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1.
Chris M. Wood Martin Grosell 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2009,179(4):459-467
Transepithelial potentials (TEP) were measured in killifish, acclimated to freshwater (FW), seawater (SW), 33% SW or cycling salinities relevant to tidal cycles in an estuary, and subsequently subjected to salinity changes in progressive
or random order. Random compared to progressive salinity changes in an upward or downward direction in FW- and SW-acclimated
fish, respectively, did not greatly influence responses to salinity change. Fish acclimated to SW or 33% SW as well as those
acclimated to cycling salinities behaved similarly (TEP more positive than +15 mV in 100% SW, decreasing to ~0 mV at 20–40%
SW, and more negative than −30 mV in FW). In contrast, FW-acclimated fish displayed a less pronounced TEP response to salinity
(0 mV in FW through 20% SW, increasing thereafter to values more positive than +10 mV at 100% SW). We conclude that when evaluated
under estuarine tidal conditions, the killifish gill exhibits adaptive electrical characteristics, opposing Na+ loss at low salinity and favouring Na+ extrusion at high salinity, changes explained at least in part by the Cl− to Na+ permeability ratio. Thus animals living in the estuaries can move to lower and higher salinities for short periods with little
physiological disturbance, but this ability is lost after acclimation to FW. 相似文献
2.
Allen PJ McEnroe M Forostyan T Cole S Nicholl MM Hodge B Cech JJ 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2011,181(8):1045-1062
We measured the ontogeny of salinity tolerance and the preparatory hypo-osmoregulatory physiological changes for seawater
entry in green sturgeon (Acipenser medirostris), an anadromous species occurring along the Pacific Coast of North America. Salinity tolerance was measured every 2 weeks
starting in 40-day post-hatch (dph) juveniles and was repeated until 100% survival at 34‰ was achieved. Fish were subjected
to step increases in salinity (5‰ 12 h−1) that culminated in a 72-h exposure to a target salinity, and treatment groups (0, 15, 20, 25, 30, 34‰; and abrupt exposure
to 34‰) were adjusted as fish developed. After 100% survival was achieved (134 dph), a second experiment tested two sizes
of fish for 28-day seawater (33‰) tolerance, and gill and gastrointestinal tract tissues were sampled. Their salinity tolerance
increased and plasma osmolality decreased with increasing size and age, and electron microscopy revealed three types of mitochondria-rich
cells: one in fresh water and two in seawater. In addition, fish held on a natural photoperiod in fresh water at 19°C showed
peaks in cortisol, thyroid hormones and gill and pyloric ceca Na+, K+-ATPase activities at body sizes associated with seawater tolerance. Therefore, salinity tolerance in green sturgeon increases
during ontogeny (e.g., as these juveniles may move down estuaries to the ocean) with increases in body size. Also, physiological
and morphological changes associated with seawater readiness increased in freshwater-reared juveniles and peaked at their
seawater-tolerant ages and body sizes. Their seawater-ready body size also matched that described for swimming performance
decreases, presumably associated with downstream movements. Therefore, juvenile green sturgeon develop structures and physiological
changes appropriate for seawater entry while growing in fresh water, indicating that hypo-osmoregulatory changes may proceed
by multiple routes in sturgeons. 相似文献
3.
Alan K. Whitfield Ricky H. Taylor Caroline Fox Digby P. Cyrus 《Reviews in Fish Biology and Fisheries》2006,16(1):1-20
The recorded salinity ranges of freshwater, estuarine and marine fish species in Lake St Lucia, a Ramsar and World Heritage Site, are documented. The freshwater group is most diverse and abundant under oligohaline conditions, although the Mozambique tilapia (Oreochromis mossambicus) was common under all salinity regimes. Estuary resident species also favoured oligohaline conditions but, in contrast to the freshwater taxa, were well represented in salinities up to 40 ‰. The marine group was most diverse and abundant within the salinity range 10–40 ‰, but a large number of species could also be found in salinities up to 70 ‰. Very few fish species were able to tolerate salinities between 70 ‰ and 110 ‰, with only O. mossambicus surviving for extended periods in salinities above 110 ‰. All the aquatic macrophytes and most of the zoobenthos within the lake appear to die out within the salinity range of 50–60 ‰, thus creating additional stress to those fish present under such conditions. The food resources least affected by extreme hypersalinity are the microphytobenthos and detritus food chains, with detritivorous fishes being dominant when the lake is in this state. Mass mortalities of fishes in Lake St Lucia have been recorded under both low (<5 ‰) and high salinity (>70 ‰) conditions. The fish kills are often triggered by exceptionally low or high water temperatures which affect the osmoregulatory abilities of these species. Hypersaline conditions and fish mortalities under the most recent closed estuary mouth conditions (2002–2005) are reviewed. If the surface area of St Lucia (35,000 ha) is compared to the total surface area of all South African estuaries (approximately 70,000 ha), then the possibility exists that the loss of the Lake St Lucia nursery area for estuary-associated marine fish species over the past few years may cause significant short-term declines in the future abundance of these taxa on both a local and regional scale. 相似文献
4.
Klaus Anger Eduardo Spivak Tomás Luppi Claudia Bas Deborah Ismael 《Helgoland Marine Research》2008,62(2):93-102
The semiterrestrial crab Neohelice (=Chasmagnathus) granulata (Dana 1851) is a predominant species in brackish salt marshes, mangroves and estuaries. Its larvae are exported towards coastal
marine waters. In order to estimate the limits of salinity tolerance constraining larval retention in estuarine habitats,
we exposed in laboratory experiments freshly hatched zoeae to six different salinities (5–32‰). At 5‰, the larvae survived
for a maximum of 2 weeks, reaching only exceptionally the second zoeal stage, while 38% survived to the megalopa stage at
10‰. Shortest development and negligible mortality occurred at all higher salt concentrations. These observations show that
the larvae of N. granulata can tolerate a retention in the mesohaline reaches of estuaries, with a lower limit of ca. 10–15‰. Maximum survival at 25‰ suggests that polyhaline conditions rather than an export to oceanic waters are optimal for
successful larval development of this species. In another experiment, we tested the capability of the last zoeal stage (IV)
for reimmigration from coastal marine into brackish waters. Stepwise reductions of salinity during this stage allowed for
moulting to the megalopa at 4–10‰. Although survival was at these conditions reduced and development delayed, these results
suggest that already the zoea-IV stage is able to initiate the reimmigration into estuaries. After further salinity reduction,
megalopae survived in this experiment for up to >3 weeks in freshwater, without moulting to juvenile crabs. In a similar experiment
starting from the megalopa stage, successful metamorphosis occurred at 4–10‰, and juvenile growth continued in freshwater.
Although these juvenile crabs showed significantly enhanced mortality and smaller carapace width compared to a seawater control,
our results show that the late larval and early juvenile stages of N. granulata are well adapted for successful recruitment in brackish and even limnetic habitats. 相似文献
5.
Alvaro Israel Milagrosa Martinez-Goss Michael Friedlander 《Journal of applied phycology》1999,11(6):543-549
Acclimation responses of the red alga Gracilaria tenuistipitata var. liui collected on the northwest coast of Philippines were determined in laboratory setups and outdoor cultivation tanks in Haifa,
Israel. Growth under laboratory conditions was influenced by all three variables studied, namely, temperature (20 or 30 °C), salinity (20, 30 or39‰) and seawater pH (6.5, 7.0, 8.0 or ≥ 9.0). In 250 mL flasks lacking pH control growth was influenced
by temperature only at 20 ‰, whereas at 39 ‰, growth rates were similar at 20 or 30 °C. In 500 mL cylinders in which pH was controlled, growth rates were significantly different at a pH of 6.5 and 7.0 for all
salinities, with maximal rates occurring in 39 ‰. At pH 8.0, and above, growth rates between salinities were similar and reduced
to approximately 50% at a pH of 9.0 compared to rates at a pH of 6.5. Photosynthesis responses generally resembled growth
responses both, in 250 mL and 500 mL cultures. In 40-L outdoor tanks, weekly growth and agar yields were apparently enhanced
by increasing light intensities (up to full sunlight) and nutrient concentrations (up to 0.2 mM PO3
2- and 2.0 mM NH4
+), and rates averaged four times higher than rates determined in the smaller flask cultures. This study shows broad salinity
tolerance of G. tenuistipitata var. liui and its ability to sustain growth rates that are among the highest measured for Gracilaria spp. in outdoor cultures.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
6.
Park JS 《Extremophiles : life under extreme conditions》2012,16(1):161-164
Substantial halophilic organisms have been found in 100–200‰ salinities. These ranges represent a highly specialized halophilic
environment to which only a few halotolerant species have adapted. Recent studies have underlined the existence of diverse
obligately halophilic protozoa in the salinity ranges of 100–200‰. The ranges of salinity under which these organisms can
grow have been examined to some extent, but the balance of specific ions that will support growth has not been investigated.
The heterotrophic nanoflagellate Halocafeteria, the type strain of which grows optimally at 150‰ salinity and 35°C, is a commonly encountered obligate halophile found in
very hypersaline environments. These extreme environments can vary in their Mg:Ca ratios (i.e. weight ratios) and sulfate
concentrations. To examine growth response of Halocafeteria to the different chemical compositions, densities of Halocafeteria seosinensis strain EHF34 were monitored in seven different ion composition media for 9 days at 1- to 2-day intervals (at 150‰ salinity
and 35°C, with no prey limitation). Halocafeteria does not grow at Mg:Ca ratios of 35 and 100 and at high sulfate concentrations of 11.6 and 31.6 g l−1. It grows well in 0.6 g l−1 sulfate media at Mg:Ca ratios of 2, 10 or 35, but not 100. The present study demonstrates that the growth of the obligate
halophile Halocafeteria can be affected by different ion compositions in hypersaline environments. Therefore, Halocafeteria may not be ubiquitous in hypersaline environments due to its ionic requirements. 相似文献
7.
Optimum temperature and salinity conditions for viable hatch were studied for turbot (Scophthalmus maximus L.) from the North Sea. Temperatures ranging from 6 to 22°C and salinities from 5 to 35‰ were used. Optimum conditions were
observed to be between 12 and 18°C at salinities between 20 and 35‰. This contrasted with corresponding data for turbot from
the southern Baltic proper, according to which survival sharply decreased in temperatures below 14°C and was high in salinities
of 10 to 15‰. Thus, it is concluded that Baltic and Atlantic turbot should be considered as different races. 相似文献
8.
The green sturgeon, Acipenser medirostris, is an anadromous species that migrates from freshwater (FW) to seawater (SW) relatively early in its life history, although
the ages and sizes of juveniles at SW entry are not known. Developmental constraints of osmoregulatory organs may either prohibit
(i.e., due to salinity tolerance limits) or minimize (i.e., due to substantial osmoregulatory or ionoregulatory energetic
costs) SW entry in small fish. Interestingly, larger green sturgeon are often encountered in brackish water (BW) estuaries,
perhaps due to an energetic advantage in occupying these near-isosmotic environments. To test hypotheses concerning fish-size
effects on the energetic costs of occupying habitats of different salinities, we measured oxygen consumption rates in green
sturgeon representing three age groups (100, 170, and 533 days post hatch; dph), which were acclimated for 5 weeks to one
of three salinities (FW, <3‰; BW, 10‰; or SW, 33‰). Also, after 7 weeks, final wet masses were compared and blood and muscle
tissue samples were taken to assess osmoregulatory abilities. There were no differences in body-mass-adjusted oxygen consumption
rates between any salinities or ages, indicating that the energetic costs were not prohibitively high to occupy any of these
salinities. The only mortalities occurred in the 100 dph SW group, where 23% of the fish died, from apparent starvation. Final
wet masses were comparable between FW and BW for each age group and with the 533 dph SW group, but were lower in SW groups
at 100 and 170 dph. Similarly, osmoregulatory abilities, in terms of plasma osmolality, Na+, K+, lactate, and protein concentrations, and muscle water content, were comparable in FW and BW groups at all ages, and with
the SW group at 533 dph. These results indicated an age/body size effect in hyperosmotic adaptability, and that juvenile green
sturgeon may be found in FW or BW at any age, but only have the ability to enter SW by 1.5 years (75 cm, 1.5 kg) of age. 相似文献
9.
Spatial changes in structural and functional characteristics of fish and macroinvertebrate communities in eastern Kentucky
were investigated in a drainage system chronically exposed to high levels of chloride salts from nearby oilfield operations.
Salinity levels at biological monitoring stations ranged from 0.12–31.3‰. Lotic regions with salinities greater than 10‰ were
dominated by larvae of the dipterans Ephydra and Culicoides. In regions with salinities less than 10‰ species richness increased more or less linearly with decreasing levels of chloride
salts. Ephemeropterans appeared to be one of the major invertebrate groups least tolerant of elevated NaCl levels and were
absent in regions with salinities greater than 2‰ Availability of food resources, such as periphyton and particulate organic
matter, did not appear to be grossly altered in disturbed regions, and it is suggested that the observed distribution of macroinvertebrate
fauna was largely in response to taxonomic differences in salt tolerance. Fish seemed to be more tolerant of highly saline
conditions, and several species were observed in regions experiencing salinities as high as 15‰. Accordingly, assemblages
of fish taxa along the salinity gradient may have been influenced by trophic factors, such as spatial limitations in availability
of invertebrate prey. 相似文献
10.
Franck Lartaud Laurent Emmanuel Marc de Rafelis Michel Ropert Nathalie Labourdette Christopher A. Richardson Maurice Renard 《Facies》2010,56(1):13-25
Cathodoluminescence (CL) microscopy of the foliated calcite shell hinge sections of live-collected oyster Crassostrea gigas collected at seven locations along a latitudinal gradient from the Netherlands in the North Sea to the Atlantic coast of
France, revealed variations in luminescence that were attributable to seasonal variations in calcification of the hinge. Photomicrographs
of hinge sections and luminescence profiles were analyzed to define a micro-sampling strategy that was adopted to drill the
hinge samples to determine their isotopic composition. Reconstructed seasonal seawater temperatures determined from the stable
oxygen isotope (δ18O) composition along growth profiles from 32 oyster shell hinges showed distinct seasonal isotopic cycles that were compared
with in situ measured seawater temperatures and salinities at each location. Comparison of the amplitude of the (δ18O) signal and the annual maximum and minimum seawater temperatures demonstrated that C. gigas shells from several locations provided a reliable record of seasonal seawater temperature variation. The exception to this
was oysters from the Netherlands and northern France where winter growth rates at low temperatures were slow so that insufficient
shell was deposited to allow adequate spatial resolution of sampling and this resulted in time-averaging of the reconstructed
seawater temperatures and an overestimation of winter seawater temperature. A potential variability in δ18Ow–salinity relationship at low salinities could also explain the high difference between measured and predicted seawater temperatures
in Dutch areas. The finding that latitudinal differences in oyster hinge growth rates and/or changes in the δ18Ow–salinity relationship can result in bias of the seawater temperature deduced from the stable isotopic composition of the
hinge should be taken into account when reconstructing latitudinal gradients in seawater temperature. 相似文献
11.
Douglas P. Middaugh Michael J. Hemmer Yara Lamadrid-Rose 《Environmental Biology of Fishes》1986,15(2):107-117
Synopsis Spawning patterns of inland silversides, Menidia beryllina, and tidewater silversides, Menidia peninsulae, were examined in the laboratory under several combinations of ‘tidal’ and diel light cycle cues. M. beryllina showed a high frequency of spawning throughout the day when held under constant conditions (24L: OD, current velocity 8 cm
sec−1) and when ‘tidal’ and diel light cycles were presented singly or in combination. In contrast, M. peninsulae demonstrated a high frequency of spawning only when presented a combination of ‘tidal’ and diel light cycle cues and spawned
predominantly at night. Menidia beryllina embryos were euryhaline. Hatching ranged from 73 to 78% at salinities of 5,15 and 30‰ M. peninsulae embryos showed an inverse relationship between the percentage hatch and the incubation salinity, 90% at 5‰ and only 65% at
30‰ Survival and growth of larval M. beryllina from the day of hatching through 16 days old was optimal at 15‰ Although survival of M. peninsulae larvae was optimal at 30%, no trend was apparent in growth of larvae held for 16 days at 5, 15 or 30‰ salinity.
Contribution No. 508 from the Gulf Breeze Environmental Research Laboratory 相似文献
12.
M.A. Sobrado 《Photosynthetica》1999,36(4):547-555
In leaves of the mangrove species Avicennia germinans (L.) L. grown in salinities from 0 to 40 ‰, fluorescence, gas exchange, and δ13C analyses were done. Predawn values of Fv/Fm were about 0.75 in all the treatments suggesting that leaves did not suffer chronic photoinhibition. Conversely, midday Fv/Fm values decreased to about 0.55-0.60 which indicated strong down-regulation of photosynthesis in all treatments. Maximum photosynthetic
rate (P
max) was 14.58 ± 0.22 μmol m-2 s-1 at 0 ‰ it decreased by 21 and 37 % in plants at salinities of 10 and 40 ‰, respectively. Stomatal conductance (g
s) was profoundly responsive in comparison to P
max which resulted in a high water use efficiency. This was further confirmed by δ13C values, which increased with salinity. From day 3, after salt was removed from the soil solution, P
max and g
s increased up to 13 and 30 %, respectively. However, the values were still considerably lower than those measured in plants
grown without salt addition.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
13.
Takayanagi T Hirokawa Y Yamamoto M Ohki T Fujiwara S Tsuzuki M 《Marine biotechnology (New York, N.Y.)》2007,9(1):56-65
Both coccolith-bearing cells (C-cells) and naked cells (N-cells) of the coccolithophorid Pleurochrysis haptonemofera can grow in salinities of more than 7‰ (about 20% of a “normal” sea water salinity [35‰]), with the highest growth rates
in salinities of more than 14‰. Microscopic observations of cells suspended in 100 mM NaCl (7‰) showed that, while N-cells
were swelling uniformly all over the cell surface, C-cells were bulging the plasma membrane from the hole of the coccosphere
at the apical (flagellar) pole of the cell. Effects of several cations and anions on the morphological change of C-cells under
hypoosmotic pressure were investigated. When 100 mM K+ was used, protoplasts were released from the coccosphere completely in almost all the cells. This phenomenon was shown with
K+ most effectively. The protoplasts could grow in the fresh medium and form the first coccolith within 9 h. 相似文献
14.
The estuarine red alga,Bostrychia radicans, was subjected to osmotic stresses ranging from hypo-osmotic (9.9‰) to hyperosmotic conditions (37.4‰). The growth rate decreased
with increasing salinities and showed a maximum in a mesohaline medium, while the photosynthetic rate and the chlorophyll
a content increased under hyper-osmotic conditions. The rate of respiration remained constant over the salinity range tested.B. radicans revealed typical characteristics of “shade plants” having a low light compensation point at 3–4 μE m−2 s−1 correlated with a low photon flux density of 70–100 μE m−2 s−1 for saturation of photosynthesis. These physiological properties may explain the success ofB. radicans in estuarine habitats. 相似文献
15.
Diversity of juvenile fish assemblages in the pelagic waters of Lebanon (eastern Mediterranean) 总被引:1,自引:0,他引:1
Oxygen consumption rates of nauplii of the brine shrimp Artemia franciscana Kellogg 1906 were determined over a range of salinities from 10 to 110 ppm, in temperatures from 0 to 30°C, using a multi-factorial
design. The oxygen micro-sensors employed have a fast response time and are capable of accurately measuring oxygen concentrations
at temperatures well below 0°C. Oxygen uptake rate ranged from 0.03 to 0.66 μmol O2 mg−1 h−1 and was sensitive to changes in both salinity and temperature. Temperature was the dominant factor affecting oxygen consumption
rates, which showed a significant increase with increasing temperature. A slight decrease was measured in oxygen consumption
with increasing salinity related to differential solubility of oxygen in waters of different salinities. Thermal sensitivity
of oxygen consumption determined from calculations of Q
10, indicated physiological adaptation of Artemia nauplii to the ranges of temperatures tested.
Handling editor: A. van Kerchove 相似文献
16.
The purpose of this study was to determine the seasonal water use patterns of dominant macrophytes coexisting in the coastal
Everglades ecotone. We measured the stable isotope signatures in plant xylem water of Rhizophora mangle, Cladium jamaicense, and Sesuvium portulacastrum during the dry (DS) and wet (WS) seasons in the estuarine ecotone along Taylor River in Everglades National Park, FL, USA.
Shallow soilwater and deeper groundwater salinity was also measured to extrapolate the salinity encountered by plants at their
rooting zone. Average soil water oxygen isotope ratios (δ
18O) was enriched (4.8 ± 0.2‰) in the DS relative to the WS (0.0 ± 0.1‰), but groundwater δ
18O remained constant between seasons (DS: 2.2 ± 0.4‰; WS: 2.1 ± 0.1‰). There was an inversion in interstitial salinity patterns
across the soil profile between seasons. In the DS, shallow water was euhaline [i.e., 43 practical salinity units (PSU)] while
groundwater was less saline (18 PSU). In the WS, however, shallow water was fresh (i.e., 0 PSU) but groundwater remained brackish
(14 PSU). All plants utilized 100% (shallow) freshwater during the WS, but in the DS R. mangle switched to a soil–groundwater mix (δ 55% groundwater) while C. jamaicense and S. portulacastrum continued to use euhaline shallow water. In the DS, based on δ
18O data, the roots of R. mangle roots were exposed to salinities of 25.4 ± 1.4 PSU, less saline than either C. jamaicense (39.1 ± 2.2 PSU) or S. portulacastrum (38.6 ± 2.5 PSU). Although the salinity tolerance of C. jamaicense is not known, it is unlikely that long-term exposure to high salinity is conducive to the persistence of this freshwater
marsh sedge. This study increases our ecological understanding of how water uptake patterns of individual plants can contribute
to ecosystem levels changes, not only in the southeast saline Everglades, but also in estuaries in general in response to
global sea level rise and human-induced changes in freshwater flows. 相似文献
17.
Juncus kraussii Hochst., an important saltmarsh macrophyte, is intensively harvested for many commercially orientated products and current populations are under threat of overexploitation. In saline, intertidal mud banks, this species occurs on higher ground, suggesting that it is adapted to lower salinities and less frequent inundation. The objectives of this study were to determine biomass accumulation, as well as morphological and physiological adaptations of J. kraussii to salinity and waterlogging stresses. Plants collected from the field were subjected to 0.2, 10, 30, 50 and 70% seawater under drained or flooded conditions for three months. Measurements were made of biomass accumulation, CO2 exchange, chlorophyll fluorescence, ion and water relations. Furthermore, seed germination responses to a range of salinities were investigated. Total dry biomass accumulation, as well as the number and height of culms, decreased with increase in salinity under both flooded and drained conditions. Generally, CO2 exchange, stomatal conductance, Photosystem II (PSII) quantum yield and electron transport rate (ETR) through PSII declined with increase in salinity in both the flooded and drained treatments. Predawn and midday ψ in culms decreased with increase in salinity, being lower under drained than flooded conditions. Inorganic solute concentrations in culms increased with increase in salinity, with Na+ and Cl− being the predominant ions. Na+/K+ ratios in culms increased significantly with increase in salinity. Proline concentrations in roots and culms, which increased with salinity, were considerably higher under drained than flooded conditions. Germination was best at salinities less than 20% seawater and decreased significantly with further increase in salinity to 110% seawater. Transfer of ungerminated salt-treated seeds to distilled water stimulated germination. This study has demonstrated that J. kraussii is a highly salt and flood tolerant species, being able to grow and survive in salinities up to 70% seawater, under both drained and flooded conditions. Maximal growth occurred at low salinities (<10% seawater) under flooded condition. 相似文献
18.
Lepidium latifolium is an aggressive plant species that is invading both wetlands and uplands across a wide range of salinities. This study examined
how salinity and moisture gradients influence the potential for invasion by L. latifolium. Three sites in the San Francisco Bay Delta with varying salinity and moisture levels were chosen as research sites. These
sites corresponded to a dry (18.32%) freshwater (3.88‰) site, a wet (40.53%) brackish (23.16‰) site, and a moderately wet
(38.33%) saline (32.33‰) site. Our results showed that inflorescence number and height were unaffected by salinity or soil
moisture. Seed production was significantly affected by salinity (P = 0.0297) and moisture levels (P = 0.0004). Seed production at the high salinity site was reduced by 29% from the freshwater site. Seed production at the
wettest site had an 87% reduction from the driest site. Seed viability was also reduced by both salinity (P < 0.0001) and soil moisture (P < 0.0001). Viability at the highest salinity site was reduced by 49% from freshwater sites and was reduced by 8% from the
wettest to driest sites. Mean seed dispersal distance was 0.23 m greater at the freshwater site, which was not statistically
significant (P = 0.1815). The deleterious effects of salinity and moisture resulted in reduced L. latifolium densities in high salinity and moisture locations, but only at the highest salinity site. With increased seed production
and viability, drier freshwater sites experience greater propagule pressure, resulting in an increased invasion potential.
Therefore, variability along salinity and soil moisture gradients serve as useful metrics for prioritizing control and eradication
efforts of L. latifolium. 相似文献
19.
Body density measurements were carried out on larval Artemia franciscana that had been held for 24 h at either 33 or 100‰ after hatching. Body density was low (1.0308–1.0342 g ml−1) by comparison with marine crustacean zooplankters or benthic freshwater crustaceans, and very stable, being only 0.3% higher
in 100‰ than in 33‰. Vertical and horizontal swimming in 2nd instar larvae was studied at 8.5, 17, 34, 50, 100, 150 and 250‰
at 23 °C. At 8.5–50‰ downwards swimming was always significantly faster than upwards swimming, but in 100‰ downwards swimming
was much slower than upwards swimming, indicating substantial positive buoyancy. At 150 and 250‰ downwards swimming was impossible.
Horizontal swimming speed was unaffected by salinity over the range 8.5–100‰, but could not be studied at 150 and 250‰ as
larvae could not leave the surface film. An asymptotic relationship between salinity and viscosity was found over the range
8.5–250‰. Calculations indicate a rise from 1.197 to 1.513 cp between 8.5 and 100‰, but this does not significantly impede
horizontal locomotion. It appears that water column use by early stage Artemia larvae, that use a pair of 2nd antennae for rowing-type locomotion, is constrained by the increasing positive buoyancy associated
with living at salinities above that corresponding to neutral buoyancy (approximately 48‰). 相似文献
20.
Clement K. M. Tsui K. W. Fan Raymond K. K. Chow E. B. Gareth Jones Lilian L. P. Vrijmoed 《Mycoscience》2012,53(1):1-9
We investigated the effects of salinity on the zoospore production of four mangrove thraustochytrid isolates, Schizochytrium sp. KF1, Aurantiochytrium
mangrovei KF6, Thraustochytrium striatum KF9 and Ulkenia sp. KF13. The zoospore motilities, which were based on curvilinear velocity (VCL) and straight-line velocity (VSL), were
monitored using the Computer-Assisted Sperm Motility Analysis (CASA) Software system. The zoospore production of four isolates
was suppressed at salinity above 15‰. Schizochytrium sp. produced the greatest number of zoospores at 15‰, while Aurantiochytrium mangrovei and Ulkenia sp. produced abundant zoospores in diluted sea water ranging from 7.5 to 15‰. Thraustochytrium striatum performed relatively poorly under all salinities. Salinity and exposure time, as well as their interactions, had significant
impacts on most zoospore velocity measurements. The optimal velocities of zoospore motility also varied among isolates. Zoospores
of Schizochytrium sp. and A. mangrovei had similar responses to salinity, with the highest motility at 7.3‰, followed by a decrease in velocities with increasing
salinity. In contrast, the zoospore of T. striatum had optimal motility at 12‰ and remained highly motile from 15 to 20‰. The velocities of zoospores of Ulkenia sp. were the lowest among the tested thraustochytrids and had optimal motility at 12‰. Zoospores of all the isolates remained
active after 4 h of exposure to aqueous medium, but the optimal salinity for each mode of swimming changed. The ecological
significance of these data are discussed. 相似文献