Effects Of Salinity Variations Research Articles

Effect of Salinity Variation on the Survival Rate of Amphiprion ocellaris (Common Clownfish)

This study investigates the impact of changes in salinity on the survival rate of Amphiprion ocellaris, commonly known as the Common Clownfish. The aim is to ascertain the minimum salinity threshold that clownfish can tolerate, thereby offering valuable insights for professionals and researchers in the field of ornamental fish. This study utilized ten fully-grown clownfish, all of which were over one year old and had an average length of 38 mm and weight of 1.50 g. Every fish was placed in a carefully regulated tank where the salinity was systematically reduced by around 3 parts per thousand (ppt) every week, beginning from an initial salinity of 32.42 ppt. The weekly monitoring involved the assessment of water quality indices, including dissolved oxygen (DO), temperature, and pH. Clownfish exhibited indications of distress, such as reduced appetite and depigmentation, when exposed to a salinity of 8 parts per thousand (ppt). Death occurred when the salinity was decreased to 7 ppt, indicating their incapacity to survive below 10 ppt. These findings suggest that common clownfish are not appropriate for freshwater environments and necessitate specific salinity levels in order to flourish. These findings have practical consequences for the ornamental fish industry, underscoring the significance of maintaining suitable salt levels to avoid misinformation and financial setbacks. Additional investigation should focus on the possibility of raising clownfish in settings with reduced salinity to improve their ability to adapt and better aquaculture techniques.

Effect of salinity variation on intestinal microbiota of the Indian white shrimp Penaeus indicus H. Milne Edwards, 1837

The effects of salinity adaptation on gut microbiota of juvenile Indian white shrimp, Penaeus indicus H. Milne Edwards, 1837 was analysed in this experiment. Intestines of shrimps adapted to two different salinities were examined using 16S rRNA amplicon sequencing. At all salinity levels, the dominant phyla recorded were Proteobacteria followed by Bacteroidota and Fusobacteriota. However, as the salinity decreased, abundance of Proteobacteria increased while richness of Bacteroidota and Fusobacteriota decreased significantly. At genus level, salinity reduction increased the abundance of Vibrio and Photobacterium; while it decreased the abundance of Spongiimonas and Hypnocyclicus. The survival of animals in both the groups was not affected but the weight gain was less in low saline group (5 ppt). The results confirm the influence of salinity in rearing water on the intestinal microbiota of shrimp. Keywords: Aquaculture, Bacteroidota, Fusobacteriota, Hypnocyclicus, Proteobacteria, Salinity, Spongiimonas

Modeling the Impact of Salinity Variations on Aquatic Environments: Including Negative and Positive Effects in Life Cycle Assessment.

Salinity is changing in aquatic systems due to anthropogenic activities (like irrigation or dam management) and climate change. Although there are studies on the effects of salinity variations on individual species, little is known about the effects on overall ecosystems, these impacts being more uncertain in transitional waters such as estuaries or fiords. The few works that do address this topic have considered these impacts using ecotoxicity models. However, these models state that an increase in the concentration of a pollutant generates an increase in the impacts, disregarding the effects of water freshening. The present research work introduces a general framework to address the impacts of salinity variations, including emission-related positive effects. We validated this framework by applying it to an estuarine area in Galicia (northwestern Spain), where sharp drops in the salt concentration have caused mass mortalities of shellfish in recent decades. This research work addresses for the first time the potential effects on the environment derived from a decrease in the concentration of essential substances, where the effects of an emission can also generate positive impacts. Moreover, it is expected that the framework can also be applied to model the environmental impacts of other essential substances in life cycle assessment (LCA), such as metals and macronutrients.

Water and Otolith Chemistry: Implications for Discerning Estuarine Nursery Habitat Use of a Juvenile Flatfish

Variations in otolith elemental composition are widely used to reconstruct fish movements. However, reconstructing habitat use and environmental histories of fishes within estuaries is still a major challenge due to the dynamic nature of these coastal environments. In this study, we performed a laboratory experiment to investigate the effects of variations in salinity (3 levels; 5, 18, 30) and temperature (2 levels; 16oC, 21oC) in the otolith elemental composition (Mg:Ca, Mn:Ca, Sr:Ca, Ba:Ca) of juvenile Senegalese sole Solea senegalensis. Temperature and salinity treatments mirrored the natural conditions of the estuarine habitats generally occupied by juvenile Senegalese sole, thereby providing information on the applicability of otolith microchemistry to reconstruct habitat use patterns within estuarine nurseries, where individual fish move across complex salinity and temperature gradients. While Sr:Ca and Ba:Ca in otoliths were both positively related to salinity, no temperature effect was observed. Partition coefficients, proxies for element incorporation rates increased with increasing salinity for Sr (DSr) and Ba (DBa). In contrast, salinity and temperature had little influence on otolith Mn:Ca and Mg:Ca, supporting physiological control on the incorporation of these elements. Our results are a stepping stone for the interpretation of otolith chemical profiles for fish collected in their natural habitats and contribute to better understanding the processes involved in otolith element incorporation.

Long-term exposure to salinity variations induces protein carbonylation in the copepod Acartia tonsa

Salinity is a key variable influencing the life history of aquatic organisms. Environmental variability in salinity has been associated with increases in the formation of reactive species, ending up in a state of oxidative stress. In copepods, information about effects of salinity variations mostly includes data from short-term experiments where the effects of salinity changes are evaluated in terms of survival and vital rates, and data involving oxidative stress biomarkers are limited. Here, we experimentally evaluate the effects of long-term salinity variations in the estuarine copepod Acartia tonsa through the analysis of protein carbonylation, vital rates (egg production, EPR; ingestion, IR) and gross growth efficiency (GGE). Cultured copepods were subjected to alternate salinity increases and decreases between S = 10 and 20, in steps of 5 units every 12 h, during 15 days (Sv treatment). A control group (no salinity change) was subjected to the same manipulation but in a constant salinity condition (S = 15). Protein carbonylation was higher in females under the Sv treatment compared to control, whereas in males this was not observed. However, males presented significantly higher levels of protein carbonylation than females, irrespective of experimental condition. EPR was higher in control while IR was higher in Sv treatment, but differences were not significant. Instead, GGE showed clear cut and significant differences between Sv and control. While decreased GGE was indicative of significantly increased metabolic expenditures under variable salinity condition, higher oxidative damage was likely a side effect of increased metabolic demands and production of reactive oxygen species.

Seasonal-to-Interannual Response of Southern Ocean Mixed Layer Depth to the Southern Annular Mode from a Global 1/10° Ocean Model

Abstract The relationship between the southern annular mode (SAM) and Southern Ocean mixed layer depth (MLD) is investigated using a global 0.1° resolution ocean model. The SAM index is defined as the principal component time series of the leading empirical orthogonal function of extratropical sea level pressure from September to December, when the zonally symmetric SAM feature is most prominent. Following positive phases of the SAM, anomalous deep mixed layers occur in the subsequent fall season, starting in May, particularly in the southeast Pacific. Composite analyses reveal that for positive SAM phases enhanced surface cooling caused by anomalously strong westerlies weakens the stratification of the water column, leading to deeper mixed layers during spring when the SAM signal is at its strongest. During the subsequent summer, the surface warms and the mixed layer shoals. However, beneath the warm surface layer, anomalously weak stratification persists throughout the summer and into fall. When the surface cools again during fall, the mixed layer readily deepens due to this weak interior stratification, a legacy from the previous springtime conditions. Therefore, the spring SAM–fall MLD relationship is interpreted here as a manifestation of reemergence of interior water mass anomalies. The opposite occurs after negative phases of the SAM, with anomalously shallow mixed layers resulting. Additional analyses reveal that for the MLD region in the southeast Pacific, the effects of salinity variations and Ekman heat advection are negligible, although Ekman heat transport may play an important role in other regions where mode water is formed, such as south of Australia and in the Indian Ocean.

Analysis on the effect of salinity in underwater wireless optical communication

This article deals with the effect of salinity variation on underwater wireless optical communication (UWOC). Effect of different concentration of salt on underwater optical communication has been carried out experimentally in terms of received power at different link lengths. Based on the analysis of experimental data, a mathematical model has been proposed to describe the saline water channel. A simulation study is performed for different data rates and link lengths. It is seen that with increased salinity the attenuation is higher and the UWOC system performance degrades with higher data rate and increased link length.

Improvement of natural spawning of black flounder, Paralichthys orbignyanus (Valenciennes, 1839) by photothermal and salinity conditioning in recirculating aquaculture system

Black flounder (Paralichthys orbignyanus) is an important commercial and recreational species inhabiting marine and estuarine waters from Rio de Janeiro (Brazil) to San Matías Gulf (Argentina) from 1 to 30 m depth, with a great potential for aquaculture in coastal or internal brackish waters. It is an estuarine-dependent species whose adults reproduce in marine water during the spring and summer. Since 2003, the reproduction of flounder broodstock in a recirculating aquaculture system (RAS) subject to a photothermal period and constant salinity of 34 psu has been carried out at the National Institute for Fisheries Research and Development (INIDEP). Final maturation of broodfish was regularly achieved through the use of a photoperiod and water temperature regimen simulating natural seasonal changes over a 10-month period, reaching 19–20 °C and 16 h L:8 h D by February. These spawning events were unstable and unpredictable, with wide variations in quality and quantity of eggs. Control of the reproductive cycle and development of cultured broodstocks are basic requirements for a successful aquaculture industry. In order to acquire a more precise control of egg production, the effect of salinity variation upon the quantity and quality of spawning eggs of the flounder broodstock in a RAS during three reproductive seasons was evaluated. For that purpose, salinity was changed according to photoperiod and temperature variations along the year as: a) fall-winter, 16–12 °C, salinity 25–15 psu, natural photoperiod at low light intensity (10 lx), and b) spring-summer, 16–19 °C, salinity 15–34 psu, artificial photoperiod and mean light intensity (200 lx). The result of the present study indicated that the combination of photothermal and salinity regimes effectively extended reproductive activity in the broodstock tank and increased both the number of spawning events and the amount of eggs in relation to previous years. 2015–2016 and 2016–2017 reproductive seasons lasted for >150 days, reporting a total of 52 and 53 spawning events and reaching 14,289,661 and 17,593,888 eggs released, of which 37.8% and 32.5% were viable eggs, respectively. The 2017–2018 reproductive season lasted 106 days with 55 spawning events and 27,548,896 eggs released (61.0% viable eggs), reaching the greatest number of total eggs obtained in any season at INIDEP since 2003.

Effects of salinity variation on growth and yessotoxin composition in the marine dinoflagellate Lingulodinium polyedra from a Skagerrak fjord system (western Sweden)

The marine dinoflagellate Lingulodinium polyedra is a toxigenic species capable of forming high magnitude and occasionally harmful algal blooms (HABs), particularly in temperate coastal waters throughout the world. Three cultured isolates of L. polyedra from a fjord system on the Skagerrak coast of Sweden were analyzed for their growth characteristics and to determine the effects of a strong salinity gradient on toxin cell quotas and composition. The cell quota of yessotoxin (YTX) analogs, as determined by liquid chromatography coupled with tandem mass spectrometry (LC–MS/MS), ranged widely among strains. For two strains, the total toxin content remained constant over time in culture, but for the third strain, the YTX cell quota significantly decreased (by 32%) during stationary growth phase. The toxin profiles of the three strains differed markedly and none produced YTX. The analog 41a-homo-YTX (m/z 1155), its putative methylated derivative 9-Me-41a-homo-YTX (m/z 1169) and an unspecified keto-YTX (m/z 1047) were detected in strain LP29-10H, whereas strain LP30-7B contained nor-YTX (m/z 1101), and two unspecified YTX analogs at m/z 1159 and m/z 1061. The toxin profile of strain LP30-8D comprised two unspecified YTX analogs at m/z 1061 and m/z 991 and carboxy-YTX (m/z 1173). Strain LP30-7B cultured at multiple salinities (10, 16, 22, 28 and 34) did not tolerate the lowest salinity (10), but there was a statistically significant decrease (by 21%) in toxin cell quota between growth at the highest versus lower permissible salinities. The toxin profile for strain LP30-7B remained constant over time for a given salinity. At lower salinities, however, the proportion of the unspecified YTX analog (m/z 1061) was significantly higher, especially with respect to nor-YTX (m/z 1101). This study shows high intra-specific variability in yessotoxin composition among strains from the same geographical region and inconsistency in toxin cell quota under different environmental regimes and growth stages in culture. This variation has important implications for the kinetics of YTX production and food web transfer in natural bloom populations from diverse geographical regions.

Effect of salinity variation on the autotrophic kinetics of the start-up of a membrane bioreactor and hybrid moving bed biofilm reactor-membrane bioreactor at low hydraulic retention time

A membrane bioreactor (MBR) and a hybrid moving bed biofilm reactor-membrane bioreactor (hybrid MBBR-MBR) for municipal wastewater treatment were studied to determine the effect of salinity on nitrogen removal and autotrophic kinetics. The biological systems were analyzed during the start-up phase with a hydraulic retention time (HRT) of 6 h, total biomass concentration of 2,500 mg L-1 in the steady state, and electric conductivities of 1.05 mS cm-1 for MBR and hybrid MBBR-MBR working under regular salinity and conductivity variations of 1.2-6.5 mS cm-1 for MBR and hybrid MBBR-MBR operating at variable salinity. The variable salinity affected the autotrophic biomass, which caused a reduction of the nitrogen degradation rate, an increase of time to remove ammonium from municipal wastewater and longer duration of the start-up phase for the MBR and hybrid MBBR-MBR.

Effects of salinity variations on the rates of photosynthesis and respiration of the juvenile giant clam (Tridacna gigas, Bivalvia, Cardiidae)

ABSTRACTGiant clams are in symbiotic relationship with the photosynthesizing zooxanthellae and dwell in the shallow coral reefs of the Indo-Pacific region where they may be exposed to fluctuating salinities during high levels of precipitation. This study evaluated the effects of reduced salinities (18, 25, and 35‰ as control) on the rates of photosynthesis and respiration in juvenile Tridacna gigas for 14 days. At 18‰, total mortality was recorded after day 4, so no photosynthetic measurements were subsequently conducted for this treatment. However, results showed no significant differences in the photosynthetic rates among treatments. Respiration rates were significantly increased at both low salinities resulting in low Pg/R ratios. After 14 days of exposure, photosynthetic parameters at 25‰ were not significantly different from the control which suggests that juvenile T. gigas may be able to acclimate to osmotic stress and adjust its photophysiology following reductions in salinity of up to 25‰.

Effects of salinity variations on pore water flow in salt marshes

AbstractSpatial and temporal salinity variations in surface water and pore water commonly exist in salt marshes under the combined influence of tidal inundation, precipitation, evapotranspiration, and inland freshwater input. Laboratory experiments and numerical simulations were conducted to investigate how density gradients associated with salinity variations affect pore water flow in the salt marsh system. The results showed that upward salinity (density) gradients could lead to flow instability and the formation of salt fingers. These fingers, varying in size with the distance from the creek, modified significantly the pore water flow field, especially in the marsh interior. While the flow instability enhanced local salt transport and mixing considerably, the net effect was small, causing only a slight increase in the overall mass exchange across the marsh surface. In contrast, downward salinity gradients exerted less influence on the pore water flow in the marsh soil and slightly weakened the surface water and groundwater exchange across the marsh surface. Numerical simulations revealed similar density effects on pore water flow at the field scale under realistic conditions. These findings have important implications for studies of marsh soil conditions concerning plant growth as well as nutrient exchange between the marsh and coastal marine system.

Effect of Salinity Variation on the Quantity of Antioxidant Enzymes in Some Rice Cultivars of North Kerala, India

Rice (Oryza sativa L.) is one of the most popular and important cereal crops, providing the staple food for more than half of the world's population, especially those living in developing countries. Salinity is one of the prominent abiotic constraints for crop plants worldwide. It affects their growth, development, productivity and ultimately the yield. It also triggers a series of morphological, physiological, biochemical and molecular changes in plants. Various abiotic stresses lead to the overproduction of reactive oxygen species (ROS) in plants which are highly reactive and toxic and may cause severe damage to proteins, lipids, carbohydrates and DNA which ultimately results in oxidative stress. Plants possess very efficient enzymatic and non-enzymatic antioxidant defense systems which work together to control uncontrolled oxidation and protect plant cells from oxidative damage by the scavenging of ROS. The major antioxidant enzymes include catalase, peroxidase, super oxide dismutase, glutathione reductase, glutathione peroxidase, ascorbate peroxidase, etc. Production of antiaoxidant enzymes by some native rice genotypes collected both from saline and non-saline rice tracts of Kerala State of Inda was studied presently in relation to relative induction of salt stress. All the genotypes showed significant upregulation in the production of antioxidant enzymes in response to increase in salt stress applied.

Investigation of microbial adaptation to salinity variation for treatment of reverse osmosis concentrate by membrane bioreactor

Even though reverse osmosis (RO) technologies are widely used for sustainable water reclamation, the control of concentrates containing a high concentration of dissolved matters originated from feed water should be considered. The effect of variations in salinity on biological wastewater treatment processes has to be evaluated for combined treatment with RO concentrate in sewage treatment plants. As a preliminary study, the effect of adaptation of seeding sludge on RO concentrate treatment was evaluated. The reactor inoculated by unadapted sludge had a significant inhibition on organic and ammonia removal. Especially, ammonia removal was completely inhibited and removal efficiency was maintained below 20% during 30 d of operation. However, the removal efficiencies gradually increased with operation time, and it reached a similar performance to adapted sludge in 40 d of operation. For a more quantitative study on a microbial adaptation strategy for variations on salt concentration (0–20 g/L), lab-scale membrane bioreactors (7L working volume) with polypropylene hollow fiber membrane module (pore size 0.4 μm) were used with different adaptation strategies: instant and stepwise mode. The performance of the reactor deteriorated with an increasing salt concentration, but it recovered after adaptation periods (30–70 d). Moreover, the inhibition effect of salt could be minimized by a gradual increase in salt concentration. Analysis results for polymerase chain reaction-denaturing gradient gel electrophoresis indicated that nitrifiers were still present in high salinity. These results confirmed that an appropriate adaptation strategy should be determined for RO concentrate treatment.

Osmoregulation in tropical zoanthid Protopalythoa variabilis (Cnidaria: Anthozoa)

This study evaluated the physiological, morphological and ethological effects of salinity variations on the tropical zoanthid Protopalythoa variabilis. This ...

Effects of Salinity Variations on Acute Toxicity of Copper Sulphate against Oreochromis niloticus Fingerlings in Laboratory Bioassays

The study was carried out to investigate the salinity tolerance and relative acute toxicity of copper sulphate (CuSO4) under fresh water in varying salinity level, against Oreochromis niloticus fingerlings. A total of 280 fingerlings of O. niloticus (mean weight; 20 ± 4 g; 4-6 weeks old) were used as test animals in this study. The test compound used was copper as CuSO4.5H2O analar grade (molecular weight 249.68 g). The dose response data were analyzed by probit analysis. The results showed that on the basis of daily mortality assessment, O. niloticus were unable to survive in water with salinity above 22ppt within a 24hr period, but the fish survived well at lower salinities below 12ppt. Based on 96hr LC50 values, toxicity of CuSO4 against the fingerlings increased with increase or decrease in salinity except at 12ppt where the toxicity was minimal. The significance of this study is in setting ecologically sound, safe limits that are relevant for the prevailing two hydrological seasons in the tropics for the discharge of heavy metals into lagoons and the advantages of breeding O. niloticus under typical brackish water conditions, instead of freshwater. Keywords: Acute toxicity, Fingerlings, Copper sulphate, Oreochromis niloticus, Salinity

The structure of the benthic macrofaunal assemblages and sediments characteristics of the Paraguaçu estuarine system, NE, Brazil

The structure of the benthic macrofaunal assemblages of the estuarine portion of Paraguaçu River, NE, Brazil, and its relationship with surface sediment characteristics (trace metals, PAHs, nutrients and grain size) and physical variables were investigated at ten stations on two contrasting occasions, summer (dry season) and winter (rainy season). A total of 1258 individuals (632 in winter and 626 in summer) and 62 taxa representing polychaetes, crustaceans, bivalves, echinoderms, bryozoans, sponges, cnidarians and cephalochordates were collected. Benthic assemblages in the upper estuary were unlike those in the lower estuary and a clear substitution of benthic taxa along the estuary was observed. Macrofaunal invertebrates in the low salinity region, composed of coarse sediments, were dominated by tellinids, venerids (bivalves), cirolanids (isopods), cyclopoids (copepods), and nereidids (polychaetes). While the high salinity region, composed of fine sediments, were dominated by nuculids (bivalves), cirratulids (polychaetes), and by amphiurids (ophiuroids). The Paraguaçu estuarine system is not severely affected by anthropogenic activities. In the great majority of the study sites, concentrations of trace metals and PAHs in the sediments were near background values. Nutrients values were also low. We formulated new models of taxon distribution and suggested detailed studies on the effects of salinity variation and studies using functional approaches to better understand the processes causing the spatial patterns in tropical estuarine benthic assemblages.

Effect of salinity on the immune responses and outbreak of white spot syndrome in the shrimpMarsupenaeus japonicus

In order to understand the role of salinity in outbreaks of white spot syndrome (WSS) in the kuruma shrimp, Marsupenaeus japonicus, the effects of salinity variation on THC (total haemocyte count), phenoloxidase (PO) activities and outbreaks of white spot syndrome were studied. The results showed that salinity variation (increasing or decreasing salinity) could cause the changes of THC and PO activities of M. japonicus. Salinity was also an important environmental factor affecting the immune responses in M. japonicus. The further from the original salinity that M. japonicus were mantained, the weaker were the immune responses of shrimps. M. japonicus were more susceptible to WSSV under salinity stress due to changes in their immune responses.

Effect of salinity variation and pesticide exposure on an estuarine harpacticoid copepod, Microarthridion littorale (Poppe), in the southeastern US

The harpacticoid copepod Microarthridion littorale (Poppe) was tested for interaction effects between salinity change and acute pesticide exposure on the survival and genotypic composition of a South Carolina population. Previous data suggested a significant link between a combined exposure to chlorpyrifos (CHPY) and dichloro-diphenyl-trichloroethane (DDT) and mitochondrial haplotype in the cytochrome b apoenzyme for this euryhaline species when exposed at 12-ppt salinity seawater. Our tests demonstrate a significant non-linear survival response for M. littorale to short-term immersion (24 h) in 3-, 12- and 35-ppt seawater, with copepods transferred to 12-ppt seawater having the lowest survival. There was significant statistical interaction between salinity and pesticide exposure for the dependent variable “survival.” However, changes in genetic composition of survivors were not significant, and they were complicated by extremely low survival in the pesticide/3 ppt and pesticide/36 ppt treatments. As noted for many studies of harpacticoids, males faired worse than females in all treatments, with none surviving pesticide exposure at 45 μg/l CHPY and 6 μg/l DDT.

Investigation of the Negombo estuary (Sri Lanka) brush park fishery, with an emphasis on community‐based management

The Negombo estuary brush park fishery in Sri Lanka was investigated from June 1998 to March 1999. The mean fish yield (all species) in the fishery was 12.46 t ha−1 yr−1. Fin fish species formed about 91% of the yield and the rest was formed by penaeid shrimps and crabs. Fish yield and the twig density in the brush park exhibited a second order polynomial relationship indicating a minimum yield at an intermediate value of twig density in the brush parks. The relationship between fish yield and duration of implantation of brush parks showed an optimal period of 30–40 days for high fish yields. Income levels of fishermen, availability of construction material and suitable sites for implantation of brush parks are some of the factors determining size and number of brush parks per fisherman and duration of installation. Indigenous knowledge within the fishing community about the effect of salinity variations, twig density and mangrove species used on the harvests greatly contribute to effective operation of this fishing practice. Cultivation of mangroves to obtain twigs and branches is a unique feature in this estuary. Indigenous knowledge on mangroves has led to the adoption of sound silvicultural practices. Although cultivating mono‐specific mangrove stands may not increase diversity of mangrove forests, it reduces denudation of naturally occurring mangrove forests because of brush park construction, and retains habitats for other organisms. Mangrove management plans in the Negombo estuary should therefore be viewed and treated in an integrated manner that takes into account both resource and social components.