Effects of varying salinity on phytoplankton growth in a low-salinity coastal pond under two nutrient conditions.
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Phytoplankton↗
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Results for “low salinity”
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Transcriptomic and RNAi analyses reveal chloride channel 3-associated osmoregulation in Litopenaeus vannamei under low-salinity stress.
Chloride channels and transporters are important for cellular volume regulation and salinity adaptation in euryhaline crustaceans, yet the intestinal transcriptional relationship between plasma-membrane and intracellular chloride pathways remains unclear in Litopenaeus vannamei. In this study, RNA interference of anoctamin 1 (ANO1) was combined with intestinal transcriptome sequencing under the production-relevant low-salinity condition of salinity 3. ANO1 silencing produced a focused transcriptional response, with 16 differentially expressed genes (DEGs) identified (11 upregulated and 5 downregulated). Functional enrichment indicated that these genes were associated with transporter activity, cytoskeletal organization, extracellular matrix-receptor interaction, membrane lipid metabolism, and vesicular processes. Notably, a transcript encoding chloride channel protein 3 (CLC-3) was significantly upregulated following ANO1 knockdown, suggesting a potential transcriptional relationship between ANO1 and CLC-3 in chloride homeostasis. Based on this finding, CLC-3 was selected for full-length cDNA cloning, sequence characterization, salinity-gradient expression analysis, and RNAi-based functional assessment. The cloned CLC-3 cDNA was 2883 bp in length and encoded an 850 amino acid protein containing a conserved voltage-gated chloride channel (Voltage-CLC) domain and two cystathionine β-synthase domains. Phylogenetic analysis placed LvCLC-3 within the intracellular CLC-c clade, and tissue distribution analysis showed the highest CLC-3 expression in the intestine. Intestinal CLC-3 expression responded nonlinearly to salinity variation, peaking at salinity 20. Under salinity 3, CLC-3 knockdown reduced ANO1, Na+/K+-ATPase alpha subunit, and Na+-K+-2Cl- cotransporter transcript levels, whereas glutamate-gated chloride channel expression increased. Mild hepatopancreatic structural alterations were also observed after CLC-3 knockdown. These findings suggest that CLC-3 is a salinity-responsive intracellular chloride-transporter candidate associated with intestinal ion-transport-related transcriptional responses after ANO1 suppression in L. vannamei, although the underlying physiological mechanism requires further validation.
Animals↗
Partitioning effects during terminal carbon and electron flow in sediments of a low-salinity meltwater pond near Bratina Island, McMurdo Ice Shelf, Antarctica.
A study of anaerobic sediments below cyanobacterial mats of a low-salinity meltwater pond called Orange Pond on the McMurdo Ice Shelf at temperatures simulating those in the summer season (<5 degrees C) revealed that both sulfate reduction and methane production were important terminal anaerobic processes. Addition of [2-(14)C]acetate to sediment samples resulted in the passage of label mainly to CO(2). Acetate addition (0 to 27 mM) had little effect on methanogenesis (a 1.1-fold increase), and while the rate of acetate dissimilation was greater than the rate of methane production (6.4 nmol cm(-3) h(-1) compared to 2.5 to 6 nmol cm(-3) h(-1)), the portion of methane production attributed to acetate cleavage was <2%. Substantial increases in the methane production rate were observed with H(2) (2.4-fold), and H(2) uptake was totally accounted for by methane production under physiological conditions. Formate also stimulated methane production (twofold), presumably through H(2) release mediated through hydrogen lyase. Addition of sulfate up to 50-fold the natural levels in the sediment (interstitial concentration, approximately 0.3 mM) did not substantially inhibit methanogenesis, but the process was inhibited by 50-fold chloride (36 mM). No net rate of methane oxidation was observed when sediments were incubated anaerobically, and denitrification rates were substantially lower than rates for sulfate reduction and methanogenesis. The results indicate that carbon flow from acetate is coupled mainly to sulfate reduction and that methane is largely generated from H(2) and CO(2) where chloride, but not sulfate, has a modulating role. Rates of methanogenesis at in situ temperatures were four- to fivefold less than maximal rates found at 20 degrees C.
Acetates↗
Electro-oxidative abatement of low-salinity reverse osmosis membrane concentrates.
The present study encompasses the application of electrolysis as novel treatment technique for the abatement of low-salinity concentrates generated from the filtrative treatment of water and wastewater. Four different materials have been tested as anode for a number of brine samples in a one-compartment electrolytic cell in galvanostatic mode. It was found that PbO(2) and SnO(2) anodes initiated electrochemical precipitation through an increase of the pH. Boron-doped diamond (BDD) and RuO(2) anodes successfully oxidised the pollutants in the brine and a linear removal of total ammonia nitrogen (TAN) and chemical oxygen demand (COD) was observed during the first phase of oxidation. Oxidation was predominantly achieved through indirect hypochlorite bulk oxidation; the higher oxidation rate and extent for the BDD anode was attributed to the higher selectivity and activity of the latter. Overall performance of the BDD electrode was higher than for RuO(2): higher rates for TAN (17.9 vs. 13.5mg/Ah) and COD (74.5 vs. 20.0mg/Ah) removal as well as higher overall current efficiencies (35.2% vs. 14.5%). Extensive colour removal was observed for both anodes (>90% decrease in absorbency at 455 nm).
Electrolysis↗
K+-Phosphatase activity of gill (Na+, K+)-ATPase from the blue crab, Callinectes danae: low-salinity acclimation and expression of the alpha-subunit.
The kinetic properties of a microsomal gill (Na(+), K(+)) ATPase from the blue crab, Callinectes danae, acclimated to 15 per thousand salinity for 10 days, were analyzed using the substrate p-nitrophenylphosphate. The (Na(+), K(+))-ATPase hydrolyzed the substrate obeying Michaelian kinetics at a rate of V=102.9+/-4.3 U.mg(-1) with K(0.5)=1.7+/-0.1 mmol.L(-1), while stimulation by magnesium (V=93.7+/-2.3 U.mg(-1); K(0.5)=1.40+/-0.03 mmol.L(-1)) and potassium ions (V=94.9+/-3.5 U.mg(-1); K(0.5)=2.9+/-0.1 mmol.L(-1)) was cooperative. K(+)-phosphatase activity was also stimulated by ammonium ions to a rate of V=106.2+/-2.2 U. mg(-1) with K(0.5)=9.8+/-0.2 mmol.L(-1), following cooperative kinetics (n(H)=2.9). However, K(+)-phosphatase activity was not stimulated further by K(+) plus NH(4) (+) ions. Sodium ions (K(I)=22.7+/-1.7 mmol.L(-1)), and orthovanadate (K(I)=28.1+/-1.4 nmol.L(-1)) completely inhibited PNPPase activity while ouabain inhibition reached almost 75% (K(I)=142.0+/-7.1 micromol.L(-1)). Western blotting analysis revealed increased expression of the (Na(+), K(+))-ATPase alpha-subunit in crabs acclimated to 15 per thousand salinity compared to those acclimated to 33 per thousand salinity. The increase in (Na(+), K(+))-ATPase activity in C. danae gill tissue in response to low-salinity acclimation apparently derives from the increased expression of the (Na(+), K( (+) ))-ATPase alpha-subunit; phosphate-hydrolyzing enzymes other than (Na(+), K(+))-ATPase are also expressed. These findings allow a better understanding of the kinetic behavior of the enzymes that underlie the osmoregulatory mechanisms of euryhaline crustaceans.
Animals↗
Clostridium vincentii sp. nov., a new obligately anaerobic, saccharolytic, psychrophilic bacterium isolated from low-salinity pond sediment of the McMurdo Ice Shelf, Antarctica.
A gram-positive, motile, rod-shaped, strictly anaerobic bacterium was isolated from an enrichment initiated with sediment taken from below the cyanobacterial mat of a low-salinity pond on the McMurdo Ice Shelf, Antarctica. The organism grew optimally at 12 degrees C, at pH 6.5, and at an NaCl concentration of< 0.5% (w/v). It survived freeze-thawing at low salt concentrations,but not exposure to temperatures over 25 degrees C for more than 20 h or short-term exposure to temperatures> 50 degrees C. Out of a variety of polysaccharides tested as growth substrates, only xylan supported growth. The organism also grew on a variety of mono- and disaccharides including the cyanobacterial cell wall constituent, N-acetyl glucosamine. Fermentation products on a mol product per 100 mol of hexose monomer fermented basis were: acetate, 72; formate, 72; butyrate, 55; hydrogen, 114; and CO2, 100. Not detectable in the culture medium(< 2 mol per 100 mol of monomer) were lactate, propionate, ethanol,n-propanol, n-butanol, and succinate. The G+C content of the DNA from the bacterium was 33 mol%, and a phylogenetic analysis indicated that it grouped closely with members of the RNA-DNA homology group 1 of the genus Clostridium. It differed from other species of this genus with regard to growth temperature optimum, substrate range, and fermentation pattern, and is therefore designated as a new species of Clostridium for which the name Clostridium vincentii is proposed. The type strain is lac-1 (DSM 10228).
Clostridium↗
The ultrastructure of the posterior midgut caecum of Pachygrapsus crassipes (Decapoda, Brachyura) adapted to low salinity.
The effects of salinity adaptation and of composition and tonicity of fixatives upon the ultrastructure of the posterior midgut caecum (PMC) of Pachygrapsus crassipes have been studied. The PMC epithelium consists of a single layer of columnar cells with a microvillous border. The apical cytoplasm contains numerous mitochondria, lysosomes, and much smooth endoplasmic reticulum. Rough endoplasmic reticulum and Golgi apparatus are situated in the perinuclear cytoplasm. This epithelium resembles other transporting epithelia in that the basal cytoplasm has an extensive system of branched tubules formed from invaginations of the lateral and basal plasma membrane. Numerous mitochondria are associated with the basal tubular system. To determine the possible contribution of the PMC to the osmoregulatory ability of Pachygrapsus, the ultrastructure of the PMC from animals adapted to 40, 50, and 100 and 150% sea water was investigated. Enlargement of basal tubules and intercellular spaces at low salinity, suggestive of fluid-transport activity, was found to be an artifact of fixation. The most consistent response when animals were acclimated to dilute salinities was that some basal mitochondria assume a more complex shape, usually appearing as rings in cross sections of the caecum. A hypothesis concerning the functional significance of these mitochondria is proposed.
Adaptation, Physiological↗
Quantitative changes in branchial carbonic anhydrase activity and expression in the euryhaline green crab, Carcinus maenas, in response to low salinity exposure.
Hemolymph osmolality, and changes in gill carbonic anhydrase (CA) activity, relative mRNA expression, and CA protein concentration were measured in the green crab Carcinus maenas acclimated to 32 ppt salinity and transferred to 10 ppt. Hemolymph osomolality stabilized at new, acclimated values, by 24 hr after transfer. There was a large increase in CA mRNA concentrations, as measured by quantitative PCR, in the posterior gills by 24 hr post-transfer that remained elevated through 4 days. By 7 days, however, CA mRNA levels began to decline. CA activity, on the other hand, did not begin to increase until 48 hr after transfer to 10 ppt, but it continued to increase through 7 days. CA protein concentration increased by 5-fold in posterior gills in crabs acclimated to 10 ppt. CA activity, mRNA expression, and CA protein concentrations did not change in anterior gills. These results indicate that low salinity-stimulated CA induction is under transcriptional regulation, and that the increase in CA activity is a result of the increase in gene expression and synthesis of new enzyme. Changes in mRNA appear to be transient, but once synthesized, the CA protein appears to persist in the gill for an extended time. In a separate set of experiments, green crabs acclimated to 32 ppt were transferred directly to salinities of 25, 20, 15, and 10 ppt. CA activity and mRNA concentrations increased with decreasing salinity, peaking at 15 ppt but decreasing between 15 and 10 ppt. The decrease may represent a breakdown in the mechanism of transport-related protein induction near the lower salinity limit of this species.
Adaptation, Physiological↗
Enterococcus-like infections in Macrobrachium rosenbergii are exacerbated by high pH and temperature but reduced by low salinity.
Macrobrachium rosenbergii (10 to 15 g and 8 to 12 g at intermolt) were challenged with an enterococcus-like bacterium (strain KM002) previously isolated and identified as the causal agent of mortality. Challenge doses and conditions of pH, salinity and temperature were varied to determine the influence of environmental factors on the development of disease and mortality. Survival was 100% for the unchallenged control groups in all trials. In pH tests, the onset of mortality was earlier at pH 8.8 to 9.5 than at pH 4.6 to 5.2 and 7.5 to 7.7. Also, as pH 8.8 to 9.5, all challenged prawns died within 6 d in high dose challenge tests. By contrast, 20% of the prawns challenged at pH 4.6 to 5.2 and 7.5 to 7.7 survived. At low dose challenge (5 x 10(4) cfu prawn(-1)), survival increased significantly except at pH 8.8 to 9.5. In salinity tests at 2 challenge doses (1 x 10(6) and 2 x 10(7) cfu prawn(-1)), onset of mortality was earliest at 15 ppt and cumulative mortality was 100% at 15 ppt and 0 ppt. By contrast, survival was 80% at 5 and 10 ppt at the low dose challenge and 40% and 60%, respectively, at the high dose challenge. When the challenge dose was reduced to 5 x 10(4) cfu prawn(-1), survival was not significantly different at different salinity levels. In temperature tests at pH 7.2 to 7.5 and at 2 challenge doses (2 x 10(7) and 4 x 10(7) cfu prawn(-1)), the onset of mortality was earliest at 33 to 34 degrees C and total mortality occurred at 27 to 28 degrees C and 33 to 34 degrees C. By contrast, there were 40% and 20% survivors, respectively, for low and high challenge doses at 30 to 31 degrees C. Reducing the challenge dose to 5 x 10(4) cfu prawn(-1) gave higher survival in all groups. However, survival at 33 to 34 degrees C was still lowest. In similar temperature tests but at pH 8.8 to 9.5, onset of mortality was somewhat accelerated and there was 100% death for all the high challenge groups. At low challenge doses, mortality was lower but still highest in the 33 to 34 degrees C group. Results indicated that mortality of M. rosenbergii caused by this Enterococcus-like bacterium was exacerbated by environmental parameters of temperature and pH different from those known to be optimal for prawn growth. By contrast, low salinity appeared to have a beneficial effect on survival. Further work is needed to determine the mechanisms underlying these effects.
Animals↗
Cadmium content of the marine sponge Microciona prolifera, other sponges, water and sediment from the eastern Florida panhandle: possible effects on Microciona cell aggregation and potential roles of low pH and low salinity.
Marine sponges from shallow bays and estuaries along the Florida panhandle contained cadmium (Cd), 1.78-27.9 microg g(-1) (dry weight). Levels > 7 microg g(-1) were never found in a variety of other benthic invertebrates. Water levels of Cd were of the order 0.22-0.43 microg ml(-1) and did not differ significantly between the two study areas (Panacea and St. Joseph Bay). Cd in organic sediment however, was significantly (P = 0.033) higher around Panacea (0.343 +/- 0.063 S.E.M.) than in St. Joseph Bay (0.18 +/-0.223 S.E.M.). Salinity of 10 and pH 6.5 were recorded following heavy rains, and can constitute a hostile environment for these organisms. Temporal variations of Cd and Cu but not Zn were observed in Microciona prolifera over a period of 2 years in St. Joseph Bay, and a negative correlation was observed between Cd content and the Ca(2+)-induced aggregation of Microciona cells suspended in Ca2+/Mg(2+)-free artificial seawater. Cells unresponsive to Ca2+ aggregated in response to releasers of Ca2+ from internal stores (thapsigargin, A23187 and tetredecylamine), suggesting that they were viable but dormant. In vitro studies showed that Cd2+ is about equipotent with Ca2+ in inducing aggregation of Microciona cells, whereas lower concentrations (1-2 x 10(-3) M), added 10 min before inducing aggregation with CaCl2, inhibited aggregation, possibly by blocking Ca2+ uptake. Microciona contained a metallothionein (MT)-like protein. Taken together these results suggest that naturally-acquired Cd may interfere with cell regulatory processes in Microciona. Possible effects of low pH and salinity on Cd uptake and detrimental effects on cell function are discussed.
Animals↗
Increased urotensin I and II immunoreactivity in the urophysis of Gillichthys mirabilis transferred to low salinity water.
The function of the fish caudal neurosecretory system is uncertain, but a role in osmoregulation has been suggested by many investigators. Our objective was to determine if acclimation to water of different salinity has an effect on immunoreactive patterns and staining intensities of the two caudal neuropeptides, urotensins I (UI) and II (UII), in Gillichthys mirabilis. Five fish, originally maintained in seawater, were transferred to deionized fresh water (FW), and five were transferred to new seawater (SW). After 24 hr spinal cords were removed and fixed, FW and SW spinal cords were paired in blocks to receive identical treatment, and cryostat sections were double immunostained for both peptides using a double sequential immunofluorescence procedure. FW spinal cord exhibited increased staining intensities for both UI and UII in their urophyses (the neurohemal organ) compared to the SW spinal cords. The magnitude of intensity difference appeared greater for UI than for UII. In addition, the FW urophyses had more loci displaying intense, perivascular UI immunoreactivity than the SW urophyses. Thus, it appears that environmental salinity has an effect on the urophysial content of UI and UII in this euryhaline fish. The increased immunoreactivity in FW fish could reflect increased synthesis and storage, decreased release of the stored peptides, or decreased peptide degradation.
Adaptation, Physiological↗
Comparative electrical properties of identified neurons in Elysia chlorotica before and after low salinity acclimation.
Identified neurons in the abdominal ganglion of Elysia chlorotica adapted to 50% seawater (SW) had significantly different electrical properties from the same cells in animals adapted to 100% SW. Resting potential, action potential (AP) overshoot, (AP) duration, threshold and after potential were all different following salinity acclimation. The resting potential of these cells behaves as an ideal potassium electrode above 10 mM [K+]. The action potential has both sodium and calcium components to the rising phase.
Acclimatization↗
The little skate Raja erinacea exhibits an extrahepatic ornithine urea cycle in the muscle and modulates nitrogen metabolism during low-salinity challenge.
Urea synthesis via the hepatic ornithine urea cycle (OUC) has been well described in elasmobranchs, but it is unknown whether OUC enzymes are also present in extrahepatic tissues. Muscle and liver urea, trimethylamine oxide (TMAO), and other organic osmolytes, as well as selected OUC enzymes (carbamoyl phosphate synthetase III, ornithine transcarbamoylase, arginase, and the accessory enzyme glutamine synthetase), were measured in adult little skates (Raja erinacea) exposed to 100% or 75% seawater for 5 d. Activities of all four OUC enzymes were detected in the muscle. There were no changes in muscle OUC activities in skates exposed to 75% seawater; however, arginase activity was significantly lower in the liver, compared to controls. Urea, TMAO, and several other osmolytes were significantly lower in the muscle of little skates exposed to 75% seawater, whereas only glycerophosphorylcholine was significantly lower in the liver. Urea excretion rates were twofold higher in skates exposed to 75% seawater. Taken together, these data suggest that a functional OUC may be present in the skeletal muscle tissues of R. erinacea. As well, enhanced urea excretion rates and the downregulation of the anchor OUC enzyme, arginase, in the liver may be critical in regulating tissue urea content under dilute-seawater stress.
Analysis of Variance↗
Isolation of haloarchaea that grow at low salinities.
Summary Archaea, the third domain of life, were long thought to be limited to environmental extremes. However, the discovery of archaeal 16S rRNA gene sequences in water, sediment and soil samples has called into question the notion of Archaea as obligate extremophiles. Until now, none of these novel Archaea has been brought into culture, a critical step for discovering their ecological roles. We have cultivated three novel halophilic Archaea (haloarchaea) genotypes from sediments in which the pore-water salinity was close to that of sea water. All previously reported haloarchaeal isolates are obligate extreme halophiles requiring at least 9% (w/v) NaCl for growth and are typically the dominant heterotrophic organisms in salt and soda lakes, salt deposits and salterns. Two of these three newly isolated genotypes have lower requirements for salt than previously cultured haloarchaea and are capable of slow growth at sea-water salinity (2.5% w/v NaCl). Our data reveal the existence of Archaea that can grow in non-extreme conditions and of a diverse community of haloarchaea existing in coastal salt marsh sediments. Our findings suggest that the ecological range of these physiologically versatile prokaryotes is much wider than previously supposed.
Base Sequence↗
Chloride regulation at low salinities by Nereis diversicolor (Annelida, Polychaeta). I. Uptake and exchanges of chloride.
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Adaptation, Physiological↗
Chloride regulation at low salinities by Nereis diversicolor (Annelida, Polychaeta). II. Water fluxes and apparent permeability to water.
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Animals↗
Relationship between ammonia excretion rates and hemolymph nitrogenous compounds of a euryhaline bivalve during low salinity acclimation.
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Amino Acids↗
Performance of high producing dairy cows offered drinking water of high and low salinity in the Arava desert.
The effect of supplying high producing Israeli Holstein cows with desalinated or salty water on milk composition and production was examined in the Arava desert of southern Israel. Daily water consumption of cows offered desalinated water was higher by 10.6 L than that of the group offered salty drinking water; DMI was similar for the two groups. Daily production of milk and 3.5% FCM was higher for the cows receiving desalinated water than for the cows receiving salty water; 35.2 versus 33.1 kg and 31.6 versus 29.8 kg, respectively. The percentage of protein in milk and the daily protein production were higher for the cows receiving desalinated water than for the cows receiving salty water: 2.89% and 1.01 kg versus 2.84% and .93 kg, respectively. The percentage of milk fat and the daily fat production were higher for the cows receiving desalinated water. These results indicate that water salinity negatively affects milk production. Improvement of water quality by desalination increased production of milk and milk constituents.
Animals↗