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PubMed2001

Bioaccumulation of cesium-137 by biota in different aquatic environments.

Macroalgae, isopods and fish species were exposed to 137Cs in brackish and sea water conditions for 18 days to determine radionuclide concentration factors. The concentration factors of 137Cs in brown shrimp and polychaete species were also investigated under brackish water conditions. At equilibrium, the concentration factors in macroalgae, isopod, fish, brown shrimp and polychate samples were found to be 2.5, 33, 2, 16 and 11 at 16 degrees C in brackish water conditions, respectively. The accumulation rate in macroalgae species was influenced by temperatures between 6 degrees C and 16 degrees C. The bioaccumulation of 137Cs in isopods at low salinity regime was increased significantly. At the same time, the bioaccumulation rate in macroalgae species also showed slight increase at low salinity. On the other hand, the bioaccumulation rate of 137Cs in the fish species in sea water was higher than in brackish water.

Animals↗
PubMed2006

The effect of abiotic stresses on carbohydrate status of olive shoots (Olea europaea L.) under in vitro conditions.

Olive plants produce both sucrose and mannitol as major photosynthetic products. Contrary to previously studied celery [Vítová et al., Mannitol utilisation by celery (Apium graveolens) plants grown under different conditions in vitro. Plant Sci 2002; 163: 907-16], in vitro these carbohydrates were found to be able to sustain growth of olive shoots roughly to the same extent at all tested concentrations (1-9% w/v). We studied the involvement of the particular components of the endogenous carbohydrate spectrum in response to different abiotic stresses (osmotic stress, salinity, low temperature) in vitro. Salinity (100mM NaCl) caused a decrease of total soluble carbohydrates, while an increase was observed during low-temperature treatment (0 and 4 degrees C). Mannitol accumulated primarily under salinity (up to 40% of total soluble carbohydrates compared to 10-20% in controls). Only a small (two-fold) increase of proline content in salinity stressed plants indicates proline does not play a significant role in olive stress response. Low temperature led to an increase of the raffinose family oligosaccharides (RFO) proportion in total carbohydrates. We conclude that olive plants exploit the high diversity of the carbohydrate spectrum in specific response to different stresses.

Abscisic Acid↗
PubMed2002

Survival of faecal indicator bacteria in tropical estuarine waters (Bangpakong River, Thailand).

AIMS: To investigate the survival of cultivable bacteria in the tropical Bangpakong estuary (Eastern Thailand) under different salinities and light conditions. METHODS AND RESULTS: Dark and light microcosm experiments using membrane diffusion chambers were carried out under three different experimental conditions, namely (i) low salinity, (ii) progressive mixing with brackish water and (iii) fast mixing with high salinity water spiked with raw urban sewage. Faecal coliforms declined faster than faecal enterococci, as shown by survival T90 values ranging from 82.2 +/- 4.2 to 14.5 +/- 0.8 h and 97.5 +/- 0.4-20.6 +/- 1.2 h, respectively. The survival of freshwater heterotrophic bacteria was higher but variable (121.2 +/- 5.0-30.1 +/- 14.3 h), whereas that of heterotrophic marine bacteria was rather stable (81.5 +/- 4.2-44.6 +/- 2.5 h). CONCLUSIONS: Overall survival was higher in low salinities. Light had a further deleterious effect, since it accelerated the decay of faecal indicators, particularly in high salinities. Faecal enterococci had a higher resistance to environmental conditions compared with faecal coliforms. SIGNIFICANCE AND IMPACT OF THE STUDY: This study is relevant to the understanding of the behaviour of different faecal indicator bacteria and the optimization of sewage treatment plants aimed at the reduction and/or elimination of faecal load discharged into estuarine waters submitted to salinity variations.

Bacteria↗
PubMed2000

Combined effects of pentachlorophenol and salinity stress on phagocytic and chemotactic function in two species of abalone.

The effect of pentachlorophenol (PCP) combined with salinity stress on specific aspects of cellular immunity was examined in two species of abalone. Chemotactic and phagocytic ability (percent phagocytosis, %P; and phagocytic index, PI), as well as gross morphological characteristics, of hemocytes withdrawn from red (Haliotis rufescens) and black abalone (H. cracherodii) after in vivo exposure to 25, 35, or 45 per thousand seawater salinity plus 1.2 mg/l PCP were determined. Abalone exposures of 3.5 and 6.5 h, respectively, were based on species-specific metabolic endpoints (MEPs) derived from previous NMR data. Hemocyte chemotaxis was found to be augmented by low salinity in red but not black abalone, while high salinity seemed to reduce chemotactic ability in both species. PCP did not potentiate the effects demonstrated by salinity variations alone in red abalone, although chemotaxis was further compromised in black abalone exposed to high salinity stress combined with PCP. Although chemotactic ability was similar among both species, both %P and PI was greater among black abalone. Low salinity may offset the effects of PCP in red but not black abalone. Whereas red abalone demonstrated a reduction in phagocytic ability upon exposure to high salinity alone, black abalone appeared more resilient to high salinity stress alone. Furthermore, while the effect of high salinity plus PCP is subadditive among red abalone, high salinity seems to potentiate the effect of PCP on black abalone. Finally, hemocytes exposed to acute salinity variations plus PCP showed varying morphological characteristics when compared to controls. Over 30% of hemocytes of high salinity plus PCP exposed abalone remained rounded and generally unattached to glass slides with only a few pseudopod extensions. Hemocyte preparations incubated in rhodamine-conjugated phalloidin were observed with fluorescence microscopy and reveal an altered actin filament pattern. Overall, black abalone demonstrate greater phagocytic ability than red abalone both in the presence and absence of PCP. Furthermore, increases in salinity are accompanied with reduced phagocytic ability with red abalone demonstrating particular sensitivity to salinity variations. While PCP inhibits ATP synthesis, salinity variations may impose an additional stress on intertidal animals exposed to transient or seasonal environmental changes.

Journal Article↗
PubMed1999

Immunolocalization of Na+,K(+)-ATPase in the organs of the branchial cavity of the European lobster Homarus gammarus (Crustacea, Decapoda).

The localization of Na+,K(+)-ATPase in epithelia of the organs of the branchial cavity of Homarus gammarus exposed to seawater and dilute seawater was examined by immunofluorescence microscopy and immunogold electron microscopy with a monoclonal antibody IgG alpha 5 raised against the avian alpha-subunit of the Na-,K(+)-ATPase. In juveniles held in seawater, fluorescent staining was observed only in the epithelial cells of epipodites. In juveniles held in dilute seawater, heavier immunoreactivity was observed in the epithelial cells of epipodites, and positive immunostaining was also observed along the inner-side epithelial layer of the branchiostegites. No fluorescent staining was observed in the gill epithelia. At the ultrastructural level, the Na+,K(+)-ATPase was localized in the basolateral infolding systems of the epipodite and inner-side branchiostegite epithelia of juveniles held in dilute seawater, mostly along the basal lamina. The expression of Na+,K(+)-ATPase therefore differs within tissues of the branchial cavity and according to the external salinity. These and previous ultrastructural observations suggest that the epipodites, and to a lesser extent the inner-side epithelium of the branchiostegites, are involved in the slight hyper-regulation displayed by lobsters at low salinity. Enhanced Na+,K(+)-ATPase activity and de novo synthesis of Na+,K(+)-ATPase within the epipodite and branchiostegite epithelia may be key points enabling lobsters to adapt to low salinity environments.

Animals↗
PubMed1981

D-Glucose transport across the apical membrane of the surface epithelium in Nereis diversicolor.

Epidermal D-glucose transport was investigated in vivo in the brackish-water polychaete worm Nereis diversicolor. Transfer across the apical membrane is rate-limiting to D-glucose uptake, but the cuticle and/or mucus presents some resistance to D-glucose diffusion between bulk solution and transporting membrane. Maximal D-glucose influx is about 10(-12) mol sec-1 per cm2 of apical plasmalemma. Under natural conditions (approximately 1 microM D-glucose in the medium), backflux from the epidermal transport pool is negligible, but a significant paracellular outflux may occur. D-glucose influx across the apical membrane is Na+-dependent and completely inhibitable by phlorizin and harmaline; phloretin is less effective, and cytochalasin B has no effect. Influx is moderately depressed by KCN and iodoacetate, alpha-methyl-D-glucopyranoside is an effective substitute of D-glucose in transport. Animals acclimated to a low salinity, in which epidermal salt transport takes place, show a marked decrease of D-glucose transport capacity. On transfer of animals from a high to a low salinity, or vice versa, the corresponding change of influx occurs after a time-lag of at least an hour. Permeability of the epidermis to simple diffusion of D-glucose is 8 X 10(-8) cm sec-1 (on basis of gross epidermal area).

Animals↗
PubMed1991

The effect of certain intrinsic and extrinsic variables on the acute toxicity of selected organophosphorus insecticides to the mummichog, Fundulus heteroclitus.

The acute toxicity of two organophosphorus (OP) insecticides, azinphosmethyl and acephate, was evaluated in the mummichog, Fundulus heteroclitus. In addition, the effects of certain intrinsic (sex) and extrinsic (salinity and multiple toxicant interraction) variables on the toxic response were also investigated. Azinphosmethyl was by far the most toxic of the two OP insecticides with a 96h LC50 approximately 100,000 x lower than that for acephate. Slight sex differences were observed in the sensitivity of mummichogs to each of the OP insecticides with male fish being marginally more sensitive. Significant effects of low salinity stress were observed only with acephate exposure and, in this case, low salinity appeared to be slightly protective. In general, all of the insecticide mixtures (azinphosmethyl/endosulfan, azinphosmethyl/fenvalerate and acephate/fenvalerate) tested exhibited simple additive toxicity.

Animals↗
PubMedDate not supplied

[Adenosine triphosphatase activity in the organs of the crab Hemigrapsus sanguineus, acclimated to sea water of different salinity].

In crabs acclimated to low salinity, the activity of Na, K-ATPase from the gills increases; the activity also increases in the antennal glands after acclimation of the animals to high salinity. The activity of Na, K-ATPase in the abdominal ganglion and in the heart does not depend on the salinity to which crabs had been acclimated. Changes in the activity of Mg-ATPase in the gills and antennal glands associated with acclimation of crabs to sea water with different salinity correspond to those in the activity of Na, K-ATPase.

Adaptation, Physiological↗
PubMed2005

Critical salinity, sensitivity, and commitment of salinity-mediated carbonic anhydrase induction in the gills of two euryhaline species of decapod crustaceans.

Two euryhaline species of decapod crustaceans, Carcinus maenas and Callinectes sapidus, were subjected to a series of acute low-salinity challenges, and changes in carbonic anhydrase (CA) activity in the gills were monitored in order to characterize the nature of salinity-sensitive CA induction. CA activity is uniformly low in all gills of both species at high salinity, but at a critical salinity of 27 ppt, CA induction occurs in the posterior, ion-transporting gills, with CA activity approximately doubling. This salinity occurs right at, or slightly above, the point at which these species make the transition from osmoconformity to osmoregulation. The regulatory mechanism that controls the levels of CA expression after the initial induction has occurred is also very sensitive. Changes in CA activity occur in response to changes in salinity as small as 20 milliosmoles. CA induction only occurs after a critical minimum amount of time of exposure to low salinity (48-72 hr in C. maenas and 12 hr in C. sapidus), but once induction is begun, it continues regardless of subsequent salinity changes. The timing is most likely due to the time it takes for changes in gene expression and resultant increases in CA mRNA to occur in response to low-salinity exposure, and the delay in CA induction could be an adaptation to avoid making metabolically expensive responses to potentially short-term environmental changes.

Animals↗
PubMed2006

Influence of food quality and salinity on dietary cadmium availability in Mytilus trossulus.

Surficial sediments (a combination of re-suspended and suspended sediments denoted as RSS) were collected from two distinct marine intertidal habitats. The two habitats differed with respect to salinity (25ppt versus 15ppt) and RSS % organic carbon content (24% versus 15%). Feeding experiments were conducted simulating the conditions in the two habitats to determine if salinity and RSS % organic carbon content affected cadmium accumulation in the pacific blue mussel Mytilus trossulus. Eleven different treatments including pure phytoplankton, collected RSS and control clay were radiolabeled with (109)Cd and pulse-fed to M. trossulus under both high (25ppt) and low salinities (15ppt). Metal uptake and accumulation was determined using the DYMBAM biodynamic metal bioaccumulation model. Although M. trossulus ingestion rates (IR) were significantly higher at 25ppt as compared to 15ppt, assimilation efficiencies (AEs) and [(109)Cd] tissue levels were significantly lower at high as compared to low salinity exposures. Of the abiotic and biotic parameters examined and in contrast to other studies, differences in salinity rather than ingestion rate or food quality (as defined by % organic carbon content) seemed to best define the observed differences in (109)Cd AE by M. trossulus.

Animals↗
PubMed2000

Seasonal variability of salinity, temperature, turbidity and suspended chlorophyll in the Tweed Estuary.

Results are presented from a campaign of measurements that were undertaken to examine seasonal variability in physical and chemical fluxes and processes within the Tweed Estuary during the period September 1996-August 1997. The study utilised monthly surveys, each of approximately 1 week duration. This article interprets a subset of the salinity, temperature, turbidity [suspended particulate matter (SPM) levels] and chlorophyll a data. Measurements discussed here were obtained throughout the estuary during high-speed transects that covered the region between the tidal river and the coastal zone. Longitudinal distributions of surface salinity depended strongly on freshwater runoff. During high runoff the surface salinity was low and the freshwater-saltwater interface (FSI) was located close to the mouth. The reverse was true at times of low runoff. Salinity stratification was generally strong. During the surveys, river runoff temperatures ranged from approximately 2 to 18 degrees C and coastal waters (approximately 33 salinity) from approximately 6 to 15 degrees C. Turbidity was low throughout the campaign (SPM < 30 mg l(-1)). Because of rapid flushing times (one or two tides), turbidity tended to mix conservatively between river and coastal waters. Higher coastal turbidity was associated with stronger wind events, and higher fluvial turbidity with spate events. Suspended chlorophyll a levels were usually low throughout the estuary (typically < 2 microg l(-1)) and showed large spatial variability. Because of the rapid flushing of the estuary, it is hypothesised that it was not possible for several algal cell divisions to occur before algae were flushed to the coastal zone. A 'bloom' occurred during the May 1997 survey, when chlorophyll a levels reached 14 microg l(-1). Higher chlorophyll a concentrations at that time occurred at very low salinities, indicating that these waters and algae were largely fluvially derived, and may have resulted from increasing springtime solar irradiation.

Chlorophyll↗
PubMed1999

Environmental upregulation of the atrial natriuretic peptide gene in the living fossil, Limulus polyphemus.

Northern blot analysis revealed that atrial natriuretic peptide (ANP) gene expression occurs in heart, hematocytes and gills of the invertebrate Limulus polyphemus, the horseshoe crab. In low salinity and on land ANP prohormone messenger RNA in Limulus' heart was 32-fold less compared to that in a vertebrate heart (i.e., rat, Rattus norvegicus). ANP gene expression doubled (P < 0.05) in Limulus' heart and gills with change from land and low salinity to medium salinity and osmolality. ANP gene expression was 10-fold higher in Limulus' gills in seawater (i.e., high salinity). The products of this ANP gene expression (i.e., ANP, long acting natriuretic peptide, vessel dilator and kaliuretic peptide) were released and increased in the circulation, i.e., hemolymph, of Limulus proportional to the increase in salinity and osmolality (P = <0.01). These results suggest that modification of ANP gene expression enables animals to adapt to freshwater, seawater, and land.

Animals↗
PubMedDate not supplied

Ontogeny of intracellular isosmotic regulation in the european lobster Homarus gammarus (L.).

Intracellular free amino acids were measured in the abdominal muscle of the three larval instars, postlarvae, and juveniles of the lobster Homarus gammarus, acclimated to seawater (35 per thousand) and to a dilute medium (22 per thousand), to study intracellular isosmotic regulation throughout the development of this species. Transfer to low salinity was followed by a highly significant drop of free amino acids level in all developmental stages. The main regulated amino acids were glycine, proline, and alanine. The level of regulation of total free amino acids changed at metamorphosis: the decrease in total free amino acids at low salinity was 46% in the three larval instars, but it was only 29% in postlarvae and 20% in juveniles. These results suggest that free amino acids, mainly glycine, proline, and alanine, are involved in intracellular isosmotic regulation in the lobster, with different levels of involvement in pre- and postmetamorphic stages. The ontogenetic changes in intracellular isosmotic regulation are discussed in relation to the changes in extracellular regulation (osmoregulation) in the lobster.

Adaptation, Physiological↗
PubMed2005

NHE3 in an ancestral vertebrate: primary sequence, distribution, localization, and function in gills.

In mammals, the Na+/H+ exchanger 3 (NHE3) is expressed with Na+/K+-ATPase in renal proximal tubules, where it secretes H+ and absorbs Na+ to maintain blood pH and volume. In elasmobranchs (sharks, skates, and stingrays), the gills are the dominant site of pH and osmoregulation. This study was conducted to determine whether epithelial NHE homologs exist in elasmobranchs and, if so, to localize their expression in gills and determine whether their expression is altered by environmental salinity or hypercapnia. Degenerate primers and RT-PCR were used to deduce partial sequences of mammalian NHE2 and NHE3 homologs from the gills of the euryhaline Atlantic stingray (Dasyatis sabina). Real-time PCR was then used to demonstrate that mRNA expression of the NHE3 homolog increased when stingrays were transferred to low salinities but not during hypercapnia. Expression of the NHE2 homolog did not change with either treatment. Rapid amplification of cDNA was then used to deduce the complete sequence of a putative NHE3. The 2,744-base pair cDNA includes a coding region for a 2,511-amino acid protein that is 70% identical to human NHE3 (SLC9A3). Antisera generated against the carboxyl tail of the putative stingray NHE3 labeled the apical membranes of Na+/K+-ATPase-rich epithelial cells, and acclimation to freshwater caused a redistribution of labeling in the gills. This study provides the first NHE3 cloned from an elasmobranch and is the first to demonstrate an increase in gill NHE3 expression during acclimation to low salinities, suggesting that NHE3 can absorb Na+ from ion-poor environments.

Amino Acid Sequence↗
PubMed1996

Response of cell volume in Mytilus gill to acute salinity change.

The response of gill cell volume in Mytilus californianus and Mytilus trossolus (=edulis) to acute changes in salinity was assessed using three independent indicators: optical measurement of lateral cell height, measurement of intracellular water content using radiolabeled tracers and measurement of the contents of the major osmolytes of the gills. Optical measurements indicated significant variation in the response of individual lateral cells of M. californianus to acute low-salinity shock. Lateral cell height increased by approximately 20% shortly after abrupt exposure to 60% artificial sea water (ASW). Following this initial swelling, we estimate that a substantial regulatory volume decrease (RVD) was present in 25% of the trials. More commonly, however, an RVD was either absent or minimal: cell height remained elevated for at least 1 h, then returned to the control height when gills were re-exposed to 100% ASW. Changes in the combined water space of all cells in the gill, measured as the difference between total water space and extracellular space ([14C]polyethylene glycol space), indicated that cell volume regulation in the gill as an organ was also absent or minimal. Cell water space was 2.16 ml g-1 dry mass in isolated gills of M. californianus acclimated to 100% sea water in the laboratory and increased to 2.83 ml g-1 dry mass after a 6 min exposure to 60% ASW. Cell water space was still 2.81 ml g-1 dry mass after 1 h in 60% ASW and returned to 2.06 ml g-1 dry mass upon re-exposure to 100% ASW. Consistent with these observations, the gill contents of the principal cytoplasmic osmolytes (taurine, betaine and K+) were unchanged (approximately 450, 250 and 230 mu mol g-1 dry mass, respectively) following exposure of gills from 100% ASW-acclimated mussels to 60% ASW. A decrease in cell water space to 2.66 ml g-1 dry mass after 4 weeks of acclimation to 60% ASW corresponded with a 37% decrease in betaine content; taurine and K+ contents were unchanged. The changes in water space and solute content of gills from freshly collected M. californianus and M. trossolus were also consistent with the absence of volume regulation; cell water space remained elevated for at least 1 h after low-salinity exposure, and solute contents were unchanged after this period. We calculated the potential energetic cost of cell volume regulation for mussels exposed to 12 h of sinusoidal fluctuations between 100% and 50% sea water; solute uptake for full volume regulation in all tissues would cost a minimum of approximately 30% of the standard metabolic rate during the period of salinity increase. The routine absence of substantial cell volume regulation in Mytilus gill may reflect the potentially high energetic cost of volume regulation in the face of the large and frequent salinity fluctuations that are regularly encountered by estuarine bivalves.

Animals↗
PubMed1982

Effect of temperature and salinity on Vibrio (Beneckea) vulnificus occurrence in a Gulf Coast environment.

Vibrio (Beneckea) vulnificus is a recently recognized halophilic organism that may cause serious human infections. Patients infected with V. vulnificus often have a history of exposure to the sea, suggesting that the organism may be a common inhabitant of marine environments. Twenty-one inshore sites around Galveston Island in the Gulf of Mexico were cultured for V. vulnificus over a 12-month period. The organism was recovered from all but one of the sites at some time during the study. It was frequently isolated during the summer and fall from environments of relatively low salinity (7 to 16%). V. vulnificus was rarely isolated from any of the sites during the winter months, when water temperatures dropped below 20 degrees C. In vitro growth characteristics of environmental isolates of V. vulnificus demonstrated salinity optima of 1.0 to 2.0% NaCl and a temperature optimum of 37 degrees C. These growth characteristics may account for the seasonal and geographical variations in occurrence of the organism. Overall, the results of these studies indicate that V. vulnificus is commonly found in Gulf Coast environments and that the occurrence of the organism is favored by warm temperatures and relatively low salinity.

Humans↗
PubMed1998

Modelling the chemical speciation of trace metals in the surface waters of the Humber system

Calculations have been performed to estimate the chemical speciation at equilibrium of six divalent trace metals (Co, Ni, Cu, Zn, Cd, Pb) in riverine, estuarine and marine surface waters of the Humber system. The Windermere Humic Aqueous Model (WHAM) was used to compute distributions of dissolved metals. In the rivers, the free aquo ion (M2+) is a major part of dissolved Co, Ni, Zn and Cd, but accounts for less than 1% of Cu and Pb. The main complexes are formed with carbonate ligands and dissolved natural organic matter, represented by fulvic acid. In the low-salinity region of the estuary and in seawater, complexation with fulvic acid is less significant, although most of the Cu is still in this form, while the speciation of Cd is dominated by chloride complexes. Adsorption of metals by suspended particulate matter was calculated with a simple model involving the concentrations of the free aquo ions (M2+) and H+, together with a constant for each metal estimated from laboratory adsorption data. Calculated adsorbed concentrations were used to predict the partition coefficient (KD) for each metal under different circumstances. The values can vary by an order of magnitude or more, depending upon solution conditions. Typical values for rivers, low-salinity water and seawater are within one order of magnitude of observations. However, there is a general tendency to underestimate KD, possible reasons being (1) neglect of electrostatic enhancement of adsorption at low ionic strengths; and (2) analytical overestimation of particulate metal in equilibrium with the solution phase. There is a strong case for the development of a more sophisticated adsorption model.

Journal Article↗
PubMed2004

Effect of three-body interactions on the phase behavior of charge-stabilized colloidal suspensions.

We study numerically the effect of attractive triplet interactions on the phase behavior of suspensions of highly charged colloidal particles at low salinity. In our computer simulations, we employ the pair and triplet potentials that were obtained from a numerical Poisson-Boltzmann study [Phys. Rev. E 66, 011402 (2002)]]. On the basis of free energy calculations, we determine the phase diagram of an aqueous suspension of identical spheres of diameter sigma=32 nm and charge Z=80 as a function of colloid concentration and salinity, both for the purely pairwise additive system and for the system with pair and triplet interactions. The main effect of including the triplet interactions is a destabilization of the body-centered-cubic (bcc) crystal phase in favor of the face-centered-cubic (fcc) crystal phase. As a consequence the phase diagram features the coexistence of a rather dilute fluid with an almost-close-packed fcc phase at low salinity and bcc-fcc coexistence with a big density jump at intermediate salinity. The triplet attractions do not affect the phase behavior at sufficiently high salinity; under these conditions the system is well described by the pairwise potential.

Journal Article↗