Optimum Salinity Range Research Articles

Responses of growth, antioxidants and gene expression in smooth cordgrass (Spartina alterniflora) to various levels of salinity

Salinity is a major environmental factor limiting the productivity and quality of crop plants. While most cereal crops are salt-sensitive, several halophytic grasses are able to maintain their growth under saline conditions. Elucidating the mechanisms for salinity responses in halophytic grasses would contribute to the breeding of salt-tolerant cereal and turf species belonging to the Poaceae family. Smooth cordgrass (Spartina alterniflora) is a dominant native halophytic grass in the Hackensack Meadowlands, the coastal salt marshes located in northeastern New Jersey. The goals of this study were to examine the growth pattern of S. alterniflora in a salinity gradient and identify an optimal range of salinity for its maximal growth. The regulation of its antioxidant system and gene expression under supraoptimal salinity conditions was also investigated. Our results showed that a salinity of 4 parts per thousand (ppt) (68 mM) was most favorable for the growth of S. alterniflora, followed by a non-salt environment. S. alterniflora responded to salts in the environment by regulating antioxidant enzyme activities and the expression of stress-induced proteins such as ALDH, HVA22 and PEPC. The plant may tolerate salinity up to the concentration of sea water, but any salinity above 12 ppt retarded its growth and altered the expression of genes encoding critical proteins.

The impact of estuarine salinity changes on the bivalves Scrobicularia plana and Cerastoderma edule, illustrated by behavioral and mortality responses on a laboratory assay

Salinity is a major factor impacting estuarine organisms, especially in cases of abrupt changes. The increased physiological stress frequently results in behavioral and physiological responses and in extreme cases may lead to mortality episodes. Mortality and behavioral activity of the bivalves Scrobicularia plana and Cerastoderma edule were evaluated under a wide range of salinity values. Specimens were sampled in the Mondego estuary (Portugal), acclimated and exposed to different salinity treatments (0–35) at constant temperature (20°C). Organisms were fed daily. Mortality and individual activity were registered during 120h laboratory assays. Both species showed an optimal salinity range for their activity (S. plana: 20–30; C. edule: 20–25), and survival was mainly affected by low salinity (S. plana: LC50120 h=5.35; C. edule: LC50120 h=11.09), with 100% mortality under critical values (S. plana: <5; C. edule: <10). Therefore, the occurrence of extreme climate events, especially floods, may in fact severely impact these species through drastic changes in salinity.

Hydrodynamic modeling and analysis of sea-level rise impacts on salinity for oyster growth in Apalachicola Bay, Florida

In this study, a previously calibrated hydrodynamic model was applied to investigate the impacts of sea level rise on salinity variations and oyster growth in Apalachicola Bay. With available observed data (winds, tides, and river flow), a case study has been conducted for the period of June 10–July 9, 2005. In addition, sea level rise impacts under a range of river flow conditions have also been examined, which include minimum monthly flow, average monthly flow, and maximum monthly flow based on the flow data from 1977 to 2013. Referring to the case study conditions under the existing sea level, model simulations were conducted to examine salinity changes in the bay in response to the sea level rise scenarios of 0.31 m, 0.5 m and 1.0 m. SLR-induced saline water intrusion mainly enters the estuary from the large opening in the east boundary. Based on the optimal salinity range for oyster growth (20–25 at Cat Point and 17–26 at Dry Bar) in Apalachicola Bay, SLR impacts were evaluated based on the model predicted salinity at Dry Bay and Cat Point. Results indicate that sea level rise results in stronger impacts on Cat Point than Dry Bar. Under the flow conditions of average monthly flow and the observed daily flow during June 10–July 9, mean salinity at Dry Bar varies within 21–24 in the optimal salinity range under 0.31 m and 0.5 m SLR conditions; and further increase above 26.0 when SLR is equal to 1.0 m. Under the conditions of average monthly flow and the observed daily flow during June 10–July 9, the mean salinity at Cat Point is within the optimal range under existing sea level, and increases above the maximum optimal salinity of 27 under the SLR scenarios of 0.31 m, 0.5 m, and 1.0 m, respectively. Extreme low and high flow conditions have also been investigated to examine the combined effects of flow and SLR. At the same sea level rise conditions, salinity under minimum flow is much higher than those under average flow, while salinity under maximum flow is much lower than those under the average flow condition.

Environmental and ecological impacts of water supplement schemes in a heavily polluted estuary

Water supplement has been used to improve water quality in a heavily polluted river with small base flow. However, its adverse impacts particularly on nearby sensitive ecosystems have not been fully investigated in previous studies. In this paper, using the Shenzhen River estuary in China as a case study, the impacts of two potential water supplement schemes (reclaimed water scheme and seawater scheme) on water quality improvement and salinity alteration of the estuary are studied. The influences of salinity alteration on the dominant mangrove species (Aegiceras corniculatum, Kandelia candel, and Avicennia marina) are further evaluated by comparing the alteration with the historical salinity data and the optimum salinity range for mangrove growth. The results obtained indicate that the targets of water quality improvement can be achieved by implementing the water supplement schemes with roughly the same flow rates. The salinity under the reclaimed water scheme lies in the range of historical salinity variation, and its average value is close to the optimum salinity for mangrove growth. Under the seawater scheme, however, the salinity in the estuary exceeds the range of historical salinity variation and approaches to the upper bound of the survival salinity of the mangrove species which have a relatively low salt tolerance (e.g. A. corniculatum). Therefore, the seawater scheme has negative ecological consequences, while the reclaimed water scheme has less ecological impact and is recommended in this study.

Osmoadaptation Strategy of the Most Halophilic Fungus, Wallemia ichthyophaga, Growing Optimally at Salinities above 15% NaCl

Wallemia ichthyophaga is a fungus from the ancient basidiomycetous genus Wallemia (Wallemiales, Wallemiomycetes) that grows only at salinities between 10% (wt/vol) NaCl and saturated NaCl solution. This obligate halophily is unique among fungi. The main goal of this study was to determine the optimal salinity range for growth of the halophilic W. ichthyophaga and to unravel its osmoadaptation strategy. Our results showed that growth on solid growth media was extremely slow and resulted in small colonies. On the other hand, in the liquid batch cultures, the specific growth rates of W. ichthyophaga were higher, and the biomass production increased with increasing salinities. The optimum salinity range for growth of W. ichthyophaga was between 15 and 20% (wt/vol) NaCl. At 10% NaCl, the biomass production and the growth rate were by far the lowest among all tested salinities. Furthermore, the cell wall content in the dry biomass was extremely high at salinities above 10%. Our results also showed that glycerol was the major osmotically regulated solute, since its accumulation increased with salinity and was diminished by hypo-osmotic shock. Besides glycerol, smaller amounts of arabitol and trace amounts of mannitol were also detected. In addition, W. ichthyophaga maintained relatively small intracellular amounts of potassium and sodium at constant salinities, but during hyperosmotic shock, the amounts of both cations increased significantly. Given our results and the recent availability of the genome sequence, W. ichthyophaga should become well established as a novel model organism for studies of halophily in eukaryotes.

Ontogenesis from embryo to juvenile and salinity tolerance of Japanese devil stinger Inimicus japonicus during early life stage.

Embryonic development and morphological characteristics of Japanese devil stinger Inimicus japonicus during early life stage were investigated. Larvae were hatched out 50 h after fertilization at temperature 21°C. Total length of the newly hatched larva was 4.03 mm, the mouth of the larva opened at 3 days after hatching (DAH), and the yolk sac of the larva disappeared at 5 DAH. After hatching, the pectoral fin first developed, then the tail fin, dorsal fin, anal fin and pelvic fin continuously developed, and all fins formed completely at 15 DAH. The metamorphosis was complete at 25 DAH, and the body color and habit of the metamorphosed individuals were different from the larvae. At 30 DAH, the morphology and habit of the juveniles were the same to adults. In order to determine the suitable salinity for larviculture of I. japonicus, salinity tolerance at different early developmental stages was compared in terms of the survival activity index (SAI) and mean survival time (MST). The results indicated that salinity tolerance varied with development stages. The optimum salinity range for newly hatched larvae was 10–25‰. Larvae showed low tolerance to low salinity (5‰) before the mouth opened, and the suitable salinities for the larvae with open mouth, yolk-sac larvae, post yolk-sac larvae were 10–15‰. The flexion larvae showed a wider salinity tolerance with range of 5–20‰. After metamorphosis, the juveniles showed a preferable adaptability of salinities of 15–20‰. The SAI and MST of individuals at various stages under different salinity conditions were positively correlated.

Study on salinity tolerance and oxygen consumption of silver pomfret(Pampus argenteus)larvae

The salinity tolerance and oxygen consumption of Pampus argenteus larvae(2 days after hatching and 4 days after hatching)were investigated at salinities of 5,10,20,30,40,50,55.Mortality,mean death time(MDT),median death time(DT50),median lethal salinity-48 h(MLS-48),and survival activity index(SAI)were employed as indices of salinity tolerance,and individual oxygen consumption was detected by respirometer.The results showed that lower(5)and higher(above 50)salinities were detrimental to P.argenteus.MLS-48 for 2-day-old larvae and 4-day-old larvae ranged from 8.15 to 24.90 and 15.54 to 34.97,respectively.DT50 and MDT of 2-day-old larvae in 10-30 environment were significantly higher than other salinities,while DT50 and MDT of 4-day-old larvae were higher in 10-40.SAI of 2-day-old larvae in 10 and 20 environment were significantly higher than other salinities,while the better value of SAI in 4-day-old larvae was in 20-30,and salinity of 20 was the best one for both kinds of larvae.From the results of individual oxygen consumption,for larvae among the suitable salinity ranges(10-30),there was no significant difference between salinities,but higher salinities caused higher oxygen consumptions of larvae.The results indicated that the optimum salinity range of P.argenteus was 15.54-24.90,and higher salinity can cause an increase of oxygen consumption in P.argenteus larvae,but there was no significant effect among tolerant salinity range.

Comparison of oxygen consumption rate and ammonia-N excretion rate between green type and red typeApostichopus japonicus

Experimental ecological method was used to compare the oxygen consumption rate and ammoniaN excretion rate betw een red type and green type Apostichopus japonicus,aiming at the investigation on the optimum environmental range for reproduction and culture conditioning of this species. Sea cucumbers w ere taken to the laboratory,acclimated for 10 d at five temperatures( 7,12,17,22 and 27 ℃),six salinities( 23,26,29,32,35 and 38) and five light colors( w hite,red,yellow,green and blue). The uniform size individuals w ere separately sampled from the red and green A. Japonicus. The results show ed that: 1) Oxygen consumption rate( OCR) and ammonia-N excretion rate( AER) w ere positively correlative to the temperature for both types A. japonicus. Under the test temperatures( 7- 27 ℃),the increasing OCR values of the red and green types sea cucumbers covered the range of 7. 58- 25. 94 and 13. 12- 25. 61 μg /( g · h)respectively. OCR for the red type w as significantly higher than the green one at 7 ℃ and 27 ℃,how ever,it significantly low er than the green one at 22 ℃( P 0. 05). 2) The AER for red type w as positively correlative to the temperature,w hile for the green one AER reached the maximum at 17 ℃ and then it declined w ith the increasing of temperature. The AER for the red and green types w ere 0. 62- 2. 57 and 0. 90- 2. 22 μg /( g·h),respectively. AER for the red type w as significantly higher than that of the green one at7 ℃,and it significantly low er than the green one at 27 ℃. 3) At test salinities of 26 to 38,both of the OCR and AER show ed a shape of ‘M 'w ith the increasing of salinity. OCR for the red and green ones w ere in range of 15. 72 to 21. 32 μg /( g·h),14. 83 to 21. 80 μg /( g ·h),and AER w as 1. 47 to 2. 83 μg /( g ·h),1. 40 to 2. 00 μg /( g·h),respectively. OCR of red type w as significantly low er than that of the green one in range of salinity 23 to 32( P 0. 05),w hereas AER only w as significantly higher at salinity of 29betw een the tw o types A. japonicus( P 0. 05). 4) Under different light color treatments OCR values for the red type and the green type covered range of 14. 33- 21. 37 and 15. 73- 21. 59 μg /( g · h),and AER covered 4. 00- 8. 86 and 6. 38- 8. 22 μg /( g · h),respectively. The OCR and AER w ere significantly different under w hite light treatment betw een the tw o types A. japonicus( P 0. 05). This study demonstrated that the red type A. japonicus could tolerate higher temperature and w as sensitive to low er temperature,w hile the green type show ed an opposite tendency; The optimum salinity range for tw o types A. japonicus w as 29-32; The green type may have broader light spectrum compared w ith the red type A. japonicus. Above all,the adaptability of the red and the green type A. japonicus to experimental conditions w ere w ell consistent w ith their natural habitats.

Hydrilla verticella as a carbon capturing plant

Global warming is a threatening problem to the entire world. As a proactive measure, scientists are developing new techniques to reduce CO2 emission to the atmosphere. Carbon capture and long time storage is a relatively new concept even though it is not economically feasible. Hence scientists have now focused on CO2 capture technology utilising salt water alga. In the present study, CO2 capturing rates of salt water algal plants Ulva fasciata , Caulerpa racemosa , Sargassum cervicone , Chaetomorpha spp , Padina spp , Corallina spp and Gracilaria spp . which are found in the ocean surrounding Sri Lanka were measured. However, it is very difficult to mimic the natural physical conditions inside the laboratory. Therefore an attempt was made to capture CO2 using an aquatic plant found in fresh water. Hydrilla verticella is an aquatic, invasive plant to Sri Lanka with a high growth rate. The CO2 capturing rate of Hydrilla verticella was compared with other salt water algal plants. When carrying out the experiment for salt water algae, the initial pH was reduced to 5 by pumping CO2 in to a fixed volume of salt water and then 30g of the specimen was placed and the variation of pH was measured with time. A Similar procedure was carried out with Hydrilla verticella by pumping CO2 in to distilled water. A control was kept under similar conditions without the specimen for each case. Ulva fasciata showed highest CO2 capture rate and Hydrilla verticella was second best. Hydrilla verticella was chosen as it is easy to manipulate for this study. The graph plotted between pH and time for Hydrilla verticella exhibited a typical photosynthetic pattern found in other plants. In this research, main parameters that have been investigated were on the salinity of the medium and the photoperiod to enhance the CO2 capture rate of Hydrilla verticella . Different salinity levels were obtained by adding different quantities of NaCl (10, 20, 30 ….70 g) in to one liter of distilled water. Results showed that this plant is adaptable to very different levels of salinity but the optimum salinity range is 10-20 gdm-3. Photoperiod was determined by exposing the samples to sun light over varying periods (0, 4, 8, 12 hrs) of time. Results showed that maximum activity was seen when exposed to 12 hrs of sunlight yet it is interesting to note that it can capture CO2 even under very low light intensities; even during night time when other plants respirate. CO2 capturing rate was the highest when the pH of the medium was in between 5-7. The concept of carbon credits came into existence as a result of increasing awareness of the need for controlling green house emissions. There are many companies that cell carbon credit to commercial and individual customer who are interested in lowering their carbon foot print on voluntary basis, hence above technique which is economically feasible can be implemented in order to mitigate global warming by reducing CO2 emission.

Effects of temperature and salinity on oxygen consumption of tawny puffer Takifugu flavidus juvenile

The respiratory rates of Tawny puffer Takifugu flavidus juvenile were measured at four temperatures (20, 23, 26 and 29 °C) and seven salinities (5, 10, 15, 20, 25, 30 and 35 g L−1). The results showed that both temperature and salinity significantly affected the oxygen consumption of tawny puffer juvenile. The oxygen consumption rate (OCR) increased significantly with an increase in the temperature from 20 to 29 °C. Over the entire experimental temperature range (20–29 °C), the Q10 value was 1.59, and the lowest Q10 value was found between 23 and 26 °C. The optimal temperature for the juvenile lies between 23 °C and 26 °C. The OCR at 25 g L−1 was the highest among all salinity treatments. The OCRs show a parabolic relationship with salinity (5–35 g L−1). From the quadratic relationship, the highest OCR was predicted to occur at 23.56 g L−1. The optimal salinity range for the juvenile is from 23 to 25 g L−1. The results of this study are useful towards facilitating an increase in the production of the species juvenile culture.

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 on embryos and larvae of tawny puffer Takifugu flavidus

Tawny puffer Takifugu flavidus is a fish species that has aquaculture potential in China because of its high market value. To determine the optimal condition of salinity for embryo development and larval culture of the species, the effects of salinity (0‰, 5‰, 10‰, 15‰, 20‰, 25‰, 30‰, 35‰, 40‰, and 45‰) on egg hatching and the survival and growth of larvae at 3–23 days post-hatch (dph) were assessed. Embryonic hatching rates were above 70% at salinities of 5‰ to 45‰, and all embryos at 0‰ died 4 days after fertilization. Survival rates (> 75%) of larvae at 24 h post-hatch at salinities of 10‰ to 40‰ were significantly higher than that at salinities of 5‰ and 45‰. The highest hatching rates and lowest percentage of mortalities occurred at salinities of 10‰ to 20‰. Results suggest that the embryos can tolerate a wide range of salinity (10–40‰), and optimal range of salinity for embryo development is between 10‰ and 20‰. The time of egg hatching was not influenced by salinity. Larvae of tawny puffer continued to survive until Day 23 of post-hatch at salinities of 5‰ to 35‰, but all larvae died within 20 dph at 45‰. The highest survival rate occurred at salinities of 15‰ to 35‰, and the highest growth rate was found at salinities of 15‰ to 25‰. The results suggest that the optimal salinity for larval survival and growth is between 15‰ and 25‰.

Dissolution Characteristics of Hydrophobically Associating Polyacrylamide in Stirred Tanks

Enhanced oil recovery (EOR) by means of polymer flooding is an important technology for the strategic development of offshore oilfields in China. Hydrophobically associating polyacrylamide (HAPAM) has been recently proposed as a new flooding agent. The solubility of HAPAM is low, which is the bottleneck for further improving the oil recovery through polymer flooding in offshore oilfield. Stirred tanks have been used on offshore platforms to enhance HAPAM dissolving. But there is little literature on the study of HAPAM dissolving characteristics in stirred tanks. In this paper, effects of temperature, salinity, stirring speed, impeller type and stirring method on the dissolution of HAPAM are reported. The experimental results manifest that the dissolving rate of HAPAM increases with temperature and stirring speed, but the viscosity of the polymer solution decreases. There is an optimal range of salinity for polymer dissolving. Combining the operation mode of up-pumping with varying stirring speed, hydrofoil impeller can accelerate the dissolution of HAPAM and maintain a high solution viscosity.

Hydrodynamic modeling and ecohydrological analysis of river inflow effects on Apalachicola Bay, Florida, USA

This paper presents an integrated hydrodynamic modeling and probability analysis approach to assess the long-term effects of changing river inflows on the estuarine ecosystem. The probability analysis method, which is popularly used in advanced hydrological frequency analysis of river flows and rainfalls, has been applied to analyze the effects of changing inflow on salinity and thus on oyster ecology in Apalachicola Bay. Long-term salinity data were predicted through the application of a calibrated 3D hydrodynamic model under two river inflow conditions over a 10-year period. The first flow represents the historic flow. The 2nd flow condition, called Scenario-1, represents a regulated flow scenario to account for the potential increasing upstream water demands. Two stations, Mid Bay and Dry Bar, in the bay were selected to examine the estuarine responses. Under the historic flow condition, the maximum probability salinity at Dry Bar in the rich oyster reef is near 24 ppt, within the optimal salinity range for oyster growth of 16–26 ppt (Harned et al., 1996); the maximum probability salinity at Mid Bay station is 27 ppt, beyond the optimal salinity for oyster growth in mid-bay area where there is no oyster reef around. While it is difficult to examine the difference between two scenarios by conventional time series analysis of river flows and salinity, probability analysis reasonably characterizes and quantifies the changes of river flow and salinity patterns over the 10-year period. The Scenario-1 has caused the increase of the probability in low flows. Higher probability of low flows for the regulated flow scenario shortens the period of optimal salinity in the oyster reef, and cause substantial increase of exceedance probability of higher salinity in the oyster reef to the level beyond the optimal salinity range for oyster growth. The probability analysis approach has demonstrated its advantage for the risk assessments of the long-term estuarine ecohydrological effects under various regulated inflow scenarios to support estuarine water resources managements.

EFFECT OF SALINITY, TEMPERATURE, AND FOOD VALUE OF FOUR MICROALGAE TO OYSTER, Crassostrea iredalei LARVAL GROWTH

Published accounts of Crassostrea iredalei are only of its distribution in the Philippines. In Indonesia, this species is known to occur on the coast of South Sulawesi as well as in Banten. The purposes of the present studies were to investigate effect of salinity, temperature and food value of four microalgae to C. iredalei larval growth. Fine filtration of water was carried out using Sartorius capsule filter cartridge (1.2 im and 0.2 im) and sterilization was achieved by passing the water through an ultraviolet light unit. Low-salinity water was prepared by diluting filtered seawater with distilled water. High-salinity water was made by adding synthetic sea salts. All cultures were kept in constant temperature baths. Experiments of 8-days (for temperature and salinity trials) and 10-days (for diet trial) duration were duplicated in 500 mL glass beakers with larval density of 104 per liter. Seawater was changed every 48 h. The algae, Isochrysis galbana, I. galbana clone T-ISO, and Pavlova lutheri were added to the glass beakers at a rate of 100 cells/iL; cell density of Chaetoceros calsitrans was 250 cells/il at the start of the experiment and after every water change. Using thermostat chambers, 5 temperatures were tested, ranging from 14o to 34o in 5 steps. Four salinities were used, they ranged from 10 to 35‰ in 5‰ steps. For environmental condition trial, I. galbana as food was used. In diet trials, 4 species of algae were tested e.g. I. galbana, I. galbana T-ISO, P. lutheri, C. calcitrans and a mixture of algae, T-ISO/C. calcitrans. The optimum salinity range for growth of larvae was recorded at 20‰—30‰ at which the mean shell length was 85.1—87.7 im. The highest survival rate was recorded at salinity of 25‰—30‰, it was 91.6%—92.7%. There were significant differences in larval growth between temperature treatments. The optimum temperature for larval growth was at 24°C—29°C, with survival rate of 91.6%—93.0%. P. lutheri and I. galbana proved to be of equal value as diet for larval growth, with survival rates of 89.4%—90.6%. The best algal food was I. galbana clone T-ISO, which resulted in mean shell length 107.7 im and survival rate 86.7%.

Effects of salinity and temperature on the expression of enzymatic biomarkers in Eurytemora affinis (Calanoida, Copepoda)

In order to establish effective enzymatic biomarkers that could provide in situ early warning of contaminant exposure in estuarine ecosystems, the potential effects of the principal abiotic factors (temperature and salinity) were investigated on common biomarkers, the acetylcholinesterase (AChE) and the glutathione S-transferase (GST) in Eurytemora affinis. Short term salinity stress effects simulated during an experimental tide indicated that enzymatic activities of this species are characterized by maximum expression related to an optimal salinity range (between 5 and 15 psu). Moreover, longer time exposure to various salinity tanks confirmed the effects of this factor on both AChE and GST activities. Therefore, optimal AChE activity was measured at 10 psu, while optimal GST activity was measured at 5 psu. Furthermore, significant effects of temperature were also recorded, particularly for AChE expression (slight effects were measured on GST expression) with an optimal condition at 11 degrees C. These experiments indicated a more pronounced effect of salinity over temperature especially on the AChE expression and confirmed the need to standardize sampling procedures in relation with environmental parameters for biomonitoring studies based on enzymatic analyses.

TIGER SHRIMP (Penaeus monodon) GROWTH AT DIFFERENT STOCKING DENSITIES IN HIGH SALINITY POND USING MANGROVE RESERVOIR

High salinity pond water ranging from 33—45 ppt between July and October is one of the problems occurred in western part of South Sulawesi brackishwater ponds. It is necessary to know if tiger shrimps grow well in such salinity, since the optimum salinity range for the growth of tiger shrimp is 15—25 ppt. The objective of the research is to know the tiger shrimp production at different stocking densities cultured in high salinity pond in mangrove reservoir. Twelve pond compartments of 500 m2 each were arranged randomly for three treatments of shrimp stocking densities i.e. 4 , 6, and 8 pcs./m2 , where each treatment was in three replications. The result of study showed that shrimp production at 6 pieces/m2 was higher than that of 4 and 8 pieces/m2, with more efficient feed conversion was obtained in this stocking density (1.3) compared to treatment 4 pieces/m2 (1.5) and treatment 8 pieces/m2 (>3).

Salinity-induced survival strategy of Vibrio cholerae associated with copepods in Cochin backwaters

The occurrence of Vibrio cholerae in water, sediment and copepods was studied over a wide range of salinity using conventional and polymerase chain reaction (PCR) techniques in the Cochin backwaters. V. cholerae occurred either as culturable or non-culturable form in this tropical estuary. During the pre monsoon period when high salinity prevailed (35.5 psu) V. cholerae was associated with copepods only in non-culturable form, but with the onset of monsoon when lower salinity prevailed, copepod-associated- V. cholerae reverted back to culturable form. The optimum salinity range for culturability was found to be 15–20 psu. This points to the fact that salinity is a major factor that which influences V. cholerae’s culturability and its association with copepods in Cochin backwaters.

Growth, survival, haemolymph osmolality and organosomatic indices of the western king prawn (Penaeus latisulcatus Kishinouye, 1896) reared at different salinities

The growth, survival, haemolymph osmolality and organosomatic indices of the western king prawn, Penaeus latisulcatus, (2.95±0.26 g mean initial weight), were measured when reared at 10, 22, 34 and 46 ppt salinity for 60 days. Mean final weight, total length and specific growth rate (SGR) of the prawns were highest at 34 ppt. Rearing at different salinities did not alter moult increments and intermoult periods of the prawns. One hundred percent mortalities were observed at 10 ppt.Survival was highest at 22 ppt and food conversion ratios were significantly lowest (P<0.0.5) in prawns cultured at 22 and 34 ppt. Haemolymph osmolality increased with the increase in medium salinity and physiological age of the prawns. Isosmotic points calculated from regression between haemolymph and medium osmolality were 28.87, 29.46 and 31.73 ppt at 0, 20 and 60 days of culture, when body weights were 2.95±0.26, 4.02±0.47, 5.79±0.64 g respectively. After 60 days of culturing, hepatopancreatic moisture levels increased with the increase in salinity, whereas tail moisture levels remained unchanged. Wet and dry hepatosomatic indices were highest at 22 ppt. Wet tail muscle index was highest at 34 ppt, whereas dry tail muscle index did not change by any salinity levels. The results suggest that the optimum salinity range for rearing western king prawns ranges from 22 to 34 ppt and 10 ppt was unsuitable for culture.

Study of salinity and temperature tolerance limits regarding four crustacean species in a temporary salt water swamp (Lake Zima, Morocco)

Abstract Tolerance boundaries of four crustacean species (Phallocryotus spinosa, Moina salina, Arctodiaptomus salinus and Ctenodaphnia mediterranea) to salinity and temperature were evaluated by studying the species in their natural environment (salted temporary swamp of Lake Zima near Marrakech, Morocco) and in the laboratory. The seasonal density evolution over the year for the four species in their natural environment reveals three phases (youth, maturity and old). The dwell time of each species depends on the environmental factor values as well as on their rate of change. Laboratory study revealed high euryhaline and eurithermal ability for the four species, with a difference in the optimal salinity range from species to species. The ranges are situated between 5 and 25% for C. mediterranea, 15 and 30% for A. salinus, 15 and 60% for M. Salina and 30 and 90% for P. spinosa. Such a range difference, measured under controlled conditions (laboratory), may well explain the variability in the behaviour of the four species in their natural environment. The tolerance range difference from species to species, together with the instability of the environmental conditions of the milieu, seem to be responsible for the quantitative and qualitative changes of the host fauna, which occur within the year and from year to year.