Dilute Seawater Research Articles

Chlorella stigmatophora for Urban Wastewater Nutrient Removal and CO2 Abatement

Batch experiments were performed to study biomass growth rate, nutrient removal and carbon dioxide bio-fixation of the marine microalgae Chlorella stigmatophora. Four different cultures at different salinities were tested: wastewater (WW), synthetic wastewater (SWW), seawater (SW) and diluted seawater (DSW). Experimental results showed that Chlorella stigmatophora grew satisfactorily in all culture media, except in SWW where inhibition occurred. In all cases, biomass experimental data were fitted to the Verlhust Logistic model (R2 > 0.982, p ≤ 0.05). Maximum biomass productivity (Pbmax ) and CO2 biofixation (PvCO2) were reached in the WW medium, 1.146 g SS·L−1·day−1 and 2.324 g CO2·L−1·day−1 respectively. The order of maximum specific growth rates (μmax) was WW >DSW>SW. In order to compare nitrogen and phosphorous removal kinetics, an estimation of the time required to reach the most restrictive concentration of total N and P in effluents as defined in the Directive 98/1565/CE (10 mg ΣN·L−1 (T10( N)) and 1 mg ΣP·L−1 (T1(P) ) was performed. In the WW test T10( N) and T1(P) needed were of 45.15 and 32.27 hours respectively and at the end of the experimental the removal was in both 100%.

Molecular cloning and expression of hepatopancreas glutamine synthetase in the Pacific white shrimp, Litopenaeus vannamei, induced by acute hypo-osmotic stress

Glutamine synthetase (GS) is a key enzyme involved in nitrogen metabolism and glutamine synthesis. A 1455bp cDNA clone encoding GS was isolated from Litopenaeus vannamei (LvGS, JN620540.1). The sequence consists of a 75bp 5′ untranslated region followed by a 1101bp open reading frame corresponding to 366 amino acids. The encoded protein has a 67% to 93% overall amino acid sequence identity with its counterparts in other various species. A phylogenetic analysis of the GS sequence showed that LvGS clustered with the invertebrate group as expected. qRT-PCR analysis indicated that LvGS was expressed in the stomach, gill, intestine, hepatopancreas, muscle, heart, and eyestalk. The profile of LvGS was up-regulated in the stomach, gills, intestines, and hepatopancreas after 48h of exposure to dilute seawater (4ppt). The mRNA levels of LvGS in the hepatopancreas significantly increased 2.9-fold after 3h to 3d of exposure to dilute seawater (P<0.05). The LvGS activity and glutamine in the hepatopancreas increased after 3h to 3d and then decreased after 7d to 20d of exposure to dilute seawater. However, the hemolymph total protein and ammonia decreased after 3h to 3d, and then increased after 7d to 20d. The hemolymph urea and uric acid significantly increased after 3h to 12h of exposure to dilute seawater. L. vannamei fully acclimated to a low salinity environment within a week. LvGS can participate in physiological osmotic adaptation to hypo-osmotic water and aid L. vannamei in resisting acute salinity changes via the manipulation of nitrogen metabolism.

Osmoregulatory response to low salinities in the European sea bass embryos: a multi-site approach

Embryonic osmoregulation effected by embryonic ionocytes in the European sea bass Dicentrarchus labrax has been studied at several sites, including the yolk sac membrane, the first gill slits and the gut ionocytes. D. labrax embryos, spawned in seawater (SW) (39 ‰), were exposed to dilute seawater (DSW) (5 ‰) during 48 h, from stage 10 pairs of somites (10S) to hatching time (HT). Control embryos originating from the same spawn were maintained in SW. Both SW and DSW embryos were examined after 24- and 48-h exposure. Nanoosmometric measurements of the embryonic fluids osmolality suggest that late embryos are confronted with the variations in external salinity and that they were able to slightly regulate their osmolality. Immunolocalization of Na⁺/K⁺ ATPase, NKCC and CFTR has shown that DSW-exposed embryos can limit ion losses due to compensatory physiological mechanisms. CFTR and NKCC were not observed in DSW embryos in the yolk sac ionocytes and in the tegumentary ionocytes of the gill slits. The quantification of mRNA indicated that NKA, NKCC1 and CFTR transcript levels increased from stage 10S to stage HT. At stage HT, following 48 h of DSW- or SW-exposure, different responses were observed according to salinity. These results, when compared to those obtained in D. labrax juveniles and adults long-term exposed to fresh water (FW), show that in embryos the physiological response following a short-term DSW exposure is different. The mechanisms of hyper-osmoregulation observed in D. labrax embryos, although not fully efficient, allow their survival for several days in DSW.

Estimate of calcification responses to thermal and freshening stresses based on culture experiments with symbiotic and aposymbiotic primary polyps of a coral, Acropora digitifera

Although coral calcification is directly related to coral health, few studies have examined the responses of coral calcification to environmental stresses, with the exception of ocean acidification. In this study, we experimentally exposed aposymbiotic (lacking symbionts) and symbiotic primary polyps of the scleractinian coral Acropora digitifera to several seawater temperatures (27, 29, 31, and 33°C) and salinities (26, 28, 30, 32, and 34) to investigate the effects of thermal and freshening stresses on coral calcification from the standpoint of coral-algal symbiosis. Calcification rates were higher for symbiotic versus aposymbiotic polyps in both sets of experiments, except for those reared at 31°C and 33°C. Calcification responses of symbiotic polyps were a non-linear function of temperature, and the threshold temperature affecting skeletal growth and bleaching was between 29°C and 31°C. Calcification rates of aposymbiotic polyps were also a non-linear function of temperature, with a maximum polyp weight at 31°C, suggesting that thermal stress also did some damage to the coral host itself. In contrast, skeletal growth of both aposymbiotic and symbiotic polyps decreased linearly with increased salinity. Observations of the microstructure of polyp samples revealed a clearly cyclic feature of skeletal surfaces that was likely related to organo-mineral deposition of calcium carbonate even under lowered-salinity conditions. However, neither type of polyp reared at 33°C evidenced this characteristic, suggesting that thermal stress had compromised the normal calcification process, which involves secretion of an organic matrix by the coral host. Our results suggest that the effects of future global warming will include a reduction in coral calcification itself and the collapse of coral-algal symbiosis, at least at the primary polyp stage. The present experiments showed that thermal stress would affect the host's physiological functionality, whereas freshening stress, which is simply the dilution of ambient seawater, would affect the mineralization process associated with coral calcification.

Salt tolerance in the halophyte Salicornia dolichostachya Moss: Growth, morphology and physiology

Salinization of agricultural land is an increasing problem. Because of their high tolerance to salinity, Salicornia spp. could become models to study salt tolerance; they also represent promising saline crops. The salinity-growth response curve for Salicornia dolichostachya Moss was evaluated at 12 salt concentrations in a hydroponic study in a greenhouse and at 5 different seawater dilutions in an outside setting. Salt concentrations ranged between 0mM and 500mM NaCl (≈seawater salinity). Plants were grown for six weeks and morphological and physiological adaptations in different tissues were evaluated.S. dolichostachya had its growth optimum at 300mM NaCl in the root medium, independent of the basis on which growth was expressed. The relative growth rate (RGR) in the greenhouse experiment was comparable with RGR-values in the outdoor growth experiment. Leaf succulence and stem diameter had the highest values at the growth optimum (300mM NaCl). Carbon isotope discrimination (δ13C) decreased upon salinity. S. dolichostachya maintained a lower leaf sap osmotic potential relative to the external solution over the entire salinity range, this was mainly accomplished by accumulation of Na+ and Cl−. Glycine betaine concentrations did not significantly differ between the treatments. Na+:K+-ratio and K+-selectivity in the shoots increased with increasing salinity, both showed variation between expanding and expanded shoot tissue. We conclude that S. dolichostachya was highly salt tolerant and showed salt requirement for optimal growth. Future growth experiments should be done under standardized conditions and more work at the tissue and cellular level needs to be done to identify the underlying mechanisms of salt tolerance.

Zoospore production and motility of mangrove thraustochytrids from Hong Kong under various salinities

We investigated the effects of salinity on the zoospore production of four mangrove thraustochytrid isolates, Schizochytrium sp. KF1, Aurantiochytrium mangrovei KF6, Thraustochytrium striatum KF9 and Ulkenia sp. KF13. The zoospore motilities, which were based on curvilinear velocity (VCL) and straight-line velocity (VSL), were monitored using the Computer-Assisted Sperm Motility Analysis (CASA) Software system. The zoospore production of four isolates was suppressed at salinity above 15%. Schizochytrium sp. produced the greatest number of zoospores at 15%, while Aurantiochytrium mangrovei and Ulkenia sp. produced abundant zoospores in diluted sea water ranging from 7.5 to 15%. Thraustochytrium striatum performed relatively poorly under all salinities. Salinity and exposure time, as well as their interactions, had significant impacts on most zoospore velocity measurements. The optimal velocities of zoospore motility also varied among isolates. Zoospores of Schizochytrium sp. and A. mangrovei had similar responses to salinity, with the highest motility at 7.3%, followed by a decrease in velocities with increasing salinity. In contrast, the zoospore of T. striatum had optimal motility at 12% and remained highly motile from 15 to 20%. The velocities of zoospores of Ulkenia sp. were the lowest among the tested thraustochytrids and had optimal motility at 12%. Zoospores of all the isolates remained active after 4h of exposure to aqueous medium, but the optimal salinity for each mode of swimming changed. The ecological significance of these data are discussed.

Zoospore production and motility of mangrove thraustochytrids from Hong Kong under various salinities

We investigated the effects of salinity on the zoospore production of four mangrove thraustochytrid isolates, Schizochytrium sp. KF1, Aurantiochytrium mangrovei KF6, Thraustochytrium striatum KF9 and Ulkenia sp. KF13. The zoospore motilities, which were based on curvilinear velocity (VCL) and straight-line velocity (VSL), were monitored using the Computer-Assisted Sperm Motility Analysis (CASA) Software system. The zoospore production of four isolates was suppressed at salinity above 15%. Schizochytrium sp. produced the greatest number of zoospores at 15%, while Aurantiochytrium mangrovei and Ulkenia sp. produced abundant zoospores in diluted sea water ranging from 7.5 to 15%. Thraustochytrium striatum performed relatively poorly under all salinities. Salinity and exposure time, as well as their interactions, had significant impacts on most zoospore velocity measurements. The optimal velocities of zoospore motility also varied among isolates. Zoospores of Schizochytrium sp. and A. mangrovei had similar responses to salinity, with the highest motility at 7.3%, followed by a decrease in velocities with increasing salinity. In contrast, the zoospore of T. striatum had optimal motility at 12% and remained highly motile from 15 to 20%. The velocities of zoospores of Ulkenia sp. were the lowest among the tested thraustochytrids and had optimal motility at 12%. Zoospores of all the isolates remained active after 4 h of exposure to aqueous medium, but the optimal salinity for each mode of swimming changed. The ecological significance of these data are discussed.

Statistical optimization of low-cost medium for economical production of Bacillus subtilis biosurfactant, a biocontrol agent for the olive moth Prays oleae

Biosurfactants are currently not a feasible alternative to chemically synthesized surfactants as a result of their potentially high production costs. In this work, Bacillus subtilis SPB1 biosurfactant was shown to be efficient in the biocontrol of the olive mothPrays oleae. Its production was improved by optimizing the medium components using inexpensive substrates. The effect of orange peels, soya bean and diluted sea water on SPB1 biosurfactant production was studied and was adjusted using central composite design. The experimental results were fitted to a second-order polynomial model that yielded a determination coefficient of R2=0.932. The optimal medium for biosurfactant production was found to be composed only by orange peels (15.5 g/L), soya bean (10 g/L) and diluted sea water (30%). The predicted and observed response were 4.3 g/L (with desirability = 0. 21) and 4.45 g/L, respectively. In comparison to original level production, two fold increases had been obtained. Key words: Bacillus subtilis, biosurfactant, central composite design, optimization, Prays oleae.

Laboratory Investigation of the Impact of Injection-Water Salinity and Ionic Content on Oil Recovery From Carbonate Reservoirs

SummaryThe impact of brine salinity and ion composition on oil recovery has been an area of research in recent years. Evidence from laboratory studies, supported by some field tests targeting mainly sandstones, has distinctly shown that injecting low-salinity water has a significant impact on oil recovery. Although the potential for carbonates has not been thoroughly investigated, some reported studies have excluded carbonates from this effect. The main objective of this paper is to investigate the potential of increased oil recovery by altering the salinity and ionic composition of the injection water for carbonate reservoirs, define the recovery mechanisms, and eventually transform the emerged trend to full-fledged reservoir technology.This paper presents the results of different laboratory studies to investigate the impact of salinity and ionic composition on oil/brine/rock interactions and draws conclusions on potential recovery mechanisms. Also, it provides a laboratory coreflooding study conducted using composite rock samples from a carbonate reservoir to investigate the impact of salinity and ionic composition on oil recovery. The experimental parameters and procedures were well designed to reflect the reservoir conditions and current field injection practices, including reservoir pressure, reservoir temperature, and salinity and ionic content of initial formation water and current types of injected water.The experimental results revealed that substantial tertiary oil recovery beyond conventional waterflooding can be achieved by altering the salinity and ionic content of field injected water. The new emerged trend is distinct from what has been addressed in previous reported studies on topics of low-salinity waterflooding for sandstones or seawater injection into high-temperature chalk reservoirs. On the subject of recovery mechanisms, the results showed that altering the salinity and ionic composition of the injected water has a significant impact on the wettability of the rock surface. Also, nuclear-magnetic-resonance (NMR) measurements indicated that dilution of seawater can cause a significant alteration in the surface relaxation of the carbonate rock and also can enhance connectivity among pore systems because of rock dissolution. The results, observations, and interpretations addressed in this study provided compelling evidence to suggest that the key mechanism for the emerged trend is wettability alteration.

A Microfluidic Long-Period Fiber Grating Sensor Platform for Chloride Ion Concentration Measurement

Optical fiber sensors based on waveguide technology are promising and attractive in chemical, biotechnological, agronomy, and civil engineering applications. A microfluidic system equipped with a long-period fiber grating (LPFG) capable of measuring chloride ion concentrations of several sample materials is presented. The LPFG-based microfluidic platform was shown to be effective in sensing very small quantities of samples and its transmitted light signal could easily be used as a measurand. The investigated sample materials included reverse osmosis (RO) water, tap water, dilute aqueous sample of sea sand soaked in RO water, aqueous sample of sea sand soaked in RO water, dilute seawater, and seawater. By employing additionally a chloride ion-selective electrode sensor for the calibration of chloride-ion concentration, a useful correlation (R2 = 0.975) was found between the separately-measured chloride concentration and the light intensity transmitted through the LPFG at a wavelength of 1,550 nm. Experimental results show that the sensitivity of the LPFG sensor by light intensity interrogation was determined to be 5.0 × 10−6 mW/mg/L for chloride ion concentrations below 2,400 mg/L. The results obtained from the analysis of data variations in time-series measurements for all sample materials show that standard deviations of output power were relatively small and found in the range of 7.413 × 10−5−2.769 × 10−3 mW. In addition, a fairly small coefficients of variations were also obtained, which were in the range of 0.03%–1.29% and decreased with the decrease of chloride ion concentrations of sample materials. Moreover, the analysis of stability performance of the LPFG sensor indicated that the random walk coefficient decreased with the increase of the chloride ion concentration, illustrating that measurement stability using the microfluidic platform was capable of measuring transmitted optical power with accuracy in the range of −0.8569 mW/ to −0.5169 mW/ . Furthermore, the bias stability was determined to be in the range of less than 6.134 × 10−8 mW/h with 600 s time cluster to less than 1.412 × 10−6 mW/h with 600 s time cluster. Thus, the proposed LPFG-based microfluidic platform has the potential for civil, chemical, biological, and biochemical sensing with aqueous solutions. The compact (3.5 × 4.2 cm), low-cost, real-time, small-volume (∼70 μL), low-noise, and high-sensitive chloride ion sensing system reported here could hopefully benefit the development and applications in the field of chemical, biotechnical, soil and geotechnical, and civil engineering.

Osmolality and ions of the perivisceral coelomic fluid of the intertidal sea urchin Echinometra lucunter (Echinodermata: Echinoidea) upon salinity and ionic challenges

The intertidal sea-urchin Echinometra lucunter (Linnaeus, 1758) has been submitted to diluted sea water (SW) of salinity 25, or concentrated sea water of salinity 45. In addition, ionic challenges have been offered, supplementing 25 SW with Mg2+, Ca2+ or K+, until the concentration of each of these ions would reach the level of full-strength 35 SW (control). Perivisceral coelomic fluid has been sampled after six hours in these treatments for measurements of osmolality and concentrations of Na+, Cl-, Mg2+, Ca2+, and K+. Urchins have been further observed until five days. SW concentration (45) lead urchins to death after two days of exposure, while urchins tolerated five days in 25 SW without any sign of distress. Urchins displayed osmoconformation and ion-conformation for NaCl, and occasional small gradients with respect to the water for Mg2+ (~6% in full-strength SW), and K+ (8.5% in 25 SW), after six hours. These results are consistent with data compiled from the literature, for echinoderms, which frequently show positive gradients (often higher than 25%) for the most relevant ions, between the coelomic fluid and external SW. Supplemented cations have shown mutual interference, mostly affecting their own coelomic fluid concentrations. Under the protocol used here, urchins of the species E. lucunter held gradients for Mg2+, Ca2+, and K+, but not for Na+ or Cl- or osmolality. They were also able to tolerate at least a 30% reduction in sea water salinity for five days, showing reasonable euryhalinity. However, when compared to other echinoderms, E. lucunter is not especially capable of maintaining large ionic gradients with respect to external SW.

&lt;i&gt;Escherichia Coli&lt;/i&gt; and Biophysicochemical Relationships of Seawater and Water Pollution Index in the Jakarta Bay

Problem statement: Relationships between Escherichia coli (E. coli) and biophysicochemical properties of seawater at different seasons and water pollution index were investigated in the Jakarta Bay, Indonesia. Approach: Water quality data taken at different seasons (Early Rainy Season (ERS) in November 2007 and Late Dry Season (LDS) in August 2008) were analyzed. Additionally, to compare pollution level at different seasons, Nemerow-Sumitomo Water Pollution Index (WPI) was used. Results: Significant correlation of E. coli occured with only few parameters in the ERS, but with more parameters in the LDS. This might be due to the rainfall intensity in the ERS that was potential to dilute seawater and reduce concentration of some parameters, especially along the offshore stations. However, at the same time, the freshwater coming from land had capacity to force out the polluted water in 13 river systems flowing into the bay; hence it could generate more pollution along the onshore stations. Seawater pollution level slightly increased in the ERS in respect to the addition of polluted water from rivers. In this season, none station was clean, 20 stations were slightly polluted, six stations were moderately polluted and six stations were highly polluted. Meanwhile in the LDS, the number of stations following the above WPI criteria were 9, 16, 3 and 4, respectively, indicating less pollution level. Conclusion/Recommendations: The overall results showed that E. coli exhibited significant correlations with more water parameters in the LDS and the WPI showed a little increase in the ERS.

Improvement of Bioinsecticides Production by Sporeless Bacillus thuringiensis Strains in Response to Various Stresses in Low Cost Medium

The use of bioinsecticides, particularly those produced by sporeless Bacillus thuringiensis strains, has been shown to be a good alternative in pest management. Two types of sporeless mutants were distinguished. The asporogenic mutants which completely lack spores produce a regular bipyramidal crystal inclusion. The oligosporogenic mutants kept the ability to produce insecticidal crystal proteins. However, sporulation in such mutants was not totally blocked and very few of them could still produce spores. In order to improve bioinsecticides production, adaptation of sporeless strains to heat shock and osmotic stress was investigated. Delta-endotoxin production by 78% of sporeless mutants was significantly improved by osmotic stress with an overproduction of about 17%, compared to the wild strain BNS3. However, toxin production was improved by only 21% of mutants after heat shock, in low cost medium. The statistical analysis proved that delta-endotoxin production, cell growth, and spore formation of asporogenic and oligosporogenic mutants depended on the type of applied stress. Each strain has an important potential when applying the adequate stress. Moreover, adaptation of sporeless mutants to NaCl may allow the substitution of all minerals of the medium by diluted sea water which appeared to be a good alternative for the economic production of bioinsecticides at industrial scale which is of great importance from the practical point of view.

Distinct patterns of water and osmolyte control between intertidal (Bunodosoma caissarum) and subtidal (Anemonia sargassensis) sea anemones

Anemones are frequently found in rocky intertidal coasts. As they have highly permeable body surfaces, exposure to the air or to salinity variations inside tidal pools can represent intense osmotic and ionic challenges. The intertidal Bunodosoma caissarum has been compared with the subtidal Anemonia sargassensis concerning their response to air exposure or salinity changes. B. caissarum maintains tissue hydration through mucus production and dome-shape formation when challenged with air exposure or extreme salinities (fresh water or hypersaline seawater, 45psu) for 1–2h. Upon exposure to mild osmotic shocks for 6h (hyposmotic: 25psu, or hyperosmotic: 37psu), B. caissarum was able to maintain its coelenteron fluid (CF) osmolality stable, but only in 25psu. A. sargassensis CF osmolality followed the external medium in both salinities. Isolated cells of the pedal disc of B. caissarum showed full capacity for calcium-dependent regulatory volume decrease (RVD) upon 20% hyposmotic shock, at least partially involving the release of KCl via K+–Cl− cotransport, and also of organic osmolytes. Aquaporins (HgCl2-inhibited) likely participate in this process. Cells of A. sargassensis showed partial RVD, after 20min. Cells from both species were not capable of regulatory volume increase upon hyperosmotic shock (20%). Whole organism and cellular mechanisms allow B. caissarum to live in the challenging intertidal habitat, frequently facing air exposure and seawater dilution.

Forward Osmosis—Reverse Osmosis Process Offers a Novel Hybrid Solution for Water Purification and Reuse

AbstractForward osmosis (FO) is an osmotically driven membrane process that uses osmotic pressure of concentrated solutions, including seawater, to extract clean water from low salinity solutions. In a new approach, FO uses the difference in salinity of seawater and impaired water as the driving force to dilute seawater with reclaimed water through a tight FO membrane. By diluting the seawater feed stream to a reverse osmosis (RO) desalination plant, the energy demand of desalination is reduced, and two tight barriers are in place to enhance rejection of contaminants that might be present in the impaired water feed stream. Bench- and pilot-scale osmotic dilution tests were conducted with synthetic seawater as a draw solution and with secondary and tertiary effluent from a domestic wastewater treatment plant as feed streams. Impaired surface water from the South Platte River in Colorado was also tested as a feed stream to the osmotic dilution process. Although water flux was generally low, flux decline cau...

Spatially-resolved taxon-specific phytoplankton production and grazing dynamics in relation to iron distributions in the Equatorial Pacific between 110 and 140°W

Phytoplankton dynamics were investigated in the eastern equatorial Pacific at 32 stations sampled during two cruises (December 2004 and September 2005). Based on standing stock analyses from HPLC pigments, flow cytometry and microscopy, we used a modified 2-treatment approach of the seawater dilution method to estimate taxon-specific phytoplankton growth and mortality rates in 8-depth per station profiles. These data were complemented by contemporaneous measurements of dissolved iron (Fe). The stations encompassed an equatorial zonal gradient (110 to 140°W) of diminishing eastward Fe availability in the euphotic zone from upwelling of the Equatorial Undercurrent (EUC). Latitudinal variation was assessed by meridional transects at 110 and 140°W. Overall, euphotic zone averaged growth rates were 0.53±0.17 d −1 (total chlorophyll a), 0.34±0.15 d −1 (divinyl chlorophyll a) and 0.86±0.32 d −1 (fucoxanthin). Microzooplankton grazing accounted for 50-60% of daily production of eukaryotic algae, whereas essentially all growth of phototrophic prokaryotes was consumed daily. Fucoxanthin, representing diatoms, was a minor component of the accessory pigments, but diatom growth rates were both significantly higher than other taxonomically defined groups and dropped off more sharply with depth (low light level). Strikingly, no spatial or temporal trends were seen in the 256 growth rate measurements for each measured pigment. However, the diminishing eastward equatorial Fe gradient was associated with deepening subsurface pigment maxima and decreasing surface-layer pigment stocks (down to the 8% light level). In addition, integrated standing stocks of total chlorophyll a and Prochlorococcus (divinyl chlorophyll a) were strongly correlated with integrated iron at equatorial upwelling stations, yet no correlation with Fe was seen for any of the eukaryotic groups, including diatoms. This latter result is contrary to expectations from previous Fe addition experiments ( in situ or in bottles), where diatom biomass increased relative to other phytoplankton. We hypothesize that the natural supply of Fe to the base of the euphotic zone from the EUC is less favorable for diatoms because of light limitation. Rather, new Fe is rapidly incorporated into a small phytoplankton-dominated community in the deep euphotic zone, and tightly coupled grazing control results in a system regulated by return of recycled Fe.

A multi-barrier osmotic dilution process for simultaneous desalination and purification of impaired water

Osmotically driven membrane processes use chemical potential difference between two aqueous solutions as a driving force for separation and concentration of feed streams or for recovery of energy. Forward osmosis was extensively studied in recent years and demonstrated that it can be successfully utilized in many applications of water treatment. In a new approach, the salinity difference between seawater and impaired water, such as reclaimed water, is used as a driving force for osmotic dilution of seawater before desalination. The osmotic dilution approach may provide at least four major benefits related to water and energy resources. These include lower energy desalination of seawater, multi-barrier protection of drinking water, reduction in reverse osmosis membrane fouling due to impurities in impaired water, and beneficial reuse of impaired water. The osmotic dilution process was investigated on both bench- and pilot-scales. Both secondary and tertiary treated effluents from a domestic wastewater treatment plant and impaired surface water were used as feed water to the process. Flux decline was minimal and under specific flow condition it was observed that membrane fouling was negligible. Additionally, the multiple membrane barriers provided high rejection of both organic and inorganic solutes and of trace organic chemicals.

Growth and Nutrition of Two Cultivars of Zinnia elegans Under Saline Conditions

Zinnia elegans, because of its economic value and the hardiness of its wild relatives, was selected as a potential salt-tolerant cut flower crop to grow in greenhouse systems using recycled agricultural wastewater. Using recycled wastewater for irrigation of cut flowers provides an alternative to high-quality water. This is especially important in coastal and inland growing regions of California where competition for high-quality water is increasing between urban and agricultural users and provides economic and environmental benefits because groundwater contamination is reduced or even prevented. A completely randomized design was used to determine the effects of water ionic composition and salinity on the growth and leaf mineral composition of Zinnia elegans. Two cultivars (Benary's Giant Salmon Rose and Benary's Giant Golden Yellow) were grown under irrigation with two different water ionic compositions mimicking dilutions of sea water (SWD) and concentrations of Colorado River water (CRW) at increasing salinity levels with electrical conductivities of 2.5 (control), 4.0, 6.0, 8.0, and 10.0 dS·m−1 in greenhouse sand tanks in Riverside, CA. Leaf mineral concentrations were determined for calcium (Ca), magnesium (Mg), sodium (Na), potassium (K), chlorine (Cl), total sulfur (S), and total phosphorus (P). At harvest, final plant measurements included time to flowering, stem length, stem diameter (recorded at the soil line), internode length (recorded at the middle of the stem), inflorescence diameter, ray length, plant shoot fresh weight, number of leaves per plant, and number of shoots per plant. For both cultivars, plant tissue concentrations of Mg, Cl, Na, and total S increased as salinity increased in the irrigation water. Conversely, plant tissue concentrations of Ca, K, and total P decreased as salinity increased in the irrigation water. Both cultivars demonstrated high selectivity for K over Na as salinity increased in CRW and SWD with ‘Golden Yellow’ demonstrating a higher selectivity than ‘Salmon Rose’. Additionally, measured growth parameters tended to decrease as salinity increased in both irrigation water types for both cultivars. Stem lengths of 79 cm and 51 cm were found for ‘Salmon Rose' growing in 10 dS·m−1 in concentrations of CRW and SWD, respectively. ‘Golden Yellow' produced stem lengths of 74 cm and 46 cm in 10 dS·m−1 in response to concentrations of CRW and SWD, respectively. Inflorescence diameters of both cultivars approximated 8.0 cm at the highest salinity for both water types. Although significant differences were found, the minimum of 46 cm indicates that marketable flowers can be produced using both water types at least as high as 10 dS·m−1.

The influence of the Pseudo-nitzschia toxin, domoic acid, on microzooplankton grazing and growth: A field and laboratory assessment

We conducted field and laboratory experiments to determine whether the Pseudo-nitzschia-derived metabolite, domoic acid (DA), functions as a microzooplankton grazing suppressant. Using the seawater dilution technique in natural plankton communities along the Pacific Northwest coast, we found no significant relationship between dissolved DA and microzooplankton grazing rate on Pseudo-nitzschia spp. Dilution experiments amended with either 50 or 80 nM dissolved DA also showed no evidence that microzooplankton community grazing was affected by DA. The relationship between Pseudo-nitzschia spp. intracellular DA and microzooplankton grazing was less clear. On a subset of data where small Pseudo-nitzschia spp. cells dominated community composition, an apparent negative relationship between intracellular DA and microzooplankton grazing was observed. However, we provide evidence that this relationship is a microzooplankton response to Pseudo-nitzschia spp. growth rate, rather than cellular DA. In laboratory experiments, two diatom-consuming dinoflagellates, Protoperidinium excentricum and P. pellucidum, were fed single and mixed diets of a toxic and non-toxic Pseudo-nitzschia species and an optimal prey, Ditylum brightwellii. P. excentricum did not grow or ingest either the toxic or non-toxic Pseudo-nitzschia. However, P. pellucidum grew as well on the toxic Pseudo-nitzschia multiseries as it did on D. brightwellii, but did not grow on the non-toxic Pseudo-nitzschia pungens. Both dinoflagellates were capable of growing if Pseudo-nitzschia spp. diets were mixed with D. brightwellii. Addition of dissolved DA also had no negative effect on dinoflagellate growth when fed the optimal diatom diet. We conclude that domoic acid has no functional role in deterring microzooplankton grazing or growth rates. Further, our findings highlight the difficulty of defining the complex mechanisms that regulate predator and prey interactions within microplankton food webs.

The response of freshwater plants to salinity pulses

To test whether a pulse of saline water affects the growth and survival of aquatic plants, the response of four common freshwater macrophytes; Triglochin procerum, Myriophyllum simulans, Cotula coronopifolia and Baumea arthrophylla was examined. Plants established in freshwater were exposed to a pulse of diluted sea water of <1000, 4000, or 8000 mg L −1 for either three or six weeks followed by four weeks in water of <1000 mg L −1. All four species survived exposure to salinity pulses. At the end of the recovery period all species had a positive relative growth rate of between 0.01 and 0.06 g g −1 day −1. It can be concluded that all four species can tolerate short periods of exposure to saline conditions and this gives some flexibility to managers when deciding the best way to utilise and dispose of saline groundwater.