High Salinity Zones Research Articles

Fluid Inclusions and Their Application in Hydrocarbon History and Genesis

The fluid inclusions characteristics and pore fluid salinity of 56 samples from clastic reservoir of the Lower Cretaceous were analyzed in the Tanzhuang Sag. The authors also discuss the hydrocarbon charge history and the genesis of secondary pores in the Lower Cretaceous. The multipeak distribution of homogenous temperature of the brine inclusions showed that the inclusions captured should be multiperiod fluids at various depths. Comparison of the homogeneous temperature of brine inclusions with the temperature on the burial history curve suggested that the source rocks had entered the stage of large-scale hydrocarbon generation. However, only individual brine inclusions containing methane were found, and no oil-bearing inclusions were seen. The absence of oil-bearing inclusions indicated that no large-scale oil charges and limited favorable mature source rocks were present in the study area. The paleosalinity varied with depth and was divided into three zones, namely two low-value zones in the shallow and deep burial and one high-value zone in the medium burial. The secondary pores were relatively developed in the high-salinity fluid zone. Secondary pores are chiefly related to the inorganic acid associated with dehydration and mutual transformation of clay materials, and to the organic acid released from limited mature organic matter.

Spartina alterniflora with high tolerance to salt stress changes vegetation pattern by outcompeting native species

Although many studies have been conducted on the interspecific competition between new arrivals and native plants, few of them have demonstrated how these processes interact with non‐resource factors to determine vegetation pattern. This study investigated how salt stress mediates competition between native Phragmites australis and invasive Spartina alterniflora and thus changes plant communities in Dongtan, a Chinese coast salt marsh. The experiments revealed that the growth and reproduction of the native species declined with increasing salinity but that the invasive species performed well in the salinity range of 0–20‰, illustrating why the invader could proliferate in the high salinity mudflats in Dongtan. Moreover, the native had a high growth rate and therefore exhibited a competitive dominance over the invader at low salinity of ca. 7‰. Thus, the invader could not displace the native, and the native communities were stable in the low salinity zones. In contrast, the growth rate of the invader became higher when salinity increased; correspondingly, it gained the competitive dominance at high salinity of ca. 11‰. As a result, the invader colonising the native communities in high salinity zones performed better and could displace the natives over time. Consequently, after invasive S. alterniflora colonisation, the vegetation pattern of Dongtan marsh gradually changed from “mudflat–sedge–P. australis” to “mudflat–S. alterniflora” and “mudflat–S. alterniflora and natives” along the elevation gradients. The findings of the case study demonstrated that if a new arrival has a wide tolerance range to major non‐resource stress in an ecosystem, it can not only displace natives by interspecific competition in high stress zones but can also spread into the zones without natives; on the other hand, natives with a narrow ecological amplitude in relation to the non‐resource stress can only persist in low stress zones. Therefore, the distribution area of new arrivals increases as the distribution area of natives decreases. Because some non‐resource stresses have substantial positive effects on native community invasibility, the practices that change the level of non‐resource stress and create favorable conditions for invasive species should be stopped.

Biology and Distribution of Mangrove Crabs in the Wouri River Estuary, Douala, Cameroon

Crabs appear as the most important group of mangrove epifauna. Their distribution seems influenced by some biotic and abiotic parameters. To verify the interactions between crab populations and relevant environmental components, six mangrove sites around the city of Douala (3°40' - 4°11'N and 9°16' - 9°52'E) were selected. During six months, four 25-min independent time-biased samples methods were conducted in the plot of 4 × 4 m2 delimited inside each zonation throughout transect. The distance from plot to water and its groundwater salinity, temperature, conductivity and pH were measured. The individual sex, fresh weight and carapace size were determined. 3016 individuals were harvested (57% of females). Perisesarma kamermani was the most abundant (29%) while Chiromates angolense was the most frequent (13.47%). Cardisoma armatum was only found in Pandanus zone. Crab species number was positively correlated with tree, suggesting that the mangrove vegetation is important to the crab fauna as a habitat and food supply. Sex ratio showed a significant difference for Chiromates buetikoferi 1:2.34 (χ2 = 33.21) and for Perisesarma huzardi 1.36:1 (χ2 = 39.98). Portunus validus live closer to water between 5 - 20 m while Cardisoma armatum was found 70 m away from water. Portunus validus was present exclusively in high salinity zones whereas Perisesarma kamermani dominate in low salinity zone. This baseline ecological study of crab mangroves is important for monitoring, management and conservation of mangrove ecosystems.

Distribution of ultraphytoplankton in the western part of the North Pacific subtropical gyre during a strong La Niña condition: relationship with the hydrological conditions

Abstract. The distribution of ultraphytoplankton was investigated in the western North Pacific Subtropical Gyre (NPSG) during La Niña, a cold phase of El Niño Southern Oscillation (ENSO). Observations were conducted in a north-south transect (33.6–13.25° N) along the 141.5° E meridian in order to study the ultraplankton assemblages in various oligotrophic conditions. Analyses were performed at the single cell level by analytical flow cytometry. Five ultraphytoplankton groups (Prochlorococcus, Synechococcus, picoeukaryotes, nanoeukaryotes and nanocyanobacteria-like) defined by their optical properties were enumerated in three different areas visited during the cruise: the Kuroshio region, the subtropical Pacific gyre and a transition zone between the subtropical Pacific gyre and the Warm pool. Prochlorococcus outnumbered the other photoautotrophs in all the investigated areas. However, in terms of carbon biomass, an increase in the relative contribution of Synechococcus, picoeukaryotes and nanoeukaryotes was observed from the centre of the subtropical gyre to the Kuroshio area. In the Kuroshio region, a peak of abundance of nanoeukaryotes observed at the surface suggested an increase in nutrients likely due to the vicinity of a cold cyclonic eddy. In contrast, in the salinity front along the isohaline 35 and anticyclonic eddy located around 22.83° N, the mainly constant distribution of Prochlorococcus from the surface down to 150 m characterised the dominance by these microorganisms in high salinity and temperature zone. Results suggested that the distribution of nanocyanobacteria-like is also closely linked to the salinity front rather than low phosphate concentration. The maximum abundance of ultraphytoplankton was located above the SubTropical Counter Current (STCC) at depths > 100 m where higher nutrient concentrations were measured. Finally, comparison of the ultraphytoplankton concentrations during El Niño (from the literature) and La Niña (this study) conditions seems to demonstrate that La Niña conditions lead to higher concentrations of Synechococcus in the Subtropical gyre and a lower abundance of Synechococcus in the Kuroshio region. Our results suggest that the west part of NPSG is a complex area, where different water masses, salinity fronts and eddies lead to a heterogeneous distribution of ultraphytoplankton assemblages in the upper layer of the water column.

Responses of the carbon and oxygen isotope compositions of desert plants to spatial variation in soil salinity in Central Asia

We examined the isotopic parameters in two C3 species (Artemisia diffusa H. Krasch and Tamarix hispida Willd.) and a C4 species [Haloxylon aphyllum (Minkw.) Iljin.] growing or planted in soils with different levels of salinity in a Central Asian desert. The oxygen isotope ratios of stem water (δ18Ostem) in T. hispida and H. aphyllum distributed in high-salinity zones were similar to the δ18O of artesian water (δ18Oartesian) and different from that in A. diffusa distributed in lower-salinity zones. This indicates that T. hispida and H. aphyllum depend on water with low salinity in the deeper soil layer, whereas A. diffusa depends on water in the shallower soil layer that would be affected by salt accumulation. The carbon isotope composition of leaf organic matter (δ13Com) and oxygen isotope enrichment in leaf organic matter above stem water (Δ18Oom) were lower in A. diffusa than in the other species. The responses of δ13Com and Δ18Oom to soil salinity observed for T. hispida suggest that the species decreased its transpiration rate and increased its intrinsic water-use efficiency in response to increasing soil salinity. The δ13Com and Δ18Oom of H. aphyllum were higher than those of the C3 species, and were not correlated with soil salinity, suggesting that H. aphyllum reduced its salt uptake by decreasing transpiration—even though it was able to access less saline water in the deeper soil layer. These results indicate that the water-use strategy of desert plants in high-salinity environments can be assessed based on their carbon and oxygen isotope ratios.

Habitat heterogeneity influences restoration efficacy: Implications of a habitat-specific management regime for an invaded marsh

Invasive species have to be managed to prevent adverse consequences. Spartina alterniflora has invaded many marshes where salinity and inundation are often key factors affecting vegetation. The former was surface clipped twice and native Phragmites australis was planted in invaded zones to examine the effects of habitat properties on the efficacy of invader control and native restoration. The results showed that two clipping treatments almost eliminated S. alterniflora in the zones with long inundation periods of 80 h/15 d but stimulated compensatory growth of S. alterniflora in the zones with short inundation periods. Transplanted P. australis performed better over time in zones with low salinity (<10.5 psu) but performed poorly in high-salinity zones, indicating that the efficacy of invader management and native restoration activities changes significantly along habitat gradients. With a progression from the dyke to the seaward side of the studied marsh, there was a long then short then long inundation period whereas salinity increased consistently. The study indicates that the high-frequency removal of the above-ground parts of S. alterniflora should be used only in the middle tidal zones and that native vegetation should be planted in zones above the mean high water level while the others zones in the saltmarsh should be restored to mud flats. Usually, invasive plants can flourish in highly heterogeneous habitats, which can influence management efficacy by influencing the re-growth of treated invaders and the performance of restored native species. Therefore, habitat-specific management regimes for invasive species can be expected to be more efficient because of their dependence on specific habitats.

Biogeochemical behavior of organic carbon in a small tropical river and estuary, Hainan, China

The biogeochemistry of a small tropical river and estuary (the Wanquan River (WQR)) in Hainan, China, was studied to obtain information on the sources, transformation and fate of riverine organic matter. Water and total suspended matter were sampled along a salinity gradient during four field campaigns in December 2006, August 2007, July–August 2008 and April 2009. We were able to observe the effect of heavy precipitation associated with the tropical cyclone Kammuri (2008) and a strong first-rain event (2009) on the export of organic carbon. Both dissolved organic carbon (DOC) and particulate organic carbon (POC) generally decreased with increasing salinity in the estuary, with minimal seasonal or annual variations. The POC concentrations were in the range of 18–178μM for the WQR and were significantly correlated with chlorophyll a concentrations. The highest average values of DOC (∼190μM) were observed in 2009. These values could be the result of the flushing effect of the first rain. In the high-salinity zone, in situ productivity could be an important source for DOC. The δ13Corg values of particles (−29.5‰ to −23.2‰), combined with the ratio of organic carbon to total nitrogen (OC/TN), reflect a mixture of terrestrial organic matter and in situ production. The amplitudes of the POC and DOC variations on the occasion of the first-rain event of 2009 were larger than those observed during Kammuri. It is estimated that 29.8tday−1 of DOC and 10.4tday−1 of POC, representing 6–10% of the annual loads, were delivered to the coast during the 10-day period of the first flush event in 2009. Our results demonstrate the important role of short-term aperiodic events on small rivers and estuaries along tropical coasts.

Elevated concentrations of dissolved Ba, Fe and Mn in a mangrove subterranean estuary: Consequence of sea level rise?

Groundwater underlying a mangrove habitat was studied to determine the geochemical nature of Ba, Fe and Mn as related to dissolved organic carbon (DOC), SO4 and salinity (Sepetiba Bay, Brazil). Wells were placed across geobotanic facies and sampled monthly for a year. We observed non-conservative behavior and elevated concentrations of dissolved metals relative to local end-members (i.e., fresh river water and seawater). Average Ba concentrations were near 2000nM in an area with low salinity (∼5.3). Dissolved Fe (up to 654μM) was two orders of magnitude greater in fresh groundwater than in the seaward sampling stations. Manganese concentrations were greatest (112μM) in the high salinity (∼65) zone, being directly influenced by salinity. Groundwater Ba, Fe and Mn showed differing site specific concentrations, likely related to ion exchange processes and redox-controlled cycling along distinct mangrove facies. The results of this work show that metal concentrations are altered relative to conservative mixing between terrestrial and marine endmembers, illustrating the importance of mangrove subterranean estuaries as biogeochemical reactors. Roughly-estimated submarine groundwater discharge-derived dissolved Ba, Fe and Mn fluxes were at least one order of magnitude greater than river-derived fluxes into Sepetiba Bay.

Dry Bean Response to Salinity in Southern Manitoba

Expansion of dry bean (Phaseolus vulgaris L.) production into saline soil areas of Manitoba has led to increased concern regarding its yield and quality response to soil salinity. The objective of this study was to evaluate the impact of salinity on dry bean productivity in southern Manitoba, including the application of a salt tolerance model for dry bean crops. Using a coulter‐based sensor (Veris 3100, Veris Technologies, Salina, KS) to measure apparent soil electrical conductivity (ECa), surveys of dry bean fields with five levels of soil salinity conditions (very low to very high salinity zones) were created for four sites over 2 yr. High values of ECa were associated with high values of soil saturation extract electrical conductivity (ECe). Across all site years, average root‐zone salinity (ECe) values ranged from 0.77 to 11.16 dS m−1 The lowest salinity zones resulted in greater crop biomass, grain yield, harvested seed weight, and grain number, and tended to have greater plant stand densities and grain protein content than the highest salinity zones. A 50% decrease in relative crop yield was caused by ECe values between 4.88 and 8.35 dS m−1 ECa surveys were found to be an excellent tool for assessing the relative soil salinity status of study fields.

Various-scale electromagnetic investigations of high-salinity zones in a coastal plain

Three different-scale electromagnetic (EM) measurements have been performed in the Kujukuri coastal plain, southeast Japan, to investigate the distribution of saline groundwater. The three techniques were audio-frequency magnetotelluric (AMT), transient electromagnetic (TEM), and small loop-loop EM measurements. The resistivity sections estimated from these data sets reveal three independent resistivity distributions extending to different depths. The AMT method reveals a regional-scale resistivity distribution across the plain to a maximum depth of approximately [Formula: see text] and the existence of deep conductive zones, which are inferred to be associated with fossil seawater trapped in a Pleistocene formation. The TEM results show a medium-scale resistivity distribution to depths of approximately [Formula: see text], in which two shallow conductive zones are recognized. It is concluded that these features are caused by present seawater intrusion and high-salinity salt-marsh deposits formed during sporadic marine regressions. The small loop-loop EM method provided a shallow resistivity profile that highlights the conductive salt-marsh deposits and resistive sandy ridges. Although these resistivity sections correspond to different depth ranges, the overlapping portions of the sections are very consistent with one another. These EM methods are useful in detecting and interpreting important resistivity features. Taking the geologic evolution of the coastal plains into consideration is crucial when interpreting resistivity profiles such as these, and our results suggest that the presence of fossil seawater is an important factor controlling resistivity at a variety of depths.

Water quality and invertebrate fauna of farm wells in an area affected by salinization in Oman

The spreading influence of salinity stress on the farmlands of coastal strip in the Wilayat of Sur, Sharqiyah region was investigated. A 4-km study transect was chosen from 2 km from the coast to 6 km inland and three zones based on farm conditions were demarcated. Within each zone three farms were randomly chosen and a total of nine farm wells were studied. Irrigation water quality clearly indicated that Zones 1, 2 and 3 could be classified as high, intermediate and low salinity zones. The improvement of water quality from high to low salinity zones was progressive and statistically significant. Seawater intrusion appears to be the cause of degradation in water quality. Irrigation water quality of high and intermediate zones was unacceptable by international standards. Expansion of farms, increased water extraction and a recharge dam upstream are all considered as factors promoting salinization. Management strategies for combating salinization are discussed. The invertebrate assemblages of the study wells have been described and the potential of some sensitive species for use as indicators of salinity stress is revealed. However, practical difficulties warrant the continued use of chemical methods to monitor salinity changes.

The estuarine geochemistry of rare earth elements and indium in the Chao Phraya River, Thailand

A new filtration method using a 0.04 μm hollow fiber filter was applied to the river, estuarine, and coastal waters in the Chao Phraya estuary for geochemical investigation. The filtered waters were analyzed for all the lanthanides, Y and In by using inductively coupled plasma mass spectrometry (ICPMS). The dissolved concentrations of rare earth elements (REEs) are significantly lower than those reported previously for other rivers, presumably because of effective removal of river colloids by the ultra-filtration. The variation of dissolved REEs in the estuary is dependent on the season. The light REEs vary considerably in the low salinity ( S < 3) zone presumably due to adsorption–desorption interaction with suspended particles. In January when the river discharge is low, the REEs show maxima in the mid salinity ( S = 5–12) zone suggesting that dissolved REEs are supplied to the waters by either desorption from suspended loads or remineralization of underlying sediments. The rapid removal of the REEs is also taking place in the turbid-clear water transition zone ( S = 12–15), presumably due to biological uptake associated with blooming of Noctilca occurred at the time of January sampling. In the medium to high discharge season (July and November), the dissolved REE(III)s at S > 3 show almost conservative trends being consistent with some of the previous works. Europium is strongly enriched in the river and estuarine waters compared to the South China Sea waters. Thus, the REE source of the Chao Phraya River must be fractionated and modified in entering to the South China Sea. Dissolved In and Ce in the high salinity ( S = 20–25) zone of the estuary are lower than those of the offshore waters, and therefore, the dissolved flux of the Chao Phraya River cannot account for the higher concentrations of dissolved In and Ce in the surface waters of the South China Sea. The negative Ce anomaly is progressively developed with increasing salinity, being consistent with continued oxidation of Ce(III) to Ce(IV) in the estuary. Fractionation of the light-to-heavy REEs seems to take place, whereas the Y/Ho fractionation is unclear in the estuarine mixing zone.

Biogeochemical Cycles of Manganese and Iron at the Oxic−Anoxic Transition of a Stratified Marine Basin (Orca Basin, Gulf of Mexico)

Chemical distributions and microbial culture data are combined to identify the biogeochemical pathways that control the cycles of manganese and iron at the oxic−anoxic transition of the Orca Basin. The redox transition coincides with an increase in salinity from 35 to 260‰; hence, mixing diagrams are used to constrain the salinity ranges over which consumption or production of solute species takes place. Analysis shows that the very high dissolved Mn(II) levels (>400 μM) at intermediate salinities (60−180‰) result from dissimilatory (microbial) reduction of manganese oxides, coupled to organic matter oxidation. The manganese oxides are continuously regenerated in the oxygenated, low-salinity region (45−52‰) by microbial oxidation of dissolved Mn(II). Precipitation of manganese carbonate in the high-salinity zone (>180‰) is the main removal mechanism of Mn to the sediments. Upward diffusing Fe(II) ions are extracted from solution within the anoxic, high-salinity range (230−260‰), through anaerobic oxidation by manganese oxides or a nonoxidative sorption process. Ferric oxyhydroxides are reduced by reaction with dissolved sulfide and are, therefore, not an important terminal electron acceptor for organic matter oxidation. Overall, the acid−base chemistry, redox transformations, and microbial activity across the salinity transition are strongly coupled to the cycle of manganese.

Phytoplankton, nutrients, and turbidity in the Chesapeake, Delaware, and Hudson estuaries

Estuaries receive continuous inputs of nutrients from their freshwater sources, but the fate of the inputs is poorly known. In order to document nutrient removal from the water column by phytoplankton, we measured the distributions of turbidity, nutrients, and phytoplankton across the salinity gradients of three estuaries: Chesapeake Bay, Delaware Bay, and the Hudson river estuary. Mixing diagrams were used to distinguish between conservative and non-conservative behavior; i.e. between loss from the water column and export to the estuarine plume on the shelf. In Chesapeake and Delaware Bays, we frequently observed a turbidity maximum in the oligohaline region, a chlorophyll maximum in clearer waters seaward of the turbidity maximum, and a nutrient-depleted zone at the highest salinities. In the Hudson River estuary, mixing diagrams were dominated by lateral waste inputs from New York City, and nutrient removal could not be estimated. In Chesapeake Bay, there was consistent removal of total N, nitrate, phosphate, and silicate from the water column, whereas in Delaware Bay, total N, ammonium, total P, and phosphate were removed. Total N and P removal in the Chesapeake and Delaware are estimated as ca. 50%, except for TP in the Chesapeake, which appeared to be conservative. Phytoplankton accumulation was associated with inorganic nutrient removal, suggesting that phytoplankton uptake was a major process responsible for nutrient removal. In the high salinity zone near and in the shelf plume, an index of nutrient limitation suggested no limitation in the Hudson, slight or no limitation in the Delaware, and widespread limitation in the Chesapeake, especially for P. These observations and information from the literature are summarized as a conceptual model of the chemical and biological structure of estuaries.

Relationships of Modern Gypsum Nodules in Sabkhas of Loess to Compositions of Brines and Sediments in Northern Egypt

The host sediment is a desert loess, forming a gypsiferous sonochak soil with a thin salt crust. The nodules occur only in areas where the capillary fringe intersects the ground surface, usually where the surface is within 1.5 m of the water table. Nodules a few centimeters beneath the surface are white, very fine grained gypsum. Nodules at lower levels are of more coarsely crystalline gypsum. Phreatic groundwater brines, although saturated for calcium sulfate, are only moderately hypersaline, about 60 mil. New evidence suggests that they are mainly of marine origin. Surface evaporation causes capillary brines above the water table to move upwards through the loess and to increase in salinity. A marked increase in the m Mg (super 2+) / m Ca (super 2+) ratio of the interstitial brines at the zone of fine-grained nodules demonstrates active precipitation there of calcium sulfate. It is because of the existence of a very high salinity zone (>300 mil) with halite, at the top of the profile, that gypsum precipitation takes place beneath the surface so as to form nodules rather than a surface crust. Na (super +) and Cl (super -) ions, in addition to Ca (super 2+) and SO 2 (super 2-) ions, seem to be necessary for the development of gypsum nodules by the per ascensum mechanism.--Modified journal abstract.

Post-depositional changes in the pore-water chemistry of the sensitive marine clays of the Ottawa area, eastern Canada

The pore-water chemistry is reported for four sites in the Ottawa area. The present cation concentrations in the pore water are compared with the best estimates of the initial salinity conditions within the sediments. It is observed that leaching has occurred at all sites and is largely associated with downward movement of infiltrating rainfall. At one of the sites upward diffusion of salts along a concentration gradient appears to have been important. High-salinity zones in the borings exhibited low sensitivities, whereas leached zones exhibited variable sensitivities. Where the sensitivity in the leached zones is high the pore water usually contains very low concentrations of Ca, Mg and K and a high proportion of Na, and where the sensitivity is low the Ca and Mg concentrations are higher, presumably as a result of a mild weathering of the soil material, and the proportion of Na is low. The roles of leaching and intense and mild weathering in influencing the geotechnical properties of these Postglacial marine clays are discussed.