Effect of salinity on hypoxia tolerance of resting green crabs, Carcinus maenas, after feeding

Mechanisms that can influence the tolerance of hypoxia in brackish waters were studied in resting and fed crabs, Carcinus maenas, at 15?°C. Mortality, blood oxygenation, acid-base status and lactate concentration were analysed in fed crabs held in full-strength normoxic seawater (32.5‰?S) and then transferred for 24?h to a partial pressure of oxygen (P_o2) of 3?kPa (1.4?mg?l^?1) and various salinities (17, 12.5, 10, 8‰?S). At salinity levels >10‰, fed crabs tolerated P_o2 values as low as 3?kPa in the ambient water and 0.5?kPa in their arterial blood for 24?h without switching to anaerobic metabolism. Only below 10‰?S did their blood-lactate content rise, leading to their death despite the fact that their blood O₂-content was twice the control value measured in full-strength normoxic seawater and their blood P_o2 did not decrease below values recorded at higher salinity levels. Addition of CO₂ to 8‰?S water (CO₂ partial pressure increasing from 0.1 to 0.3?kPa) decreased blood-lactate production and mortality, suggesting that at 10‰?S impairment of the O₂ supply is limited by an excessive blood O₂-affinity. The results are discussed in terms of the distribution (?10‰?S) of C. maenas along salinity gradients in estuaries and bays.     

Salinity tolerance,salinity preference and temperature tolerance in the high-shore harpacticoid copepod Tigriopus brevicornis

Tigriopus brevicornis (O. F. Müller) were collected in 1992 from rock pools close to U.M.B.S. Millport, Isle of Cumbrae, U.K. and acclimated to various combinations of salinity and temperature for at least 1 wk prior to laboratory experiments. Higher salinities of acclimation enhanced tolerance to high salinity stress, while tolerance of low salinities was hardly affected by acclimation salinity. Acclimation to low temperature (10°C) extended the survivable salinity range for T. brevicornis. High-salinity acclimation enhanced the survivable temperature range. Copepods acclimated to 60 survived significantly lower and higher temperatures than did 34-acclimated individuals. At high temperature, 75-acclimated female copepods had the highest median lethal temperature, 38.9°C. Females were significantly more resistant to high temperatures than males. The copepods were seen to have a very low median lethal temperature when frozen into solid ice for 2 h; 50% mortality occurred at-16.9°C in 10°C, 34-acclimated T. brevicornis. Salinity preference experiments demonstrated an ability to discriminate between salinities differing by as little as 3. Copepods acclimated to 34 chose salinities near their acclimation salinity; individuals acclimated to 5 favoured slightly higher salinities, while copepods acclimated to 60 chose rather lower salinities.     

Relative salinity tolerance of warm season turfgrass species

Fresh water, coupled with soil salinization in many areas has resulted in an increased need forscreening of salt tolerant turf grasses. Relative salinity tolerance of eightwarm season turfgrass species were examined in this study in sand culture. Grasses were grown in a glasshouse, irrigated with either distilled water or saline sea water adjusted to 24, 48 or 72 dSm-1. Salt tolerances of the grasses were assessed on the basis of their shoot and root growth, leaf firing and turf quality. Regression analysis indicated that Zoysiajaponica (Japanese lawn grass) (JG), Stenotaphrum secundatum (St. Augustine) (SA), Cynodon dactylon (satiri) (BS), Zoysia teneuifolia (Korean grass) (KG), Digitaria didactyla (Serangoon grass) (SG), Cynodon dactylon (Tifdwarf) (TD), Paspalum notatum (Bahia grass) (BG) and Axonopus compressus(Pearl blue) (PB) suffered a 50% shoot growth reduction at 36.0, 31.8, 30.9, 28.4, 26.4, 25.7, 20.0 and 18.6 dSm1 of salinity, respectively and a root growth reduction at44.9, 43.7, 33.4, 31.0, 29.5 27.5, 21.5 and 21.4 dSm- of salinity, respectively. Leaf firing and turf quality of the selected species, as a whole, were also found to be affected harmoniously with the change in root and shoot growth. On the basis of the experimental results the selected species were ranked for salinity tolerance as JG>SA>BS>KG>SG >TD>BG>PB.     

Effects of size upon salinity tolerance and volume regulation in the hermit crab Pagurus bernhardus

Whereas small Pagurus bernhardus (L.) occur in large numbers in the intertidal areas of rocky shores, large hermit crabs living in whelk shells are most uncommon, although they are easily collected by sublittoral dredging. Experiments were carried out to assess the salinity tolerance, and the ability to regulate body volume in a dilute medium, of both small and large hermit crabs. Large, offshore hermit crabs are significantly less tolerant of 60% sea water (100%=34 S) than small, littoral specimens. Small littoral crabs increase in weight by about 15% in the first hour in 60% sea water, but increased urine output prevents swelling thereafter; indeed, there is considerable loss in weight, presumably caused by solute loss. Large, offshore, crabs increase in weight by about 15% in the first hour, thus exhibiting a higher permeability to water than small crabs, and continue to increase in weight, since urine output is not sufficient to cope with the water load. Dissections suggest that insufficient release of urine causes the low urine output in large hermit crabs, rather than inadequate production of primary urine. Calculations indicate that the nephropores of large hermit crabs are too small to allow a sufficiently high urine output to remove a large water load, unless greater pressures are developed inside the excretory systems of large hermit crabs than occur in those of small littoral individuals. In view of the soft, flexible nature of the walls of the excretory system and abdomen of P. bernhardus, it seems unlikely that high pressures could be maintained within the excretory system. It is concluded that the stenohalinity of large, offshore hermit crabs may exclude them from the littoral zone, or may be the result of exclusion by other factors, since there will be no selective advantage for large hermit crabs in maintaining the degree of euryhalinity possessed by the small littoral crabs, if the large crabs are confined to the sublittoral zone.     

Genetic experssion of temperature tolerance in the copepod Eurytemora affinis in different salinity and temperature environments

The genetic expression of temperature tolerance in Eurytemora affinis Poppe in different environments was investigated by testing temperature tolerances of broods in pairs of salinity and temperature environments. Three methods were used to identify interaction between genotype and environment: (1) the correlation between mean tolerances of halves of broods grown in the two environments, (2) brood by environment interaction and (3) heritabilities in the two environments. All correlations between means of half broods were positive, only one of six brood by environment interactions was significant and the heritability estimates were not markedly different. Thus, the variability in temperature tolerance in different salinities and in different temperatures seems to be due to the same genes; and selection pressure on temperature tolerance is in the same direction with seasonal changes in temperature and salinity.     

Effects of constant and cyclic temperatures on the salinity tolerance of the estuarine sandhopper Orchestia chiliensis

The survival of Orchestia chiliensis (Milne Edwards, 1840) was investigated at salinities between 0.3 and 68 and constant or 10 C° cyclic temperatures between 5° and 25° C. Mortality increased with age, temperature and at salinity extremes. Small individuals show little seasonal acclimatisation apart from increased thermal tolerance at the highest exposure temperature. Larger individuals show a lateral shift in the mortality curve to the right in summer, giving increased survival at most salinities. Salinity had less effect on amphipods in cyclic regimes and survival was similar in 5° to 15° C and 10° to 20° C cycles. Mortality of larger individuals was higher in the 15° to 25° C cycle, but seasonal acclimatisation gave increased resistance at all fluctuating temperatures during the summer. Mortality in cyclic temperatures was higher than at similar constant temperatures. O. chiliensis does not actively evade immersion and diel temperature changes of 10 C° represent an important stress factor. This would affect all life stages and influence field populations both in the winter and the summer.     

The mechanism of crustacean salinity tolerance: Cell volume regulation by K+ and glycine effluxes

The regulation of muscle fiber K⁺ and free amino acid (FAA) concentrations during hypoosmotic stress was investigated in the moderately euryhaline crab Cancer irroratus. After 6 h of exposure to 60% ASW, muscle fiber K⁺ concentration declined from 185 mM to 140 mM. Following this, the blood glycine levels began to increase, indicating an FAA efflux from the cells. These data indicate that both muscle fiber K⁺ and FAA contribute to cell volume regulation in C. irroratus. The early release of K⁺ limits the initial rate of cell hydration. The subsequent efflux of glycine accounts for the volume regulation response of the muscle fibers. The cell volume regulatory system of C. irroratus is a coordinated use of both inorganic ions and FAA.     

Particulate organic carbon and nitrogen in the eastern pacific ocean

Particulate organic carbon and nitrogen in sea water were measured in samples collected along a line 155°W; 50° N-15°S, during the cruise of R.V. “Hakuho-Maru” (KH-69-4). High concentrations of particulate matter were generally found at or near the sea surface; the concentrations decreased rapidly with depth. A consistent minimum was located in the depth range 150 to 250 m through the entire section sampled. The subsurface maximum layers roughly coincided with the chlorophyll maximum, but several irrregularities were noted. One of the most remarkable features of the vast stratum below 200 m depth was the presence of distinctively regional variation in concentration of particulate material through the entire section. In the section, we could define at least 6 large water parcels, vertically oriented, all with significantly different concentrations of both carbon and nitrogen. Variation in the deep water ranged from less than 5 μgC/l to more than 50 μgC/l. Correlation analysis between carbon concentration and apparent oxygen utilization (AOU) of ambient water for all samples showed that the carbon from particle-poor water parcels consistently decreased with increasing AOU, levelling to a practically constant low of around 5 to 10 μgC/l, whereas the carbon from particle-rich parcels was anomalously high (10 to 50 μgC/l) in the range of high AOU, and showed no consistent trend of convergence. The intergrated amount of particulate carbon in the total water column at each station was in the range 20 to 150 gC/m². More than 90% of this total amount was in the water column below 200 m depth, and the correlation of total amount of particulate material between the surface layer (0 to 200 m) and the water column below 200 m depth was highly significant. These observations are considered to indicate that the downward transport of these materials may be much quicker than so far estimated, at least in some localized areas.     

Different salinity tolerance mechanisms in Atlantic and Chesapeake Bay conspecific oysters: glycine betaine and amino acid pool variations

Crassostrea virginica (Gmelin) collected in 1989 from several sites within the Chesapeake Bay have narrower salinity tolerances than conspecific oysters collected in 1989 from several Atlantic coast sites (Georgia to Cape Cod). The basis of this physiological difference appears to be the biochemical mechanisms that control cellular osmolality following salinity stress. When adapted to the same salinity, the amino acid pools of both gill and adductor muscles of Atlantic oysters are larger than those of Bay oysters and different in composition. The Atlantic oyster tissues rely primarily on taurine for salinity tolerance, while the Bay oyster tissues have relatively less taurine, depending instead upon alanine, glycine and proline to adapt to high salinity. In addition, Atlantic oyster gill and adductor have 10 to 25 times the glycine betaine concentrations of these tissues from Bay oysters, depending upor the salinity of acclimation. The betaine concentration varies with salinity in Atlantic oysters, but does not change in Bay oysters. The results suggest that these biochemical differences are the basis of the narrower salinity tolerance in Bay oysters. The biochemical differences may reflect genetic differences between Bay and Atlantic oysters.     

土壤干旱胁迫对Larrea tridentata叶片膜脂过氧化和保护酶活性的影响

Larrea tridentata是一种亚热带沙漠中常绿的含树脂的灌木,有很高的生态价值和药用价值。在不同土壤干旱胁迫条件下,测量了L.tridentata叶片具有生物学活性物质的含量变化。结果表明,随着土壤水分胁迫的加重,L.tridentata保护酶活性与MDA含量的整体趋势都是先升高,在土壤水势达到-2.415 MPa时,有所下降。L.tridentata体内重要的渗透调节物质脯氨酸的质量分数总体成上升趋势。可见,保护酶及渗透调节对L.tridentata提高自身的抗旱性有重要作用。     

土壤干旱胁迫对Larrea tridentata叶片矿质营养元素含量的影响

研究了土壤干旱胁迫对Larrea tridentata叶片10种营养元素含量的影响.结果表明:N、P、K、Ca、Mg含量在土壤干旱胁迫下的变化趋势基本相同,都是在轻度水分胁迫时略有下降,随着土壤水分胁迫的加重,含量逐渐增加,只有P含量在重度水分胁迫(土壤水势为-2.415 MPa)时有所下降;在土壤水势超过了萎蔫系数后,L.tridentata的各大量营养元素含量仍能维持在较高水平有助于增强其抗旱性;L.tridentata叶片微量元素(Fe、B、Mn、Cu、Mo)含量对土壤干旱胁迫的反映不敏感,各微量营养元素的含量在土壤干旱胁迫时与正常土壤水分状态时没有显著差异;总的来讲,在土壤水分胁迫状况下,L.tridentata能通过对自身营养元素调节的方式来提高自身的抗旱性,表现出较强的抗旱性.     

Effect of low salinity on the activity,feeding, growth and absorption efficiency of Luidia clathrata (Echinodermata: Asteroidea)

Exposure of Luidia clathrata (Say) to low salinity (17 S) results in a decrease in activity and rate of feeding, but has little effect on the absorption efficiency. Growth, as indicated by changes in body size and energy content of the body wall and pyloric caeca, is reduced in low salinity due to a decrease in feeding rate (energy consumption) and to a decrease in efficiency of utilization of material and energy absorbed. The low efficiency indicates that either additional energy is required for maintenance or energy is used inefficiently in low salinity. Thus, L. clathrata is limited energetically in low salinities, although it lives and reproduces there.     

Ecological studies of the coral predator Acanthaster planci in the south pacific

Ecological surveys involving over 500 man-days between 1966 and 1969 indicate that the coral-eating sea star, Acanthaster planci, is a normal component of the coral reef community throughout the tropical Pacific, and that its abundance in the past has probably been underestimated. The sea star is not uncommon in certain environments, particularly back-reef and lagoon slopes. Sheltered, inner reefs are generally preferred over less protected reefs. Recently reported population explosions of A. planci at Guam and on the Great Barrier Reef of Australia appear to be isolated, widely-separated, local infestations of unknown cause. The infestation on the Great Barrier Reef has not spread beyond the area off Cairns and Innisfail. Approximately 40 of the more than 1000 reefs comprising the Great Barrier Reef complex have been infested heavily.     

Effects of salinity gradients on the tolerance and bioenergetics of juvenile blue crabs (Callinectes sapidus) from waters of different environmental salinities

Juvenile Callinectes sapidus Rathbun were collected from brackish and hypersaline coastal environments in August 1986 and July 1987, respectively. The brackish collection site was a salt-marsh near Grand Isle, Louisiana (USA), and the hypersaline site was in the barrier island system on the north end of the Laguna Madre near Corpus Christi, Texas (USA). On the dates of collection, salinities fluctuated daily between 20 and 30 S and between 30 and 45 S at the brackish and hypersaline collection sites, respectively. The high-salinity 21 d LC₅₀ (50% mortality) was 56.0 for brackish-water individuals and 66.5 S for hypersaline individuals. The brackish-water individuals survived 0 S. The lowsalinity 21 d LC₅₀ was 0.5 S for the hypersaline individuals. Respiration and excretion comprised a small portion of the energy budget and did not vary with salinity for individuals from brackish water. However, both respiration and excretion increased with decreasing salinity in individuals from the hypersaline environment. Respiration accounted for more energy than excretion. As energetic expenditure (due to respiration and excretion) was relatively small, scope for growth usually paralleled energy absorption. Scope for growth responses to salinity differed significantly between crabs from the two environments. Peaks in scope for growth for both the brackish-water and hypersaline individuals corresponded to salinities normally encountered by these crabs in their natural habitats. Individuals from the brackish-water population had maximal energy absorption and scope for growth at 10 and 25 S. Individuals from the hypersaline population displayed maximal energy absorption at 35 S and maximal scope for growth at 35 and 50 S.     

Larrea tridentata叶片解剖结构与保水特性的研究

为了解L.tridentata叶片在解剖学方面适应干旱的特征以及叶片的保水特性,采用石蜡切片法观察L.tridentata叶片的解剖结构,同时测定叶片保水曲线。结果显示：L.tridentata叶片厚233.6μm,表皮细胞大,具有较厚的表皮细胞外壁与角质层,上表皮外壁与角质层总厚度为23.7μm;栅栏组织发达,在叶片中占55%,细胞细长,排列紧密。从叶片保水曲线上看,L.tridentata叶片从失水到基本恒重的时间为120 h左右,显示其叶片抗脱水能力强。     

Zinc-65 specific activities in the migratory pacific hake Merluccius productus

Pacific hake [Merluccius productus (Ayres)], migrating northward along the California coastline during summer, encounter the southwesterly flowing plume of the Columbia River. Radioactive ⁶⁵Zn associated with the plume waters is taken up by the migrating hake. Smaller fish reflect this contamination earlier than larger fish. Zinc-65 specific activities increase toward the north as far as 46°N, off the mouth of the Columbia River, and then decline northward along the coast of Washington.     

拉瑞尔Larrea tridentata光合特性对CO2摩尔分数和干旱的响应

利用Li-6400光合测定系统测定拉瑞尔L.tridentata的光合生理特性及其对CO2摩尔分数升高和干旱的响应。结果表明：土壤水势在-0.884 5 MPa以上,L.tridentata的光合器没有任何损害,抵御干旱的能力很强;适当的增加CO2摩尔分数有利于提高光饱和点、光量子利用效率和最大净光合速率,且CO2摩尔分数升高的正效应要大于土壤水分胁迫的负效应,因而在一定程度上CO2摩尔分数的增加,提高了L.tridentata的抗旱能力;随着光合有效辐射的增强和CO2摩尔分数的升高,叶片净光合速率、CO2饱和点和羧化速率都有增大趋势,叶片对高摩尔分数CO2利用效率提高;不同土壤水分条件下,叶片气孔导度和蒸腾速率都随着CO2摩尔分数的升高而降低,水分利用效率随着CO2摩尔分数的升高而升高;既能饱和叶片的RubisCO,又不至于造成气孔大量关闭的CO2摩尔分数在700~800μmol.mol-1左右,说明目前的CO2摩尔分数还不足以饱和拉瑞尔的RubisCO酶。未来CO2摩尔分数升高,将对拉瑞尔的光合作用有所促进,并可能提高拉瑞尔对干旱的适应能力。     

Spatial segregation amongst goby species within an Australian estuary,with a comparison of the diets and salinity tolerance of the two most abundant species

The present study was undertaken to determine whether the various species of gobies that are found within the large Swan Estuary in south-western Australia are segregated within that system, and to attempt to determine the basis for any differences in their spatial distributions. The Swan Estuary comprises a long entrance channel (lower estuary), two wide basins (middle estuary) and the saline reaches of the tributary rivers (upper estuary). A total of 26232 gobies, representing seven species, was collected using a 3 mm-mesh seine net at 15 sites throughout this estuary on at least one occasion monthly over seven consecutive seasons between September 1983 and March 1985. Favonigobius lateralis and Pseudogobius olorum contributed 47.0 and 47.8%, respectively, to the total catch of gobies at all sites. The densities of each species at each site were used to determine the relative contribution of each species to the gobiid fauna at each of the sites in the lower, middle and upper estuary. Comparisons of these data with those published on the distribution and abundance of gobiid larvae confirmed that F. lateralis, which was found predominantly in the lower estuary, is a marine species that spawns in high salinities near the estuary mouth or in inshore coastal waters. In contrast, the life cycle of P. olorum and Papillogobius punctatus are typically completed within the saline reaches of the upper estuary, and that of Arenigobius bifrenatus within both this region and parts of the middle estuary where the substrate is particularly soft. Afurcagobius suppositus also spawns in this area, as well as in fresh water. Tridentiger trigonocephalus, represented by only eight individuals, is an introduced, marine species that was found mainly in the lower estuary. A single representative of the marine species Callogobius depressus was caught. The relatively low numbers of gobies caught in the middle estuary, where they contributed only about 3.5% to the total number of all gobies at all sites, may represent an aversion to the presence of rougher waters in the large basins. Circumstantial evidence suggests that the sandy substrate and consistently high salinities found in the lower estuary are preferred by F. lateralis, whereas the silty surface to the substrate and lower salinities of the upper estuary are preferred by Pseudogobius olorum. Densities of three of the four most abundant species were higher in either spring or summer than in winter, reflecting the influx of 0 + recruits, and possibly also the tendency for species in estuaries to congregate in the shallows during the warmer periods of the year. F. lateralis fed mainly on polychaetes and crustaceans, whereas P. olorum ingested predominantly algae, reflecting differences in mouth morphology and feeding behaviour, rather than the type of food available.     

Seasonal and areal changes in standing stocks of phytoplankton,zooplankton and micronekton in the eastern tropical pacific

Five standing stocks were measured together at similar latitudes and longitudes on seasonally repetitive cruises in 3 areas — western, eastern, and southern — of the eastern tropical Pacific. The stocks were chlorophyll a at 0 to 150 m depth (mg/m²), night and day zooplankton at 0 to 200 m depth (ml/1000 m³), and night crustacean micronekton and fish-pluscephalopod micronekton at 0 to 200 m depth (ml/1000 m³). The logarithms of the measurements of each stock in each area were subjected to analysis of variance with the following factors: season (2 month period), latitude, and longitude. Seasonal coverage was most comprehensive, with 7 successive periods, in the western area (approximately 16° N to 3° S latitude, 100° to 122° W longitude). Most stocks in most parts of the western area had a simple seasonal cycle of low amplitude, with a single maximum and minimum that usually differed by a factor <2; some stocks in some parts of the area exhibited no seasonal cycle; all statistically significant cycles, except for fish-plus-cephalopod micronekton, were similar in phase. In the other two areas, located broadly to the east and south of the western area, suitable measurements were made at only 2 periods (opposite seasons) of the year. There were indications of phase differences between chlorophyll a and zooplankton in the eastern area, which should be further investigated. Most standing stocks declined gradually from east to west, and were higher in known upwelling areas and areas of shoal thermocline than elsewhere.     

Suitability of estuarine nursery zones for juvenile weakfish (Cynoscion regalis): effects of temperature and salinity on feeding,growth and survival

Juvenile weakfish, Cynoscion regalis (Bloch and Schneider, 1801), exhibit significant spatial diffrences in growth rate and condition factor among estuarine nursery zones in Delaware Bay. The potential influence of temperature and salinity on the suitability of estuarine nursery areas for juvenile weakfish was investigated in laboratory experiments by measuring ad libitum feeding rate, growth rate and gross growth efficiency of juveniles collected in Delaware Bay in 1990 (40 to 50 mm standard length; 1.4 to 2.1 g) in 12 temperature/salinity treatments (temperatures: 20, 24, 28°C; salinities: 5, 12, 19, 26 ppt) representing conditions encountered in different estuarine zones during spring/summer. Feeding rates (FR) increased significantly with temperature at all salinities, ranging from 10 to 15% body wt d^-1 at 20°C to 33–39% body wt d^-1 at 28°C. Specific growth rates (SGR) ranged from 1.4 to 9.4% body wt d^-1 (0.3 to 1.5 mm d^-1) and gross growth efficiencies (K ₁) varied from 13.6 to 26.4% across temperature/salinity combinations. Based on nonlinear multiple regression models, predicted optimal temperatures for SGR and K ₁ were 29 and 27°C, respectively. Salinity effects on SGR and K ₁ were significant at 24 and 28°C where predicted optimal salinity was 20 ppt. At these warmer temperatures, SGR and K ₁ were significantly lower at 5 than at 19 ppt despite higher FR at 5 ppt. Therefore, maximum growth rate and growth efficiency occurred under conditions characteristic of mesohaline nurseries. This finding is consistent with spatial patterns of growth in Delaware Bay, implying that physicochemical gradients influence the value of particular estuarine zones as nurseries for juvenile weakfish by affecting the energetics of feeding and growth. Laboratory results indicate a seasonal shift in the location of physiologically optimal nurseries within estuaries. During late spring/early summer, warmer temperatures in oligohaline areas permit higher feeding rate and faster growth compared to mesohaline areas. By mid-late summer, spatial temperature gradients diminish and mesohaline areas provide more suitable physicochemical conditions for growth rate and growth efficiency whereas oligohaline areas become energetically stressful. Substantial mortality occurred at 5 ppt and 28°C, providing additional evidence that oligohaline conditions are stressful during late summer. Furthermore, juveniles provided a choice among salinities in laboratory trials preferred those salinities which promoted higher growth rates. The extensive use of oligohaline nurseries by juvenile weakfish despite the potential for reduced growth rate and growth efficiency suggests this estuarine zone may provide a substantial refuge from predation.