluid like modern diffuse effluent, but not unmodified seawater, could supply sufficient Fe, Mn, and Zn to enrich dolomite in these elements compared to limestone. If the flux of dolomitizing fluid was similar to that of modern diffuse effluent, ∼0.02 cm³/cm² · s, the duration of fluid flow and mineral-fluid reaction was short, ∼100 years. The total duration of dolomitization, however, could have been much longer if fluid flow was episodic, as in modern seafloor hydrothermal systems, depending on the time elapsed between episodes of flow. Conversion of limestone to dolomite likely occurred by a mechanism intermediate between the end-member cases of replacement at constant oxygen and carbon and replacement at constant volume.

Double pulse laser-induced breakdown spectroscopy of bulk aqueous solutions at oceanic pressures: interrelationship of gate delay, pulse energies, interpulse delay, and pressure

Laser-induced breakdown spectroscopy (LIBS) has been identified as an analytical chemistry technique suitable for field use. We use double pulse LIBS to detect five analytes (sodium, manganese, calcium, magnesium, and potassium) that are of key importance in understanding the chemistry of deep ocean hydrothermal vent fluids as well as mixtures of vent fluids and seawater. The high pressure aqueous environment of the deep ocean is simulated in the laboratory, and the key double pulse experimental parameters (laser pulse energies, gate delay time, and interpulse delay time) are studied at pressures up to 2.76x10(7) Pa. Each element is found to have a unique optimal set of parameters for detection. For all pressures and energies, a short (< or = 100 ns) gate delay is necessary. As pressure increases, a shorter interpulse delay is needed and the double pulse conditions effectively become single pulse for both the 1.38x10(7) Pa and the 2.76x10(7) Pa conditions tested. Calibration curves reveal the limits of detection of the elements (5000 ppm Mg, 500 ppm K, 500 ppm Ca, 1000 ppm Mn, and 50 ppm Na) in aqueous solutions at 2.76x10(7) Pa for the experimental setup used. When compared to our previous single pulse LIBS work for Ca, Mn, and Na, the use of double pulse LIBS for analyte detection in high pressure aqueous solutions did not improve the limits of detection.

Methane seeps on an Early Jurassic dysoxic seafloor

The rhythmically bedded limestone–marl–shale succession of the Blue Lias Formation (Lias Group, Early Jurassic age) of Kilve in Somerset (SW England) preserves a suite of large conical concretions that formed around methane seeps. These are 1–2 m high, and elliptical in plan (axes 2–4 m), with an outer limestone shell forming the flanks of the cone. The cone flank is composed of micritic carbonate (20–30 cm thick), which locally includes sheets and pods of intraclasts and bioclasts. The cycle-forming limestone beds of the host strata are composed of dark grey micrite with carbon-isotope values ( δ 13C = 0.6 to 0.8‰) consistent with carbon sourced from a mixture of seawater and by sulphate reduction, and oxygen-isotope values ( δ 18O = − 6‰) suggesting some degree of later diagenesis. The pale grey micrite that forms the sides of the mounds includes three-dimensional ammonites and intraclasts, and thus cemented close to the sediment–water interface prior to compaction. The mound-forming carbonate is markedly isotopically light with respect to carbon, but not with respect to oxygen ( δ 13C = − 24.3 to − 26.4; δ 18O = − 2 to − 3.5‰). The isotope signature indicates that cements were probably derived from a mixture of sources that included biogenic methane. The intraclasts within the limestone suggest that syn-depositional physical brecciation and mixing of cements had occurred, and thus mixing of methane rich-fluids with the overlying surface waters is likely also to have occurred. The relatively heavy oxygen-isotope values may be indicative of anaerobic oxidation of methane. The mound-bearing interval of the Blue Lias Formation is benthos-poor and comprises predominantly laminated black shales, characteristic of poor bottom water oxygenation. The largest of the mounds is however, capped with fossiliferous breccias. Thus the mounds either formed benthic islands that elevated the biota into an oxic zone or, alternatively, they may have supported a chemotrophic community. Although cold seep deposits have been documented previously they are still comparatively rare. This example is one of the oldest in Europe, and is unusual amongst described ancient seeps in preserving relief that extended above the ancient seafloor.

Aerial infrared imaging reveals large nutrient‐rich groundwater inputs to the ocean

Regional high‐resolution (0.1°C, 0.5 m) low‐altitude thermal infrared imagery (TIR) reveals the exact input locations and fine‐scale mixing structure of massive, cool groundwaters that discharge into the coastal zone as both diffuse flows and as &gt;30 large point‐sourced nutrient‐rich plumes along the dry western half of the large volcanic island of Hawaii. These inputs are the sole source of new nutrient delivery to coastal waters in this oligotrophic setting. Water column profiling and nutrient sampling show that the plumes are cold, buoyant, nutrient‐rich brackish mixtures of groundwater and seawater. By way of example, we illustrate in detail one of the larger plumes, which discharges ca. 12,000 m3 d−1 (ca. 8,600 m3 d−1 freshwater), rates comparable in volume to high‐flux groundwater outputs in better‐known tropical karst terrains. We further show how nutrient mixing trends may be integrated into TIR sea surface temperatures to produce surface water nutrient maps of regional extent.

On the use of prompt gamma-ray neutron activation analysis for determining phase amounts in multiphase flow

Prompt gamma-ray neutron activation analysis (PGNAA) is considered for the measurement of the in situ multiphase flow amounts of oil, gas, water and salt in a deep sea oil well. PGNAA has the advantages for this application that: (1) useful characteristic prompt gamma rays are produced by neutron interactions with almost all elements, (2) it is a rapid non-destructive measurement method, (3) a large sample volume is measured and (4) it can be used under the relatively extreme conditions present for undersea oil recovery. Feasibility calculations have been made with the previously developed Monte Carlo–library least-squares (MCLLS) measurement approach used with the specific purpose Monte Carlo code named CEARCPG that was previously developed at CEAR for PGNAA bulk material analysis. A slight modification of the MCLLS measurement approach previously developed for the nonlinear PGNAA and energy dispersive x-ray analysis (EDXRF) measurement applications is used for the present application. This modification allows the use of the very accurate forward Monte Carlo calculation of the PGNAA response and consists of using first the three components oil plus gas, water and salt as library spectra rather than the normal use of individual elemental libraries. Then the gamma-ray transmission density gauge response from the Cs-137 source is used to obtain the amount of gas. This approach allows one to determine the four parameters of primary interest directly. The arrangement considered is the use of a Cf-252 neutron source and a Cs-137 gamma-ray source with a large NaI detector placed on the opposite side of a right circular cylindrical sample holder for an assumed homogeneous mixture of oil, gas and seawater. A background that was previously obtained experimentally in bulk analysis applications was added in various amounts to the response here to make the calculations more reasonable. More experimental results for benchmarking will be taken in the future. Results indicate that this approach would be accurate and is feasible.

Dissolution of biogenic silica from land to ocean: Role of salinity and pH

The dissolution rates of diatom frustules, phytoliths, two diatomaceous lake sediments, a siliceous ooze from the Southern Ocean, a diatomite deposit, and a synthetic amorphous silica were measured in flow‐through reactors supplied with either seawater or freshwater. Although the rates varied by more than one order of magnitude among the different siliceous materials, for any given solid the rate was systematically higher in seawater than freshwater, on average by a factor of five. Flow‐through reactor experiments with the diatom frustules and synthetic silica using mixtures of freshwater and seawater indicated that most of the rate increase occurred for seawater fractions between 0 and 50%. The observed rate enhancement is attributed to the higher pH of seawater and the catalytic effect of seawater cations on the hydrolysis of siloxane bonds at the silica surface. Because of their abundance in seawater, Na+ and Mg2+ are mainly responsible for the salinity‐induced rate increase. The large difference in dissolution kinetics between freshwater and seawater helps explain the very efficient recycling of biogenic silica in marine environments compared with freshwater lakes. Enhanced dissolution at the land‐ocean transition of biogenic silica produced by terrestrial plants and freshwater diatoms may represent a significant, but largely overlooked, source of nutrient silicon for estuarine and nearshore marine ecosystems.

Absorption-based highly sensitive and reproducible biochemical oxygen demand measurement method for seawater using salt-tolerant yeast Saccharomyces cerevisiae ARIF KD-003

Salt-tolerant yeast Saccharomyces cerevisiae ARIF KD-003 was applied to highly sensitive and reproducible absorbance-based biochemical oxygen demand (BOD AB- ScII ) measurement for seawater. In the previous work, we have studied the BOD AB- ScI method using normal Baker's yeast S. cerevisiae, and the excellent feature of the Baker's yeast as uniformly sustainable in solution could successfully be utilized. However, the BOD AB- ScI responses were disappeared by the existence of chloride ion as well as seawater. In the present method, uniformity in solution was also observed with S. cerevisiae ARIF KD-003, and salt-tolerance of the yeast was observed even in saturate concentration of sodium chloride. Next, characterizations of the influences of pH and incubation temperature were investigated. After optimum conditions were obtained, two calibration curves were made between 0.33 and 22 mg O 2 L −1 BOD using standard solution of glucose glutamic acid (GGA) or mixture of GGA and artificial seawater. Then, excellent reproducibility as the averages of relative standard deviation (R.S.D. av) in two calibration curves (nine points each) was successfully obtained at 1.10% at pure water or 1.03% at artificial seawater standard, respectively. In addition, the 3 σ lower detection limit was calculated to be 0.07 mg O 2 L −1 BOD, and 0.11 mg O 2 L −1 BOD was experimentally detected by increase of the sample volume at 1.5-folds. The storage stability of the S. cerevisiae ARIF KD-003 was obtained at least 4 weeks.

Hydrochemical changes in a small tropical island’s aquifer: Manukan Island, Sabah, Malaysia

Small islands groundwater are often exposed to heavy pumpings as a result of high demand for freshwater consumption. Intensive exploitation of groundwater from Manukan Island’s aquifer has disturbed the natural equilibrium between fresh and saline water, and has resulted increase the groundwater salinity and leap to the hydrochemical complexities of freshwater–seawater contact. An attempt was made to identify the hydrochemical processes that accompany current intrusion of seawater using ionic changes and saturation indices. It was observed that the mixing between freshwater–seawater created diversity in geochemical processes of the Manukan Island’s aquifer and altered the freshwater and seawater mixture away from the theoretical composition line. This explained the most visible processes taking place during the displacement.

Influence of Saline Irrigation Water and Gypsum on Leaf Nutrient Accumulation, Protein, and Oil Seed in Soybean Cultivars

ABSTRACT Due to the limitation of irrigation water, irrigating with saline water is a common practice used by farmers. Application of saline irrigation water has undesirable effects on growth and yield of plants. Some amendment materials such as gypsum can adjust the undesirable effects. In addition, some plant varieties are tolerant to saline conditions. In this regard, in 2001–2002 growing season three soybean cultivars (‘Sahar’, ‘JK’, and ‘Hill’) were selected, three levels of gypsum (0, 1.5, and 3 g pot− 1), and four levels of electrical conductivity of irrigation water namely 0.7 (well water), 2.5, 4, and 7 dS m− 1 (mixture of Caspian seawater and well water) were applied in a completely randomized factorial design with three replications in a greenhouse experiment. The results showed that with increasing saline irrigation water the amounts of potassium (K+), sodium (Na+), calcium (Ca2 +), and sodium (Na+)/Ca2 + ratio increased in leaves. The yield, oil, and protein in seed and the K+/Na+ ratio amounts accumulated in leaves decreased. Interactive effects of salinity and varieties in K+ and Ca+ 2accumulated in leaves and grain protein and oil were significant. Concentrations of K+ in leaves of the ‘Hill’ cultivar were more than in the ‘Sahar’ and ‘JK’ varieties. Calcium accumulation in ‘JK’ leaves was more than in the other varieties. The protein content in ‘JK’ was more than other varieties and the amount of oil seed in ‘Hill’ and ‘JK’ varieties was more than in the ‘Sahar’ variety. Application of gypsum increased the yield, Ca2 +, and K+ concentrations in leaves and grain protein, but decreased the amount of oil seed (not significant). Meanwhile, interactive effects of salinity, variety, and gypsum in increasing the accumulation of Ca2 +, K+, Na+, and Na+/Ca2 + in leaves were significant.

Fractionation and Reactivity of Platinum Group Elements During Estuarine Mixing

The fractionation of platinum group elements (PGE) rhodium(III), palladium(II), and platinum(IV), has been studied after their addition in aqueous form to unfiltered river water samples (Tugela river, South Africa) and to mixtures of river water and seawater. The particulate fraction of PGE averaged about 70 (Rh), 50 (Pd), and 25% (Pt) of total metal and was dependent on both particle concentration and salinity. The aqueous (<0.45 microm) pool of PGE was dominated by entities of less than 0.1 microm in diameter, and for Pd and Rh hydrophobic complexes of metal, operationally defined by their retention on a C-18 column, were significant. Distribution coefficients, based on the w/w concentration of metal on particles relative to the corresponding concentration in the aqueous pool, either increased (Rh and Pd) or declined (Pt) with increasing salinity. These observations are interpreted in terms of a number of general and metal-specific mechanisms. Thus, the behavior of Pd appears to be controlled by its association with relatively small (<0.1 microm) dissolved organic ligands, a significant fraction of which is hydrophobic and is subject to salting out upon estuarine mixing. Rhodium may also be partly subject to this mechanism of removal, but kinetic considerations and results of X-ray analysis of filter-retentates suggest that adsorption of cationic hydroxychlorides and the destabilization and precipitation of hydroxy-complexes induced by the rise in pH across the estuarine gradient are more important. Unlike Pd, the binding of Pt by organic ligands is kinetically hindered. Thus, in contrast to Pd, particle-water reactivity of Pt is controlled by electrostatic interactions between the particle surface and inorganic aqueous species. The results of this study improve our understanding of and ability to predict the transport and fate of PGE in estuaries where these metals are mobilized or discharged.

Preserving Shipboard AFFF Fire Protection System Performance While Preventing Hydrogen Sulfide Formation

There is a very serious problem aboard US Navy ships from generation of toxic hydrogen sulfide (H2S) in Aqueous Film-Forming Foam (AFFF) solutions used for shipboard fire protection. This is the result of the action of sulfate reducing bacteria (SRB) in mixtures of seawater and AFFF, which remain stagnant for significant time periods in shipboard fire protection system piping. Similar to microbial generation of H2S in sewage, over time microbes present in seawater consume organic materials in the AFFF mixture and can deplete the dissolved oxygen. If the reduction-oxidation potential falls low enough, anaerobic action of the SRB on the sulfate present in seawater can then result in H2S generation, reaching dangerous levels. The recommended ceiling for exposure to H2S is only 10 ppm. If the microbes causing oxygen depletion and/or the SRB can be eliminated (or sufficiently minimized), the dangerous generation of H2S would not occur. The Navy Technology Center for Safety and Survivability is participating in a research project for the Naval Sea Systems Command (NAVSEA) to evaluate several treatment modalities for their ability to inhibit H2S formation in AFFF/seawater mixtures and for possible deleterious effects on AFFF performance. Various approaches have been considered employing laboratory evaluations (dynamic surface tension and Ross-Miles foamability), and 28 ft2 (2.6 m2) pool fire extinguishment and burnback protection field tests (Military Standard MIL-F-24385F). The protocol selected for NAVSEA shipboard H2S generation mitigation testing is a combination of a commercial broad-spectrum biocide with a molybdenum compound which is a specific inhibitor of SRB.

Behavior of dissolved cadmium in surface water of Urasoko Bay, Ishigaki Island, Japan

The concentrations of dissolved cadmium (Cd) were monitored in the surface water of Urasoko Bay and the mouth of the stream that runs into the bay. Urasoko Bay is located on the northern coast of Ishigaki Island, Okinawa, which is surrounded by a fringing reef. Water samplings were carried out from August 2006 to August 2007, and adding to these samplings, freshwater from the upper stream and brackish water that exudates at the beach site were collected from April to June 2007. The concentration of dissolved Cd showed no tendency to decrease from the upper stream to the bay site. The results of Cd behaved non-conservatively in the Cd-salinity plot, which was attributed to daily variations in the Cd concentrations of upper stream water and the irregular input of Cd possibly adsorbed particles into the stream and beach water (the mixture of groundwater and seawater before exudation on the beach).

ＮａＣｌ水溶液を用いた氷スラリー製造装置による製氷能力に関する研究

It is well known that the temperature of slurry ice manufactured with the concentration of salt water in the range of 1.0∼2.0wt% can be accurately maintained in the range from -0.5 to -1.5°C. Now, pioneering work on a slurry ice manufacturing apparatus has already been made practicable by researchers in Canada and Germany. In their approach, ice particles made with the concentration of salt in sea water are blended with a solution consisting of a mixture of sea water and fresh water. However, the apparatus is very large. The authors therefore intend to develop a slurry ice manufacturing apparatus that uses only one unit to produce slurry ice from the solution of salt with a concentration below 1.0wt%. As a result, the authors successfully developed the generator in the apparatus on the basis of the method in which the ice layer produced on the heat transfer surface is swept out using scrapers. In addition, in order to establish the design engineering of this generator, experiment has been carried out to study the amount of ice produced from 1.0∼4.0wt% NaCl solution and measure the concentration of salt. The results indicate the following: (i) The speed at which ice is produced is determined by the initial concentration of the salt solution and remains constant when IPF≤20 IPF : ice packing factor). (ii) The speed of ice production can also be controlled by adjusting the temperature of the refrigerant. (iii) The thermal conductance of the ice layer tends to change with the salt concentration of the solution.

Numerical simulations of single‐pass hydrothermal convection at mid‐ocean ridges: Effects of the extrusive layer and temperature‐dependent permeability

We develop numerical models of hydrothermal convection at oceanic spreading centers to understand the interplay between deeply circulating high‐temperature hydrothermal fluid and cooler seawater circulating in basalts of the upper crust. We assume the deep circulation follows an idealized single‐pass geometry and consider the effects of the thickness h and permeability of the extrusive layer kext both on the shallow circulation and on the temperature and heat output of the high‐temperature discharge. We also attempt to model the effect of mineral precipitation on mixing in the shallow crust by emplacing a low‐permeability vertical barrier in the extrusives to separate the high‐temperature discharge from the circulation in the extrusives. Finally, we investigate the effects of temperature‐dependent permeability on the mixing scenarios. The results show that maximum discharge temperature Tv is impacted more by the ratio kext/kd, where kd is the permeability of the deep discharge channel, than by h. Generally, high‐temperature discharge (Tv &gt; 250°C) occurs provided kd &gt; kext. In this case, the presence of a low‐permeability barrier further enhances Tv. Low‐temperature discharge (Tv &lt; 150°C) can occur provided kext &gt; 10kd. For systems such as the Galapagos Spreading Center, where vent temperatures are ∼20°C, kext/kd &gt; 104, and the extrusive layer is likely to be thick. The results also suggest that sites of diffuse flow will occur either between high‐temperature vents along the ridge axis or off axis. The chemical composition of the fluid at these distal sites would be seawater, perhaps modified by low‐temperature water‐rock reactions. In contrast, the diffuse flow fluids near high‐temperature vents are mixture of seawater with high‐temperature hydrothermal fluid. Finally, the results show that the 150°C isotherm, which lies nearly horizontally at some distance from the discharge channel, may be within the extrusive layer, near the extrusive‐dike interface, or within the low‐permeability dike layer. This result supports the idea that the seismically defined layer 2A‐2B boundary within the oceanic crust may represent a mineral precipitation front rather than a lithologic boundary.

Salinization of groundwater in the North German Basin: results from conjoint investigation of major, trace element and multi-isotope distribution

Conjoint consideration of distribution of major, rare earth elements (REE) and Y (combined to REY) and of H, O, C, S, Sr isotopes reveals that four types of groundwater are distinguishable by their chemical composition presented by spider patterns. REY patterns indicate thermo-saline deep water and two types of shallow saline groundwaters. Presence of connate waters is not detectable. Sr isotope ratios distinguish three sources of Sr: fast and slow weathering of biotite and K-feldspar in Pleistocene sediments, respectively, and dissolution of limestones. δ13C(DIC) indicate dissolution of limestone under closed and open system conditions. Numerous samples show δ13C(DIC) > 13‰ which is probably caused by incongruent dissolution of calcite and dolomite. The brines from below 1,000 m represent mixtures of pre-Pleistocene seawater or its evaporation brines and infiltrated post-Pleistocene precipitation. The shallow waters represent mixtures of Pleistocene and Recent precipitation salinized by dissolution of evaporites or by mixing with ascending brines. The distribution of water types is independent on geologic units and lithologies. Even the Tertiary Rupelian aquiclude does not prevent salinization of the upper aquifer.

Degradation and responses of coprostanol and selected sterol biomarkers in sediments to a simulated major sewage pollution event: A microcosm experiment under sub-tropical estuarine conditions

A microcosm experiment was conducted to investigate the degradation of coprostanol and related sterol biomarkers and Escherichia coli in ‘natural’ sediments from a highly mixed (marine and estuarine) sub-tropical environment following a simulated pollution event. This experiment revealed that sterols are synthesised and degraded over time by auto- and hetero trophic organisms within the sediment matrix from a onetime addition of a sewage/effluent seawater mixture. Coprostanol was the only sterol to degrade continually, with only minor fluctuations (synthesis/degradation) over a time period of two months. Results further revealed a sharp decline of coprostanol within the first week. From this it could be concluded that, without any further addition, external inputs of coprostanol are reduced to background levels within this time period. Therefore, removal of coprostanol after six days was 94% and 73% in mud and sand, respectively. The rate of removal of coprostanol was much higher in mud than sand, reflecting a higher level of microbial activity in muddy sediments for assimilation of sterols. Bacterial indicators levelled off more quickly than coprostanol degraded (i.e. within 2 days), which shows that coprostanol is a more conservative sediment quality indicator for tracing human derived sewage in coastal sediments than indicator bacteria.

Haloplanus natans gen. nov., sp. nov., an extremely halophilic, gas-vacuolate archaeon isolated from Dead Sea–Red Sea water mixtures in experimental outdoor ponds

To study biological phenomena in the Dead Sea and to simulate the effects of mixing Dead Sea water with Red Sea water, experimental mesocosms were operated at the Dead Sea Works at Sedom, Israel. Dense communities of red halophilic archaea developed in mesocosms filled with 80 % Dead Sea water and 20 % Red Sea water after enrichment with phosphate. The most common type of colonies isolated from these brines belonged to the genus Halorubrum. A few white-pinkish opaque colonies contained pleomorphic flat cells with gas vesicles. Three strains isolated from the latter colonies were characterized in depth. Their 16S rRNA gene sequences showed only 91 % similarity to the closest cultured relative (Haloferax mediterranei), indicating that the new strains represent a novel species of a new genus. The name Haloplanus natans gen. nov., sp. nov. is proposed for this novel organism. The type strain of Haloplanus natans is RE-101(T) (=DSM 17983(T)=JCM 14081(T)).