Dilute Seawater Research Articles

Experimental investigation of the influence of fluid-fluid interactions on oil recovery during low salinity water flooding

This study aims to investigate the role of fluid-fluid interactions during low salinity water flooding, using crude oil from an Iranian oil reservoir. To minimize the effects of mineral heterogeneity and wettability alteration, a synthetic sintered glass core was utilized and all coreflooding experiments were performed at low temperatures without any aging process. The effect of fluid-fluid interactions were investigated in both secondary and tertiary injection modes. pH measurements as well as UV-Vis spectroscopy and interfacial tension (IFT) analysis were performed on the effluent brine samples. Resultsshow that fluid-fluid interactions, mainly the dissolution of crude oil polar components into the brine, significantly affect brine physical and interfacial properties. In secondary injection scenario, two times diluted seawater (2SW), which has the lowest IFT value, exhibits the highest (81%) oil recovery factor. While the lowest recovery factor (60.75%) was observed for the case of formation water (FW) injection. To explore the effect of contacting time, after 48 h soaking, brine injection was resumed. The effluent pH measurement at this stage showed a reduction, where the UV-Vis spectroscopy and IFT measurements confirmed dissolution of the crude oil polar components into the brine. The results showed that as brine salinity decreases, the amount of dissociated polar components increases. pH value of ten times diluted sea water (10SW) was reduced from its initial value of 7.45 to 4.22, while FW exhibits minor pH variation. Consequently, 10SW, which dissolved highest amount of polar components, depicts the highest recovery factor (6%) after soaking. Contrary to this, in tertiary injection mode, the high amount of saline brine in the core (because of FW injection at secondary stage) hinders the potential for more production for SW, 2SW and 10SW injection as all resulted to lower recovery factor compared to their secondary counterparts.

Effect of salinity, single and binary ionic compounds’ low salinity water on wettability alteration in carbonate rocks

Low salinity water flooding is one of the emerging enhanced oil recovery technologies as it has been proven economical and environmentally friendly. However, the recovery mechanism of low salinity water (LSW) is still under debatable due to the complex effect of low salinity water and its ionic compositions. Therefore, this study aims to discover the optimum seawater dilution salinity and influence of single and binary ionic compounds low salinity water on wettability alteration of carbonate core slices at optimum salinity. To achieve that, a modified Design of Experiments (DOE) has been implemented. Contact angle measurement was carried out to characterize the wettability of core slices at 0 hour, after 24 hours and after 48 hours. The results revealed that dilution of seawater reduced the contact angle of carbonate core slices towards more water wet until the optimum salinity of 1750ppm. Further dilution to 700ppm only shown a slight impact in shifting the wettability of the carbonate slices towards more water wet. In single ionic compound LSW, MgCl2 showed the greatest ability in altering wettability. In binary ionic compounds LSW, it was found out that MgCl2 mixed with ionic compounds containing monovalent ion is more effective in altering contact angle than MgCL2 mixed with ionic compounds containing divalent ion which serve as a new finding in current low salinity water study on carbonate rocks.

Quality of lettuce Lactuca sativa (var. Tropicana M1) grown with two low-salinity shrimp effluents

In a previous study, we investigated the use of shrimp effluents from well water (WW) and diluted seawater (DSW) (both with 2.7 dS m−1 electrical conductivity (EC)), and a hydroponic solution (HS) as the control treatment in greenhouse lettuce production. This new paper completes the previous one by focusing on the quality of lettuce harvested. Compared to the lettuce from the other treatments, WW-lettuce exhibited higher levels of phenolic compounds and a higher antioxidant capacity, mainly in the soluble fraction. The lettuce cultivated with DSW showed no significant difference in total phenolics and flavonoids with respect to the HS lettuce. These results reveal that the functional properties (antioxidant properties, polyphenols and flavonoid content) are even better in the lettuce produced with WW and DSW shrimp effluents. In contrast, agronomical properties (weight, number of leaves and yield) were found to be better in the case of lettuce grown with the hydroponic solution (control).

DNA BARCODING APPLICATION OF MITOCHONDRIAL COI GENE TO IDENTIFY SOME FISH SPECIES OF FAMILY GOBIIDAE IN VIETNAM

The Red river system is a typical example of Southeast Asian rivers that is strongly impacted by human and climatic conditions, especially in the recent period. In this paper, we aim to investigate the longitudinal variation of the water quality of the Red river, in the section from Hanoi city to the Ba Lat estuary. The sampling campaigns were conducted in the dry seasons in 2017 and 2018. The monitoring results showed that the average concentrations of nutrients (NO2-, NO3-, NH4+, PO43-) were still lower than the allowed values of the Vietnamese standard limits for surface water quality (QCVN 08:2015/BTNMT, column A1) whereas the average concentrations of Cl- and TSS exceeded the allowed values of the QCVN 08:2015/BTNMT, column A1 4.6 and 2.3 times, respectively. NO3- and dissolved silica (DSi) concentrations showed a significant variation from the Hanoi site to the Ba Lat site (6.62 mg/l to 1.19 mg/l for NO3- and 5.21 mg/l to 2.14 mg/l for DSi) whereas SO42-, NO2- and Cl- increased markedly in this longitudinal section, especially from the point SH6 where the salinity started to increase. Based on the three different methods for classification of trophic levels and on the different variables observed during the dry seasons in 2017–2018, the nutrient concentrations of the Red river water tended to slightly increase from the site Hanoi (SH1) to the site SH5 at Nam Dinh, indicating the increase of nutrient external input along the river whereas it tended to decrease from the site SH6 (at mesotrophic/eutrophic level) to the last observed site SH9 (at oligotrophic/mesotrophic level) at the sea due to the dilution of seawater. Seawater in dry season could affect directly the river downstream about 35 km far from the sea. The results may be a guide for planning of water use including agricultural irrigation in the Red river estuary.

English

The main objective of this work was to study the effect of sulphur application and irrigation water quality on some soil properties of the calcareous, alluvial and sandy soils. A lysimeter experiment was conducted and filled with calcareous, alluvial and sandy soils to evaluate the impact of using elemental sulfur on the yields and mineral uptake of wheat plant. The experiment was cultivated with wheat plant (Triticum Vulgare L.), and irrigated by saline water (diluted sea water recording EC values of 2000, 3000 and 4000 mgl-1). The rate of sulfur applications were 0, 476 and 952 kg Sha-1. The results showed that increasing salinity to 4000 mgl-1 gradually and significantly decreased the fresh and dry weights of wheat were as follow: Sandy > alluvial > calcareous soils, and the reductions in the grain yield under the same condition were 27, 15 and 23% relative to the control for calcareous, alluvial and sandy soils, respectively. Salinity levels also significantly reduced the total uptake of NPK of all crops cultivated in different soils under study. Under sulfur application, the fresh and dry weights of wheat significantly increased relative to the control treatment. Under high salinity level 4000 ppm and high rate of sulfur (952 kg Sha-1), the increment in the crop under study and cultivated in calcareous, alluvial and sandy soils were 74, 60 and 46% for wheat grain yield, relative to the control, respectively. Also, sulfur applications significantly increased total uptake of NPK of wheat crop cultivated in different soils, especially calcareous soil. The chemical composition of soils under study after cropping showed that each of electrical conductivity (EC), sodium adsorption ratio (SAR) and soil pH increased with increasing salinity levels in the irrigation water, while, sulfur application decreased each of EC and pH and reduced SAR. Key words: Water quality, elemental sulfur, Egyptian soils, wheat.

The hybrid impact of modified low salinity water and anionic surfactant on oil expulsion from carbonate rocks: A dynamic approach

According to the undeniable needs for economical enhancement of oil production, special attention is paid to water based supplementary oil recovery methods. Besides, combination of modified sea water (SW) and chemicals, is taken into further investigations. In laboratory scale, most of the findings are related to the impact of smart water or chemical assisted smart water on spontaneous imbibition and few researches have addressed forced imbibition of oil by co-injection of surfactants and manipulated water. Moreover, the effect of saline waters on relative permeability has not been sufficiently studied. This paper considers the simultaneous role of modified diluted sea water (dSW) and sodium dodecyl sulfate (SDS) in oil expulsion from calcite rocks. The interplay between different ions and SDS was examined through compatibility and Fourier Transform Infrared Spectroscopy tests. In advance of flooding, fluid-fluid and rock-fluid interactions were determined. In line with contact angle and interfacial tension measurements, more amount of oil was recovered by increasing Mg2+ concentration. We detected that SDS would aggregate in the presence of excess Ca2+ and the critical performance of SO42− is partly restricted where SDS is present. A new approach was initiated to investigate acidic group desorption through this study as well. Accordingly, desorption of polar components from the rock surface by cooperation of SDS and Mg2+ was known as the key factor in increasing oil recovery. We believe this paper is beneficial for detecting the leading mechanism(s) dealing with chemical assisted smart water flooding.

Osmo-ionic regulation and carbonic anhydrase, Na+/K+-ATPase and V-H+-ATPase activities in gills of the ancient freshwater crustacean Aegla schmitti (Anomura) exposed to high salinities

Aeglidae anomuran crabs originated in the sea, but invaded and diversified in southern South American freshwater (FW) streams. We here aimed at examining their tolerance of increased salinity, after a long time of evolution in FW (~33 million years). Aegla schmitti were exposed to FW and dilute seawater of salinities 15, 20, and 25‰ for 1, 5 and 10 days. Mortality in 35‰ was also assessed. Hemolymph osmolality, Na+, K+, Cl−, and Mg2+ ions, and hydration levels of the abdominal muscle were assayed. The activities of the Carbonic Anhydrase (CA), Na+/K+-ATPase (NKA) and V-H+-ATPase (VHA) were also assayed in the gills. A. schmitti preserves osmoregulatory mechanisms of its marine ancestors. It is able to survive in high salinities (25‰) for at least 10 days. Mortality in 35‰ was of 56% after 1 day, and of 100% after 7 days. In 25‰, NaCl is apparently hyporegulated at all times, while hemolymph osmolality rises after 5 days. CA and NKA activities remained unchanged in all experimental conditions, while VHA activity decreased after 10 days in 25‰. Hemolymph NaCl data was compatible with either hyporegulation and/or putative influx of NaCl into cells for regulatory volume increase (RVI). Further studies should deepen the understanding of the roles of low permeabilities and saturation of high affinity uptake systems in truly FW decapods, in their responses to high salinities. Moreover, the fate of extracellular NaCl as secretion in true hypo-regulation and/or influx into cells for RVI should also be investigated.

Melt Procedure Affects the Photosynthetic Response of Sea Ice Algae

The accuracy of sea ice algal production estimates is influenced by the range of melting procedures used in studies to obtain a liquid sample for incubation, particularly in relation to the duration of melt and the approach to buffering for osmotic shock. In this research, ice algal photophysiology from 14C incubations was compared in field samples prepared by three melt procedures: i) a rapid ≤ 4 h melt of the bottommost (< 1 cm) ice algal layer scraped into a large volume of filtered seawater (salinity 27 - 30), ii) melt of a bottom 5 cm section diluted into a moderate volume of filtered seawater over 24 h (salinity 20 - 24), and iii) melt of a bottom 5 cm section without any filtered seawater dilution over about 48 h (salinity 10 -12). Maximum photosynthetic rate, photosynthetic efficiency and production at zero irradiance were significantly affected by the melt treatment employed in experiments. All variables were greatest in the highly diluted scrape sample and lowest in the bulk-ice samples melted in the absence of filtered seawater. Laboratory experiments exposing cultures of the common sea ice diatom Nitzschia frigida to different salinities and light conditions suggested that the field-based responses can be attributed to the rapid (< 4 h) adverse effects of exposing cells to low salinities during melt without dilution. The observed differences in primary production between melt treatments were estimated to account for over 60% of the variability in production estimates reported for the Arctic. Future studies are strongly encouraged to replicate salinity conditions representative of in situ values during the melting process to minimize hypoosmotic stress, thereby most accurately estimating primary production.

Effect of salinity and ion type on formation damage due to inorganic scale deposition and introducing optimum salinity

Abstract Smart water injection is recognized as an effective EOR process to alter the wettability and interfacial tension to obtain higher micro/macro sweep efficiencies. This water contains reactive ions such as Mg 2 + , Ca 2 + and SO 4 2 - which can act as potential-determining ions and change the surface charge of calcite rocks. One of the major concerns in the execution of an effective water-flood process, especially in tight carbonate reservoirs, is the chemical incompatibility between the formation brine and the injecting water. In the present study, laboratory fluid compatibility tests were carried out and software simulation was done to investigate the most important challenges of the water-flooding process in one of the West Iranian oil fields with the possibility of developing formation damage. The chemical incompatibility between injected smart water and formation water leads to inorganic scale deposition. For this purpose, sea water as the basis of smart water was prepared to examine the impact of determining ions such as Mg 2 + , Ca 2 + , and SO 4 2 - and, to examine the effect of the salinity of the injected brine on the total amount of CaSO 4 scale precipitation. According to the obtained results, as the concentration of SO 4 2 - in the injecting sea water increases from 1 / 4 to 1 times its concentration in ordinary sea water, the CaSO 4 precipitation increases smoothly, and then it is accelerated as the concentration increases beyond that. Therefore, even though the increasing of the sulfate concentration improved the wettability alteration ability of the smart water, calcium sulfate deposition was noticed, resulting in permanent formation damage. The test results also showed that CaSO 4 deposition increases as the concentration of Ca 2 + in the sea water increases. On the other hand, the presence of Mg 2 + ion in sea water increases the solubility of CaSO 4 and subsequently, lower scale formation was noticed by increasing the concentration of magnesium. This study also showed that there is an optimum salinity in which the minimum amount of mineral scale is deposited, and 5 times dilution of sea water is determined as the optimum salinity. The findings would enable us to optimize the ion contents of smart water for both, better oil sweep efficiency and lower risk of formation damage. In the end, this paper discusses the laboratory fluid compatibility results and scale prediction analysis for different smart water injection utilizations.

Wettability Alteration of Carbonate Reservoir Cores—Laboratory Evaluation Using Complementary Techniques

Summary The objective of this paper was to assess the applicability of relatively low-salinity brine and different surfactants for enhanced oil recovery (EOR) in carbonate reservoirs in the Middle East. Phase behavior, interfacial tension (IFT), contact angle, spontaneous imbibition, and ζ-potential experiments were performed. The experimental work flow included a phase-behavior study followed by IFT, contact-angle measurements, spontaneous-imbibition measurements, and ζ-potential measurements at varying salinities and surfactant concentrations. Contact-angle-measurement results indicated that surfactant solutions, in addition to lowering IFT, tend to change the core wettability from oil-wet or neutral-wet to more water-wet. Furthermore, the best results were achieved by adding an anionic surfactant. Moreover, spontaneous imbibition and ζ-potential measurements provided additional supporting data that diluted seawater (DSW), in a dilute anionic or nonionic surfactant solution, alters the wettability of carbonates to a favorable wetting state for improving oil recovery. This research presents a set of diverse experimental data that confirms adding low concentrations of anionic and nonionic surfactants to DSW improves oil recovery from carbonate reservoirs.

Sensitivity to salinization and acclimation potential of amphibian (Pelophylax perezi) and fish (Lepomis gibbosus) models

Predictions of the International Panel for Climate Changes on sea level rise foresee that the number of coastal regions impacted with salinization will increase in a near future. The present work intended to evaluate the sensitivity to salinization of two freshwater vertebrate species (the frog Pelophylax perezi and the fish Lepomis gibbosus) and their ability to acclimate to this stressor. For this, three specific objectives were targeted: (i) to assess if NaCl may be used as a safe surrogate for risk assessment of seawater (SW) intrusion for freshwater vertebrates; (ii) to evaluate the sensitivity of two freshwater vertebrate models to increased salinity (both due to NaCl or SW); (iii) to determine the capacity of the studied species to acclimate to low levels of salinization. To assess specific objectives (i) and (ii), organisms were exposed to serial concentrations of NaCl or SW dilutions. To assess the capacity of acclimation of both species to salinization, organisms were exposed to low serial concentrations of NaCl during the embryonic development or for a period of two months, respectively, and their sensitivity to NaCl was re-evaluated after this period.Results showed that fish juveniles were more tolerant (96-h LC50 of 21.3 mS cm−1 for NaCl and 23.6 mS cm−1 for SW) than frog embryos (96-h LC50 of 10.7 mS cm−1 for NaCl and 10.7 mS cm−1 for SW) and tadpoles (96-h LC50 of 19.4 mS cm−1 for NaCl and 8.72 mS cm−1 for SW). The fish was able to cope with conductivities of almost one third of SW conductivity, while effect conductivities computed for the amphibian were much lower than SW conductivity (≈ 52 mS cm−1). The two-fold difference between the sensitivity of the two tested species reinforces the idea that ecological risk assessment for amphibians based on fish toxicity data may underestimate the risk to the former. Acclimation to low levels of salinity caused an increase in tolerance to salinization in P. perezi tadpoles but not in fish.

The effect of salinity and alkalinity on growth and the accumulation of copper and zinc in the Chlorophyta Ulva fasciata

Copper and zinc accumulation in macroalgae is a complex issue. While these metals exist as micronutrients and can serve to add nutritional value to the macroalgae when consumed by both plants and animals, elevated levels of the metals can reduce growth or even kill the algae. Many water parameters can influence the toxicity of the metals, though past studies have rarely isolated individual water parameters. This study aimed to independently determine the effects that salinity and alkalinity have on the growth and accumulation of these two metals on the macroalgae Ulva fasciata, distinguishing the effects of salinity and alkalinity as whole parameters from the collective effects of the water different constituents. The effect of salinity was determined using sodium chloride additions rather than seawater dilution, as performed in past studies, while alkalinity was tested using sodium bicarbonate additions to artificial seawater. The results of the study reinforce previous findings that copper is very toxic to macroalgae, even at low concentrations (50 µg L−1) though the effects of zinc remain inconclusive at 50 µg L−1, since the experiment was conducted over only a two-week trial period. The research suggests that salinity and alkalinity have no significant effect on the toxicity of copper to the growth of the macroalgae, but alkalinity significantly reduced copper and increased zinc accumulation in U. fasciata. The results of this study warrant further research in the field to investigate which other components of seawater and macroalgae reduce metal toxicity in the macroalgae. Additionally, these findings suggest the need for further refinement of toxicity models when adapted to macroalgae.

An experimental investigation into the spontaneous imbibition of surfactant assisted low salinity water in carbonate rocks

Surfactant assisted smart water injection is one of the areas of research interests in enhanced oil recovery. Simultaneous use of smart water and surfactants has drawn great attention in last decades. Majority of studies highlight co-injection of cationic surfactant and sea water/low salinity water. Therefore, this paper opens a new approach by examining the effect of diluted sea water, termed as dSW, containing Sodium Dodecyl Sulfate (SDS) on spontaneous imbibition in carbonate media. Reservoir core plugs and oil samples were provided, saline waters were synthesized in laboratory and different tests were accomplished. It was observed that the brine spiked in Mg2+ is able to improve water wetness of calcite by reducing contact angle from 114° to 42° and reduction in interfacial tension (IFT) from 34.2 to 13.9 mN/m. Measurement of oil properties before and after imbibition, showed that Mg2+ plays the main role in increasing microscopic sweep efficiency and improving ultimate oil recovery. Moreover, faster imbibition rate and higher capillary number was gained by increasing Mg2+ concentration. Ca2+ was found to be a disturbing ion as it led to incompatible condition in the fluid system. We confirmed that in the presence of excess Ca2+, SDS molecules not only aggregate in the bulk of solution, but also another form of incompatibility, known as salt bridge, was occurred. It was also demonstrated that activity of SO42- was concealed in the presence of SDS.

Elevated pCO2 alters marine heterotrophic bacterial community composition and metabolic potential in response to a pulse of phytoplankton organic matter.

Factors that affect the respiration of organic carbon by marine bacteria can alter the extent to which the oceans act as a sink of atmospheric carbon dioxide. We designed seawater dilution experiments to assess the effect of pCO2 enrichment on heterotrophic bacterial community composition and metabolic potential in response to a pulse of phytoplankton-derived organic carbon. Experiments included treatments of elevated (1000 p.p.m.) and low (250 p.p.m.) pCO2 amended with 10 μmol L-1 dissolved organic carbon from Emiliana huxleyi lysates, and were conducted using surface-seawater collected from the South Pacific Subtropical Gyre. To assess differences in community composition and metabolic potential, shotgun metagenomic libraries were sequenced from low and elevated pCO2 treatments collected at the start of the experiment and following exponential growth. Our results indicate bacterial communities changed markedly in response to the organic matter pulse over time and were significantly affected by pCO2 enrichment. Elevated pCO2 also had disproportionate effects on the abundance of sequences related to proton pumps, carbohydrate metabolism, modifications of the phospholipid bilayer, resistance to toxic compounds and conjugative transfer. These results contribute to a growing understanding of the effects of elevated pCO2 on bacteria-mediated carbon cycling during phytoplankton bloom conditions in the marine environment.

Impact of Brine Composition and Concentration on Capillary Pressure and Residual Oil Saturation in Limestone Core Samples

Low salinity water flooding (LSF) is a relatively simple and cheap EOR technique in which the salinit y of the injected water is optimized (by desalination and/or modification) to improve oil recovery over conventional waterflooding. Extensive laboratory experiments investigating the effect of LSF are available in the literature. Sulfate-rich as well as diluted brines have shown promising potential to increase oil production in limestone core samples. To quantify the low salinity effect, spontaneous imbibition and/or tertiary waterflooding experiments have been reported. For the first time in literature, this paper presents a comprehensive study of the centrifuge technique to investigate low salinity effect in carbonate samples. The study is divided into three parts. At first, a comprehensive screening was performed on the impact of different connate water and imbibition brine compositions/combinations on the spontaneous imbibition behavior. Second, the subsequent forced imbibition of the samples using the centrifuge method to investigate the impact of brine compositions on residual saturations and capillary pressure. Finally, three unsteady-state (USS) core floodings were conducted in order to examine the potential of the different brines to increase oil recovery in secondary mode (brine injection at connate water saturation) and tertiary mode (exchange of injection brine at mature recovery stage). The experiments were performed using Indiana limestone outcrops. The main conclusions of the study are spontaneous imbibition experiments only showed oil recovery in case the salinity of the imbibing water (IW) is lower than the salinity of the connate water (CW). No oil production was observed when the imbibing water had a higher salinity than the connate water or the salinity of the connate water and imbibing brine were identical. Moreover, the spontaneous imbibition experiments indicated that diluting the salinity of the imbibing water has a larger potential to spontaneously recover oil than the introduction of sulfate-rich sea water. The centrifuge experiments confirmed a connection between the overall salinity and oil recovery. As the salinity of the imbibing brines decreases, the capillary imbibition pressure curves showed an increasing water-wetting tendency and simultaneous reduction of the remaining oil saturation. The lowest remaining oil saturation was obtained for diluted sea water as CW and IW. The core flooding experiments reflected the results of the spontaneous imbibition and centrifuge experiments. Injecting brine at a rate of 0.05 cc/min, sea water and especially diluted sea water resulted in a significant higher oil recovery compared to formation brine. Moreover, when comparing secondary mode experiments, the remaining oil saturation after flooding by diluted sea water, sea water and formation water was 30.6 %, 35.5 % and 37.4 %, respectively. In tertiary injection mode, sea water did not lead to extra oil recovery while diluted sea water led to an additional oil recovery of 5.6 % in one out of two tertiary injection applications.

Susceptibility of Nanophyetus salmincola Cercariae to Formalin, Hydrogen Peroxide, and Seawater.

The ability of formalin, PEROX-AID (hydrogen peroxide), and seawater to kill waterborne Nanophyetus salmincola cercariae was evaluated invitro. Newly emerged cercariae survived for extended periods in freshwater, with 53-73% survival occurring in negative control groups after 24h. Exposure to dilutions of formalin reduced this survival time, with 0% of cercariae surviving after30min in 450μL/L, 40min in 225μL/L, and 300min in 113μL/L. Exposure to PEROX-AID (hydrogen peroxide) for 1h resulted in reduced cercarial survival (16.4%) only at the highest concentration (100μL/L), compared with 100% survival in the untreated controls and all lesser concentrations. Exposure to dilutions of seawater resulted in reduced cercarial survival only at high salinities (15.2-30.3‰), where 10-min exposures resulted in 0-20% survival. These results provide insights into options for prophylactic water treatment at salmonid enhancement facilities that experience high mortalities due to infections with Nanophyetus salmincola. Further, the intolerance of live cercariae to high salinities indicates that exposure to fish occurs primarily in the freshwater portions of watersheds.

Sensitivity of freshwater species under single and multigenerational exposure to seawater intrusion.

Salinization of coastal freshwater ecosystems is already occurring in some regions of the world. This phenomenon raises serious concerns on the protection of coastal freshwater ecosystems, since many of them support and shelter a large number of species and are considered hotspots of biodiversity. This work intended to assess the adverse effects that salinization, caused by the intrusion of seawater (SW), may pose to freshwater organisms. In this study, three specific goals were addressed: (i) to assess if sodium chloride (NaCl) may be used as a surrogate of natural SW at early-stages of risk assessment; (ii) to identify the most sensitive freshwater species to salinity NaCl; and (iii) to determine if increased tolerance to salinity may be acquired after multigenerational exposure to low levels of salinization (induced with NaCl). A total of 12 standard monospecific bioassays were carried out by exposing organisms from different taxonomic groups (Cyanobacteria: one species, Tracheophyta: two species, Rotifera: one species, Arthropoda: two species and Mollusca: one species) to a series of concentrations of NaCl (ranging from 0.95 to 22.8 mS cm-1) or dilutions of SW (ranging from 1.70 to 52.3 mS cm-1). In general, NaCl exerted similar or higher toxicity than SW, both at lethal and sublethal levels, suggesting that it may be proposed as a protective surrogate of SW for first tiers of salinization risk assessment. Among all tested species, the cyanobacterium Cylindrospermopsis raciborskii, the daphnid Daphnia longispina and the rotifer Brachionus plicatilis were the most sensitive taxa to salinization (EC50 ≤ 4.38 mS cm-1). Given their position at the basis of the food web, it is suggested that small increments of salinity may be enough to induce structural changes in freshwater communities or induce changes in trophic relations. No clear evidences of increased tolerance after multigenerational exposure to low levels of salinity were found.This article is part of the theme issue 'Salt in freshwaters: causes, ecological consequences and future prospects'.

An effective microinjection method for genome editing of marine aquaculture fish: tiger pufferfish Takifugu rubripes and red sea bream Pagrus major

Genome editing technology is becoming increasingly accepted as a way to improve traits in marine fish aquaculture. In fish, microinjection is a major method for introducing RNA or protein into eggs for genome editing; however, this method has not yet been established in aquaculture fish. We successfully established microinjection methods achieving high survival rates for tiger pufferfish and red sea bream by optimizing the following three parameters: (1) the soaking solution of fertilized eggs during microinjection, (2) the elapsed time from in vitro fertilization to microinjection, (3) the elapsed time from stripping to microinjection. In tiger pufferfish, Iwamatsu solution or diluted sea water is effective as the soaking solution. In vitro fertilization can be performed at intervals of 15 min from fertilization until 2.5 h after stripping. Similarly, in red sea bream, Leibovitz’s L-15 medium or Iwamatsu solution is effective as the soaking solution and in vitro fertilization can be performed at intervals of 10 min from fertilization until 2.5 h after stripping. We anticipate our findings will contribute to effectively establish genome edited aquaculture breeds.

Sensitivity to near-future CO2 conditions in marine crabs depends on their compensatory capacities for salinity change

Marine crabs inhabit shallow coastal/estuarine habitats particularly sensitive to climate change, and yet we know very little about the diversity of their responses to environmental change. We report the effects of a rarely studied, but increasingly prevalent, combination of environmental factors, that of near-future pCO2 (~1000 µatm) and a physiologically relevant 20% reduction in salinity. We focused on two crab species with differing abilities to cope with natural salinity change, and revealed via physiological and molecular studies that salinity had an overriding effect on ion exchange in the osmoregulating shore crab, Carcinus maenas. This species was unaffected by elevated CO2, and was able to hyper-osmoregulate and maintain haemolymph pH homeostasis for at least one year. By contrast, the commercially important edible crab, Cancer pagurus, an osmoconformer, had limited ion-transporting capacities, which were unresponsive to dilute seawater. Elevated CO2 disrupted haemolymph pH homeostasis, but there was some respite in dilute seawater due to a salinity-induced metabolic alkalosis (increase in HCO3− at constant pCO2). Ultimately, Cancer pagurus was poorly equipped to compensate for change, and exposures were limited to 9 months. Failure to understand the full spectrum of species-related vulnerabilities could lead to erroneous predictions of the impacts of a changing marine climate.

Mercury and other trace metals in lettuce (Lactuca sativa) grown with two low-salinity shrimp effluents: Accumulation and human health risk assessment

Shrimp farming effluents from two sources of low-salinity water, well water (WW) and diluted seawater (DSW) (salinity, 1.7 g L−1; electrical conductivity, 2.7 dS m−1), were used to grow lettuce (L. sativa) in order to assimilate the nutrients present in shrimp effluents and produce edible biomass. The two treatments, WW and DSW, were tested in triplicate. Additionally, one hydroponic system in triplicate was constructed to grow lettuce using a nutritive solution as the control treatment (HS). The production variables of lettuce in the two crop varieties (Parris Island (VPI) and Tropicana M1 (VTM1)) showed a general trend of DSW > HS > WW with regards to the size, weight and total foliage, except for the number of leaves, which was higher with HS treatment than with WW and DSW treatments. The accumulation of Cu, Hg, Mn and Zn in edible lettuce tissue and the health risk by the intake of lettuce were evaluated. Heavy metal concentrations in edible lettuce tissue for the three treatments showed the same trend of Mn > Zn > Cu > Hg, with concentration ranges of 47.1 to 188.7, 35.7 to 66.2, 4.1 to 6.4, and 0.01 to 0.02 mg kg−1 (dry weight), respectively. Such concentrations did not exceed the safe limits (CAC, 1984). The health risk index and target hazard quotient were <1, which indicates that the population exposed to these metals due to intake from lettuce consumption is unlikely to have adverse health effects when shrimp farming effluents are used to grow lettuce plants.