Decrease In Salinity Research Articles

Mollusc <i>Anadara kagoshimensis</i>, Allien Species, in Structures of the Benthic Communities on the Crimea Shelf

The frequency of occurrence of the mollusc-invader, Anadara kagoshimensis (Tokunaga, 1906), increased from 5 to 17–23% in zoobenthos of the South Coast of the Crimea Shelf for the last fifteen years. At the same time, the rate of the non-native mollusc was not significant and fluctuated: 0.73–23.29% from the biomass and 0.19–2.20% from abundance of the macrozoobenthos in the benthic communities. The mollusc A. kagoshimensis has been registered in the three communities: Chamelea gallina, Gouldia minima–Pitar rudis and Gouldia minima. The mollusc Anadara has not formed an independent community here. Influence of this alien species on bottom communities of the Crimean Coast was not such considerable as on bottom communities in northwest or in east parts of Black Sea Shelf. The structure of benthic communities had no significant changes on the shelf of the Southern Coast of the Crimea, compared with 70–80 of the last century. The first registration and the settlement of the mollusc-invader on the Crimea Shelf coincides with salinity decrease and temperature rise of coastal waters which are observed during last decade.

Deciphering the laminated botryococcus-dominated shales in saline lacustrine basin, Western Qaidam Basin, NW China: Implications for shale oil potential

Given the high lipid content and potentially huge biomass, the explosive occurrence Botryococcus is regarded as a significant marker of high-quality oil source rocks in petroliferous basins. However, they are rarely discovered in saline lacustrine source rocks, and the formation mechanism of these alga-rich shales remains uncertain. In this study, abundant Botryococcus fossils were firstly found, accounting for an average of 43.5% of the total organic debris from the upper Xiaganchaigou Formation in the Yingxiongling and Zhahaquan hydrocarbon-rich sags of the western Qaidam Basin. The Botryococcus-dominated palynofacies assemblages were usually interpreted as derived from a distal oxic shelf environment. These Botryococcus-dominated sediments were characterized by a perfect laminated texture and composed of detrital, carbonate, and clay laminae. The Botryococcus fossils exclusively occur in the detrital laminae with large-grained quartz and feldspar and low carbonate content, possibly reflecting increased river input under relatively heavy precipitation. The cyclothymic deposition between these Botryococcus-rich detrital laminae and other laminae probably indicates that sufficient terrestrial nutrient inputs and lake salinity decreases driven by periodic heavy precipitation result in Botryococcus bloom under fresh or brackish water environments. These Botryococcus-dominated shales in the western Qaidam Basin usually have a high oil-prone hydrocarbon generation potential, as evidenced by their organic geochemistry parameters. These sediments have biomarker features extremely similar to crude oil with a high relative abundance of C20–C24 tricyclic terpanes, phytane, C27ααR sterane, and a unimodal distribution of n-alkanes with the maximum at n-C18. Therefore, these Botryococcus-dominated shales are possibly important oil sources of these prolific oil sags. Additionally, these high-quality source rock sequences can reach a few tens of meters in thickness and evidently have significance for future shale oil resources.

Implications of changing trends in hydroclimatic and water quality parameters on estuarine habitats in the Gulf Coastal Plain

Florida’s low elevation and geographic location make it particularly vulnerable to climate change effects such as sea level rise, increased intensity and frequency of storm events, and altered precipitation. Climate change is expected to exacerbate hydrological cycling with potential widespread implications for estuarine habitats that thrive under specific salinity regimes. We used historical data from sites in the eastern Gulf Coastal Plain, USA to examine trends and trend variability of several climatic, hydrologic, and estuarine water quality variables which have implications on seagrass and oyster habitat extent in downstream estuarine environments. We analyzed temperature, precipitation, low-flow and high-flow metrics (including the highest or lowest daily, 7-day average, and 30-day average) for each season annually over the period 1985–2020. We also analyzed estuarine water clarity metrics and salinity within waterbody segments of four estuary systems within the study area. Hydroclimate results showed that temperature increased at most sites. While there was variation in streamflow, the overall trend was declining streamflow. Declining trends were observed in most water clarity metrics, indicating improved clarity, especially in winter. Salinity generally declined across the study area. While overall streamflow decreased, main river stems to the estuaries had increasing trends in maximum streamflow characteristics, likely contributing to the decrease in estuarine salinity across the region. These results indicate that trends in streamflow (both magnitude and timing) in the watershed affect downstream estuarine water quality. These results have important implications on seagrass and oyster restoration and management efforts in the region, indicating that it is important to understand changing climatic and hydrologic conditions and how they may impact the estuarine resources.

Assessment of Risks Associated with Extreme Climate Events in Small-Scale Bivalve Fisheries: Conceptual Maps for Decision-Making Based on a Review of Recent Studies

Extreme climate events, such as heatwaves and torrential rain, affect the physiology and functioning of marine species, especially in estuarine habitats, producing severe ecological and socioeconomic impacts when the affected species support important fisheries, such as artisanal shellfisheries. Studies of the impact of sudden decreases in salinity and increases in temperature were reviewed with the aim of producing comprehensive conceptual maps to aid the management of fisheries of the native clams Ruditapes decussatus and Venerupis corrugata, the introduced Ruditapes philippinarum, and the cockle Cerastoderma edule in Galicia (NW Spain). The maps show the effects on mortality, scope for growth, ability to burrow, changes in gonad development or predation risk. While V. corrugata will generally be more affected by low salinity (5 to 15) or high temperature (30 °C) during only two tidal cycles, C. edule populations may recover. Both species are also expected to become more vulnerable to predators. The clams R. philippinarum and R. decussatus will be more resistant, unless extreme events occur after massive spawning episodes; however, the presence of the intertidal seagrass Zostera noltei may buffer the negative effects of high sediment temperature on the growth of some species, such as R. decussatus. Finally, recommendations for assessing climate risk and designing management actions for shellfisheries are given.

Ambient salinity affects silver nanoparticles (AgNPs) induced toxicity in the marine bivalve, the rock oyster, Saccostrea cucullata

Silver nanoparticles (AgNPs) penetrate water sources in a variety of ways. Although some studies have reported their toxicity experimentally, little is known on the interactive impacts of nanoparticles and environmental factors on sea organisms. We investigated the interactions of salinity changes and AgNPs exposure in the rock oyster, Saccostrea cucullata off the Oman sea. The exposure test was done by challenging the oysters with environmentally relevant concentrations of AgNPs (Low concentration: 10 µg/l, middle concentration: 20 µg/l, high concentration: 30 µg/l) at different salinities (Low salinity: 12 g/l, middle salinity: 24 g/l, high concentration: 36 g/l) for 30 days, and then the immune components in hemolymph [Total hemocyte concentration (THC), phagocytosis], antioxidant enzyme activities [superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione S-transferase (GST)] in digestive gland, oxidative stress index (MDA: malondialdehyde) and immune-related gene expressions (pro-Cathepsin L, Rho protein, Ficolin, LPS/−1,3-glucan protein, DOCK 180 protein, Lysozyme, Defensin) in hemocyte were measured. Exposure of oysters to 20–30 µg/l AgNPs at 24 and 36 g/l salinities significantly increased hemocyte counts, phagocytosis, antioxidant enzyme activities and also up-regulated immune-related gene the expressions compared to 10 µg/l AgNPs treatment (P < 0.05). At salinity, 12 g/l, the exposure of the oysters to 10–30 µg/l AgNPs significantly decreased hemocyte counts, phagocytosis, antioxidant enzymes, and down-regulated the immune-related gene expressions (P < 0.05). In same salinity, GST activity showed significant decreases in the oysters exposed to 20–30 µg/l AgNPs (P < 0.05). The oxidative stress index (MDA) significantly elevated at salinity of 12 g/l (for oysters exposed to 10–30 µg/l AgNPs) and 24–36 g/l (for oysters exposed to 20–30 µg/l AgNPs). The results of the present study showed that a decrease in water salinity with can intensify toxicity in the rock oyster.

Experimental investigation of freezing desalination using silicon oil for ice production

Because of its potential benefits in lowering process energy consumption, freezing desalination as a seawater desalination method has attracted a lot of attention. However, significant mass loss caused by extensive washing is a fundamental problem preventing the development of freezing desalination technologies. For freezing desalination technology to be widely adopted, the washing process must be eliminated. In this study, a fluid-layer-based method for separating ice is introduced. The density differences between the generated ice and the silicon oil intermediate fluid layer facilitate the separation of the product water without the need of conventional crushing or washing processes. The aim of this work is to study the feasibility and applicability of using silicon oil as an intermediary fluid layer in ice separation during the freezing desalination process. The outcomes show promise for a feasible freezing desalination technique utilizing silicon oil as an intermediate separation layer. It was also observed that as feed salinity decreases, the desalination rate increases. For instance, the distillation rate is 50.89 % and 67.3 % at an initial feed salinity equal 45,000 and 10,000 ppm, respectively. Overall, the initial feed salinity and COP are found to have an impact on specific energy usage.

Comparative study on seasonal variations in physico-chemical characteristics of four soda lakes of Ethiopia (Arenguade, Beseka, Chitu and Shala)

Soda lakes are productive natural ecosystems with substantial economic and non-economic values. Currently, they are facing considerable environmental threats that can lead to further degradation. The objective of this study was to investigate comparative spatiotemporal variations of physicochemical properties of four Ethiopian soda lakes in comparison with their historical data. Central (open-water) sampling sites were selected from four Ethiopian soda lakes: Arenguade, Beseka, Chittu and Shala. Water samples were collected from open sampling stations from January to December 2020 and analyzed at Limnology laboratory of Addis Ababa University. The geographical position of each lake was determined by means of Global Positioning System (GPS). All physicochemical factors exhibited significant differences between seasons (ANOVA, P < 0.05), except salinity in Lake Shala. The concentrations of physicochemical parameters were generally high during the dry seasons in the studied lakes due to the low incidence of rainfall, caused by recurrent drought, resulting in higher evapotranspiration rates as they are characterized by a long dry season. Lakes Arenguade and Beseka showed considerable decrease in conductivity, alkalinity and salinity, compared to data from the 1960s and 1990s, which might be attributed to dilution effect. The same parameters show slightly increasing trend in Lake Arenguade which might be due to high evaporation rate. In general, the physicochemical parameters of the study lakes showed temporal variations, which could be attributed to the dilution effect, evaporation, and hydrological characteristics of the Ethiopian Rift Valley. In the face of climate change and recurring droughts, in the Ethiopian Rift Valley, the outcomes of this study might be used as input for the long-term planning, of water resources management and devising mitigation strategies.

Trait response of three Baltic Sea spring dinoflagellates to temperature, salinity, and light gradients

Climate change is driving Baltic Sea shifts, with predictions for decrease in salinity and increase in temperature and light limitation. Understanding the responses of the spring phytoplankton community to these shifts is essential to assess potential changes in the Baltic Sea biogeochemical cycles and functioning. In this study we use a high-throughput well-plate setup to experimentally define growth and the light acquisition traits over gradients of salinity, temperature and irradiance for three dinoflagellates commonly occurring during spring in the Baltic Sea, Apocalathium malmogiense, Gymnodinium corollarium and Heterocapsa arctica subsp. frigida. By analysing the response of cell volume, growth, and light-acquisition traits to temperature and salinity gradients, we showed that each of the three dinoflagellates have their own niches and preferences and are affected differently by small changes in salinity and temperature. A. malmogiense has a more generalist strategy, its growth being less affected by temperature, salinity, and light gradients in comparison to the other tested dinoflagellates, with G. corollarium growth being more sensitive to higher light intensities. On the other hand, G. corollarium light acquisition traits seem to be less sensitive to changes in temperature and salinity than those of A. malmogiense and H. arctica subsp. frigida. We contextualized our experimental findings using data collected on ships-of-opportunity between 1993-2011 over natural temperature and salinity gradients in the Baltic Sea. The Apocalathium complex and H. arctica subsp. frigida were mostly found in temperatures&amp;lt;10°C and salinities 4-10 ‰, matching the temperature and salinity gradients used in our experiments. Our results illustrate that trait information can complement phytoplankton monitoring observations, providing powerful tools to answer questions related to species’ capacity to adapt and compete under a changing environment.

Effects of salinity changes on larval survival, growth, and development of the edible sea cucumber, Holothuria leucospilota (Brandt, 1835) at two developmental stages

For large-scale artificial breeding of sea cucumber (Holothuria leucospilota), it is necessary to understand how environmental parameters affect larval rearing. In this study, the effects of salinity changes on survival, growth, and development of the mid- and late-auricularia of H. leucospilota were estimated within a 7-day culture period. Salinity shock is usually accompanied by water replacement during hatching. To replicate the occurrence of salinity changes in actual larval production, 1/2 of the larval rearing water (initial salinity ∼31.6 ppt) was replaced daily by the experimental waters at different salinity levels (18, 22, 26, 30, 34, 38, and 42 ppt). On day 7, larval survival rates varied with salinity, while the highest survival rates (44.37–46.63% for mid-auricularia; 50.71–53.98% for late-auricularia) were observed in normal salinities (30 and 34 ppt) and the lowest survival rates (15.71–23.96% for mid-auricularia; 24.11–29.57% for late-auricularia) were observed in extreme salinities (18, 22, and 42 ppt). For any sampling event, the body length of mid-auricularia in normal salinities (30 and 34 ppt) were continued to increase during the 7-day culture period. The highest length of late-auricularia was reached on day 3 (880.01 ± 84.38 and 889.06 ± 112.11 µm, respectively), then decreased to 745.31 ± 127.64 and 742.94 ± 98.43 µm on day 7 due to metamorphosis. On day 7, the proportion of mid-auricularia larvae without development potential was the lowest (36.67%) at a salinity level of 34 ppt, and the proportions were increased with both decreasing/increasing salinities. However, this proportion was much lower for the late-auricularia at the same salinity. The decrease in salinity could promote metamorphosis of the late-auricularia, and the highest proportion of doliolaria (24.32%) was observed at salinity level of 26 ppt on day 7. In extreme salinities (18, 22, and 42 ppt), the hyaline spheres (indication of larval competence) in late-auricularia were less obvious than those in other salinities. The ability in resisting salinity shock was increased with larval development, where late-auricularia had better tolerance to salinity shock than mid-auricularia, whereas larvae at both stages were more tolerant to hypertonic than hypotonic conditions. Based on our results, we propose to rear the mid- and late-auricularia at a comparatively high level of salinity (e.g., ∼31 ppt) to promote their survival and performance, while to decrease the salinity (e.g., ∼26 ppt) in the last period of late-auricularia to increase their competence to metamorphose into doliolaria.

Acute metabolic responses of two marine brachyuran crabs to dilute seawater: The aerobic cost of hyper regulation.

Hepatuspudibundus ("flecked box crab") is a stenohaline osmoconfomer, and restricted to marine habitats. Callinectes danae ("swimming crab Dana") lives in coastal/estuarine waters and is a weak hyper regulator. There is no consensus on which strategy is more expensive metabolically face salinity challenges: conformation with higher dependence on cell volume regulation, or hyper regulation, alleviating the need for intense cell volume regulation. Crabs were probed for their acute response to dilute seawater through exposures to salinities 35‰, 30‰, 25‰, and 20‰for 2, 4, and 6 h. Hemolymph osmolality, lactate, and ions (chloride, sodium, magnesium, potassium) were assayed, as well as muscle water content. Water dissolved oxygen, ammonia, and pH levels were also measured. H. pudibundus conformed for osmolality and displayed increase in muscle hydration along the decrease in salinity down to 25‰, while C. danae efficiently maintained hemolymph osmo ionic stability, consumed more oxygen, acidified more the water, and released more ammonia. In 25‰,both species spent energy: H. pudibundus putatively controlling cell volume, and C. danae regulating hemolymph concentrations. In 20‰, H. pudibundus closed itself, avoiding the contact of the interface epithelia with the external environment and producing much lactate, whereas C. danae spent more energy (aerobic) in extracellular osmo ionic stability. Under these conditions, anisosmotic extracellular regulation (together with additional cell volume regulation) is more oxygen consuming than osmoconformation with a putatively more intense challenge to cell volume. The exposure to hyposalinity limits the occupation of estuarine environments by H. pudibundus in short and middle term.

Orbital and sub-orbital pacing of mudstones in the Dongying Depression, eastern China: Implications for middle Eocene East Asian climate evolution

The middle Eocene was a key phase in East Asian and global climate evolution; however, the understanding of the astronomical driving mechanisms of key climate changes during this phase in eastern China is lacking. A 390-m-thick, continuous lacustrine mudstone succession in the Dongying Depression (eastern China) provides an ideal middle Eocene sedimentary record. This study established an astronomical time scale (ca. 38.97−43.55 Ma) for the Dongying mudstones by double tuning of gamma-ray logs and calcite series. Based on the tuned pollen, geochemical element and nitrogen isotope data, paleo-humidity and paleo-salinity evolution profiles were constructed, showing that Dongying mudstones experienced a phased decrease in salinity and an increase in humidity. The rapid wetting accompanied by abnormal high salinity during ca. 40.0−40.6 Ma indicates that Dongying mudstones responded to the middle Eocene Climatic Optimum (MECO) event. Multi-parameter analysis showed that the rhythmic changes of Dongying mudstones at different scales were driven by multi-scaled astronomical cycles. This study focused on the intensity changes of recorded obliquity and semi-precession signals. The signals of semi-precession weakened in the dry pre-MECO period, while those of obliquity weakened in the wetter MECO period. Considering the limitation of latitude on the influence of the two cycles on the surface sunshine, we speculate that the signals of obliquity and semi-precession may reflect the intensities of high-latitude dry airflow and low-latitude wet airflow, respectively, liking to the current East Asian monsoon (EAM) system. This study expends understanding of the role of astronomical forcing on the onset and strengthening of the EAM.

Impact of ocean warming on net primary production in the northern Indian Ocean: role of aerosols and freshening of surface ocean.

Warming due to climate change stratifies the upper ocean and reduces nutrient input to the photic zone resulting in a decline in net primary production (NPP). On the other hand, climate change increases both anthropogenic aerosol input into the atmosphere and the river discharge due to the melting of glaciers on land resulting in enhanced nutrient inputs to the surface ocean and NPP. To examine the balance between these two processes, spatial and temporal variations in the rate of warming, NPP, aerosol optical depth (AOD), and sea surface salinity (SSS) were studied between 2001 and 2020 in the northern Indian Ocean. Strong heterogeneity in the warming of the sea surface was observed in the northern Indian Ocean with significant warming in the south of 12°N. Insignificant trends in warming were observed in the northern Arabian Sea (AS), north of 12°N, during winter and fall, and western Bay of Bengal (BoB) during winter, spring, and fall associated with higher levels of anthropogenic AOD (AAOD) due to a reduction in incoming solar radiation. The decline in NPP was observed in the south of 12°N in both AS and BoB and correlated inversely with SST suggesting that a weak supply of nutrients due to upper ocean stratification controlled NPP. Despite warming, the weak trends in NPP in the north of 12°N were associated with higher AAOD levels and their rate of increase suggesting that the deposition of nutrients from the aerosols seems to be compensating for declining trends due to warming. The decrease in sea surface salinity confirmed an increase in river discharge, and nutrient supply led to weak NPP trends in the northern BoB. This study suggests that the enhanced atmospheric aerosols and river discharge played a significant role in warming and changes in NPP in the northern Indian Ocean, and these parameters must be included in the ocean biogeochemical models for accurate prediction of possible changes in the upper ocean biogeochemistry in the future due to climate change.

An Assessment of the Oceanic Physical and Biogeochemical Components of CMIP5 and CMIP6 Models for the Ross Sea Region

AbstractThe physical and biogeochemical performance of 16 CMIP5 and 16 CMIP6 Earth System models (ESM) are examined relative to present day (1976–2005) observational data sets for a Ross Sea Region (RSR) containing the Ross Gyre (RG) and the Ross Sea Continental Shelf. A relative ranking scheme using error metrics and published ESM properties (including climate sensitivity parameters and anomalous deep ocean convection statistics) enables identification of a “best” ensemble of models for the RSR. Over the RSR the CMIP6 models are generally found to have improved physical representations compared to the CMIP5 set (based on our metrics for sea ice concentration, sea surface temperature, salinity, and height, and mixed layer depth), but the CMIP5 and CMIP6 biogeochemical representations remain similar. Examination of mean properties for the period 2081 to 2100 for RCP8.5 and SSP585 for CMIP5 and CMIP6, respectively, shows significant surface temperature increases, with significant decreases in sea surface salinity, sea ice concentration, and mixed layer depth across the RSR. Biogeochemically, there are generally small increases in surface values for chlorophyll, integrated primary production, and zooplankton carbon concentrations. The projections also have robust reductions in surface nitrate, phosphate, and silicate across the RSR. For that part of the RG circulation to the east of 180°E—which we refer to as the “inner RG”—significant barotropic transport increases are found by the end of century.

Investigation of salinity and ion effects on low salinity water flooding efficiency in a tight sandstone reservoir

Low salinity water flooding (LSW) has been proven to be a low-cost and accessible enhanced oil recovery method in conventional reservoirs. However, its applications and potentials in tight reservoirs are mysterious in tight sandstone reservoirs due to the low porosity and low permeability.A series of laboratory experiments were designed to investigate ionic composition and salinity on the performance of LSW in a tight oil formation. More specifically, zeta potential and contact angle were measured to examine rock surface charge distribution and wettability changes. Pressure-controlled mercury injection (PMI) and permeability tests were conducted to analyze the pore & throat and permeability changes during LSW injection. Thereafter, displacement experiments were implemented to analyze oil recovery under different LSW injection schemes.The experimental observation demonstrates that LSW injection expands the double electric layer on the oil/brine and rock/brine interfaces, resulting in the expected wettability modification. However, the presence of divalent ions in the LSW undermines this effect. On the other hand, the permeability reduction resulting from salinity decrease can be alleviated by introducing divalent ions into LSW. The coreflooding experiments reveal that continuous injection of monovalent brine would reduce the ultimate oil recovery. Alternatively, a mixture of monovalent and divalent ions in LSW is utilized to revive the permeability and maintain the wettability modification. Furthermore, an optimized lower divalent ion concentration is found to be conducive to refining the cutoff throat radius and achieving a higher oil recovery from tight oil reservoirs.

Impact of drying-wetting cycles on shear properties, suction, and collapse of sebkha soils

Sebkha soils are known as saline formations that was rencontred generally in arid and semi-arid regions. With the alternation of drying-wetting cycles (D-W) these soils present variable morphological and geotechnical properties. These cycles D-W have an important effect on the mechanical behavior of sebkha soils which poses enormous problems for the construction of structures in general. In this study, compacted sebkha soil samples from Ain M'Lila, Algeria were subjected to three D-W cycles based on the natural drying process to reach the targeted water contents of 13, 11.4, 7 and 4%, in a laboratory environment. For each of these water contents, laboratory tests were conducted to study the effect of the D-W cycles on the collapse potential Cp, suction, and shear strength of the soil. The results obtained showed that the three components of suction, i.e., total, matric, and osmotic suctions decreased when the number of D-W cycles increased. Moreover, the collapse potential Cp increased with an increase in the number of D-W cycles. Moreover, the results obtained illustrated that the shear strength parameters were affected by the number of D-W cycles a significant decrease in cohesion and an increase in the internal friction angle were observed when the number of D-W cycles was increased. Finally, a correlation was found between the soil salinity and the three factors studied these were affected by the decrease in salinity under the effect of D-W cycles.

A Comparative Study on the Difference in Temperature and Salinity Tolerance of Crassostrea nippona and C. gigas Spat

Although Crassostrea nippona and C. gigas are occasionally found to be sympatric, little is known about the differences in tolerance against environmental stresses between species, which may potentially result in severe economic losses due to the neglect of species-specific biological characteristics in farming practices. Therefore, two independent and consecutive experiments were performed to evaluate the differences in temperature and salinity tolerance between C. nippona and C. gigas spat and determine the optimal environmental conditions for the aquaculture of C. nippona spat. The experimental results of dynamic treatment showed that the accumulative survival rate (ASR) of C. nippona spat was generally lower than that of C. gigas throughout temperature changes and salinity decreases, while the ASR of C. nippona spat was superior to that of C. gigas with increasing salinity. In addition, the daily growth rate (DGR) of both species was significantly inhibited at 18 °C and peaked at 25 °C with increasing temperature (p &lt; 0.05) at each experimental salinity. At 32 °C, the survival rate (SR) of C. nippona spat was significantly lower than that of C. gigas on day 10 at all salinities tested (p &lt; 0.05), whereas the difference in the SR between species at 35 psu gradually disappeared with prolonged stress time. The data indicated that C. gigas spat was suitable for rearing at temperatures of 25 and 32 °C at all salinity levels, except the combination of 32 °C and 35 psu. By contrast, combinations of 25 °C and salinities of 21–35 psu were considered as the optimal environmental conditions for the long-term culture of C. nippona spat. These present findings contribute to a better understanding of the tolerance of C. nippona spat to environmental stresses and suggest that particular attention should be paid to the inferior adaptability of C. nippona when farming in locations outside their natural habitats.

Seagrass macrobenthic biodiversity does not vary in conformity with a leaky-lagoonal confinement gradient

Coastal lagoon ecology often changes on progression from the open, well-flushed mouth region to the depositional zone furthest from the open sea. This is generally considered consequent on increasing ‘confinement’ and associated features, rather than on the often co-occurringly decreasing salinity. The 12 km Rainbow Channel connecting part of Moreton Bay, a microtidal leaky lagoon, to the adjacent Pacific provides a gradient of increasing confinement without any significant salinity change, i.e. a tenfold increase in water residence time for a salinity decrease of <1. Macrobenthic faunal assemblages characterising intertidal Zostera seagrass at strategic points along its length were compared to test whether their nature changed in conformity with confinement models. Results suggest that it does not; faunal abundance, species richness, evenness and composition remaining effectively unchanged along the gradient. Seagrass systems may constitute a special case because they decouple renewal times of the overlying water and local organic enrichment/decomposition; as may leaky lagoons because of their high tidal velocities.

Estimation of low salinity water flooding efficiency to improve oil recovery in sandstone reservoir in Kazakhstan

Background: The regular increase in demand for hydrocarbons necessitates the introduction of optimal technologies to improve the development of reserves. The method of utilization of water with low salinity as an injected agent seemed promising in solving this issue.&#x0D; Aim: The aim of this article is to assess the potential of low-salt water to increase production and oil recovery in the terrigenous field of Kazakhstan.&#x0D; Materials and methods: For the study, low-salinity water injection into the reservoir was simulated on the ECLIPSE 100 simulator. The impact of salt concentration on production and oil displacement efficiency in the considered field during the secondary injection were determined by simulating flooding of solutions with different salinity. The model has been running for 18 years. Analysis of salinity reduction efficiency was carried out by comparing oil recovery after flooding with high salinity water.&#x0D; Results: The decrease in water salinity led to an increase in oil recovery by 1.32%. Such a slight increase in production is due to the initial hydrophilic properties of the rock. To obtain a response from the contact of low-salt water with rock, the presence of adsorbed oil on the surface of minerals is required. It can be said with high probability that in this reservoir, an increase in the oil recovery factor with a decrease in salinity is due to active interactions at the oil-water interface, one of which is an increase in viscoelastic properties.&#x0D; Conclusion: A slight difference in the efficiency of oil displacement between the studied low-salinity waters indicates the presence of the optimal salinity of the injected water. The initial hydrophilic property of the reservoir rock surface excludes wettability change as a reason for the increase in oil production. Further study of low-salt water flooding on core material from the studied field is recommended to obtain accurate data and understand how low salinity can affect the distribution of oil in the rock.

Genesis of the Brazin Iron Skarn Deposit, NW Iran: Analysis of formation conditions of calc-silicates and the evolution of fluids responsible for the massive magnetite precipitation

The Brazin iron skarn occurs along the contact zone between Late Cretaceous flysch-type sequences and an Oligocene-Miocene granodiorite. The prograde skarn stage is identified by the formation of garnet and clinopyroxene, whereas the retrograde stage is dominated by epidote, scapolite, calcite, and quartz. Metal minerals include magnetite + pyrite + chalcopyrite ± pyrrhotite. Garnet with andradite-grossularite-almandine solid-solution is ubiquitous throughout the skarn zones. Two principal types of garnet were identified in the skarn zones: (I) weakly-altered euhedral coarse-grained isotropic garnet exhibits minor variation in the overall composition (And25.95–39.41 Grs54.95–62.25 Alm + Sps + Py5.39–13.04); (II) strongly-altered anhedral to subhedral isotropic to anisotropic garnet shows a wide variation in the overall range of composition (And25.91–55.25 Grs41.37–61.15 Alm + Sps + Py1.48–12.85) in which FeOt increases, whereas Al2O3 decreases rimward.Clinopyroxene with a salitic-ferrosalitic composition is homogenous, has low to relatively high Fe/(Fe + Mg) ratios, and is poor in TiO2, MnO, and Na2O. It displays a decrease in the diopside content with increasing distance from the causative intrusion, whereas the ferrosalite content is enriched near the marble and hornfels fronts.The fluid system evolves from high temperatures (>580 °C), saline fluids (>53 wt% NaCl equivalent) in the late crystallization stage under lithostatic pressure of ∼750 bar at a depth of ∼3 km. Fluid in the later retrograde stage has lower temperatures (<430 °C) and salinities (<40 wt% NaCl equivalent). Mixing and dilution between the initial hydrothermal and external fluids might cause a decrease in fluid temperature and salinity causing the formation of the magnetite.

Biogeochemical cycling of dissolved manganese in the Arabian Sea

The study of marine biogeochemical cycling of Mn, a bio-essential trace metal, is crucial to decipher its relative role in controlling the production and diversity of marine phytoplankton. Furthermore, Mn oxides and oxyhydroxides act as sinks for other trace elements in the water column, and Mn redox cycling may exert a major control on the vertical distribution of these elements. Dissolved Mn (dMn) concentrations are measured along two GEOTRACES-India (GI) transects, GI05 and GI10, for a basin-wide investigation of biogeochemical controls on the dMn distribution in the Arabian Sea (AS). Surface dMn distribution shows a strong spatial gradient, with relatively dMn-rich levels in the eastern AS (3.4–5.7 nmol kg−1) compared to the central and western AS (1.2–2.3 nmol kg−1). This correlates with the higher model estimates of soluble Mn input from the atmospheric dust deposition in the eastern AS (∼1.5–2.0 times of input in the western and central AS), and probable additional Mn input from riverine discharge and shallow shelf region of the eastern AS. In the south-eastern AS, a correlated increase in surface dMn with a decrease in salinity indicates the Mn input by the advection of dMn-rich, low-salinity Bay of Bengal (BoB) surface waters to the AS under the influence of the Northeast Monsoon Current. Our mass balance estimates for dMn in the euphotic waters (upper 100 m) suggest important contributions from atmospheric Mn deposition (14–99% of the total estimated input flux), and dMn input/dilution (13–74% of the total estimated input or removal flux) due to lateral/vertical advective-eddy diffusive mixing. Mn-oxidation and passive scavenging are determined to be the dominant processes for the dMn removal (61–99%) from the euphotic zone (upper 100 m), while export via Mn bio-assimilation is comparatively negligible.In the AS denitrification zone, the observed dMn maxima in the upper thermocline depths (∼200–400 m) result from the in situ reductive dissolution of Mn oxides and oxyhydroxides, and lateral advective-eddy diffusive Mn flux from the reducing sediments of the western Indian margin. Outside the denitrification zone, in the northern and western AS, a shift of dMn maxima to the lower thermocline waters (∼500 m) indicates the change in the source region and dMn input from the reducing margins of the north (Pakistan Margin) and north-western AS (Oman Margin), intersecting the core of the oxygen minima at the depth range of 400–600 m.Deep water (>1500 m) dMn concentrations are low (<0.3 nmol kg−1) in most of the AS regions. Anomalous dMn enrichment in the deep waters is observed in the southern and western AS, presumably indicating the influence of hydrothermal plumes emanating from the active hydrothermal vents over the Carlsberg Ridge and spreading ridges in the Gulf of Aden. A correlated and localized increase in dMn and dAl levels close to the Murray Ridge hints at dMn input from the sediment resuspension over the ridge and subsequent Mn dissolution in low-oxygen waters (DO < 20 µM) and/or diffusive flux from the Mn-rich pore waters.