共查询到20条相似文献,搜索用时 31 毫秒
1.
2.
A. N. Maeda-Martínez 《Marine Biology》2008,154(4):643-648
Osmotic pressure and major ions (Cl−, Na+, Mg2+, Ca2+) of the egg capsule fluid in the slipper limpet Crepidula fornicata were investigated in relation to embryonic development. Calcium permeability of the capsule wall was studied at oviposition,
by dipping freshly laid egg capsules in 45Ca as a tracer. This study also determined total calcium content of the embryos at different developmental stages. Osmolarity
and major ion concentrations in egg capsule fluid were higher than seawater at uncleaved and trochophore stages, and then
dropped to the same level as sea water at veliger stage. Concentrations of Cl− and Na+ were relatively high at oviposition, peaked at trochophore stage, and finally dropped close to concentrations of seawater
at hatching. In contrast, concentrations of Mg2+ and Ca2+ decreased steadily during capsular development. Radiotracer permeability experiments in freshly laid egg capsules confirmed
that the capsule wall is impermeable to this ion at that stage. However, because of the dissolution of the inner layer of
the wall during the final part of capsular development, the wall becomes permeable to calcium and probably to the rest of
the major ions studied. 相似文献
3.
The physico-chemical microenvironment of larger benthic foraminifera was studied with microsensors for O2, CO2, pH, Ca2+ and scalar irradiance. Under saturating light conditions, the photosynthetic activity of the endosymbiotic algae increased
the O2 up to 183% air saturation and a pH of up to 8.6 was measured at the foraminiferal shell surface. The photosynthetic CO2 fixation decreased the CO2 at the shell down to 4.7 μM. In the dark, the respiration of host and symbionts decreased the O2 level to 91% air saturation and the CO2 concentration reached up to 12 μM. pH was lowered relative to the ambient seawater pH of 8.2. The endosymbionts responded immediately to changing light conditions,
resulting in dynamic changes of O2, CO2 and pH at the foraminiferal shell surface during experimentally imposed light–dark cycles. The dynamic concentration changes
demonstrated for the first time a fast exchange of metabolic gases through the perforate, hyaline shell of Amphistegina lobifera. A diffusive boundary layer (DBL) limited the solute exchange between the foraminifera and the surrounding water. The DBL
reached a thickness of 400–700 μm in stagnant water and was reduced to 100–300 μm under flow conditions. Gross photosynthesis
rates were significantly higher under flow conditions (4.7 nmol O2 cm−3 s−1) than in stagnant water (1.6 nmol O2 cm −3 s−1), whereas net photosynthesis rates were unaffected by flow conditions. The Ca2+ microprofiles demonstrated a spatial variation in sites of calcium uptake over the foraminiferal shells. Ca2+ gradients at the shell surface showed total Ca2+ uptake rates of 0.6 to 4.2 nmol cm−2 h−1 in A. lobifera and 1.7 to 3.6 nmol cm−2 h−1 in Marginopora vertebralis. The scattering and reflection of the foraminiferal calcite shell increased the scalar irradiance at the surface up to 205%
of the incident irradiance. Transmittance measurements across the calcite shell suggest that the symbionts are shielded from
higher light levels, receiving approximately 30% of the incident light for photosynthesis.
Received: 6 July 1999 / Accepted: 28 April 2000 相似文献
4.
E. Pfeiler 《Marine Biology》1997,127(4):571-578
Bonefish (Albula sp.) larvae (leptocephali) from the Gulf of California complete metamorphosis in ˜10 d in natural seawater (35‰S; Ca2+ conc = 10.5 mM). The increase in ossification that occurs near the end of the non-feeding metamorphic period, in addition to the ability
of larvae to complete metamorphosis in dilute seawater (8‰ S) prompted the present study, where the effects of varying the
external calcium ion concentration, [Ca2+]e, of artificial seawater (ASW) on the survival, development and internal (whole-body) calcium ion content, (Ca2+)i, of unfed metamorphosing larvae were investigated. Early-metamorphosing larvae placed in␣ASW, where [Ca2+]e = 10.1 mM, survived for up to 10 d and developed normally without exogenous nutrients. In shorter-term experiments (4 to 5 d), no differences
in survival were found for larvae in ASW with [Ca2+]e rang-ing from 1.5 to 10.1 mM. However, in Ca2+-free ASW, most larvae died within 27 h and no larvae survived more than 42 h; the median lethal time (LT50), and its 95% confidence limits, were 14.5 (10.0 to 20.9) h. High mortality (81% after 20 h) also occurred in 1.0 mM Ca2+ ASW, but 2 of 16 larvae tested survived for 96 h. The 96 h median tolerance limit (TLM), corrected for control mortality, was 1.2 mM Ca2+. In natural seawater, larval (Ca2+)i remained relatively constant ( = 0.419 mg larva−1)␣in early- and intermediate-metamorphosing larvae, and then increased to a mean value of 0.739 mg larva−1 in advanced larvae, indicating that Ca2+ was␣taken up from the medium at this stage; the increase in (Ca2+)i corresponded to the period of ossification of the vertebral column. Internal (whole-body) magnesium ion content (Mg2+)i showed no significant change during metamorphosis ( = 0.089 mg larva−1). No significant differences in (Ca2+)i were found in advanced larvae in natural seawater and those in ASW, with [Ca2+]e ranging from 2.0 to 10.1 mM. However, clearing and staining revealed that ossification of the vertebral column had not yet occurred in advanced larvae
from 2.0 to 10.1 mM Ca2+ ASW. Also, low [Ca2+]e (1.0 to 2.0 mM) usually produced deformed larvae that swam erratically, at times showing “whirling” behavior.
Received: 21 August 1996 / Accepted: 26 August 1996 相似文献
5.
U. Postel G. Petrausch S. Riestenpatt D. Weihrauch J. Malykh W. Becker D. Siebers 《Marine Biology》1998,130(3):407-416
Inhibition of Na+/K+-ATPase from gill plasma membranes of the shore crab Carcinus maenas by cadmium was investigated and compared with inhibitory effects by known antagonists (ouabain and Ca2+). For comparative considerations the Cd2+-inhibition of the enzyme from dog kidney was also tested. Na+/K+-ATPase from dog kidney and from crab gill differed greatly in sensitivity against ouabain. The inhibition constant K
i of the dog enzyme amounted to 9.1 × 10−7 mol l−1, i.e. more than 300-fold smaller than the K
i of 2.9 × 10−4 mol l−1 determined for the crab enzyme. Ca2+ inhibited the activity of Na+/K+-ATPase from crab gill plasma membranes with a K
i of 4.3 × 10−4 mol l−1. The Na+/K+-ATPase from crab gill was inhibited by Cd2+ with a K
i of 9.1 × 10−5 mol l−1. Cd2+ inhibited the Na+/K+-ATPase from dog kidney with a K
i (6.4 × 10−5 mol l−1) comparable to that observed in the crab gill enzyme. Under experimental conditions Cd2+-inhibition of Na+/K+-ATPase was irreversible. Repeated washing, centrifugation and homogenization of the plasma membranes (four times) with Cd2+-free buffer did not restore any activity lost in the presence of 1 × 10−3 mol l−1 Cd2+. Since ouabain-insensitive (nonspecific) ATPases in the plasma membrane fraction of crab gills were inhibited by Cd2+ in the same way as Na+/K+-ATPase, the heavy metal is considered as an unspecific ATPase inhibitor. Comparing these results with literature data on
Cd2+-binding to electrophoretically separated proteins suggests that Na+/K+-ATPase is a Cd2+-binding enzyme. The results obtained on Na+/K+-ATPase were reflected by Cd2+-inhibition of the branchial ion-transport functions depending on this enzyme. The transepithelial short-circuit current of
isolated gill half lamellae, a direct measure of area-specific active ion uptake, and the transepithelial potential difference
of isolated, perfused whole gills, also indicative of active ion uptake, were inhibited by the heavy metal in a time- and
dose-dependent mode. Remarkably these inhibitions were also irreversible. These findings are ecologically and biomedically
significant: even when the actual environmental or tissue concentrations measured are low, biological microstructures such
as Na+/K+-ATPase may accumulate the heavy metal by tight binding over prolonged periods until the first inhibitory effects occur.
Received: 25 June 1997 / Accepted: 25 August 1997 相似文献
6.
Analysis of the isotope composition of calcareous structures of marine organisms has proved useful in providing biological
data. The present study constitutes the first detailed work undertaken on the isotope composition of coleoid cephalopods.
We analysed the carbon- and oxygen-isotope composition [δ13C (CO2−
3) and δ18O (CO2−
3), respectively] of the cuttlebone aragonite of wild and cultivated specimens of Sepia officinalis Linnaeus, 1758. δ13C (CO2−
3) ranged from −2.94 to 1.00‰, δ18O (CO2−
3) from −0.18 to 2.08‰. The carbon-isotope composition is not in equilibrium with the carbon species of the ambient seawater,
and does not reflect the deposition of CaCO3 in seawater. The potential influence of environmental factors and biological processes on the carbon-isotope composition
of the cuttlebone is discussed. In contrast to δ13C, the oxygen-isotope composition of cuttlebone aragonite appears to be in isotopic equilibrium with the ambient seawater.
Seasonal changes in isotopic temperature revealed by our analyses agreed with changes in the temperature of the ambient seawater.
CaCO3 was deposited all year round. A maximum life span of 2 yr, a year-round spawning season, and variable growth rates among and
within individuals have been inferred from the isotopic temperatures.
Received: 14 April 1998 / Accepted: 26 November 1998 相似文献
7.
The major inorganic and organic osmolytes responsible for hydrating the oocytes during pre-ovulatory meiotic maturation in
autumn- and spring-spawning stocks of Atlantic herring are examined. Despite the ovulated eggs of spring-spawning herring
being 1.6- to 2-fold larger than the autumn-spawning stock, the GSI (27 ± 3%) and degree of oocyte hydration (70–72% water)
were similar. Normalising the data with respect to dry mass revealed that the physiological mechanisms underlying the maturational
influx of water were the same for both classes of egg. Cl−, K+ and Pi together with a small pool of free amino acids (FAA) represented the driving forces for oocyte hydration. K+ (autumn and spring) and Pi (spring) maintained their concentrations in the ovulated eggs, while all other ions, including Cl−, Na+, NH4
+ and Mg2+ were significantly diluted. In contrast the FAA concentration increased during the hydration process. Amongst the inorganic
ions, Cl− showed the greatest increase in the ovulated eggs. The FAA content doubled from 1.5 to 3.3% of dry mass during oocyte hydration
and accounted for 29% of the calculated ovoplasmic osmolality in the ovulated eggs from both autumn- and spring-spawners.
This significant osmotic effect of the small pool of FAA was due to the low water content of the benthic eggs. The differential
movement of the inorganic and organic osmolytes that underly oocyte hydration in Atlantic herring are discussed in relation
to current models of transmembrane ion flux. 相似文献
8.
Pankaj Kumar Manish Kumar A. L. Ramanathan Maki Tsujimura 《Environmental geochemistry and health》2010,32(2):129-146
Arsenic contamination in groundwater is of increasing concern because of its high toxicity and widespread occurrence. This
study is an effort to trace the factors responsible for arsenic enrichment in groundwater of the middle Gangetic Plain of
India through major ion chemistry, arsenic speciation, sediment grain-size analyses, and multivariate statistical techniques.
The study focuses on the distinction between the contributions of natural weathering and anthropogenic inputs of arsenic with
its spatial distribution and seasonal variations in the plain of the state Bihar of India. Thirty-six groundwater and one
sediment core samples were collected in the pre-monsoon and post-monsoon seasons. Various graphical plots and statistical
analysis were carried out using chemical data to enable hydrochemical evaluation of the aquifer system based on the ionic
constituents, water types, hydrochemical facies, and factors controlling groundwater quality. Results suggest that the groundwater
is characterized by slightly alkaline pH with moderate to strong reducing nature. The general trend of various ions was found
to be Ca2+ > Na+ > Mg2+ > K+ > NH4
+; and HCO3
− > Cl− > SO4
2− > NO3
− > PO4
3− > F− in both seasons. Spatial and temporal variations showed a slightly higher arsenic concentration in the pre-monsoon period
(118 μg/L) than in the post-monsoon period (114 μg/L). Results of correlation analyses indicate that arsenic contamination
is strongly associated with high concentrations of Fe, PO4
3−, and NH4
+ but relatively low Mn concentrations. Further, the enrichment of arsenic is more prevalent in the proximity of the Ganges
River, indicating that fluvial input is the main source of arsenic. Grain size analyses of sediment core samples revealed
clay (fine-grained) strata between 4.5 and 7.5 m deep that govern the vertical distribution of arsenic. The weathering of
carbonate and silicate minerals along with surface-groundwater interactions, ion exchange, and anthropogenic activities seem
to be the processes governing groundwater contamination, including with arsenic. Although the percentage of wells exceeding
the permissible limit (50 μg/L) was less (47%) than that reported in Bangladesh and West Bengal, the percentage contribution
of toxic As(III) to total arsenic concentration is quite high (66%). This study is vital considering that groundwater is the
exclusive source of drinking water in the region and not only makes situation alarming but also calls for immediate attention. 相似文献
9.
Cod (Gadus morhua) were exposed to hypercapnia (water Pco2 = 7.5 mmHg), elevated copper level (0.4 ppm) or a combination of both in order to study extra- and intracellular acid-base
regulation and the influence hereupon of copper. During pure hypercapnia, the extracellular respiratory acidosis was completely
compensated within 12 to 24 h via a chloride-mediated increase in extracellular [HCO3
−]. Exposure to copper in normocapnic seawater caused a large and progressive increase in plasma [Na+] and [Cl−] and a metabolic acidosis. Exposure to copper in hypercapnic seawater was associated with smaller elevations of plasma [Na+] and [Cl−] than in normocapnic seawater, showing that hypercapnia had a protective effect on the copper-induced osmoregulatory disturbances.
The compensation of the hypercapnic acidosis was, however, slow and incomplete in fish exposed to both copper and hypercapnia.
Extracellular pH remained depressed by 0.3 pH units after 72 h. The data reveal that acid-base regulation was immediately
and persistently inhibited by copper. The limited acid-base regulation during combined copper and hypercapnia exposure was
chloride-mediated as during hypercapnia alone. Intracellular pH recovery was complete and very rapid in ventricular and skeletal
muscle tissues during environmental hypercapnia, whereas acid-base compensation in liver tissue was slower, the kinetics being
similar to that in the extracellular compartment. Intracellular pH compensation was significantly slowed down by copper. Copper
concentration increased drastically in gill tissue already at 3 h, while copper concentrations in liver, muscle and plasma
were significantly elevated only after 48 h, with liver showing the largest elevation.
Received: 15 November 1996 / Accepted: 2 December 1996 相似文献
10.
The toxicity of fenitrothion was determined in larvae (nauplii, Zoeae 1 to 3, Mysis 1 to 3), postlarvae (PL stages) and juvenile
shrimp (Penaeus japonicus Bate), in two media, seawater (SW) and diluted seawater (DSW) (1100 and 550 mosM kg−1, ≃ 37 and 19‰ S). The effects of fenitrothion on the osmoregulatory capacities (OC) of juveniles were recorded. A gill and
epipodite histopathological study was also conducted. For larvae in seawater, 24 and 48 h LC50s ranged from 32.9 μg l−1 (Zoeae 2) to 10.7 μg l−1 (Mysis 3), and from 3.9 μg l−1 (Zoeae 3) to 2.0 μg l−1 (Mysis 3), respectively; 48 and 96 h LC50s in postlarvae (PL) at the same salinity ranged from 1.8 μg l−1 (PL1) to 0.6 μg l−1 (PL5), and from 0.3 μg l−1 (PL7) to 0.4 μg l−1 (PL15). In juveniles, 96 h LC50s were 0.8 μg l−1 in seawater and 1.5 μg l−1 in diluted seawater. From hatching to juvenile stages, the overall trend was a rapid decrease (from nauplii to PL5–PL7) followed
by a slight increase (from PL7 to PL15 and juveniles) in the shrimp's ability to tolerate the insecticide. In juveniles kept
in seawater and in diluted seawater, fenitrothion decreased the osmoregulatory capacity (OC = difference between the hemolymph
osmotic pressure and the osmotic pressure of the medium) at both lethal and sublethal concentrations. This effect was time-
and dose-dependent. In SW, the decrease in hypo-OC was ˜ 25% at sublethal concentrations and ˜ 35% at the 96 h LC50. In DSW, the decrease in hyper-OC was ˜ 10 to 15% at sublethal concentrations. In SW, shrimp were able to recover their OC
in less than 48 h when transferred to water free of pesticide. In DSW, recovery at 48 h was only possible after exposure to
the lowest tested sublethal concentration. Haemocytic congestions (thrombosis) of the gills, lamellae necrosis and other alterations
of gills and epipodites (breakage of the cuticle, reduction of the hemolymph lacunae) were noted in juveniles exposed to lethal
and sublethal concentrations of fenitrothion.
Received: 7 October 1996 / Accepted: 13 November 1996 相似文献
11.
Marine organisms are exposed to increasingly acidic oceans, as a result of equilibration of surface ocean water with rising
atmospheric CO2 concentrations. In this study, we examined the physiological response of Mytilus edulis from the Baltic Sea, grown for 2 months at 4 seawater pCO2 levels (39, 113, 243 and 405 Pa/385, 1,120, 2,400 and 4,000 μatm). Shell and somatic growth, calcification, oxygen consumption
and
\textNH4 + {\text{NH}}_{4}^{ + } excretion rates were measured in order to test the hypothesis whether exposure to elevated seawater pCO2 is causally related to metabolic depression. During the experimental period, mussel shell mass and shell-free dry mass (SFDM)
increased at least by a factor of two and three, respectively. However, shell length and shell mass growth decreased linearly
with increasing pCO2 by 6–20 and 10–34%, while SFDM growth was not significantly affected by hypercapnia. We observed a parabolic change in routine
metabolic rates with increasing pCO2 and the highest rates (+60%) at 243 Pa.
\textNH4 + {\text{NH}}_{4}^{ + } excretion rose linearly with increasing pCO2. Decreased O:N ratios at the highest seawater pCO2 indicate enhanced protein metabolism which may contribute to intracellular pH regulation. We suggest that reduced shell growth
under severe acidification is not caused by (global) metabolic depression but is potentially due to synergistic effects of
increased cellular energy demand and nitrogen loss. 相似文献
12.
M. I. Silva H. D. Burrows S. J. Formosinho L. Alves A. Godinho M. J. Antunes D. Ferreira 《Environmental Chemistry Letters》2007,5(3):143-149
Advanced oxidation processes, such as photocatalysed oxidation, provide an important route for degradation of wastes. In this
study, the lowest excited state (3MLCT) of Ru(bpy)32+ is used to break down chlorophenol pollutant molecules to harmless products. This has the advantage of using visible light
and a short-lived catalytically active species. Photolysis of deaerated aqueous solutions of a variety of mono- and poly-substituted
chlorophenols has been followed in the presence of Ru(bpy)32+/S2O82− with near visible light (λ > 350 nm) by UV/visible absorption spectroscopy, luminescence, potentiometry, NMR and HPLC techniques.
Upon irradiation, a decrease is observed in the chlorophenol concentration, accompanied by the formation of Cl−, H+ and SO42− ions as the main inorganic products. Benzoquinone, phenol, dihydroxybenzenes and chlorinated compounds were the dominant
organic products. As the ruthenium(II) complex is regenerated in the reaction, the scheme corresponds to an overall catalytic
process. The kinetics of the rapid chlorophenol photodechlorination has been studied, and are described quite well by pseudo-first
order behaviour. Further studies on this were made by following Cl− release with respect to the initial Ru(bpy)32+ and S2O82− concentrations. A comparison is presented of the photodechlorination reactivity of the mono and polychlorophenols studied
at acidic and alkaline pH. 相似文献
13.
Microsensor studies of photosynthesis and respiration in the symbiotic foraminifer Orbulina universa 总被引:1,自引:0,他引:1
Oxygen and pH microelectrodes were used to investigate the microenvironment of the planktonic foraminifer Orbulina universa and its dinoflagellate endosymbionts. A diffusive boundary layer surrounds the foraminiferal shell and limits the O2 and proton transport from the shell to the ambient seawater and vice versa. Due to symbiont photosynthesis, high O2 concentrations of up to 206% air saturation and a pH of up to 8.8, i.e. 0.5 pH units above ambient seawater, were measured
at the shell surface of the foraminifer at saturating irradiances. The respiration of the host–symbiont system in darkness
decreased the O2 concentration at the shell surface to <70% of the oxygen content in the surrounding air-saturated water. The pH at the shell
surface dropped to 7.9 in darkness. We measured a mean gross photosynthetic rate of 8.5 ± 4.0 nmol O2 h−1 foraminifer−1. The net photosynthesis averaged 5.3 ± 2.7 nmol O2 h−1. In the light, the calculated respiration rates reached 3.9 ± 1.9 nmol O2 h−1, whereas the dark respiration rates were significantly lower (1.7 ± 0.7 nmol O2 h−1). Experimental light–dark cycles demonstrated a very dynamic response of the symbionts to changing light conditions. Gross
photosynthesis versus scalar irradiance curves (P vs E
o curves) showed light saturation irradiances (E
k) of 75 and 137 μmol photons m−2 s−1 in two O. universa specimens, respectively. No inhibition of photosynthesis was observed at irradiance levels up to 700 μmol photons m−2 s−1. The light compensation point of the symbiotic association was 50 μmol photons m−2 s−1. Radial profile measurements of scalar irradiance (E
o) inside the foraminifera showed a slight increase at the shell surface up to 105% of the incident irradiance (E
d).
Received: 26 January 1998 / Accepted: 11 April 1998 相似文献
14.
Movement rate, oxygen consumption, and respiratory tree ammonium concentration were measured in situ in the holothurians Pearsonothuria graeffei and Holothuria edulis in the Agan-an Marine Reserve, Sibulan, Philippines (9°20′30″N, 123°18′31″E). Measurements were made both day and night for
both species during April–July 2005. P. graeffei had significantly higher movement rate during the day than at night (1.14 and 0.27 m h−1, respectively; three-way ANOVA, P < 0.05) while H. edulis had higher movement rate at night compared to the day (0.83 and 0.07 m h−1, respectively), spending the daylight hours sheltering under coral. More than 80% of H. edulis had movement rate of zero during the day. Oxygen consumption of P. graeffei was significantly higher during the day than at night (1.61 and 0.83 μmol O2 g−1 h−1, respectively; two-way ANCOVA, P < 0.05), but the reduction at night was not as pronounced as the reduction in movement. H. edulis had a 75% reduction in oxygen consumption during the day compared to night (0.51 and 1.96 μmol O2 g−1 h−1, respectively), matching this species’ reduced movement rates during the day. Ammonium concentration in water withdrawn from
the respiratory trees of P. graeffei during the day (12.0 μM) was three times higher than in respiratory tree water sampled at night (4.3 μM) and 15 times higher
than ambient seawater (0.8 μM; three-way ANOVA, P < 0.05). Ammonium concentration in the respiratory tree water of H. edulis was six times higher at night (14.6 μM) than during the day (2.2 μM) and 16 times higher than that of ambient seawater (0.9 μM).
Even though H. edulis and P. graeffei are found within the same coral reef environment, they may affect different substrates and reef organisms due to their different
habitats and distinct but opposite diel cycles. 相似文献
15.
The objectives of this study were to determine the effects of sediment contamination on the benthic macrofauna and to predict
macrofaunal changes following remediation at a Superfund (uncontrolled hazardous waste) site in San Francisco Bay, California,
USA. DDT and its metabolites (ΣDDT) were the contaminants of concern. With few small-scale exceptions, all (>100) other sediment
contaminants ever measured at the site were present at background or non-toxic levels. In hierarchical regressions [Y=f(X
1, X
2, X
3), where X
1=sediment %silt + clay, X
2=sediment total organic carbon (OC), and X
3=log
10 (ΣDDT μg g−1 OC)] with data from samples collected at the study site, log10(ΣDDT μg g−1 OC) explained a highly significant amount of the variance in the infaunal index (II ) and log10(number of Amphipoda excluding Grandidierella japonica + 1) after statistically controlling for the potential effects of sediment %silt + clay and OC. The ratios of change of II and log10(number of Amphipoda excluding G. japonica + 1) with respect to log10(ΣDDT μg g−1 OC) were about −9:1 and −0.4:1, respectively. Most of the 92 species collected were present at low to moderate densities
over the entire range of ΣDDT sediment concentrations. The bivalve Theora lubrica, tubificids, most polychaetes, a tanaid (Zeuxo normani), and an amphipod (G. japonica), were common, while four other amphipods (Ampelisca abdita, Corophium heteroceratum, Photis brevipes, Dulichia rhabdoplastis), a phoronid (Phoronis cf. pallida), a bivalve (Cryptomya californica), and a cumacean (Eudorella pacifica), were rare or absent from sites with high ΣDDT sediment-concentrations.
Received: 1 August 1997 / Accepted: 13 August 1997 相似文献
16.
Photosynthetic rates of eight seagrass species from Zanzibar were limited by the inorganic carbon composition of natural
seawater (2.1 mM, mostly in the form of HCO3
−), and they exhibited more than three time higher rates at inorganic carbon saturation (>6 mM). The intertidal species that grew most shallowly, Halophila ovalis, Halodule wrightii and Cymodocea rotundata, showed the highest affinity for inorganic carbon (K
1/2 = ca. 2.5 mM), followed by the subtidal species (K
1/2 > 5 mM). Photosynthesis of H. wrightii, C. rotundata, Cymodocea serrulata and Enhalus acoroides was >50% inhibited by acetazolamide, a membrane-impermeable inhibitor of carbonic anhydrase, indicating that extracellular
HCO3
− dehydration is an important part of their inorganic carbon uptake. Photosynthetic rates of H. wrightii, Thalassia hemprichii, Thalassodendron ciliatum, C. serrulata and E. acoroides were strongly reduced by changing the seawater pH from 8.2 to 8.6 in a closed system. In H. ovalis, C. rotundata and Syringodiumisoetifolium, photosynthesis at pH 8.6 was maintained at a higher level than could be caused by the ca. 30% CO2 concentration which remained in the closed experimental systems at that pH, pointing toward HCO3
− uptake in those species. It is suggested that the ability of H. ovalis and C. rotundata to grow in the high, frequently air-exposed, intertidal zone may be related to a capability to take up HCO3
− directly, since this is a more efficient way of HCO3
− utilisation than extracellular HCO3
− dehydration under such conditions. The inability of all species to attain maximal photosynthetic rates under natural conditions
of inorganic carbon supports the notion that seagrasses may respond favourably to any future increases in marine CO2 levels.
Received: 19 March 1997 / Accepted: 31 March 1997 相似文献
17.
The ability of endosymbioses between anthozoans and dinoflagellate algae (zooxanthellae) to retain excretory nitrogen and
take up ammonium from seawater has been well documented. However, the quantitative importance of these processes to the nitrogen
budget of such symbioses is poorly understood. When starved symbiotic Anemonia viridis were incubated in a flow-through system in seawater supplemented with 20 μM ammonium for 91 d under a light regime of 12 h light at 150 μmol photons m−2 s−1 and 12 h darkness, they showed a mean net growth of 0.197% of their initial weight per day. Control anemones in unsupplemented
seawater with an ammonium concentration of <1 μM lost weight by a mean of 0.263% of their initial weight per day. Attempts to construct a nitrogen budget showed that, over
a 14 d period, ≃40% of the ammonium taken up could be accounted for by growth of zooxanthellae. It was assumed that the remainder
was translocated from zooxanthellae to host. However, since the budget does not balance, only 60% of the growth of host tissue
was accounted for by this translocation. The value for host excretory nitrogen which was recycled to the symbionts equalled
that taken in by ammonium uptake from the supplemented seawater, indicating the importance of nitrogen retention to the symbiotic
association.
Received: 23 December 1997 / Accepted: 12 September 1998 相似文献
18.
Talavera Mendoza O Armienta Hernández MA Abundis JG Mundo NF 《Environmental geochemistry and health》2006,28(3):243-255
Leachates from the El Fraile tailings impoundment (Taxco, Mexico) were monitored every 2 months from October 2001 to August 2002 to assess the geochemical characteristics. These leachates are of interest because they are sometimes used as alternative sources of domestic water. Alternatively, they drain into the Cacalotenango creek and may represent a major source of metal contamination of surface water and sediments. Most El Fraile leachates show characteristics of Ca–SO4, (Ca+Mg)–SO4, Mg–SO4 and Ca–(SO4+HCO3) water types and are near-neutral (pH=6.3–7.7). Some acid leachates are generated by the interaction of meteoric water with tailings during rainfall events (pH=2.4–2.5). These contain variable levels of SO4
2− (280–29,500 mg l−1) and As (<0.01–12.0 mg l−1) as well as Fe (0.025–2352 mg l−1), Mn (0.1–732 mg l−1), Zn (<0.025–1465 mg l−1) and Pb (<0.01–0.351 mg l−1). Most samples show the highest metal enrichment during the dry seasons. Leachates used as domestic water typically exceed the Mexican Drinking Water Guidelines for sulfate, hardness, Fe, Mn, Pb and As, while acidic leachates exceed the Mexican Guidelines for Industrial Discharge Waters for pH, Cu, Cd and As. Speciation shows that in near-neutral solutions, metals exist mainly as free ions, sulfates and bicarbonates, while in acidic leachates they are present as sulfates and free ions. Arsenic appears as As(V) in all samples. Thermodynamic and mineralogical evidence indicates that precipitation of Fe oxides and oxyhydroxides, clay minerals and jarosite as well as sorption by these minerals are the main processes controlling leachate chemistry. These processes occur mainly after neutralization by interaction with bedrock and equilibration with atmospheric oxygen. 相似文献
19.
Rosborg I Nihlgård B Gerhardsson L Sverdrup H 《Environmental geochemistry and health》2006,28(3):215-229
The water chemistry of 20 municipal water treatment plants in southern Sweden, representing various bedrock situations, and water qualities, were investigated. Four water samples, raw and treated, were collected from each plant and analyzed by predominantly ICP-OES and ICP-MS at four occasions from June to December, 2001. The concentrations of Ca, Mg, K, Na, HCO3 and a number of micronutrients, varied considerably in treated waters from the studied plants (ranges; Ca: 9.1–53.7 mg L−1, Mg: 1.4–10.9 mg L−1, K: 1.1–4.8 mg L−1, Na; 5.4–75.6 mg L−1, HCO3: 27–217 mg L−1). The elimination of Fe and Mn from raw water was efficient in all treatments investigated, giving concentrations in treated waters below the detection limits at some plants. Softening filters gave waters with Ca-concentrations comparable to the softest waters in this study. Adjustment of pH by use of chemicals like lye, soda or lime, modified the consumer water composition significantly, besides raising the pH. It was estimated that drinking water contributed to approximately 2.2–13% of the daily Ca uptake, if the gastrointestinal uptake efficiency from food and water was estimated to be around 50%. The corresponding figures for Mg was 1.0–7% and for F 0–59%. None of the studied elements showed any significant time trends in raw or treated waters during the follow-up period. The concentrations of potentially toxic metals such as Al, Pb and U were low and did not indicate risks for adverse health effects (ranges; Al: 0.5–2.3 μg L−1, Pb: 0–0.3 μg L−1, U: 0.2.5 μg L−1). 相似文献
20.
Swapan Khanra Claudio Minero Valter Maurino Ezio Pelizzetti Binay K. Dutta Davide Vione 《Environmental Chemistry Letters》2008,6(1):29-34
Here we show that the photolysis of FeCl2+ upon UV irradiation of Fe(III) at pH 0.5, yielding Cl• and then Cl2−•, upon further reaction with Cl−, induces phenol degradation. The photolysis of FeCl2+ can be highlighted and studied as the huge interference by FeOH2+ can be avoided under such conditions. Our data allowed the assessment of a photolysis quantum yield for FeCl2+ of 5.8 × 10−4 under UVA irradiation, much lower compared to the literature value of 0.5. The discrepancy can be explained if the photolysis
process is efficient but photoformed Fe2+ and Cl• undergo recombination inside the solvent cage. 相似文献