Effect Of Salinity Gradient Research Articles

Salinity-driven nitrogen removal and bacteria community compositions in microbial fuel cell-integrated constructed wetlands.

The effects of salinity gradients (500-4000mg·L-1 NaCl) on electricity generation, nitrogen removal, and microbial community were investigated in a constructed wetland-microbial fuel cell (CW-MFC) system. The result showed that power density significantly increased from 7.77 mW m-2 to a peak of 34.27 mW m-2 as salinity rose, indicating enhanced electron transfer capabilities under saline conditions. At a moderate salinity level of 2000mg·L-1 NaCl, the removal efficiencies of NH4+-N and TN reached their maximum at 77.34 ± 7.61% and 48.45 ± 8.14%, respectively. This could be attributed to increased microbial activity and the presence of critical nitrogen-removal organisms, such as Nitrospira and unclassified Betaproteobacteria at the anode, as well as Bacillus, unclassified Rhizobiales, Sphingobium, and Simplicispira at the cathode. Additionally, this salinity corresponded with the highest abundance of Exiguobacterium(3.92%), a potential electrogenic bacterium, particularly at the cathode. Other microorganisms, including Geobacter, unclassified Planctomycetaceae, and Thauera, adapted well to elevated salinity, thereby enhancing both electricity generation and nitrogen removal.

Impact of salinity gradient, water pollution and land use types on greenhouse gas emissions from an urbanized estuary

Estuaries have been recognized as one of the major sources of greenhouse gases (GHGs) in aquatic systems; yet we still lack insights into the impact of both anthropogenic and natural factors on the dynamics of GHG emissions. Here, we assessed the spatiotemporal dynamics and underlying drivers of the GHG emissions from the Scheldt Estuary with a focus on the effects of salinity gradient, water pollution, and land use types, together with their interaction. Overall, we found a negative impact of salinity on carbon dioxide (CO2) and nitrous oxide (N2O) emissions which can be due to the decrease of both salinity and water quality when moving upstream. Stronger impact of water pollution on the GHG emissions was found at the freshwater sites upstream compared to saline sites downstream. In particular, when water quality of the sites reduced from good, mainly located in the mouth and surrounded by arable sites, to polluted, mainly located in the upstream and surrounded by urban sites, CO2 emissions from the sites doubled while N2O emissions tripled. Similarly, the effects of water pollution on methane (CH4) emissions became much stronger in the freshwater sites compared to the saline sites. These decreasing effects from upstream to the mouth were associated with the increase in urbanization as sites surrounded by urban areas released on average almost two times more CO2 and N2O than sites surrounded by nature and industry areas. Applied machine learning methods also revealed that, in addition to salinity effects, nutrient and organic enrichment stimulated the GHG emissions from the Scheldt Estuary. These findings highlight the importance of the interaction between salinity, water pollution, and land use in order to understand their influences on GHG emissions from dynamic estuarine systems.

Research on Measuring Pure Membrane Electrical Resistance under the Effects of Salinity Gradients and Diffusion Boundary Layer and Double Layer Resistances.

Forward osmosis membranes are an emerging technology with great potential applicability in energy-efficient wastewater treatments and the differentiation between two solutions. Such solutions often differ in their concentrations or compositions. In this study, the membrane electrical resistances of three different membranes, including cation or anion-exchange membranes and forward osmosis membranes, were analyzed by Luggin capillary coupled with AC impedance spectroscopy (EIS) so as to obtain the real membrane and ion transfer impedance values near the membrane interface. The results reveal that the membrane impedance obtained by both the DC and AC approaches decreased as the lowest external solution concentration increased. Furthermore, the relationship between the membrane conductivity and the internal salt solution concentration was also investigated. It can be seen that the external ion concentration is directly proportional to the free ion concentration in the membrane, and the free ion concentration in the membrane is closely related to the membrane electrical resistance.

Effects of salinity gradients on the skin and water microbial community and physiological responses of tilapia (Oreochromis niloticus) in the pre‐slaughter

This study investigated the use of salt as a mitigating agent for bacterial contamination and physiological responses of tilapia in a simulation of pre-slaughter transport. Bacteria concentration, haematological parameters and muscle dehydration were evaluated. Adult tilapia (568 ± 141 g) were fasted for 24 h and subjected to a simulation of transport for 4 h in four salinities: 0, 7, 14 and 21 g of salt L−1. The concentration of 21 g of salt L−1 resulted in the lowest concentration of aerobic mesophilic heterotrophic bacteria on the skin of tilapia and in the transport water. Salinity did not influence the haematological parameters of haematocrit, monocytes, eosinophils, basophils, haemoglobin and mean corpuscular haemoglobin concentration. The concentrations of 14 and 21 g of salt L−1 had the lowest plasma protein values and led to lymphopaenia and neutrophilia. The concentration of 7 g of salt L−1 had values similar to baseline level for lymphocyte, neutrophil, white blood cell counts and plasma protein. Hyperglycaemia and thrombocytopaenia occurred in all treatments. Increased dehydration of muscle tissue with increased salinity was observed. The concentration of 7 g of salt L−1 promoted the fewest physiological changes. However, it is recommended the transport at high salinity of 21 g of salt L−1 for bacterial control.

Development of a process for the treatment of synthetic wastewater without energy inputs using the salinity gradient of wastewaters and a reverse electrodialysis stack

Electrochemical processes are considered very effective methods for the treatment of wastewater contaminated by organics resistant to conventional biological processes and various inorganic pollutants. Large sites that treat wastewaters usually deal with a large number of waters often characterized by different salinity contents, that could be potentially used to provide the energy necessary for the electrochemical remediation. Hence, in this work a reverse electrodialysis (RED) process for the treatment of synthetic wastewaters contaminated by organics, without energy inputs, using the salinity gradient of different wastewaters, was studied, for the first time. It was found that two synthetic wastewaters with different NaCl content can be effectively used in a RED system to drive anodic and cathodic processes for the removal of their organic contents without external energy supplies. The effects of salinity gradient, external resistance and set-up of the process was evaluated. Under optimized operating conditions, a fast and high removal of TOC (about 70% every hour) in the anodic compartment and a good stability of operating conditions for all the monitored time (10 h) were achieved. In addition, about 67% of the solution with high salinity used in the stack to provide the salinity gradient was effectively treated in the anodic compartment of the stack.

The effect of salinity gradient and heavy metal pollution on arbuscular mycorrhizal fungal community structure in some Algerian wetlands

Algerian natural wetlands suffer from anthropogenic disturbances due to industrial development and urbanization. This study was designed to draw attention to arbuscular mycorrhizal fungi (AMF) distribution and community assemblages following heavy metal and salinity concentrations in two wetlands subjected to domestic and industrial effluents. Rhizospheric soil and roots of 18 plant species were collected in two wetlands along a decreasing salinity gradient. The results showed that 72.72% of plant species exhibit an association within arbuscular mycorrhizas (AM), and 36.36% a dual association between AM and dark septate endophytes (DSE). A total of 33 AMF morphospecies were distinguished on the basis of morphological criteria dominated by taxa belonging to Glomeraceae and Acaulosporaceae. Soil contamination was investigated by determining metallic trace elements (MTE) (Cd, Cu, Ni, Pb, Cr and Zn) using an atomic absorption spectrophotometer. Values of the pollution index revealed wetlands that were particularly polluted by lead. Two˗way ANOVA showed significant variations in metal content among sampling locations and transects. Principal component analysis showed that species richness, and mycorrhizal frequency were slightly affected by MTE. This opens possibilities for their utilization in polluted soil remediation.

Helminth Fauna of the Shortfin Molly Poecilia mexicana (Actinopterygii) in Two Neotropical Brackish Water Bodies of Mexico

Although information on the fauna of helminths of the shortfin molly Poecilia mexicana in freshwater environments is extensive, to date, there have been no studies on helminths that parasitize this fish in brackish water bodies. To increase the knowledge about the host-parasite association in this kind of habitats, during April 2014, 80 fish specimens of P. mexicana from 2 localities in Veracruz, Mexico, were examined for helminths: Arroyo Moreno (AM) and Laguna Mandinga (LM). Arroyo Moreno is an anthropogenically polluted mangrove swamp, and LM is a saline environment with low marine influence. The helminth species record in both fish populations included 9 taxa: 7 digeneans, 1 cestode, and 1 nematode, with 6,261 individuals, most of them collected in fishes from AM (5,768). In general, a high proportion of allogenic larval stages was observed, which agreed with the pattern observed in helminth fauna of tropic freshwater fish. In addition, these parasite assemblages were dominated by digeneans, worms that generally are numerically dominant in many helminth communities of freshwater fishes in Mexico. The euryhaline nature of P. mexicana establishes it as an adequate system to study the effects of salinity gradients focused on helminth communities.

Effects of salinity gradients on benthic invertebrate and diatom communities in a German lowland river

The Lippe is a lowland river located in the Western part of Germany and has been heavily impacted by coal mining activities ever since. Although mining activities significantly decreased during the last decades, the associated discharge of salt-enriched mine water into the river still poses a persistent threat to the local benthic invertebrate and diatom communities. To analyze the effect of salt pollution on invertebrate and diatom species, biological and chemical data were compiled for this study from a publicly available database. Changes in the community composition due to increased salt concentrations were explored by Non-Metrical-Multidimensional Scaling. Indicator species and salinity thresholds for single species and communities were identified using the method TITAN (Threshold Indicator Taxa Analysis). The method is an analytical approach to detect changes in frequency and abundance of species along an environmental gradient by combining the methods of change point analysis (nCPA) and indicator species analysis. The obtained salinity preferences and individual and community thresholds were compared to the literature and existing salinity classifications. For both diatoms and benthic invertebrates, Non-Metrical-Multidimensional Scaling showed a clear split between samples of high and low salinities. Significant salinity thresholds were determined for 50 invertebrate and 58 diatom species of which 23 respectively 18 species were described as ‘reliable’ indicators according to the specifications given by Baker and King (2010). A majority of salt-tolerant indicator organisms were invasive species. For both organism groups, major changes in community composition were detected at a conductivity value exceeding 900μS/cm. A reduction of the average salinity to below this threshold may have positive effects on the overall species richness and the persistence of sensitive taxa in the river Lippe. Individual and community thresholds may however be data-dependent to a certain degree and subjected to fluctuations considering the potential interdependencies between salinity and additional physico-chemical and environmental parameters (e.g. water temperature, lime content).

Detection of Water and Sediments Pollution of An Arid Saltern (Sfax, Tunisia) by Coupling the Distribution of Microorganisms With Hydrocarbons

We investigated the coupling of abundance of bacteria, phytoplankton and ciliates with hydrocarbons in the surface water and sediments of five interconnected ponds in the arid Sfax solar salterns. This study aimed at determining the potential sources of hydrocarbons and the effects of salinity gradients on microorganism metabolism. Hydrocarbon analysis was performed by gas chromatography (GC-FID) and gas chromatography coupled with mass spectrometry (GC-MS). The GC-FID allowed the detection of aliphatic hydrocarbons and n-alkanes ranging from n-C13 to n-C30. Total aliphatic hydrocarbon concentrations varied from 92.5 mg. l−1 in the first pond (having marine characteristics) to 661.1 mg. l−1 in the last pond (crystallizer) (316.8 ± 120.1 mg. l−1) for water samples and from 26.7 to 127.8 μg. g−1 dry weight for sediment samples. The GC-MS enabled us to detect halogenated hydrocarbons (bromoalkanes and chloroalkanes) and n-alkenes. The distribution of n-alkanes indices coupled to several environmental factors suggests that a major fraction of hydrocarbons resulted from both prokaryotic (bacteria) and eukaryotic (protists) developments. A low hydrocarbon fraction might be petrogenic.

Effect of salinity gradients on the distribution of phytoplankton pigments in a stratified estuary

Effect of salinity gradients on the distribution of phytoplankton pigments in a stratified estuary

Normoxic and anoxic energy metabolism of the southern oyster drillThais haemastoma during salinity acclimation

The energetic cost associated with salinity acclimation was determined in the marine gastropodThais haemastoma by direct calorimetry under normoxic and anoxic conditions. Snails were collected from Caminada Pass near Grand Isle, Louisiana (Longitude 90°2′W; Latitude 29°2′N) in September 1987. Metabolic heat flux of snails acclimated to and measured at 10 or 30‰ S was similar at 15.06 or 16.39 J g−1 dry wt h−1, respectively, (corresponding to 0.76 or 0.83 ml O2 g−1 dry flesh wt h−1) under normoxic conditions, and 2.39 or 2.53 J g−1 dry wt h−1 under anoxic conditions. Inter-individual variability was high, obscuring the effect of salinity gradient on heat flux. When standardized to the pre-transfer control level of each individual under anoxic conditions, a significant increase (55%) of energy expenditure was observed for snails transferred to hyperosmotic conditions. In contrast, heat flux varied insignificantly in individuals in the anoxic 30 to 10‰ S transfer. After transfer of individuals from 10 to 30‰ S under normoxic conditions, heat flux was depressed initially to 38% of the control rate, but recovered after 14 h to a higher metabolic rate (56%) than the pre-transfer control rate. After transfer of individuals from 30 to 10‰ S under normoxic conditions, the standardized heat flux decreased to 28% of the control rate, followed by a 20 h period of recovery to the control rate. The energy cost of intracellular hypoosmotic regulation was less than hyperosmotic regulation under anoxic conditions. The retraction of the foot ofT. haemastoma after normoxic salinity transfers did not generally correlate with the time course of metabolic heat flux.

Effect of salinity gradients and heterotrophic microbial activity on biodegradation of nitrilotriacetic acid in laboratory simulations of the estuarine environment.

The biodegradation of nitrilotriacetic acid (NTA), a synthetic replacement detergent builder, in the estuarine environment was examined by using a laboratory estuarine simulation. Two interdependent microcosms were used; each of five vessels was equilibrated with a saline gradient between 1.30 and 17.17%, with the final vessel subsequently being increased to a maximum salinity of 31.6%. Each microcosm was seeded simultaneously with heterotrophic bacteria from both fresh and saline sources. Viable counts demonstrated the ability of each microcosm to sustain a mixed heterotrophic bacterial community throughout the range of salinities for 183 days after a stabilization period. Isolation studies demonstrated that both systems contained four bacterial species, representatives of the genera Vibrio and Flavobacterium and members of the coryneform group and the family Enterobacteriaceae. Total bacterial numbers and species diversity decreased with increased salinity. NTA was administered at low and high concentrations, one concentration to each microcosm, initially with the least amount of saline. Removal of both concentrations of NTA occurred and was attributed to biodegradation after a period of bacterial acclimatization. Subsequent dosing of NTA to vessels of higher salinity demonstrated that biodegradation was incomplete at observed mean salinities of greater than 9.18% at low influent NTA concentrations and greater than 5.08% at high influent NTA concentrations. Therefore, acclimatization was dose dependent. It was concluded that NTA acclimatization at the higher salinities ceased because of salinity stress-induced failure of NTA catabolism and not the disappearance of a particular bacterial species.

コア掃攻テストによるマイセラー・ポリマー攻法の評価 サリニティ・グラディエントの効果

コア掃攻テストによるマイセラー・ポリマー攻法の評価 サリニティ・グラディエントの効果