Effect Of Low Salinity Research Articles

Physiological and behavioural responses of different life stages of a serpulid polychaete to hypoxia

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 477:135-145 (2013) - DOI: https://doi.org/10.3354/meps10175 Physiological and behavioural responses of different life stages of a serpulid polychaete to hypoxia Y. S. Leung1, P. K. S. Shin1, J. W. Qiu2, P. O. Ang3, J. M. Y. Chiu4, V. Thiyagarajan4, S. G. Cheung1,* 1Department of Biology and Chemistry, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong, SAR 2Department of Biology, Hong Kong Baptist University, Hong Kong, SAR 3School of Life Sciences, Chinese University of Hong Kong, New Territories, Hong Kong, SAR 4School of Biological Sciences, The University of Hong Kong, Pokfulam, Hong Kong, SAR *Corresponding author. Email: bhsgche@cityu.edu.hk ABSTRACT: Hypoxia has become a major threat to coastal marine ecosystems worldwide. Among various groups of marine invertebrates, sessile ones are more susceptible to hypoxia since they cannot move away from hypoxic waters. The serpulid polychaete Hydroides elegans Haswell, 1883 is a fast-proliferating, dominant, sessile-fouling species in the tropical Pacific, which includes Hong Kong. We studied the effects of hypoxia on the fertilization success, embryogenesis and physiological and behavioural responses in both larval and adult stages of H. elegans. Results showed that fertilization success was reduced and embryogenesis was retarded at a dissolved oxygen (DO) level of 2 mg O2 l-1. At this DO level, the swimming velocity of the 2 d old larvae significantly increased, which may serve as an escape response. H. elegans showed a very high tolerance to hypoxia in both larval and adult stages, as indicated by the 24 and 48 h lethal DO concentation (LC50). However, the respiration rate and clearance rate of adult H. elegans were significantly reduced at 2 mg O2 l-1. Partial recovery was observed 2 d after normoxia was resumed. Previous studies have demonstrated that adult H. elegans suffer from high mortality and that there are no new recruits in summer when the temperature is high and DO concentration low. The results are interpreted as the effect of low salinity. Our study has strengthened the notion that low salinity contributes to adult mortality in summer; however, the lack of summer recruitment is possibly a result of the combined effect of low salinity and hypoxia. KEY WORDS: Hypoxia · Hydroides elegans · LC50 · Embryogenesis · Respiration rate · Clearance rate Full text in pdf format PreviousNextCite this article as: Leung YS, Shin PKS, Qiu JW, Ang PO, Chiu JMY, Thiyagarajan V, Cheung SG (2013) Physiological and behavioural responses of different life stages of a serpulid polychaete to hypoxia. Mar Ecol Prog Ser 477:135-145. https://doi.org/10.3354/meps10175 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 477. Online publication date: March 12, 2013 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2013 Inter-Research.

Enhanced Oil Recovery (EOR) by Combined Low Salinity Water/Polymer Flooding

Recently, low salinity brine injection has been given a great interest as a technique for enhanced oil recovery (EOR) by waterflooding. Varying experimental results have been reported in the literature, from many promising results to limited or no effects of low salinity. The application of low salinity water in combination with other established EOR processes (e.g., surfactant flooding and polymer flooding) is of great interest. The combined processes involve dampening capillarity to avoid trapping of mobilized oil, reducing residual oil saturation (Sor), and altering frontal stability and sweep. In this article, we address the questions of timing of LS injection and the added benefit of polymer injection. Secondary-mode (at initial water saturation) and tertiary-mode (after seawater residual oil saturation) low salinity waterflooding experiments were performed on outcrop Berea sandstone core material. The main results are the oil recovery efficiencies of these two different flooding modes. These results...

Environmental salinity modulates the effects of elevated CO2 levels on juvenile hard shell clams, Mercenaria mercenaria

Ocean acidification due to increasing atmospheric CO2 concentrations results in a decrease in seawater pH and shifts in the carbonate chemistry that can negatively affect marine organisms. Marine bivalves such as the hard-shell clam, Mercenaria mercenaria, serve as ecosystem engineers in estuaries and coastal zones of the western Atlantic and, as for many marine calcifiers, are sensitive to the impacts of ocean acidification. In estuaries, the effects of ocean acidification can be exacerbated by low buffering capacity of brackish waters, acidic inputs from freshwaters and land, and/or the negative effects of salinity on the physiology of organisms. We determined the interactive effects of 21 weeks of exposure to different levels of CO2 (~395, 800 and 1500 μatm corresponding to pH of 8.2, 8.1 and 7.7, respectively) and salinity (32 versus 16) on biomineralization, shell properties and energy metabolism of juvenile hard-shell clams. Low salinity had profound effects on survival, energy metabolism and biomineralization of hard-shell clams and modulated their responses to elevated PCO2. Negative effects of low salinity in juvenile clams were mostly due to the strongly elevated basal energy demand, indicating energy deficiency, that led to reduced growth, elevated mortality and impaired shell maintenance (evidenced by the extensive damage to the periostracum). The effects of elevated PCO2 on physiology and biomineralization of hard-shell clams were more complex. Elevated PCO2 (~800-1500 μatm) had no significant effects on standard metabolic rates (indicative of the basal energy demand), but affected growth and shell mechanical properties in juvenile clams. Moderate hypercapnia (~800 μatm PCO2) increased shell and tissue growth and reduced mortality of juvenile clams in high salinity exposures; however, these effects were abolished under the low salinity conditions or at high PCO2 (~1500 μatm). Mechanical properties of the shell (measured as microhardness and fracture toughness of the shells) were negatively affected by elevated CO2 alone or in combination with low salinity, which may have important implications for protection against predators or environmental stressors. Our data indicate that environmental salinity can strongly modulate responses to ocean acidification in hard-shell clams and thus should be taken into account when predicting the effects of ocean acidification on estuarine bivalves.

Effects of salinity on survival of the exotic seagrass Zostera japonica subjected to extreme high temperature stress

Abstract Zostera japonica is a non-indigenous seagrass that is expanding along the Pacific Coast of North America. The ecophysiology of this seagrass is poorly studied and management of the species is fragmented. This split-plot mesocosm experiment was designed to evaluate the response of Z. japonica to chronic, extreme temperature and salinity stress to facilitate development of models to predict potential Z. japonica colonization. We collected Z. japonica plants from Padilla Bay, Washington and Yaquina Bay and Coos Bay, Oregon and exposed them to a constant water temperature of 15°C or 35°C at three different salinities (5, 20 and 35). After 7 days exposure, shoot survival ranged between 6% and 42%; after 9 days exposure, only a few plants from the Yaquina Bay population survived. At a ambient temperature (15°C), no differences were detected among the three salinity treatments. However, at a temperature of 35°C, the survival of plants grown at a salinity of 5 was significantly lower than at higher salinities (20 and 35). Although the effect of population was weak, the northern population appeared to be more susceptible to the combined effects of heat stress and low salinity than the southern populations. We suggest that Z. japonica will continue to spread southward along the Pacific coast of North America until it reaches systems that regularly exceed the temperature tolerances of this non-indigenous seagrass.

Broad Salinity Tolerance as a Refuge from Predation in the Harmful Raphidophyte Alga Heterosigma akashiwo (Raphidophyceae).

The ability of harmful algal species to form dense, nearly monospecific blooms remains an ecological and evolutionary puzzle. We hypothesized that predation interacts with estuarine salinity gradients to promote blooms of Heterosigma akashiwo (Y. Hada) Y. Hada ex Y. Hara et M. Chihara, a cosmopolitan toxic raphidophyte. Specifically, H.akashiwo's broad salinity tolerance appears to provide a refuge from predation that enhances the net growth of H.akashiwo populations through several mechanisms. (1) Contrasting salinity tolerance of predators and prey. Estuarine H.akashiwo isolates from the west coast of North America grew rapidly at salinities as low as six, and distributed throughout experimental salinity gradients to salinities as low as three. In contrast, survival of most protistan predator species was restricted to salinities >15. (2) H.akashiwo physiological and behavioral plasticity. Acclimation to low salinity enhanced H.akashiwo's ability to accumulate and grow in low salinity waters. In addition, the presence of a ciliate predator altered H.akashiwo swimming behavior, promoting accumulation in low-salinity surface layers inhospitable to the ciliate. (3) Negative effects of low salinity on predation processes. Ciliate predation rates decreased sharply at salinities <25 and, for one species, H.akashiwo toxicity increased at low salinities. Taken together, these behaviors and responses imply that blooms can readily initiate in low salinity waters where H.akashiwo would experience decreased predation pressure while maintaining near-maximal growth rates. The salinity structure of a typical estuary would provide this HAB species a unique refuge from predation. Broad salinity tolerance in raphidophytes may have evolved in part as a response to selective pressures associated with predation.

Effect of Low Salinity on Ventilation in the Oyster Crassostrea gigas

Effect of Low Salinity on Ventilation in the Oyster Crassostrea gigas

Effect of Low Salinity on Growth and Survival of Tiger Puffer Takifugu rubripes, and the Purification of Rearing Water in Closed Recirculating Seed Production

Effect of Low Salinity on Growth and Survival of Tiger Puffer Takifugu rubripes, and the Purification of Rearing Water in Closed Recirculating Seed Production

Effects of Low Salinity on Survival, Hemolymph Osmolality and Tissue Water Content of the Manila clam Ruditapes philippinarum

Effects of Low Salinity on Survival, Hemolymph Osmolality and Tissue Water Content of the Manila clam Ruditapes philippinarum

Comparing salinity tolerance in early stages of the sporophytes of a non-indigenous kelp (Undaria pinnatifida) and a native kelp (Saccharina latissima)

The short-term effects of low salinities on the survival of germlings of an introduced kelp Undaria pinnatifida and a native kelp Saccharina latissima were assessed under laboratory conditions. This experiment was designed to compare the differential stress tolerance to salinity of the early life history stages of sporophytes of these two kelps that co-occur on European Atlantic coasts. Germlings (young sporophytes) of both species were exposed for 4 days to salinities ranging from 31 (control) to 26, 21, 16, 11, and 6 psu. Afterwards, they were post-cultured in control seawater (31 psu) for another 4 days to corroborate the viability of injured germlings. Results showed that germlings of the introduced kelp were less resistant to low salinity, surviving to as low as 16 psu; whereas the germlings of the native kelp survived in salinities as low as 11 psu. Despite the observed differences, both species are relatively tolerant to low salinity. Our observations also indicated that, at least in a short term, gametophytes of both species were able to survive in salinities as low as 6 psu. The significance of low-salinity tolerance to the distribution of these kelps and for their offshore cultivation is discussed.

Chronic hypoxia and low salinity impair anti-predatory responses of the green-lipped mussel Perna viridis

The effects of chronic hypoxia and low salinity on anti-predatory responses of the green-lipped mussel Perna viridis were investigated. Dissolved oxygen concentrations ranged from hypoxic to normoxic (1.5 ± 0.3 mg l−1, 3.0 ± 0.3 mg l−1 and 6.0 ± 0.3 mg l−1), and salinities were selected within the variation during the wet season in Hong Kong coastal waters (15‰, 20‰, 25‰ and 30‰). The dissolved oxygen and salinity significantly affected some anti-predatory responses of mussel, including byssus production, shell thickness and shell weight, and the adductor diameter was only significantly affected by salinity. Besides, interactive effects of dissolved oxygen and salinity on the byssus production and shell thickness were also observed. In hypoxic and low salinity conditions, P. viridis produced fewer byssal threads, thinner shell and adductor muscle, indicating that hypoxia and low salinity are severe environmental stressors for self-defence of mussel, and their interactive effects further increase the predation risk.

The Effect of Salinity On Experimental Infections of A Hematodinium SP. In Blue Crabs, Callinectes sapidus

The parasitic dinoflagellate Hematodinium sp. parasitizes blue crabs along the Atlantic seaboard of the United States. Infections in blue crabs have only been reported from waters where salinity is >11 practical salinity units (psu). Blue crabs maintain a hyperosmotic internal concentration at low salinities (0-5 psu), roughly comparable to 24 psu, and should be capable of maintaining an infection in low-salinity waters even if Hematodinium spp. cells are intolerant of low salinities. We tested this notion by observing the effect of low salinity on the progression of disease in crabs experimentally infected with the parasite. Blue crabs were acclimated to 5 psu or 30 psu salinity treatments. They were inoculated with Hematodinium sp. and necropsied 3, 7, 10, and 15 days post-inoculation. The low-salinity treatment did not have an effect on the proliferation of Hematodinium sp. infections in blue crabs; moreover, a greater proportion of infections in crabs in the low-salinity treatment developed dinospore stages than did those in the high-salinity treatment, indicating that salinity may affect the development of the parasite. However, dinospores from in vitro cultures rapidly became inactive when held in salinities <15 psu. Our experiments indicate that Hematodinium spp. can develop in blue crabs at low salinities, but that the parasite is incapable of transmission in this environment, which explains the lack of natural infections in crabs at low salinities.

Effect of low salinity on ion accumulation, gas exchange and postharvest drought resistance and habit of Coriandrum sativum L.

Drought resistance of crops is one of the great challenges for the world’s agricultural systems. Although the concept of ‘drought hardening’ has been known for many years, very little has been done on pre-harvest treatment that can help leafy vegetable crops resist drought stress on a retailer’s shelf. Our hypothesis was that for pot-grown vegetables a saline treatment could be found that would reduce transpiration pre- and post-harvest, but not harvestable yield. Coriander (Coriandrum sativum L.) was used as a model plant; several accessions (k-4, k-43, k-52, k-60 and k-62) from N.I. Vavilov Research Institute of Plant Industry, Russia and two commercial cultivars—Kashmir and Americanum—were studied. Plant growth, weight, transpiration, net CO2 assimilation, respiration, wilting, apparent petioles rigidity, leaf sodium content, elemental analysis and osmotic potential were assessed. We found that minor salinity (12.5 mM Na2SO4) triggered both drought and salt resistance mechanisms, which regulate appearance and shelf-life of pot-grown coriander. We found that the drought avoidance mechanisms (i.e. decreased transpiration and increased water use efficiency) and salt tolerance mechanisms induced by pre-harvest treatment could significantly postpone wilting and improve post-harvest habit of a leafy vegetable crop.

Effects of low environmental salinity on the cellular profiles and expression of Na+, K+-ATPase and Na+, K+, 2Cl− cotransporter 1 of branchial mitochondrion-rich cells in the juvenile marine fish Monodactylus argenteus

The goal of this study was to determine the osmoregulatory ability of a juvenile marine fish, silver moony (Monodactylus argenteus), for the purpose of developing a new experimental species for ecophysiological research. In this study, M. argenteus was acclimated to freshwater (FW), brackish water (BW), or seawater (SW). The salinity tolerance of this euryhaline species was effective, and the fish survived well upon osmotic challenges. The largest apical surface of mitochondrion-rich cells was found in the FW individuals. Immunohistochemical staining revealed that Na(+), K(+)-ATPase immunoreactive (NKA-IR) cells were distributed in the interlamellar region of the gill filaments of the silver moony in all experimental groups. In addition to the filaments, NKA-IR cells were also found in the lamellae of the FW individuals. The number of NKA-IR cells in the gills of the FW individuals exceeded that of the BW and SW individuals. The NKA-IR cells of FW and SW individuals exhibited bigger size than that of BW fish. The NKA activities and protein expression of the NKA α-subunit in the gills of the FW individuals were significantly higher than in the BW and SW groups. Additionally, the relative amounts of Na(+), K(+), 2Cl(-) cotransporter 1 (NKCC1) were salinity-dependent in the gills. Immunofluorescent signals of NKCC1 were localized to the basolateral membrane of NKA-IR cells in all groups. In the gills of the FW individuals, however, some NKA-IR cells did not exhibit a basolateral NKCC1 signal. In conclusion, the present study illustrated the osmoregulatory mechanisms of this easy- and economic-to-rear marine teleost with euryhaline capacity and proved the silver moony to be a good experimental animal.

Spreading and physico-biological reproduction limitations of the invasive American comb jelly Mnemiopsis leidyi in the Baltic Sea

Hydrodynamic drift modeling was used to investigate the potential dispersion of Mnemiopsis leidyi from the Bornholm Basin in the Baltic Sea where it has been observed since 2007 further to the east and north. In the brackish surface layer dispersion is mainly driven by wind, while within the halocline dispersion is mainly controlled by the baroclinic flow field and bottom topography. Model runs showed that the natural spreading via deep water currents from the Bornholm Basin towards north and east is limited by topographic features and low advection velocities. Based on the information on ranges of salinity and temperature, which limit survival and reproduction of this ctenophore within the Baltic Sea, areas have been identified where the American comb jelly, M. leidyi could potentially survive and reproduce. While, we could show that M. leidyi might survive in vast areas of the northern Baltic Sea its reproduction is prevented by low salinity (<10 psu) and temperature (<12°C). Thus, due to the combined effect of low salinity and temperature, it is not probable that M. leidyi could establish permanent populations in the central or northern Baltic Sea. However, it seems that in the southern parts of the Baltic Sea environmental conditions are suitable for a successful reproduction of M. leidyi.

Effects of various mixed salt-alkaline stresses on growth, photosynthesis, and photosynthetic pigment concentrations of Medicago ruthenica seedlings

Soil salinization and alkalinization frequently co-occur in naturally saline and alkaline soils. To understand the characteristics of mixed salt-alkali stress and adaptive response of Medicago ruthenica seedlings to salt-alkali stress, water content of shoots, growth and photosynthetic characteristics of seedlings under 30 salt-alkaline combinations (salinity 24–120 mM and pH 7.03–10.32) with mixed salts (NaCl, Na2SO4, NaHCO3, and Na2CO3) were examined. The indices were significantly affected by both salinity and pH. The interactive effects between salt and alkali stresses were significant, except for photosynthetic pigments. Water content of shoots, relative growth rates of shoots and roots and pigment concentrations showed decreasing trends with increasing salinity and alkalinity. The root activity under high alkalinity and salinity treatments gradually decreased, but was stimulated by the combined effects of low alkalinity and salinity. The survival rate decreased with increased salinity, except at pH 7.03–7.26 when all plants survived. Net photosynthetic rate, stomatal conductance and intercellular CO2 concentration decreased with increased salinity and pH. M. ruthenica tolerated the stress of high salt concentration when alkali concentration was low, and the synergistic effects of high alkali and high salt concentrations lead to the death of some or all seedlings. M. ruthenica appeared to be saltalkali tolerant. Reducing the salt concentration or pH based on the salt components in the soil may be helpful to abate damage from mixed salt-alkaline stress.

Growth, tolerance to low ­salinity, and osmoregulation in decapod crustacean larvae

Marine invertebrate larvae suffer high mortality due to abiotic and biotic stress. In planktotrophic larvae, mortality may be minimised if growth rates are maximised. In estuaries and coastal habitats however, larval growth may be limited by salinity stress, which is a key factor select- ing for particular physiological adaptations such as osmoregulation. These mechanisms may be ener- getically costly, leading to reductions in growth. Alternatively, the metabolic costs of osmoregulation may be offset by the capacity maintaining high growth at low salinities. Here we attempted identify general response patterns in larval growth at reduced salinities by comparing 12 species of decapod crustaceans with differing levels of tolerance to low salinity and differing osmoregulatory capability, from osmoconformers to strong osmoregulators. Larvae possessing tolerance to a wider range in salinity were only weakly affected by low salinity levels. Larvae with a narrower tolerance range, by contrast, generally showed reductions in growth at low salinity. The negative effect of low salinity on growth decreased with increasing osmoregulatory capacity. Therefore, the ability to osmoregulate allows for stable growth. In euryhaline larval decapods, the capacity to maintain high growth rates in physically variable environments such as estuaries appears thus to be largely unaffected by the energetic costs of osmoregulation.

Mangroves: obligate or facultative halophytes? A review

Salinity plays significant roles in regulating the growth and distribution of mangroves, and the salt tolerance mechanisms of mangroves have been the focus of research for several decades. There are contradictory views regarding the relationship between mangroves and salt: (1) Mangroves are facultative halophytes, i.e. freshwater is a physiological requirement and salt water is an ecological requirement for mangroves because they are capable of growing in freshwater. The former prevents excess respiratory losses while the latter prevents invasion and competition from non-halophytes. (2) Mangroves are obligate halophytes, i.e. salt is necessary for their growth. Mangroves cannot survive in freshwater permanently and salt water is a physiological requirement. Up to now, mangroves are usually considered as facultative halophytes. In this review, we provided five lines of evidence to evaluate these two contradictory views: (1) the results of laboratory culture experiments and field investigations; (2) the viviparous nature of mangroves; (3) the salt accumulation of mangroves under freshwater or low salinity; (4) the effect of salinity on the photosynthetic rate and in vitro enzyme activities, and (5) the effects of salinity fluctuation on mangrove growth and physiology. Contrary to widely accepted view, our evaluations of the aforementioned evidence suggest that mangroves are obligate halophytes. Mangroves can grow in freshwater for a limited time by drawing upon the nutrients and salt reserves in their hypocotyls while prolonged culture in freshwater is fatal to them. Mangroves have the ability to absorb Na+ and Cl− rapidly and preferentially under low-salinity conditions. Not all of the enzymes in mangroves are sensitive to salt. In fact, the activities of some enzymes are even stimulated by low or moderate salinity. Plants grown under constant salinity in a laboratory setting are unlikely to behave in the same way as those in their natural habitat with fluctuating salinity. Thus, studies on the effects of freshwater or low salinity and salinity fluctuation on mangroves, as well as the physiological mechanisms that allow maintenance of function under fluctuating salinity conditions should be strengthened in future research.

Effect of low salinity on microbial floc composition and performance of Litopenaeus vannamei (Boone) juveniles reared in a zero-water-exchange super-intensive system

This study aimed to evaluate the effect of low salinity on the water quality, microbial flocs composition and performance of Litopenaeus vannamei juveniles reared over 40 days in a zero-water-exchange super-intensive system at 0, 2, 4 and 25 g L−1. At 0 g L−1, the mortality was total at the 26th day, and consequently, these salinity data were not included in the statistical analysis. Among the water quality parameters, only pH and the total suspended solids concentration were significantly influenced by salinity. However, a trend towards intensification of the nitrification processes was observed as the salinity increased, with the lowest ammonia and the highest nitrite and nitrate concentrations found at 25 g L−1. The concentrations of ciliates and flagellates diminished and increased, respectively, with the increase in salinity. Diatoms predominated at 25 g L−1, whereas at 2 and 4 g L−1, chlorophytes were more abundant. Microbial floc crude protein content was reduced with the increase in salinity, whereas ash content demonstrated the inverse trend. The best overall growth performance and survival were observed at 25 g L−1. However, satisfactory productivity was also found at 4 g L−1, suggesting the viability of rearing L. vannamei at low salinity under zero-water-exchange conditions.

Effects of low salinity on antioxidant enzymes activities in kidney and muscle of juvenile silver pomfret Pampus argenteus

Silver pomfret ( Pampus argenteus) is an important fish species in China, whose fatality is strongly affected by marine salinity. To better understand the tolerance of sliver pomfret to varying environmental salinity at its early developmental stages, the influence of salinity on the activities of five antioxidant enzymes – superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPX), glutathione-S-transferase (GST), and glutathione reductase (GR) – in the kidney and muscle of juvenile silver pomfret was investigated in this study. Divided groups A, B, C, D at random, the juvenile silver pomfrets were then treated with different salinity levels of 25, 20, 15, and 10 with time periods of 24, 48, 96, and 120 h respectively. Generally speaking, the results show that the renal and muscular SOD as well as the renal CAT activities first rise then drop ( P < 0.05), while the muscular CAT activity increases with the elapse of treatment time ( P < 0.05) and peaked at 96 h, then decreased at 120 h, while the muscular CAT activity in group D increased consistently and peaked at 120 h. The renal GPX activity decreases significantly ( P < 0.05) as the salinity drops and treatment time prolongs with its lowest level occurring at 96 h in group D, while the muscular GPX activity increases first then decrease ( P < 0.05); moreover the renal and muscular GPX activities vary reversely in compensation. On a whole, the renal and muscular GST and GR activities first rise then drop ( P < 0.05) with the drop of salinity and elapse of time. To sum up, the results acquired from study indicate that the salinity decrease could effectively stimulate and enhance the antioxidant enzyme activity in the kidney and muscle of the juvenile silver pomfrets, thus effectively eliminating the excessive reactive oxygen species (ROS) and minimizing the body damage. Characterized by certain sequentiality and tissue specificity, the activation of the antioxidant enzymes could also be inhibited when the salinity varies beyond the tolerance range of the body.

Effects of Low Salinity and Low Temperature on Survival, Growth, and Energy Budget of JuvenileExopalaemon carinicauda

A 4 × 4 factorial experiment was conducted to determine the effects of low salinity (0.2, 3, and 6; and the control salinity, 21) and low temperature (7°C, 9°C, and 11°C; and the control temperature, 25°C) on survival, growth, and energy budget of juvenile shrimp Exopalaemon carinicauda. The duration of the experiment was 60 days. Results showed that E. carinicauda juveniles have a greater ability to survive extreme salinity conditions at temperatures of 11–25°C, and their capability to withstand temperature extremes was greater at salinities of 3–21. The specific growth rate, food consumption, feed efficiency, and apparent digestibility coefficient of E. carinicauda showed remarkable increase paralleled with salinity elevation. Similarly, the specific growth rate, food consumption, and apparent digestibility coefficient of E. carinicauda also exhibited significant increasing tendency as the temperature rises. However, feed efficiency is found to be decreased with elevated temperature. In general, the shrimp maintained at the control salinity (21) and control temperature (25°C) had a significantly higher specific growth rate, whereas those maintained at a salinity of 0.2 and a temperature of 7°C exhibited a significantly lower value. The pattern of energy allocation is found to be varied in accordance with salinity and temperature, inasmuch as 68.46–78.98% of consumed energy was lost through respiration, 5.37–13.70% was invested in growth, 8.02–13.28% was for feces production, 4.55–5.83% was for excretion, and only 0.62–0.73% was for exuviae. The current study also reveals that there is an increased tendency for percentage of intake energy invested in growth (the energy value expressed as the percentage of intake energy, %C), whereas that lost in excretion and feces (%C) exhibited a remarkable decrease with increase of salinity. The percentage of intake energy invested in growth and lost in feces (%C) showed decreased trends, whereas that lost in respiration and excretion (%C) is found to be decreased as the temperature is elevated. As far as the pattern of intake energy allocation is concerned, it was apparent that salinity affects the growth of E. carinicauda juveniles mainly by influencing energy conversion efficiency, whereas temperature affects primarily food consumption and energy conversion efficiency as well. The interaction of low salinity and low temperature on survival and growth of E. carinicauda were also discussed.