Rapid Changes In Salinity Research Articles

Rapid decreases in salinity, but not increases, lead to immune dysregulation in Nile tilapia, Oreochromis niloticus (L.)

Rapid changes in salinity, as with other environmental stressors, can have detrimental effects on fish and may trigger increased susceptibility to disease. However, the precise mechanisms of these effects are not well understood. We examined the effects of sudden increases or decreases in salinity on teleost immune function using Nile tilapia, Oreochromis niloticus (L.), as the fish model in a battery of bioassays of increasing immune system specificity. Two different salinity experiments were performed: one of increasing salinity (0 to 5, 10 and 20gL(-1) ) and one of decreasing salinity (20 to 15, 10 and 5 gL(-1) ). Histopathology of anterior kidney, gills, gonads, intestines and liver of exposed fish was performed, but no remarkable lesions were found that were attributable to the salinity treatment regimes. The spleen was removed from each fish for analysis of cytokine expression, and peripheral blood was used for haematology, cortisol and phagocytosis assays. In the increasing salinity experiments, no significant changes were observed in any immune system assays. However, in the decreasing salinity experiments, lymphopenia, neutrophilia and monocytosis were observed in the peripheral blood without modification of the packed cell volume, plasma protein or plasma cortisol levels. Phagocytosis was increased in response to decreases in salinity from 20gL(-1) to 15gL(-1) , 10gL(-1) and 5gL(-1) , whereas phagocytic index was not significantly altered. Transforming growth factor-β (TGF-β) transcription increased during the same decreases in salinity. However, the TGF-β value at 5gL(-1) was less than those in the 15 and 10gL(-1) salinity treatments. Interleukin-1β (IL-1β) transcription did not significantly respond to either salinity regime. In total, acute salinity changes appeared to trigger reactive dysregulation of the immune response in tilapia, a situation which, when combined with additional co-occurring stressors such as sudden changes in temperature and/or dissolved oxygen, could make fish more susceptible to infectious diseases. Accordingly, these findings may help to explain how sudden environmental changes may initiate disease outbreaks and lead to critical declines in cultured or wild fish populations.

Prediction on Water Quality of Point-Source Pollution for Lunchoo River, Malaysia Rafidah Shahperi Department of Environmental Engineering, Faculty of Civil Engineering Universiti Teknologi Malaysia, Johor Bahru 81310, Malaysia Tel: 60-075-531-530 E-ma

The growth in urbanization, industrialization and irrigated agriculture are imposing growing demands and pressure on water resources. As a case in point, Lunchoo River, Malaysia was considered on of the contributing factor to water quality deterioration with regional consequences on the aquatic ecosystem. Moreover, it also deemed to affect the health of the downstream sub-basin user group. Influenced by tidal, restricted exchange between estuaries and the open sea allows rapid change in salinity, temperature, nutrients and sediment load. Therefore, a balance is vital between development and a good quality of life. In the present study, limitation on point source pollutant and low flow conditions are investigated. An understanding of the existing river and waste stream characteristic is necessary to determine the background level of pollutant. In addition, output generated from this study is an important key towards an optimal management of water resources. Results showed that in making prediction of water quality for Lunchoo River, it is essential to characterize the volume and properties of the river and wastewater stream. Moreover, both hydraulic and constituent flow rate fluctuated greatly in most part of the experimental field.

Effects of salinity on reproduction and survival of the calanoid copepod Pseudodiaptomus pelagicus

Four experiments were conducted on the calanoid copepod, Pseudodiaptomus pelagicus, to determine the effects of salinity on survival, development time, reproductive output, and population growth in order to define the optimal salinity for culture. To determine the appropriate experimental salinity range we exposed nauplii and adults to abrupt salinity changes from 35 g/L to 5, 10, 15, 35, 42, and 48 g/L at 30 °C and determined survival after 24 hours. The second experiment stocked early stage nauplii into 1 L beakers after which they were cultured using standard procedures for 10 days at six salinities (10, 15, 20, 25, 30, 35 g/L); from this survival, sex ratio, time to maturation, and fecundity were measured. The third experiment evaluated the effects of salinity on brood size, brood interval, and nauplii production by stocking individual adult pairs and monitoring nauplii production daily for 10 days. The fourth experiment determined the effects of salinity on population growth and composition of the population produced by stocking 10 adult pairs and culturing them until five days after the first mature adults were observed. Results from the abrupt salinity change experiment showed nauplii survival decreased following abrupt changes in salinity from 35 g/L to < 15 g/L and > 35 g/L. Additionally, adults do not tolerate rapid changes in salinity from 35 g/L to < 15 g/L but are rather tolerant of changes in salinity up to 48 g/L. Survival from early nauplii to adult was not significantly affected by salinity but survival declined at 35 g/L. Time to first maturation and maturation of the entire population was significantly influenced by salinity and took from 6.3 to 9.5 days. In the individual paired adults experiment, salinity significantly affected nauplii production by affecting brood interval and brood size. The percentage of ovigerous females peaked at 20 g/L and declined at salinities above and below this value. When developing production objectives, aquaculturists must consider salinity because of its numerous effects on the culture of P. pelagicus. The optimal salinity range to achieve high survival and the greatest nauplii production is 15–25 g/L.

Effects of salinity and anatomical hook location on the mortality and physiological response of angled‐and‐released sand whiting Sillago ciliata

Three experiments were done with sand whiting Sillago ciliata: the first two assessed the short-term mortality and physiological response of individuals after being mouth hooked and then subjected to rapid changes in salinity, while the third experiment investigated their longer-term fate after ingesting hooks (independent of salinity changes). In experiment one, 48 tanks containing a single S. ciliata were randomly assigned as either one of three treatments or a control. The fish in treatments one and two were exposed to salinity changes during their angling and subsequent release while those in treatment three were only subjected to angling and air exposure. Control fish remained untouched. Fish were then monitored for up to 6 days for mortalities before blood samples were taken to determine concentrations of plasma cortisol and glucose. Blood samples were also taken from five wild-caught fish to provide baseline estimates of the above variables. None of the treatment or control fish died over the 6 days, and there were no significant differences in blood cortisol or glucose between treatment, control and wild fish. In experiment two, 102 S. ciliata and 52 experimental tanks were used. The treatments were repeated as above, however, six individuals from each treatment and control group were removed and sampled for blood (and then glucose and cortisol) at 0, 24, 48 and 72 h post release. Some changes in behaviour due to the salinity changes occurred as well as a significant main effect of time for cortisol, with all fish having significantly elevated acute stress at the first sample time. In experiment three, 52 S. ciliata were placed into individual tanks. Twenty-six of these fish were allowed to ingest baited J-hooks, played for 60 s, removed from their tanks, and then released after their lines were cut (50 mm from their mouths). Control fish were not touched. All fish were then monitored over 21 days. Six of the treatment fish died (between 3 h and 14 days), while the remaining hooked fish resumed feeding within 5 days and 25% ejected their hooks (between 1 and 19 days). It was concluded that (1) salinity and mouth hooking had few independent or interactive effects on the mortality or physiological response of angled-and-released S. ciliata and (2) while hook ingestion caused some mortalities, the protracted physiological effects were limited, with all surviving fish resuming feeding and some eventually ejecting their hooks.

Changes in the immune response and metabolic fingerprint of the mussel, Mytilus edulis (Linnaeus) in response to lowered salinity and physical stress

Mussels, such as Mytilus edulis, are common keystone species on open coasts and in estuaries and are frequently used in environmental monitoring programmes. Mussels experience a wide range of environmental conditions at these locations, including rapid changes in salinity and physical disturbance (both natural and from aquaculture practices). This paper addressed the hypothesis that reduced salinity will lower mussel blood immune function and influence mussel blood metabolic responses, and that this will in turn increase the susceptibility of mussels to other stresses such as physical disturbance. To test these hypotheses, experiments were conducted in controlled laboratory tank conditions and mussel blood was analysed using a combination of metabolic fingerprinting with FT-IR and immunological assay techniques. Reducing seawater salinity to half that of normal caused a significant reduction in several measures of immune function, including the concentration of haemocytes, percentage of eosinophilic haemocytes and phagocytosis. Mechanical shaking of mussels for 10 min caused a reduction in the level of respiratory burst activity. However, there was no evidence of additive or interactive effects of lowered salinity with shaking on the immune response. Analysis of mussel blood metabolic fingerprints revealed differences in response to half salinity ( vs. full salinity) but there were no detectable effects of shaking. Increasing frequency and magnitude of flood events at coastal sites due to climate change could lead to longer, and more frequent, periods of reduced salinity. The potential impact on the immune function of this keystone species within or near estuaries could have knock-on effects on the wider ecosystem including altered nutrient cycling, changes in biodiversity and aquaculture production.

급격한 염분변화에 따른 담수어 3종의 프로락틴 및 성장호르몬 유전자 발현변화

The changes in osmolality and the gene expression profiles of prolactin (PRL) and growth hormone (GH) with rapid changes in salinity were compared in the eel (Anguilla japonica), crucian carp (Carassius carassius), and masu salmon (Oncorhynchus masou). Fish stocked in freshwater (FW) were abruptly transferred to experimental tanks containing FW, 50% seawater (50% SW), or 100% SW (SW). Blood samples and pituitary glands were collected 2 and 24 hrs after the exposure. No mortality was observed in SW eel (n=6), whereas all of the crucian carp (n=6) and two masu salmon (n=6) exposed to SW died after land 24 hrs, respectively. The PRL mRNA levels of the eel and masu salmon decreased in 50% SW and SW compared to those of the fish kept in FW after 24 hrs, whereas the PRL levels of crucian carp were higher in 50% SW than in FW. Unlike the PRL mRNA levels, the GH mRNA levels of the eel did not differ significantly among three different salinities, while the GH mRNA levels of crucian carp and masu salmon increased significantly in 50% SW and SW after 24 hrs. The serum osmolalities increased marginally in the eel and masu salmon in 50% SW at 24 hrs (19% and 9%, respectively), whereas those of crucian carp increased abruptly in 50% SW (50% increase). These results suggest that the synthesis of PRL and GH is important in relation to the osmoregulatory system with environmental changes in salinity.

Adaptation as a potential response to sea-level rise: a genetic basis for salinity tolerance in populations of a coastal marsh fish.

Relative sea-level rise is resulting in the intrusion of saline waters into marshes historically dominated by fresh water. Saltwater intrusions can potentially affect resident marsh species, especially when storm-related tidal surges cause rapid changes in salinity. We examined the role of historical salinity exposure on the survival of Gambusia affinis from two locations in coastal Louisiana. At each location, we sampled fish populations from fresh, intermediate and brackish marshes. Individuals were then exposed to a salinity of 25‰ and survival time was measured. We found that fish from brackish and intermediate marshes had an increased tolerance to salinity stress relative to fish from freshwater environments. We then tested the descendents of fish from the fresh and brackish marshes, reared for two generation in fresh water, to determine if there was a genetic basis for differential survival. We found that descendents of individuals from brackish marshes showed elevated survivals relative to the descendents of fish with no historical exposure to salinity. The most reasonable mechanism to account for the differences in survival relative to historical exposure is genetic adaptation, suggesting that natural selection may play a role in the responses of resident marsh fishes to future increases in salinity.

Temporal and spatial variations in nutrient stoichiometry and regulation of phytoplankton biomass in Hong Kong waters: Influence of the Pearl River outflow and sewage inputs

In 2001, the Hong Kong government implemented the Harbor Area Treatment Scheme (HATS) under which 70% of the sewage that had been formerly discharged into Victoria Harbor is now collected and sent to Stonecutters Island Sewage Works where it receives chemically enhanced primary treatment (CEPT), and is then discharged into waters west of the Harbor. The relocation of the sewage discharge will possibly change the nutrient dynamics and phytoplankton biomass in this area. Therefore, there is a need to examine the factors that regulate phytoplankton growth in Hong Kong waters in order to understand future impacts. Based on a historic nutrient data set (1986–2001), a comparison of ambient nutrient ratios with the Redfield ratio (N:P:Si = 16:1:16) showed clear spatial variations in the factors that regulate phytoplankton biomass along a west (estuary) to east (coastal/oceanic) transect through Hong Kong waters. Algal biomass was constrained by a combination of low light conditions, a rapid change in salinity, and strong turbulent mixing in western waters throughout the year. Potential stoichiometric Si limitation (up to 94% of the cases in winter) occurred in Victoria Harbor due to the contribution of sewage effluent with high N and P enrichment all year, except for summer when the frequency of stoichiometric Si limitation (48%) was the same as P, owing to the influence of the high Si in the Pearl River discharge. In the eastern waters, potential N limitation and N and P co-limitation occurred in autumn and winter respectively, because of the dominance of coastal/oceanic water with low nutrients and low N:P ratios. In contrast, potential Si limitation occurred in spring and a switch to potential N, P and Si limitation occurred in eastern waters in summer. In southern waters, there was a shift from P limitation (80%) in summer due to the influence of the N-rich Pearl River discharge, to N limitation (68%) in autumn, and to N and P co-limitation in winter due to the dominance of N-poor oceanic water from the oligotrophic South China Sea. Our results show clear temporal and spatial variations in the nutrient stoichiometry which indicates potential regulation of phytoplankton biomass in HK waters due to the combination of the seasonal exchange of the Pearl River discharge and oceanic water, sewage effluent inputs, and strong hydrodynamic mixing from SW monsoon winds in summer and the NE monsoon winds in winter.

How does salinity tolerance influence the distributions of Brachionus plicatilis sibling species?

Environmental salinity is important in defining Brachionus plicatilis sibling species distributions. However, while salinity influences distributions, sibling species often co-exist. Three different mechanisms potentially account for the partial co-occurrence of sibling species: (1) siblings have differing salinity tolerances that partially overlap; (2) siblings physiological tolerances may be commonly broad, but relatively small differences in tolerances differentiate distributions via interactions e.g. competition; or (3) siblings distributions may be influenced by physical factors other than salinity. Here, we assess the extent of salinity tolerance in three B. plicatilis sibling species (B. plicatilis 6TUR, B. plicatilis IOM and B. rotundiformis 6TOS) by measuring population growth rate (μ, day−1) and egg development time in response to salinity (5–60‰) and salinity fluctuations (≤ Δ40‰). Sibling species were identified by analysis of the mitochondrial COI gene, and salinity responses were compared by regression analysis. Responses differed significantly between siblings, although the broad trends were similar. Positive growth occurred at all salinities, and highest growth rates ranged between 0.93 and 1.08 day−1 at 16–18‰. Rapid changes in salinity reduced growth rates, but net mortality occurred only in one treatment (100% mortality on transfer from 10 to 40‰). Egg development time was largely invariant with salinity except for B. plicatilis IOM and where rotifers were transferred from 30 to 60‰. We indicate that several siblings are similarly euryhaline and tolerate salinity fluctuations. Undoubtedly, wide tolerances in B. plicatilis are adaptations to ephemeral and seasonally variable habitats. Given common broad salinity tolerances, it is unlikely that the differential distributions of sibling species are a direct result of physiological constraints. Instead, we illustrate using a simple model that subtle differences in physiological tolerances may have important impacts on interactions between sibling species, which may in turn influence distributions.

Foraminiferal responses to polluted sediments in the Montevideo coastal zone, Uruguay

A study of foraminiferal assemblages was carried out in 24 sediment samples collected from the Montevideo coastal zone (south-eastern coastal region of South America) to assess the response of the benthic foraminifera to the polluted sediments. The area is affected by different pollutants such as sewage, hydrocarbons and heavy metals derived from different sources. Biological data were analyzed with multivariate techniques of cluster analysis and a principal component analysis (PCA) was performed for abiotic factors. The results allowed the recognition of different species assemblages corresponding to different sub-environments, which reflected the prevalent ecological conditions. The Montevideo Bay, particularly, its inner part showed an extremely poor foraminiferal fauna—including a totally azoic station—and high percentages of abnormal tests, when compared with the adjacent Punta Carretas and Punta Yeguas zones. Mean faunal density showed a strong relationship with organic matter, oxygen and heavy metal concentrations, as well as redox potential and pH values of each sub-environment. Although the adjacent zones presented a moderate pollution degree, it was noticed that a positive effect on the foraminiferal density specially on Ammonia tepida, caused by the sewage pipe located in Punta Carretas, a pure organic contamination. Differences among foraminiferal assemblages seemed to be related to the combined action of the several kinds of pollutants and the natural abiotic variables, like the rapid salinity changes that occurred in this area.

Palygorskite in the uppermost Cretaceous–Eocene rocks from Marrakech High Atlas, Morocco

Uppermost Cretaceous–Eocene series of the Marrakech High Atlas consist of alternations of marl, dolomite, limestone, gypsum and phosphatic beds. The rocks were deposited in a shallow, coastal marginal basin characterised by rapid changes in salinity. Palygorskite occurs as interwoven fibrous mats forming fine laminae and as coatings and pore-filling, and pore-bridging cements in dolomitic marls. This textural evidence suggests a direct chemical precipitation, mostly post-dating dolomitization. A magnesium concentration in presence of dolomite was sufficient for palygorskite precipitation; the necessary Si and Al were derived by dissolution of silicates under alkaline conditions. The maximum development of palygorskite was near the top of the upper sedimentary system, which was deposited during a marine transgression.

The Holocene evolution and palaeosalinity history of Beall Lake, Windmill Islands (East Antarctica) using an expanded diatom-based weighted averaging model

A mid-Holocene climate optimum is inferred from a palaeosalinity reconstruction of a closed saline lake (Beall Lake) from the Windmill Islands, East Antarctica using an expanded diatom salinity weighted averaging (WA) regression and calibration model.The addition of 14 lakes and ponds from the Windmill Islands, East Antarctica, to an existing weighted averaging regression and calibration palaeosalinity model of 33 lakes from the Vestfold Hills, East Antarctica expands the number of taxa and lakes and the range of salinity in the existing model and improves the model's predictive ability. This improved model was used to infer Holocene changes in lake water salinity in Beall Lake, Windmill Islands.Six changes in diatom-inferred salinity in Beall Lake are put into broad chronological context based on three radiocarbon dates: as the East Antarctic Ice Sheet (EAIS) retreated from the Windmill Islands during the early Holocene (∼9000–8130 corr. yr BP), Beall Lake formed as a melt water-fed freshwater lake, which gradually became more saline as marine influence increased from ∼8000 corr. yr BP. Between ∼8000 and 4800 corr. yr BP, the diatom assemblage included planktonic marine taxa such as Chaetoceros spp. and cryophilic taxa such as Fragilariopsis cylindrus, which indicate favourable summer growth conditions. A mid-Holocene warm period produced a climate that was warmer and more humid with increased precipitation and snow accumulation. This is reflected in the Beall Lake core as a reduction in the salinity of the lake diatom assemblage from ∼4800–4600 corr. yr BP. Holocene isostatic uplift rates in the Windmill Islands vary from 5–6 m/1000 yr. By applying this uplift rate, it is calculated that the bedrock would have risen above sea level by ∼4000 yr BP.The Beall Lake core diatom assemblage from ∼4600–2900 corr. yr BP includes both marine cryophilic and planktonic taxa together with freshwater benthic and planktonic lacustrine taxa. This mix of species indicates the emergence of the lake from the sea around ∼4600 corr. yr BP. From ∼2800 corr. yr BP, retreat of the ice margin led to increasing melt water inputs and associated freshening of the lake basin until ∼1900 corr. yr BP. The lake basin had no oceanic influence by this time, allowing a terrestrial freshwater flora to establish and thrive for the next ∼1000 yr.At ∼1850 corr. yr BP, a sudden and rapid salinity change is evident in Beall Lake. A late Holocene warm period between 2000 and 1000 yr BP has been observed in ice core records from Law Dome (an ice cap abutting the Windmill Islands to the east and north). It is therefore inferred that, at ∼1850 corr. yr BP, summer temperatures within the Beall Lake catchment area were much higher than present summer temperatures.The climate optimum identified in the Beall Lake core ∼4800 yr BP confirms mid-Holocene warming of the Windmill Islands and suggests a synchronous mid-Holocene climate optimum occurred across coastal East Antarctica. In addition, the abrupt climate change inferred at ∼1850 yr BP suggests that higher resolution sampling of sediment cores from coastal East Antarctic limnological oases will provide more evidence of rapid climate change events over coastal East Antarctica in future.

The effects of rapid salinity change on in vivo arginine kinase flux in the juvenile blue crab, Callinectes sapidus

The effect of acclimation salinity and salinity changes on the concentration of high-energy phosphate metabolites and arginine kinase (AK) flux was examined in vivo in juvenile blue crabs using 31P-nuclear magnetic resonance (NMR). Crabs were acclimated for 7 days to a salinity of 5 or 35‰ and then placed in a flow apparatus that could sustain the animals while NMR spectra were acquired. Crabs were subjected to either hyperosmotic salinity changes, where an animal acclimated to 5‰ was exposed to a salinity of 35‰, or hyposmotic changes, which involved the reciprocal exchange. Neither acclimation salinity nor salinity change had a significant effect on the concentrations of arginine phosphate, inorganic phosphate or ATP. 31P-NMR saturation transfer experiments were used to determine the effect of salinity on the forward and reverse flux of the AK reaction. There was no significant effect of acclimation salinity or salinity change on the flux rate through this reaction. This is in contrast to previous results, which showed that AK flux in isolated muscle was sensitive to prevailing osmotic conditions (Holt and Kinsey, J. Exp. Biol. 205 (2002) 1775–1785). The present study indicates that the integrated osmoregulatory capacity of the intact animal is sufficient to preserve cellular energy status and enzyme function during acute salinity changes.

New aspects of migratory behavior of phytoplankton in stratified waters: Effects of halocline strength and light on Tetraselmis sp. (Prasinophyceae) in an artificial water column

There is very little information in the literature about how phytoplankton flagellates respond to rapid changes in salinity (e.g., haloclines of different strength). Here we present such data obtained from experiments with Tetraselmis sp. (Prasinophyceae) in a specially designed artificial water column. The experiments were performed with surface salinities varying from 27.4 to 33.4‰, whereas bottom salinities were essentially constant (34.0–34.6‰). Cells were introduced near the bottom. The first stage of the ascent was an accumulation of cells in the lower part of the halocline. The second was a transit to the upper part of the halocline after a variable time lag, and the third stage was a further ascent to the surface layer, again after a variable time lag. Our results reveal a strong positive phototaxis of the swimming cells under continuous surface irradiances in the range 17–144 µmol quanta m−2 s−1. Maximum swimming speeds were found to be 0.9 m h−1. Increasing halocline strength (△S = 0.7, 3.0, and 6.6‰), resulted in reduced swimming activity, but the cells managed to pass through after an adaptation period. Under a 14 : 10 light : dark (LD) cycle, the cell concentrations of the bottom layer decreased gradually for each cycle, and cells accumulated in the surface layer during the light period. During the dark period, cell concentrations were also increasing in the halocline for each cycle. A downward migration started about 2 h before the light period ended and was slower than the ascent of cells from the halocline. It therefore seems that positive phototaxis was stronger than the positive geotaxis as a driving force of cell motility. We conclude that strong haloclines can prevent phytoplankton flagellates in the surface layer from reaching the nutrient‐rich deeper layer during the night and therefore play an important regulating role in the bloom dynamics of phytoplankton.

Control of Phosphate Concentration through Adsorption and Desorption Processes in Groundwater and Seawater Mixing at Sandy Beaches in Tokyo Bay, Japan

Field observation was conducted to monitor phosphate concentrations in groundwater and seawater mixing at two sandy beaches in Futtsu and Miura in Tokyo Bay, Japan. Dissolved phosphate concentrations were measured along transects from fresh groundwater aquifer to seawater adjacent the beaches. The concentrations were often high (up to 46 µM) in fresh groundwater samples (Cl− < 0.2‰). Coastal seawater, on the other hand, exhibited low phosphate concentrations (1.5 µM or less). Along the transects, phosphate generally displayed non-conservative behavior during mixing of fresh and saline waters in the aquifer; concentrations as high as 100 µM were found around the upper limit of seawater intrusion (Cl− = ∼2‰). Laboratory experiments were executed to identify the processes that control the phosphate behavior in the mixing processes. The results revealed that adsorption-desorption processes by the aquifer sand particles could significantly control the phosphate concentrations in the groundwater. Furthermore, the adsorption and/or desorption was found to be a function of salinity; the equilibrium concentration of dissolved phosphate in slurry of sand and water was the highest in freshwater and decreased considerably in saline water. The extreme concentration of phosphate may be caused by release from sand particles coinciding with the rapid change in salinity with tide.

Effects of Rapid Changes in Salinity and Temperature on the Elemental Composition of Sagittal Otoliths Taken from the Juvenile Japanese Flounder

Effects of Rapid Changes in Salinity and Temperature on the Elemental Composition of Sagittal Otoliths Taken from the Juvenile Japanese Flounder

Applicability of measurements of thermo-saline environment on/in sand bar by buried data-loggers to observation of disintegration process of sand bar due to flood flow

Field observation of heat and salinity on/in sand bar by using buried data-loggers was carried out in the Yasaka river mouth in Oita Prefecture in order to obtain environmental data of spawning ground of horseshoe crab Tachypleus tridentatus. Temporal changes in salinity and temperature on the surface and 15cm below the ground level have been measured at 20 minutes intervals since July, 1997. During the observation, large flood occurred on September 16 due to heavy rainfall of Typhoon 9719 and sand bar was partly eroded out due to flood flow. During this flood rapid decrease in underground temperature as well as rapid change in salinity was measured due to the exposure of the apparatus to the surface. Exact erosion time was observed, implying that this method can be applied to the observation of disintegration process of river mouth bar due to flood flow.

Haemolymph and mantle fluid ammonia and ninhydrin positive substances variations in salinity-challenged mussels ( Mytilus edulis L.)

Ambient salinity change-induced variability of ammonia efflux rates, concentrations of ninhydrin positive substances (NPS) and dissolved ammonia (DA) in the haemolymph and mantle cavity fluid of Mytilus edulis were examined. Hypo-osmotic challenges evoked rapid (< 1 h) increases of DA efflux rates, to levels which persisted for the 4 h exposure period, and concomitant increases in haemolymph and mantle fluid NPS and DA levels. Exposure to hyper-osmotic media induced decreased DA efflux rates (cf. normal seawater levels in all cases). Such results suggest that intertidal M. edulis, which may normally experience rapid salinity changes, can make rapid adjustments to such osmotic stresses. Haemolymph hypoglycaemia (cf. control group) accompanied all salinity changes which suggests increased glucose utilisation occurs during the initial adjustments to external media salinity changes.

What Can Stable Isotopes Say about Salinity? An Example from the Late Miocene Pannonian Lake

The mid-to late Miocene Lake was a primarily closed, saline lake which during its lifetime underwent a series of rapid salinity changes associated with faunal extinctions/radiations. The first two of these, at the Badenian/Sarmatian and Sarmatian/Pannonian boundaries signify the transition from a marine basin to a brackish lake and are marked by major faunal changes. The isotopic composition of molluscs from the lake, however, does not undergo major changes. The third transition, at the end of the Pannonian and into the Pontian, is also marked by major faunal changes, thought initially to reflect further freshening of the lake. Both carbon and oxygen isotope ratios of lake molluscs decrease by 4 to 6%oo at this transition. A consideration of salinity and oxygen isotope mass balances for a closed or nearly-closed lake shows that major changes in salinity accompany relatively minor changes in water balance and isotopic composition. This result explains why the oxygen isotope ratio of lake waters did not change during the initial freshening of the lake and suggests that the major isotopic changes observed later are not directly related to changes in the lake water balance which caused the salinity changes. The isotopic variations were driven mainly by other climatic factors, most likely changes in humidity and isotopic composition of inflow.

Influence of rapid changes in salinity and temperature on the mobility of the rotifer Brachionus plicatilis

Influence of rapid changes in salinity and temperature on the mobility of the rotifer Brachionus plicatilis