Argo Float Reveals Biogeochemical Characteristics Along the Freshwater Gradient Off Western Patagonia

The coastal region off Chilean Patagonia has been poorly studied due to the lack of available observations. Here we analyzed, by the very first time, biogeochemical (BGC) data to elucidate the role that biological and physical processes play on nitrate, oxygen, pH and hydrographic variables, along a salinity gradient off central Patagonia. Argo float profiles covering the upper ocean from December 2015 to July 2019 reveal that offshore waters are characterized by low temperatures and high salinities related to high oxygen and medium-high values of pH and nitrate. As the Argo float drifted onshore, freshwater influences the upper 50–100 m with low salinity and high temperature. Waters under the influence of the continental runoff were characterized by medium-to-high oxygen and pH levels, and the lowest nitrate concentrations. Interestingly, oxygen-deficient waters located beneath the freshwater-modified layer showed the lowest pH and highest nitrate. A comprehensive analysis of the temporal and vertical variability of the oxygen:nitrate ratio, in conjunction with biological-related and physical parameters, indicates that the BGC variability seems to be the result of a synergistic interaction between physical and biological processes, where the stratification sets up the environment and promotes the biological response that, in turn, is auto-regulated by modifying the chemical composition in the freshwater-influenced zone. The arrival of future floats with additional sensors (Chlorophyll/Fluorescence, Photosynthetically Active Radiation, Backscatter, etc.) will add new BGC properties that improve our understanding of the coastal marine response to the increasing freshwater input off western Patagonia in the context of climate change.

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Nonionic Surfactant to Enhance the Performances of Alkaline–Surfactant–Polymer Flooding with a Low Salinity Constraint

Applied Sciences ◽

10.3390/app10113752 ◽

2020 ◽

Vol 10 (11) ◽

pp. 3752 ◽

Cited By ~ 1

Author(s):

Shabrina Sri Riswati ◽

Wisup Bae ◽

Changhyup Park ◽

Asep K. Permadi ◽

Adi Novriansyah

Keyword(s):

Nonionic Surfactant ◽

Oil Recovery ◽

Anionic Surfactant ◽

Pore Volume ◽

Salinity Gradient ◽

Reference Case ◽

Low Salinity ◽

Asp Flooding ◽

Optimum Salinity ◽

Alkaline Surfactant Polymer

This paper presents a nonionic surfactant in the anionic surfactant pair (ternary mixture) that influences the hydrophobicity of the alkaline–surfactant–polymer (ASP) slug within low-salinity formation water, an environment that constrains optimal designs of the salinity gradient and phase types. The hydrophobicity effectively reduced the optimum salinity, but achieving as much by mixing various surfactants has been challenging. We conducted a phase behavior test and a coreflooding test, and the results prove the effectiveness of the nonionic surfactant in enlarging the chemical applicability by making ASP flooding more hydrophobic. The proposed ASP mixture consisted of 0.2 wt% sodium carbonate, 0.25 wt% anionic surfactant pair, and 0.2 wt% nonionic surfactant, and 0.15 wt% hydrolyzed polyacrylamide. The nonionic surfactant decreased the optimum salinity to 1.1 wt% NaCl compared to the 1.7 wt% NaCl of the reference case with heavy alcohol present instead of the nonionic surfactant. The coreflooding test confirmed the field applicability of the nonionic surfactant by recovering more oil, with the proposed scheme producing up to 74% of residual oil after extensive waterflooding compared to 51% of cumulative oil recovery with the reference case. The nonionic surfactant led to a Winsor type III microemulsion with a 0.85 pore volume while the reference case had a 0.50 pore volume. The nonionic surfactant made ASP flooding more hydrophobic, maintained a separate phase of the surfactant between the oil and aqueous phases to achieve ultra-low interfacial tension, and recovered the oil effectively.

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Heavy Metals in Sediments from the Central New South Wales Coastal Region

Marine and Freshwater Research ◽

10.1071/mf9780777 ◽

1978 ◽

Vol 29 (6) ◽

pp. 777 ◽

Cited By ~ 13

Author(s):

A de Forest ◽

SP Murphy ◽

RW Pettis

Keyword(s):

Heavy Metals ◽

Environmental Assessment ◽

Analytical Methods ◽

New South ◽

New South Wales ◽

Coastal Region ◽

South Wales ◽

Coastal Marine ◽

Sea Bed ◽

Shelf Region

Coastal marine sediments were collected from 20 oceanographic stations along the central New South Wales coastal region in September 1975. Chemical and physical properties of the sediments were determined to establish analytical methods suitable for use in environmental assessment studies. Statistical analyses of the data indicated that this region is typical of an unpolluted continental shelf region, in which the sea bed is mainly composed of sand with some silt.

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Large seasonal and spatial variation in nano- and microphytoplankton diversity along a Baltic Sea—North Sea salinity gradient

Scientific Reports ◽

10.1038/s41598-020-74428-8 ◽

2020 ◽

Vol 10 (1) ◽

Author(s):

Malin Olofsson ◽

James G. Hagan ◽

Bengt Karlson ◽

Lars Gamfeldt

Keyword(s):

Community Structure ◽

Temporal Variation ◽

High Salinity ◽

Salinity Gradient ◽

Seasonal Succession ◽

Phytoplankton Diversity ◽

Cell Abundance ◽

Low Salinity ◽

Spatio Temporal ◽

The Impact

Abstract Aquatic phytoplankton experience large fluctuations in environmental conditions during seasonal succession and across salinity gradients, but the impact of this variation on their diversity is poorly understood. We examined spatio-temporal variation in nano- and microphytoplankton (> 2 µm) community structure using almost two decades of light-microscope based monitoring data. The dataset encompasses 19 stations that span a salinity gradient from 2.8 to 35 along the Swedish coastline. Spatially, both regional and local phytoplankton diversity increased with broad-scale salinity variation. Diatoms dominated at high salinity and the proportion of cyanobacteria increased with decreasing salinity. Temporally, cell abundance peaked in winter-spring at high salinity but in summer at low salinity. This was likely due to large filamentous cyanobacteria blooms that occur in summer in low salinity areas, but which are absent in higher salinities. In contrast, phytoplankton local diversity peaked in spring at low salinity but in fall and winter at high salinity. Whilst differences in seasonal variation in cell abundance were reasonably well-explained by variation in salinity and nutrient availability, variation in local-scale phytoplankton diversity was poorly predicted by environmental variables. Overall, we provide insights into the causes of spatio-temporal variation in coastal phytoplankton community structure while also identifying knowledge gaps.

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Physiological energetics of the estuarine crab Hemigrapsus crenulatus (Crustacea: Decapoda: Varunidae): responses to different salinity levels

Journal of the Marine Biological Association of the United Kingdom ◽

10.1017/s0025315409990889 ◽

2010 ◽

Vol 90 (2) ◽

pp. 267-273 ◽

Cited By ~ 18

Author(s):

Mauricio Urbina ◽

Kurt Paschke ◽

Paulina Gebauer ◽

Oscar R. Chaparro

Keyword(s):

Salinity Gradient ◽

Ingestion Rate ◽

Assimilation Efficiency ◽

Decapod Crustacean ◽

Growth Potential ◽

Low Salinity ◽

Physiological Processes ◽

Salinity Levels ◽

Nitrogen Ratio ◽

Physiological Energetics

Hemigrapsus crenulatus is an abundant and frequent decapod crustacean inhabiting estuarine environments, where it must tolerate large shifts in salinity. The present study evaluates the effect of salinity (5, 13, 21 and 30 psu) on the adult physiological processes related to the energy balance. The growth potential (SFG) and the respired oxygen:excreted nitrogen ratio were used as indices of stress. Ingestion, excretion and respiration rates showed a significant dependence on salinity, being higher at low salinities. The assimilation efficiency remained constant along the studied salinity gradient. The assimilation and ingestion rates were inversely related with the salinity. Given this scenario, the growth potential remained constant within the studied salinity gradient, as did the oxygen:nitrogen ratio. The results suggest that the increased energy losses at low salinity due to respiration and excretion are compensated by an increment in the ingestion rate, contributing to the success of H. crenulatus in dynamic habitats such as estuaries.

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Salinity tolerances of three succulent halophytes (Tecticornia spp.) differentially distributed along a salinity gradient

Functional Plant Biology ◽

10.1071/fp16025 ◽

2016 ◽

Vol 43 (8) ◽

pp. 739 ◽

Cited By ~ 7

Author(s):

Louis Moir-Barnetson ◽

Erik J. Veneklaas ◽

Timothy D. Colmer

Keyword(s):

Growth Rates ◽

Shoot Growth ◽

High Salinity ◽

Salt Lake ◽

Salinity Gradient ◽

Saline Soils ◽

Low Salinity ◽

Substrate Limitation ◽

Extreme Salinity ◽

Osmotic Potentials

We evaluated tolerances to salinity (10–2000 mM NaCl) in three halophytic succulent Tecticornia species that are differentially distributed along a salinity gradient at an ephemeral salt lake. The three species showed similar relative shoot and root growth rates at 10–1200 mM NaCl; at 2000 mM NaCl, T. indica subsp. bidens (Nees) K.A.Sheph and P.G.Wilson died, but T. medusa (K.A.Sheph and S.J.van Leeuwen) and T. auriculata (P.G.Wilson) K.A.Sheph and P.G.Wilson survived but showed highly diminished growth rates and were at incipient water stress. The mechanisms of salinity tolerance did not differ among the three species and involved the osmotic adjustment of succulent shoot tissues by the accumulation of Na+, Cl– and the compatible solute glycinebetaine, and the maintenance of high net K+ to Na+ selectivity to the shoot. Growth at extreme salinity was presumably limited by the capacity for vacuolar Na+ and Cl– uptake to provide sufficiently low tissue osmotic potentials for turgor-driven growth. Tissue sugar concentrations were not reduced at high salinity, suggesting that declines in growth would not have been caused by inadequate photosynthesis and substrate limitation compared with plants at low salinity. Equable salt tolerance among the three species up to 1200 mM NaCl means that other factors are likely to contribute to species composition at sites with salinities below this level. The lower NaCl tolerance threshold for survival in T. indica suggests that this species would be competitively inferior to T. medusa and T. auriculata in extremely saline soils.

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Numerical study of dispersion and hydrodynamic connectivity of near-surface waters in Lake Huron

Water Quality Research Journal ◽

10.2166/wqrjc.2012.121 ◽

2012 ◽

Vol 47 (3-4) ◽

pp. 238-251 ◽

Cited By ~ 1

Author(s):

Jun Zhao ◽

Yerubandi R. Rao ◽

Jinyu Sheng

Keyword(s):

Surface Waters ◽

Numerical Study ◽

Three Dimensional ◽

Coastal Region ◽

Lake Huron ◽

Physical Parameters ◽

Three Dimensional Model ◽

Near Surface ◽

Georgian Bay ◽

Main Lake

A nested-grid hydrodynamic modeling system is used to examine the circulation and dispersion in Lake Huron and adjacent areas with specific attention to physical parameters pertinent to the estimation of hydrodynamic connectivity of near-surface waters. The nested system is forced by monthly mean surface heat flux and 12-hourly wind stress computed from wind speeds extracted from the National Centers for Environmental Prediction of the National Center for Atmospheric Research (NCEP/NCAR) 40-year reanalysis data. The three-dimensional model currents are used to calculate the retention and dispersion of conservative, near-surface particles carried by the currents. The near-surface dispersion is relatively low in Saginaw Bay, eastern Georgian Bay and the eastern North Channel; and relatively high over the western part of the main lake and the coastal region of south Lake Huron. The hydrodynamic connectivity in the surface water and connectivity matrices are calculated from particle movements carried passively by model currents superposed by a random walk process. The model results demonstrate that the hydrodynamic connectivity in the North Channel and Georgian Bay (ranging from 0.9 to 2.2%) is much weaker than those in the main lake (5.3 to 21.9%).

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Insignificant enhancement of export flux in the highly productive Subtropical Front, east of New Zealand: a high resolution study of particle export fluxes based on <sup>234</sup>Th:<sup>238</sup>U disequilibria

Biogeosciences Discussions ◽

10.5194/bgd-8-9535-2011 ◽

2011 ◽

Vol 8 (5) ◽

pp. 9535-9576

Author(s):

K. Zhou ◽

S. D. Nodder ◽

M. Dai ◽

J. A. Hall

Keyword(s):

New Zealand ◽

Salinity Gradient ◽

Salinity Range ◽

Water Type ◽

Export Flux ◽

Low Salinity ◽

Iron Fertilization ◽

Natural Iron ◽

Poc Export ◽

Particle Export

Abstract. We evaluated the downward Particulate Organic Carbon (POC) export fluxes in the Subtropical Frontal zone (STF) of the Southern Ocean. The site is characterized by enhanced primary productivity which has been suggested to be stimulated through so-called natural iron fertilization processes at its northern boundary where iron-depleted subantarctic water (SAW) mixes with oligotrophic, iron-replete subtropical water (STW). We adopted the small-volume 234Th method to achieve highest spatial sampling resolution as possible based on a cruise to the STF to the east New Zealand in austral late autumn-early winter, May–June 2008. The inventories of fluorescence, particulate 234Th and POC observed in the upper 100 m were all elevated in the mid-salinity part of the water type (34.5<S<34.8), compared with low (S<34.5) and high (S>34.8) salinity waters. However, Steady-State 234Th fluxes were similar cross all of the salinity gradient being 1484 in the mid-salinity, and 1761 and 1304 dpm m−2 d−1 in the high and low salinity zones respectively. Bottle POC/Th ratios at the depth of 100 m were used to convert the Th fluxes into POC export flux. The POC flux was again not enhanced in the mid-salinity range where the primary production was highest, being 7.4 mmol C m−2 d−1 as compared to 9.9 mmol C m−2 d−1 in high salinity waters, and 5.9 mmol C m−2 d−1 in low salinity waters. This study implied that natural iron fertilization does not necessarily lead to the enhancement of POC export in STF regions.

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Hydrogeochemical and Isotopic Investigations on the Origins of Groundwater Salinization in Çarşamba Coastal Aquifer (North Turkey)

10.21203/rs.3.rs-388681/v1 ◽

2021 ◽

Author(s):

Abdourazakou MAMAN HASSAN ◽

Arzu Ersoy

Keyword(s):

Transition Zone ◽

Coastal Aquifer ◽

Major Ions ◽

Coastal Region ◽

Environmental Isotopes ◽

Classification Systems ◽

Physical Parameters ◽

Rock Interaction ◽

Hydrogeochemical Process ◽

Groundwater Samples

Abstract The aim of this study is to determine the origins of salinization and the main hydrogeochemical process that controls the chemistry of Çarşamba coastal aquifer in Turkey. Therefore, a total of 33 groundwater samples and three seawater samples were analyzed in the coastal region of Çarşamba Plain in July 2019 and for these samples’ physical parameters, major ions and environmental isotopes (δ18O, δ2H and 3H) values were determined. Piper, Chadha, Gibbs diagrams and Stuyfzand Classification Systems were used to determine the origins of salinization and the key hydrogeochemical process controlling the groundwater chemistry. According to Stuyfzand classification system, the study showed that the freshwater and fresh-brackish water main types are the most widespread in the study area. Six water subtypes were observed in the study area that include CaHCO3, CaMix, NaMix, NaCl, NaHCO3 and MgHCO3. In addition, the subtypes CaMix indicated the locations of the transition zone, where the groundwater rich in Ca and HCO3 and gradually enriched in Na changes from CaMix with HCO3 as dominant anion to eventually CaCl and NaCl subtypes. Furthermore, the subtypes NaMix, NaHCO3 and MgHCO3 showed the locations of the transition zone where the flushing of the saline aquifer by freshwater takes place. All groundwater samples from study area had a positive cation exchange code and show that four hydrogeochemical facies composed of CaHCO3; Ca-Mg-Cl and NaCl and NaHCO3. Besides, groundwater samples have been influenced by two main mechanisms: the water-rock interaction and evaporation-crystallization. According to δ18O, δ2H and 3H analysis, the water samples have meteoric origin, shallow circulation, and a short residence time.

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The variation of stygofauna along a gradient of salinization in a coastal aquifer

Hydrology Research ◽

10.2166/nh.2015.153 ◽

2015 ◽

Vol 47 (1) ◽

pp. 89-103 ◽

Cited By ~ 9

Author(s):

M. Shapouri ◽

L. Cancela da Fonseca ◽

S. Iepure ◽

T. Stigter ◽

L. Ribeiro ◽

...

Keyword(s):

Seawater Intrusion ◽

Coastal Aquifer ◽

Salinity Gradient ◽

Groundwater Resources ◽

Groundwater Salinity ◽

Low Salinity ◽

Composition And Structure ◽

Shallow Wells ◽

Southern Portugal ◽

Highly Correlated

We examined the variation of stygofauna composition collected in wells, along a gradient in groundwater salinity/conductivity in a coastal aquifer from southern Portugal. The studied coastal aquifer is considered vulnerable to salinization due to seawater intrusion, caused by overexploitation of the aquifer. Knowing the response of the stygofauna species to present levels of groundwater salinity makes it possible to understand and measure the effects of saltwater intrusion on stygofauna, rendering them potential bioindicators of this environmental pressure. Biotic and abiotic sampling was conducted in six shallow wells located in the fresh–saltwater interface of the Arade estuary along the salinity gradient established in the groundwater from the estuary to inland locations (microSiemens/cm). Groundwater salinity was highly correlated with taxa distribution. The stygobites Eucyclops hadjebensis and Acanthocyclops sensitivus, the cosmopolitan Megacyclops viridis and Cypria ophtalmica were particularly associated with low-salinity conditions, whereas Eucyclops graeteri, Megacyclops brachypus and Daphnia pulicaria were related to high-salinity waters. Multivariate analyses indicated that stygofauna assemblages varied significantly with location. We suggest that stygofauna composition and structure can be a useful complementing tool for monitoring seawater intrusion into coastal aquifers, where reduction or deterioration in groundwater resources is predicted.

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Testing the D / H ratio of alkenones and palmitic acid as salinity proxies in the Amazon Plume

Biogeosciences ◽

10.5194/bg-12-7239-2015 ◽

2015 ◽

Vol 12 (23) ◽

pp. 7239-7249 ◽

Cited By ~ 9

Author(s):

C. Häggi ◽

C. M. Chiessi ◽

E. Schefuß

Keyword(s):

Palmitic Acid ◽

Isotope Composition ◽

Salinity Gradient ◽

Isotopic Fractionation ◽

Light Limitation ◽

Fractionation Factor ◽

Low Salinity ◽

Lipid Biomarker ◽

Stable Hydrogen Isotope Composition ◽

Oceanic Environments

Abstract. The stable hydrogen isotope composition of lipid biomarkers, such as alkenones, is a promising new tool for the improvement of palaeosalinity reconstructions. Laboratory studies confirmed the correlation between lipid biomarker δD composition (δDLipid), water δD composition (δDH2O) and salinity; yet there is limited insight into the applicability of this proxy in oceanic environments. To fill this gap, we test the use of the δD composition of alkenones (δDC37) and palmitic acid (δDPA) as salinity proxies using samples of surface suspended material along the distinct salinity gradient induced by the Amazon Plume. Our results indicate a positive correlation between salinity and δDH2O, while the relationship between δDH2O and δDLipid is more complex: δDPAM correlates strongly with δDH2O (r2 = 0.81) and shows a salinity-dependent isotopic fractionation factor. δDC37 only correlates with δDH2O in a small number (n = 8) of samples with alkenone concentrations > 10 ng L−1, while there is no correlation if all samples are taken into account. These findings are mirrored by alkenone-based temperature reconstructions, which are inaccurate for samples with low alkenone concentrations. Deviations in δDC37 and temperature are likely to be caused by limited haptophyte algae growth due to low salinity and light limitation imposed by the Amazon Plume. Our study confirms the applicability of δDLipid as a salinity proxy in oceanic environments. But it raises a note of caution concerning regions where low alkenone production can be expected due to low salinity and light limitation, for instance, under strong riverine discharge.

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