Low Salinity Values Research Articles

Improved sea surface salinity data for the Arctic Ocean derived from SMAP satellite data using machine learning approaches

Salinity is among the key climate characteristics of the World Ocean. During the last 15 years, sea surface salinity (SSS) is measured using satellite passive microwave sensors. Standard retrieving SSS algorithms from remote sensing data were developed and verified for the most typical temperature and salinity values of the World Ocean. However, they have far lower accuracy for the Arctic Ocean, especially its shelf areas, which are influenced by large river runoff and have low typical temperature and salinity values. In this study, an improved algorithm has been developed to retrieve SSS in the Arctic Ocean during ice-free season, based on Soil Moisture Active Passive (SMAP) mission data, and using machine learning approaches. Extensive database of in situ salinity measurements in the Russian Arctic seas collected during multiple field surveys is applied to train and validate the machine learning models. The error in SSS retrieval of the developed algorithm compared to the standard algorithm reduced from 3.15 to 2.15 psu, and the correlation with in situ data increased from 0.82 to 0.90. The obtained daily SSS fields are important to improve accurate assessment of spatial and temporal variability of large river plumes in the Arctic Ocean.

Pore water signatures and gas hydrates occurrence in and around the Olimpi mud volcano field, south of Crete

Mud volcanoes in the Mediterranean Sea have been subject of scientific research since the 1970s and contributed to the understanding of these seafloor features and their role in the subduction budgets worldwide. Recently, the need to better characterize the connection of these mud volcanoes with the deeper lithologies of the accretionary prism and its implications led to expedition POS410 (2011) and SO278 (2020). During these expeditions, mud volcanoes which had been investigated in ODP Leg 160 (1996) were resampled and complemented with new sites along the Mediterranean Ridge accretionary complex. We present pore water data from six mud volcanoes and two brine pools in and around the Olimpi Mud Volcano Field (OMVF). The data highlight strong depletion in Cl (<200 mM), Na (∼200 mM), Mg and K (with concentrations ∼0 mM) and striking water isotope ratios (δ18O of +9.79‰ V-SMOW and δD of −26.33‰ V-SMOW), indicating dehydration of clay minerals at depth. At five locations, the interstitial waters are characterized by extremely high salinities (Cl > 5000 mM and Na >6500 mM), therefore drastically expanding the previous reports of highly saline pore waters in the OMVF. The measurements further reveal that Gelendzhik mud volcano, located in the western part of the OMVF along a major strike-slip fault, shows an unusual pore water downcore profile and its water isotopes signature differ strongly from the other structures (δ18O of +13.63‰ and δD of +1.83‰). Upon further investigation through XRF scans and hydrates stability calculations we tied the anomalous low salinity values of the Gelendzhik MV pore waters results from the presence of gas hydrates in the sediments. This is the first, indirect evidence of gas hydrates in the OMVF, several years after this hypothesis was formulated by De Lange and Brumsack (1998) and then quickly discarded.

Modeling the effects of large-scale interior headland restoration on tidal hydrodynamics and salinity transport in an open coast, marine-dominant estuary

The effects of large-scale interior headland restoration on tidal hydrodynamics and salinity transport in an open coast, marine dominant estuary (Grand Bay, Alabama, U.S.A) are investigated using a two-dimensional model, the Discontinuous-Galerkin Shallow Water Equations Model (DG-SWEM). Three restoration alternatives are simulated for present-day conditions, as well as under 0.5 m of sea level rise (SLR). Model results show that the restoration alternatives have no impact on tidal range within the estuary but change maximum tidal velocities by ±5 cm/s in the present-day scenarios and by ±7 cm/s in the scenarios with 0.5 m of SLR. Differences in average salinity concentrations for simulated tropical and frontal seasons show increases and decreases on the order of 2 pss in the embayments surrounding the restoration alternatives; differences were larger (on the order of ±4 pss) for the scenarios with 0.5 m of SLR. There were minimal changes in average salinity outside of the estuary and no changes offshore. The size and position of the alternatives played a role in the salinity response as a result of changing the estuarine shoreline geometry and affecting the fetch within the bay. SLR was more impactful in increasing exposure to low salinity values (i.e., less than 5 pss) than the presence of the restoration alternatives. Overall, the modeled results indicate that these large-scale restoration actions have limited and localized impacts on the hydrodynamics and salinity patterns in this open coast estuary. The results also demonstrate the nonlinear response of salinity to SLR, with increases and decreases in the maximum, mean and minimum daily salinity concentrations from present-day conditions. This nonlinear response was a result of changes in the directions of the residual currents, which affected salinity transport.

O AMBIENTE ESTUARINO E A VARIAÇÃO DE pH: LIMITES NATURAIS E OBSERVAÇÃO EXPERIMENTAL DO EFEITO DA ACIDIFICAÇÃO SOBRE A BIODISPONIBILIDADE DE FÓSFORO

THE ESTUARINE ENVIRONMENT AND pH VARIATION: NATURAL LIMTS AND EXPERIMENTAL OBSERVATION OF THE ACIDIFICATION EFFECT ON PHOSPHORUS BIOAVAILABILITY. This study shows the variation of pH in the Cananéia-Iguape Estuarine-Lagoon Complex (CIELC). Data from 3 years (2019, 2021, 2022) were obtained in 17 points presenting the following ranges: temperature (14.88-27.05 ºC), pH (7.16-8.40) and DIP (0.20-11.28 µmol L-1) along a saline gradient (0.05-32.09) under different hydrodynamics, biogeochemical processes and anthropogenic influence. The pH buffering capacity due to the presence of weak acid salts in saline water (S ≥ 30) was associated to the lowest DIP, decreasing with low salinity values, confirming the direct correlation among salinity and pH. The highest temperatures in the winter of 2021, corroborated with the abnormal climate event in that year. An in vitro experiment showed results of the interaction of PID and sediments with different textures, with and without the presence of the benthic microbiota under a considerable decreasing of the pH (acidification) in relation to the natural condition of this environment. The P sediment flux characterized Iguape sector as a P sink with or without biota, Ararapira sector as a P source with biota and Cananéia, as P source without biota. The salt water buffered the pH and sediment buffered DIP both associated to the biogeochemical and hydrodynamic processes contribute to the homeostasis in the system.

Hydrographic structure of the continental shelf in Santos Basin and its causes: The SANAGU and SANSED campaigns (2019)

This study describes the hydrography and water masses of the Santos Basin Continental Shelf (SBCS) during two hydrographic campaigns (SANAGU, SANSED) in 2019. Coastal Water (CW) is the dominant water mass in the southern portion of the SBCS, with relatively low salinity values (S<35.5 g kg–1), and satellite data show that local precipitation and river discharge could not account for the low salinity observed during the cruises in the southern region of the domain. The low salinity observed is explained by the transport from the south influenced by Subtropical Shelf Water (STSW), which was influenced by the La Plata River discharge. In the northern region of the SBCS, the South Atlantic Central Water (SACW) dominates the bottom layers of the water column, with the wind playing a major role in the uplift of this water mass, as evidenced by a wind impulse analysis. In this part of the shelf, Tropical Water (TW) was the second water mass in volume and occupied the surface layers and offshore the shelf. CW is restricted to a thin surface layer, which reaches distances of a few kilometers from the coast. Our analysis show the differences in the hydrographic structure of the SBCS and suggests that the SBCS can be divided in two regions with distinct characteristics: 1) the area southwest of São Sebastião, where the hydrographic parameters were modulated by the presence of the Subtropical Shelf Water (STSW); 2) the area northeast of São Sebastião, where the uplifting of SACW was the dominant process.

The zonation of cimandiri estuary based on sea surface salinity from sentinel-2 imagery and its relation with the catching spots distribution of anguilla spp. larvae

Estuary zone is a transition zone between river environment and marine environment. The meeting between river and sea in the estuary zone causes a mixture of fresh water that has a low salinity value and sea water that has a high salinity value. The meeting of both causes the value of salinity in the estuary zone to fluctuate. This makes the estuary region inhabited by various biota. This study focused on Cimandiri Estuary, where Cimandiri Estuary is a catching area for eel larvae (Anguilla spp.). Cimandiri Estuary zonation mapping in this study using Sentinel-2 imagery. In addition to mapping the estuary zone, this study also aims to analyze the relationship between the catch of eel fish larvae with the level of salinity in the wet and dry months. Estuary zone mapping is done by applying the Cilamaya Algorithm to the Sentinel-2 image to get the distribution of surface salinity values. In wet months where the amount of rainfall is high, the value of salinity and catch will decrease. But on the contrary in the dry months where rainfall is low, the salinity value and catch of eel fish larvae will increase.

ROFI Zone (Region of Freshwater Influence) and Its Impact on Total Dissolved Solids in the Coastal District of Sukadana Kayong Utara

Coastal areas are characterized by complex dynamics between freshwater entering through the estuary from land and seawater from open water. This study aims to calculate the salinity anomaly found on the sandy coast of Mayang, estimate the number of fractions and the volume of mass transport of fresh water entering the waters through the river flow and measure the total dissolved solids (TDS) in the west season. Water mass characteristics data collection using Water Checker. The determination of 17 data collection stations is assumed to be representative in representing the overall condition of the research location. The results of the anomaly salinity calculation show the low anomalous salinity values that are distributed horizontally on the coast. The distribution of salinity as anomaly values transversely on lines 1 to 4 ranges from -1 to -15. Freshwater fraction is concentrated as far as 1.16 km from the coast of Pasir Mayang with concentration values ranging from 0.44% to 0.13%. The mass transport of fresh water in the Pasir Mayang coastal waters is 1,130 m3s -1. The value of the transport volume of fresh water depends on rainfall and the flow of fresh water through rivers and then into sea waters. The total dissolved solids at the study site at each station ranged from 7.88 ppm to 17.8 ppm.

Crystallization processes and genesis of scheelite in a quartz vein-type W deposit (Xianghuapu, South China)

Scheelite is widely developed in quartz vein-type tungsten (W) polymetallic deposits, and CL images, REE patterns and SrO isotope distributions of this mineral provide important constraints regarding its precipitation mechanism. We undertook a systematic investigation of the geochemistry (using in-situ SrO isotopes, EPMA, and LA-(MC)-ICP-MS), CL images, and fluid inclusions along core-to-rim transects of single scheelite grains from the Xianghuapu W deposit (South China) to constrain the source of ore-forming materials and reconstruct the crystallization history of the deposit. The scheelite grains show heterogeneous signatures in CL images recording a three-stage (core–mantle–rim) crystallization history. The scheelites also show decreasing concentrations of REEs from core to rim (core mean = 20.1 ppm, SD = 13.2; mantle mean = 18.7 ppm, SD = 17.8; rim mean = 5.80 ppm, SD = 5.27), as well as contrasting REE patterns and MREE distributions. There are significant variations in concentration, from core to rim of the scheelite, of MREEs (core mean = 10.0 ppm, SD = 6.43; mantle mean = 4.89 ppm, SD = 5.33; rim mean = 0.79 ppm, SD = 0.68) and HREEs (core mean = 39.4 ppm, SD = 23.4; mantle mean = 22.3 ppm, SD = 20.3; rim mean = 4.74 ppm, SD = 4.07). The 87Sr/86Sr ratios and δ18Oscheelite values decrease from core (87Sr/86Sr = 0.740817–0.743807; mean 18Oscheelite = −6.2‰) and mantle (87Sr/86Sr = 0.740048–0.745267; mean δ18Oscheelite = −7.0 ‰) to rim (87Sr/86Sr = 0.733809–0.738398; mean δ18Oscheelite = −7.9 ‰). In addition, the homogenization temperatures of fluid inclusions from the scheelite grains also decrease from core (225–236 °C, mean = 230 °C, SD = 8.20) and mantle (184–217 °C, mean = 201 °C, SD = 11.2) to rim (153–178 °C, mean = 166 °C, SD = 7.04), but the salinity of fluid inclusions changes less (mean = 1.48 wt%, 0.84 wt%, and 0.75 wt%, respectively). The low salinity and δ18OH2O values of the fluid suggest a large amount of meteoric water was mixed into the metallogenic system, resulting in a pH increase and triggering scheelite precipitation. The high Sr contents and change in 87Sr/86Sr ratios reveal that W mineralization was mainly related to Jurassic granitic magmatism, and extensive fluid-rock interaction occurred during the scheelite crystallization process. From core to rim, the magmatic Sr decreased, while the proportion of Sr derived from the limestone wall rock increased. The inhomogeneous REE and SrO isotope distributions may be a ubiquitous feature of quartz vein-type W deposits in magmatic settings globally, and in situ LA-(MC)-ICP-MS analysis can assist in revealing the complex crystallization processes of scheelite in such deposits.

Are fluid inclusions in gypsum reliable paleoenvironmental indicators? An assessment of the evidence from the Messinian evaporites

Abstract The paleosalinity of water from which the gypsum precipitated during the Messinian salinity crisis is a controversial issue. Recent microthermometry studies on primary fluid inclusions in gypsum provided very low salinity values not compatible with precipitation from seawater, and suggested strong mixing between seawater and nonmarine waters enriched in calcium sulfate. We applied a new microthermometric protocol on gypsum crystals from nine Mediterranean sections that were experimentally stretched to measure a larger population of fluid inclusions. The results show salinities ranging from 9 to 238 wt‰ NaCl equivalent, largely falling within the evaporation path of normal seawater. The data from previous studies were obtained mostly from those fluid inclusions capable of nucleating a stable bubble after a weak stretching, which probably correspond to those having a lower salinity acquired through post-depositional crack-and-seal processes. Our data suggest instead that the primary gypsum precipitated from a marine brine, later modified by post-trapping processes during tectonics and exhumation.

Salinity induces unique changes in lipid classes and fatty acids of the estuarine haptophyte Diacronema vlkianum

Studies on the influence of salinity on microalgal lipids have focused mainly on chlorophyte species and knowledge about photosynthetic secondary endosymbionts is limited. Haptophytes exemplify this situation and represent an interesting model to advance knowledge about the high phylogenetic variability of microalgae in their response to salinity. The estuarine Pavlovophyceae Diacronema vlkianum underwent particular lipid class and fatty acid changes under the effect of salinity. Variability due to salinity was higher in the fatty acid profile compared with that of the lipid class profile. Triacylglycerols decreased with salinity in actively growing cells and increased only when salinity rose to 50 and cell growth ceased. Hypersalinity caused a slight, although significant, sulpholipid decrease and a 4-fold increase in phosphatidylglycerol, suggesting a key role for this phospholipid in salt tolerance. Conversely, the betaine lipid diacylglycerol hydroxymethyl-N,N,N-trimethyl-β-alanine was specifically decreased with high salinity. The fatty acids that decreased the most with salinity were 14:0, 16:1n-7, 20:4n-6, 20:5n-3 and 22:6n-3, while higher levels of 16:1n-9, 17:1, 18:2n-6 and 18:3n-3 were induced by high salinity. Despite fatty acid changes, the unsaturation index did not vary with salinity, but nutritional value of D. vlkianum decreased at a salinity of 50 due to a lower presence of 20-C polyunsaturated fatty acids. This pattern of lipid variation in D. vlkianum with salinity has not been described in any other microalgae. Although D. vlkianum grows within a wide salinity range, production of nutritional and functional lipids is more favourable at low salinity values.

Assessment of groundwater salinization using PEST and sensitivity analysis: case of Zeuss-Koutine and Mio-Plio-Quaternary aquifers

Groundwater is the main source of water in arid regions. In the Southeast of Tunisia, Zeuss-Koutine and Mio-Plio-Quaternary underflow aquifers of Jeffara plain are considered the main source of water supply for drinking, agriculture, and industry. The study area is characterized with several known groundwater pollution sources (industrial and wastewater effluents, domestic wastes, etc.). This paper explains how sensitivity analysis can be useful tools in risk assessment of groundwater salinization. The main concern is whether the contamination sources threaten the drinking and irrigation water wells of the area. The groundwater flow and transport model of salts is set up to answer this question using MODFLOW, MT3DMS, and PEST tools. The preliminary results of the model are associated with large uncertainty. Thus, the effect of boundary conditions, dispersivity and porosity, on the migration of pollutants was investigated to estimate this uncertainty and build confidence in the model results. All variables and parameters were given a value from a range of realistic values. The sensitivity analyses show that the model is more sensitive to the salinity of the infiltrated water and the dispersivity. The results showed that the salinization process affects the areas close to the Mediterranean Sea and the Sebkha of Oum Zessar. The recharge areas have the low salinity values ranging from 1 to 2.5 g/l. High salinity reaching 3 g/l in the southeast of the Zeuss-Koutine aquifer is due to the inflow from the Triassic aquifer through Tajra fault.

On the Use of Multivariate Analysis and Land Evaluation for Potential Agricultural Development of the Northwestern Coast of Egypt

The development of the agricultural sector is considered the backbone of sustainable development in Egypt. While the developing countries of the world face many challenges regarding food security due to rapid population growth and limited agricultural resources, this study aimed to assess the soils of Sidi Barrani and Salloum using multivariate analysis to determine the land capability and crop suitability for potential alternative crop uses, based on using principal component analysis (PCA), agglomerative hierarchical cluster analysis (AHC) and the Almagra model of MicroLEIS. In total, 24 soil profiles were dug, to represent the geomorphic units of the study area, and the soil physicochemical parameters were analyzed in laboratory. The land capability assessment was classified into five significant classes (C1 to C5) based on AHC and PCA analyses. The class C1 represents the highest capable class while C5 is assigned to lowest class. The results indicated that about 7% of the total area was classified as highly capable land (C1), which is area characterized by high concentrations of macronutrients (N, P, K) and low soil salinity value. However, about 52% of the total area was assigned to moderately high class (C2), and 29% was allocated in moderate class (C3), whilst the remaining area (12%) was classified as the low (C4) and not capable (C5) classes, due to soil limitations such as shallow soil depth, high salinity, and increased erosion susceptibility. Moreover, the results of the Almagra soil suitability model for ten crops were described into four suitability classes, while about 37% of the study area was allocated in the highly suitable class (S2) for wheat, olive, alfalfa, sugar beet and fig. Furthermore, 13% of the area was categorized as highly suitable soil (S2) for citrus and peach. On the other hand, about 50% of the total area was assigned to the marginal class (S4) for most of the selected crops. Hence, the use of multivariate analysis, mapping land capability and modeling the soil suitability for diverse crops help the decision makers with regard to potential agricultural development.

Assessment of the Combined Effect of Temperature and Salinity on the Outputs of Soil Dielectric Sensors in Coconut Fiber

Dielectric sensors are useful instruments for measuring soil moisture and salinity. The soil moisture is determined by measuring the dielectric permittivity, while bulk electrical conductivity (EC) is measured directly. However, permittivity and bulk EC can be altered by many variables such as measurement frequency, soil texture, salinity, or temperature. Soil temperature variation is a crucial factor as there is much evidence showing that global warming is taking place. This work aims to assess how variations in the temperature and salinity of coconut fiber affect the output of EC5 (voltage) and GS3 (permittivity and bulk EC) Decagon sensors. The results showed that the effect of temperature and salinity on the output of the sensors can lead to substantial errors in moisture estimations. At low salinity values, permittivity readings decreased as temperature increased, while voltage readings were not affected, regardless of substrate moisture. The GS3 sensor underestimated the bulk EC when it is measured below 25 °C. The temperature dependence of the voltage of EC5 was not significant up to 10 dS m−1, and the permittivity of the GS3 was more affected by the interaction between temperature and salinity. The effect that salinity has on the permittivity of the GS3 sensor can be reduced if a permittivity–moisture calibration is performed with saline solutions, while the effect resulting from the interaction between temperature and salinity can be minimized using a regression model that considers such an interaction.

Two generations of garnets and their relevance for the hydrothermal fluid evolution of the Hongyuntan deposit, NW China

The Hongyuntan deposit, which is one of the typical volcanic-hosted Fe deposits in the Aqishan–Yamansu metallogenic belt of the Eastern Tianshan Orogenic Belt, primarily consists of Fe and skarn minerals (especially garnet). Two generations (three types) of garnets were identified in the Hongyuntan deposit based on field and optical characteristics. Hongyuntan garnets are Fe-rich and belong to the grossular–andradite solid solution series (And = 50.99%–100.00%, average: 79.06%). Garnets of the first generation (Grt1) are massive aggregates and are fine-grained with well-developed oscillatory zonings. They have Type I (two-phase liquid and vapor) and Type II (multi-phase daughter mineral-bearing) fluid inclusions and experienced high temperature (540–560 °C) and salinity (9.2–63.2 wt% NaCl eqv) conditions. The Grt1 have high ΣREE, LfREE/HREE, δEu, U, Y, and high field strength element (HFSE: sum of Nb, Ta, Zr, and Hf) contents. Garnets of the second generation (Grt2) are vefin types and are characterized by irregular shapes with irregular zonings. Type A garnets of the second generation (Grt2-A) usually coexist with mafgnetite and have Type I and Type II fluid inclusions with relatively high temperature (480–500 °C) and salinity (9.5–36.6 wt% NaCl eqv) values. Compared to Grt1, Grt2-A have low And, U, and LREE/HREE together with medium ΣREE, δEu, HFSE, and Y contents. Type B garnets of the second generation (Grt2-B) usually coexist with epidote and quartz. They merely have Type I fluid inclusions with medium–low temperature (260–280 °C) and salinity (6.6–12.7 wt% NaCl eqv) values. Grt2-B have high And, δEu, and LREE/HREE contents but very low ΣREE, HFSE, and Y contents.The fluid inclusions and geochemical properties of the garnets indicate that the temperature, salinity, oxygen fugacity (fO2), and pH of the ore-forming fluid fluctuated, indicating Hongyuntan deposit likely experienced superimposed mineralization. Grt1 originated in a magmatic–hydrothermal fluid and formed through diffusive metasomatism under relatively high fO2, neutral pH, and low water/rock (W/R) ratio conditions. The reduced Fe and other siderophile elements in the ore-forming fluid, which formed Grt1, are believed to be the material basis for iron ores in the later main metallogenic stage. Grt2-A demonstrate the characteristics associated with transitional fluid, which most likely originated from the episodic hydrothermal supplies. However, the ore-forming fluid system gradually opened up during the crystallization of Grt2-B, and the decreasing temperatures and depletion of ore-forming materials were ultimately unfavorable for the deposition of magnetite.

Dynamics of the Carbonate System in the Western Indonesian Seas During the Southeast Monsoon

AbstractWe present a unique water column data set of dissolved inorganic carbon (DIC) and total alkalinity (TAlk) from a cruise to the western Indonesian Seas during the southeast monsoon, covering the Karimata Strait, western Java Sea, and Sunda Strait. Salinity‐normalized TAlk (NTAlk) in the surface water ranged 2,297–2,348 μmol kg−1, very close to typical values observed in the tropical ocean. In the Karimata Strait, the Kapuas River plume was observed, featuring low salinity, DIC, and TAlk. In the western Java Sea, where waters were well mixed, we observed relatively homogeneous distributions of salinity, DIC, and TAlk. In the Sunda Strait, waters intruding from the Java Sea occupied the upper layer, and below was the Indian Ocean water with lower values of salinity, DIC, and TAlk. In its deep portion, depth profiles of normalized DIC and NTAlk were very similar to those observed in the Indian Ocean. Physical processes and air‐sea gas exchange exerted predominant controls on the carbonate system in the Karimata Strait and western Java Sea. While both processes play large roles in the Sunda Strait, a net DIC removal of 31 ± 23 μmol kg−1 in the surface mixed layer were revealed. The drawdown of DIC is consistent with an overall supersaturation of dissolved oxygen (102–107%), suggesting significant organic carbon production. In the subsurface‐intermediate waters of the Sunda Strait mainly influenced by the advection of Indian Ocean water, a net DIC consumption of 54 ± 45 μmol kg−1 was distinct, likely stimulated by the nutrients supplied from the Indian Ocean.

Fluid inclusion and stable isotope constraints (C, O, H) on the Dağbaşı Fe–Cu–Zn skarn mineralization (Trabzon, NE Turkey)

The Dağbaşı Fe–Cu–Zn skarn mineralization developed along the contact between the block and lens shaped limestones of the Lower Cretaceous Berdiga Formation and the Upper Cretaceous Dağbaşı Granitoid. The exoskarn-type mineralization is characterized by prograde stage garnet and pyroxene, while the retrograde stage is characterized by epidote, tremolite, actinolite, and chlorite. Quartz and calcites were observed in both stages of the skarn development. The ore minerals mainly consist of magnetite and hematite, with a lesser amount of pyrrhotite, pyrite, chalcopyrite, sphalerite, and minor galena. The homogenization temperatures (Th) and salinity values of the prograde stage halite-bearing fluid inclusions are in the range of 412–514 °C and 48.8–61.8 wt% NaCl equ., respectively. The second stage liquid- and vapor-rich fluid inclusion assemblage reveals that boiling at temperatures of 353–458 °C took place after the formation of halite-bearing fluid inclusions. Final stage liquid-rich fluid inclusions were characterized by low Th (160 and 327 °C) and salinity values (0.5 and 6.2 wt% NaCl equ.). The decreasing salinity trend of the fluid inclusions versus Th indicated that meteoric water was involved in the hydrothermal solutions. Eutectic temperatures (Te) of the prograde stage fluid inclusions were found to be CaCl2 dominated, while retrograde stage inclusions contained different salt combinations rather than a specific salt type. The minimum trapping pressures of the early stage brine fluid inclusions were calculated to be between 710 and 884 bar, while later stage inclusions had much lower trapping pressures between ~195 and 445 bar. The δ18O isotopes of prograde stage quartz, garnet, and pyroxenes are close to the composition of the hydrothermal solutions of magmatic sources. Moreover, retrograde stage quartz, epidote, tremolite-actinolite, and calcite minerals and their equilibrated solutions were found to be highly depleted by δ18O isotopes. Therefore, the fluid inclusion and stable isotope constraints suggest that the hydrothermal solutions of magmatic origin were responsible for the prograde skarn stage, while a mixture of magmatic and meteoric solutions were responsible for the ore formation in a shallow skarn environment.

Abundance and seasonal variability of aloricate ciliates and tintinnids in a eutrophic coastal lagoon system of the Gulf of California, Mexico

The heterotrophic ciliates, mainly composed of aloricate (naked) ciliates, are the dominant size fraction and play an important role in low impacted subtropical coastal systems of central region of the Gulf of California, México, by consuming up to 70% of phytoplankton biomass (pico- and nanoplankton). However, there is no information concerning microzooplankton populations for lagoons highly impacted by anthropogenic activities. This study established a baseline of regional abundance and spatio-temporal variability of aloricate ciliates and tintinnids, in the eutrophic lagoon system Topolobampo-Santa María-Ohuira. Their total abundance ranged from 10 to 56.1×103 org L−1 for ciliate, and 10 to 14.80×103 org L−1 for tintinnids. Aloricate ciliates mean abundances were approximately four times higher than that of tintinnids, with higher values occurring in winter–spring and punctuated by minor spurts during the rainy months. The study found that eutrophication levels (6.5 to 7.3 TRIX units) were the main factor contributing to their abundance, though tropic interactions and lagoon hydrological characteristics were also relevant. Their distribution revealed that substantial population increases resulted from nutrient enriched residual agricultural drainage at Santa María and Ohuira that exacerbated eutrophication conditions. Canonical correspondence analysis identified that lower values of salinity was due to the influence of wastewater effluent discharge and was the main variable that was related with tintinnids; while dissolved oxygen and chlorophyll-a, variables associated to large primary production, were related to ciliates. The deteriorated water quality of Santa María and Ouhira lagoons likely delineated the low macro-zooplanktonic biomasses and consequently the higher aloricate ciliates and tintinnids abundances.

Spatial and temporal dynamics of dissolved nutrients and factors affecting water quality of Chilika lagoon

Water quality of Chilika lagoon was assessed for pre- and post-monsoon seasons. A marked spatial and temporal variability in the water quality was observed in this study. Principal component analysis (PCA) reveals the influence of salinity, anthropogenic factors, as well as vegetation on the water quality. The higher concentration of nitrate (NO3−) and phosphate (PO43−) in certain pockets of the lagoon water was due to the prevalence of agricultural, municipal, and domestic waste. A positive correlation between PO43− and DSi indicates their terrigenous input from freshwater influx. Cyclone Phailin had profound impact on several water quality parameters. pH, dissolved oxygen (DO), and dissolved inorganic carbon (DIC) are governed largely by the presence of macrophytes. The impact of severe cyclone Phailin can be assessed from the very low salinity values persisting in the lagoon even 2.5 months after the cyclone hit Odisha coast. Some toxic heavy metals like Copper (Cu), Lead (Pb), Nickel (Ni), Cobalt (Co), Manganese (Mn), and Iron (Fe) exceeded the Environmental Protection Agency (EPA) standards at many locations in both the seasons. Non-conservative behavior of nutrients indicates well mixed nature of lagoon which is also indicative of good primary productivity. Northern sector (NS) of the lagoon is susceptible to eutrophication being riverine influenced region. Southern sector has more stable ion chemistry as a result of least freshwater discharge, constant supply of saline water, and lesser water renewal.

Fluid compartmentalization of Devonian and Mississippian dolostones, Western Canada Sedimentary Basin: petrologic and geochemical evidence from fracture mineralization

Integrated petrographic, geochemical, and fluid inclusion study of fracture mineralization and associated host rock in selected Mississippian and Devonian carbonates extending from southeastern Alberta to northwestern British Columbia, Canada, aims to quantify the type and nature of fluid precipitated saddle dolomite and late calcite cement and their origin. Petrographic and isotopic evidence from both the Devonian and Mississippian fracture-filling carbonates indicate the presence of a hydrothermal fluid source. The δ18O isotopic values for the Devonian saddle dolomite (−14.62‰ to −3.75‰ VPDB, average −11.12‰) combined with enriched 87Sr/86Sr isotopic ratios (0.70827–0.71599, average 0.71006) and higher homogenization temperatures (Th = 74–194.6 °C, average 126.8 °C) and salinity values (7.7–26.6 wt.% NaCl, average 16.2 wt.% NaCl) show significant differences from the Mississippian saddle dolomite, which is characterized by less negative δ18O isotopic values (−12.53‰ to −7.82‰ VPDB, average −9.14‰), less radiogenic 87Sr/86Sr isotopic ratios (0.70859–0.70943, average 0.70887), and lower homogenization temperatures (Th) and salinity values of fluid inclusions (87.6–214.2 °C, average 136.3 °C; 2.0–13.2 wt.% NaCl, average 9.6 wt.% NaCl). Later fracture- and vug-rimming blocky calcite cement records comparable or slightly lower values of δ18O (−16.31‰ to −4.08‰ VPDB, average −9.76‰) and 87Sr/86Sr (0.70784–0.709743, average 0.70868) and much lower salinity values (0–22.5 wt.% NaCl, average 2.86 wt.% NaCl) for samples mostly from the Mississippian age group. These results possibly suggest two different hydrothermal episodes related to early (Antler) and late (Laramide) tectonic events that affected the Western Canada Sedimentary Basin with possible compartmentalization of hydrothermal systems and their associated brines in the basin.

Disentangling Environmental Drivers of Phytoplankton Biomass off Western Iberia

Phytoplankton are the main primary producers in marine ecosystems, supporting important food webs. They are recognized as important indicators of environmental changes in oceans and coastal waters. Ocean colour remote sensing has been extensively used to study phytoplankton throughout the world, yet there is still much to understand in terms of what influences phytoplankton variability at regional scales. The main aim of this study was to investigate the drivers of phytoplankton variability in the Western Iberian Coast (WIC), for the period 1998-2016. Satellite chlorophyll a (CHL) data was acquired from the Copernicus Marine Environment Monitoring Service (CMEMS). A positive annual trend of CHL was observed at the northern coastal WIC, near Galicia, and a negative trend was observed in southern areas, near the Gulf of Cadiz. An empirical Orthogonal Function (EOF) analysis was implemented to identify regions with similar patterns of CHL variability. Six regions were obtained. A set of climate indices, satellite and model variables were then used as environmental predictors in Generalized Additive Models (GAMs) that explained between 18.0 to 49.3% of the total variance of CHL anomalies calculated from a detrended and deseasoned dataset. In the northern oceanic region positive anomalies were linked to high North Atlantic Oscillation (NAO) values and negative anomalies to high mixed layer depths. In the southern oceanic region, positive CHL anomalies were found to be associated with high concentrations of nitrogen, that may indicate nitrogen limitation. Phytoplankton in coastal areas were found to respond to basin-wide (e.g. Atlantic Multidecadal Oscillation-AMO) and coastal processes (e.g. upwelling and continental runoff), yielding positive anomalies with low salinity values. In very small coastal areas near major rivers, such as Douro and Guadalquivir, the positive response of phytoplankton to increased nitrogen concentrations and decreased salinity was evident. Considering the changes in climate expected for this region, related to the decrease in precipitation and increase in summer temperatures, as well as some apparent weakening of upwelling, possible significant impacts on the phytoplankton community can be anticipated. These results are therefore also relevant for environmental management, especially in the context of the European Marine Strategy Framework Directive (MSFD).