共查询到20条相似文献,搜索用时 31 毫秒
1.
Mary J. Harner Jeff S. Piotrowski Ylva Lekberg Jack A. Stanford Matthias C. Rillig 《Aquatic Sciences - Research Across Boundaries》2009,71(3):331-337
Riparian areas are diverse systems where flooding creates new sites for establishment of vegetation. Symbioses with soil microorganisms,
such as mycorrhizal fungi, affect vascular plant growth and community composition. It is unknown, however, how mycorrhizal
fungi are dispersed along rivers and what potential they have to inoculate roots of plants establishing on recently deposited
sedimentary surfaces of flood plains. We measured AMF inocula in sediment deposited by an average spring flood along an expansive
riverine flood plain in Montana, USA, to determine whether AMF inocula were present in sediments and what types of propagules
(spores, hyphae, or colonized root fragments) contribute to AMF infectivity. Flood-deposited sediments contained sufficient
inocula for AMF to colonize host plants (Sorghum sudanense) grown in a greenhouse, and both AMF hyphal lengths and spore densities were correlated with infectivity. Availability of
mycorrhizal inocula, which is patchily distributed in this system, may lead to microsites that differ in ability to support
establishment and growth of early-successional plants. 相似文献
2.
Net autotrophy in a fluvial lake: the relative role of phytoplankton and floating-leaved macrophytes
Monica Pinardi Marco Bartoli Daniele Longhi Pierluigi Viaroli 《Aquatic Sciences - Research Across Boundaries》2011,73(3):389-403
This study combined water- and sediment flux measurements with mass balances of dissolved gas and inorganic matter to determine
the importance of pelagic and benthic processes for whole-system metabolism in a eutrophic fluvial lake. Mass balances of
dissolved O2, inorganic carbon (DIC), nitrogen (DIN), phosphorous (SRP), particulate N (PN) and P (PP) and Chl a were calculated at a nearly monthly frequency by means of repeated sampling at the lake inlet and outlet. Simultaneously,
benthic fluxes of gas and nutrients, including denitrification rates, and the biomass of the dominant pleustophyte (Trapa natans) were measured, and fluxes of O2 and CO2 across the water–atmosphere interface were estimated from diel changes in outlet concentrations. On an annual scale, Middle
Lake exhibited CO2 supersaturation, averaging 313% (range 86–562%), but was autotrophic with a net O2 production (6.35 ± 2.05 mol m−2 y−1), DIC consumption (−31.18 ± 18.77 mol m−2 y−1) and net export of Chl a downstream (8.38 ± 0.95 mol C m−2 y−1). Phytoplankton was the main driver of Middle Lake metabolism, with a net primary production estimated at 33.24 mol O2 m−2 y−1, corresponding to a sequestration of 4.18 and 0.26 mol m−2 y−1 of N and P, respectively. At peak biomass, T. natans covered about 18% of Middle Lake’s surface and fixed 2.46, 0.17 and 0.02 mol m−2 of C, N and P, respectively. Surficial sediments were a sink for O2 (−14.47 ± 0.65 mol O2 m−2 y−1) and a source of DIC and NH4
+ (18.84 ± 2.80 mol DIC m−2 y−1 and 0.83 ± 0.16 mol NH4
+ m−2 y−1), and dissipated nitrate via denitrification (1.44 ± 0.11 mol NO3
− m−2 y−1). Overall, nutrient uptake by primary producers and regeneration from sediments were a minor fraction of external loads.
This work suggests that the creation of fluvial lakes can produce net autotrophic systems, with elevated rates of phytoplanktonic
primary production, largely sustained by allochtonous nutrient inputs. These hypereutrophic aquatic bodies are net C sinks,
although they simultaneously release CO2 to the atmosphere. 相似文献
3.
Zhang Nai Tian ZuoJi Leng YingYing Wang HuiTong Song FuQing Meng JianHua 《中国科学D辑(英文版)》2007,50(8):1171-1178
The Raman spectrograms of hydrocarbon standard samples show that: (1) the Raman spectrogram of normal paraffin has very strong peaks of methyl and methylene (from 2700 cm-1 to 2970 cm-1); (2) branch methyl has the particular peak of 748 cm-1±; (3) six cyclic has the particular peak of 804 cm-1±; (4) phenyl has two particular peaks of 988 cm-1± and 3058 cm-1± and the 988 cm-1± peak is stronger than the 3058 cm-1± peak; and (5) hexene has three alkenyl spectrum peaks of 1294 cm-1±, 1635 cm-1± and 2996 cm-1±, with the 1635 cm-1± peak being the strongest, showing that the number of carbon in hy-drocarbon does not affect its Raman spectrogram, and the hydrocarbon molecular structure and base groups affect its Raman spectrogram, the same hydrocarbons (such as normal paraffin) have the same Raman spectrogram; the types (such as CH4, C2H6, C3H8) and the content of hydrocarbon in oil inclu-sions are not estimated by their characteristic Raman peaks. According to the Raman spectrograms of hydrocarbon compositions, the Raman spectrogram of hydrocarbon inclusion can be divided into five types: saturated hydrocarbon Raman spectrogram, fluoresce Raman spectrogram, saturated hydro-carbon bitumen Raman spectrogram, bitumen Raman spectrogram, and ethane Raman spectrogram. And according to the characteristics of Raman spectrogram, hydrocarbon inclusions can be divided into five types: saturated hydrocarbon inclusion, less saturated hydrocarbon (oil or gas) inclusion, saturated hydrocarbon bitumen inclusion, bitumen inclusion, and methane water inclusion. 相似文献
4.
H. R. von Gunten M. Sturm H. N. Erten E. Rössler F. Wegmüller 《Aquatic Sciences - Research Across Boundaries》1987,49(3):275-283
Sediment cores from central Lake Constance were dated with210Pb and137Cs. A sedimentation rate of (0.11±0.02) g·cm−2·y−1 was determined with the210Pb method.137Cs measurements revealed sedimentation rates of (0.11±0.01) g·cm−2·y−1 and (0.08±0.01) g·cm−2·y−1 respectively for two different cores sampled at the same location. The lower Cs-dated value indicates incomplete core recovery
and demonstrates the sensitivity of this simple dating method to small losses of material at the water/sediment interface.
An unambiguous application of the137Cs method is, therefore, only possible if complete core recovery is ensured. Sedimentation rates based on particulate matter,
collected in sediment traps at various water depths, agree with the results of the radioisotope methods. Estimates of 30–125
days residence times for suspended particulate matter were calculated from7Be measurements. 相似文献
5.
Seasonal biogeochemical and microbiological studies of small lakes in taiga zone of northwestern Russian (Arkhangelsk Province) 总被引:1,自引:0,他引:1
N. M. Kokryatskaya S. A. Zabelina A. S. Savvichev O. Yu. Moreva T. Ya. Vorobjeva 《Water Resources》2012,39(1):105-117
The results of biogeochemical and microbiological studies of three small lakes in southwestern Arkhangelsk province are presented.
The lakes differ in their morphometric characteristics, thermal and oxygen regimes, and the extent of anthropogenic impact
they experience. In the periods of summer and winter stratification, anaerobic water layers with higher phosphates, ammonium,
and sulfide sulfur (hydrogen sulfide) are found to form in the bottom horizon of deep-water zones of the lakes. The highest
concentrations of sulfide sulfur (150–210 μg dm−3) were recorded in the shallow Beloe Lake during winter low-water period, while in summer, sulfide concentration did not differ
from those obtained in other lakes (∼10 μg dm−3). The abundance of sulfate-reducing bacteria in lake bottom sediments varied from 10 to 100000 cell cm−3, and the rate of sulfate reduction process varied from 29 to 3746 μg S dm−3 day−1. Seasonal variations were revealed in hydrogen sulfide distribution over the water column and in the rate of sulfate reduction
process in the upper horizons of bottom sediments in the examined lakes. 相似文献
6.
Liverpool Bay is a region of freshwater influence which receives significant freshwater loading from a number of major English
and Welsh rivers. Strong tidal current flow interacts with a persistent freshwater-induced horizontal density gradient to
produce strain-induced periodic stratification (SIPS). Recent work (Palmer in Ocean Dyn 60:219–226, 2010; Verspecht et al. in Geophys Res Lett 37:L18602, 2010) has identified significant modification to tidal ellipses in Liverpool Bay during stratification due to an associated reduction
in pycnocline eddy viscosity. Palmer (Ocean Dyn 60:219–226, 2010) identified that this modification results in asymmetry in flow in the upper and lower layers capable of permanently transporting
freshwater away from the Welsh coastline via a SIPS pumping mechanism. Observational data from a new set of observations from
the Irish Sea Observatory site B confirm these results; the measured residual flow is 4.0 cm s−1 to the north in the surface mixed layer and 2.4 cm s−1 to the south in the bottom mixed layer. A realistically forced 3D hydrodynamic ocean model POLCOMS succeeds in reproducing
many of the characteristics of flow and vertical density structure at site B and is used to estimate the transport of water
through a transect WT that runs parallel with the Welsh coast. Model results show that SIPS is the dominant steady state,
occurring for 78.2% of the time whilst enduring stratification exists only 21.0% of the year and enduring mixed periods, <1%.
SIPS produces a persistent offshore flow of freshened surface water throughout the year. The estimated net flux of water in
the surface mixed layer is 327 km3 year
−1, of which 281 km3 year−1 is attributable to SIPS periods. Whilst the freshwater component of this flux is small, the net flux of freshwater through
WT during SIPS is significant, the model estimates 1.69 km3 year−1 of freshwater to be transported away from the coast attributable to SIPS periods equivalent to 23% of annual average river
flow from the four catchment areas feeding Liverpool Bay. The results show SIPS pumping to be an important process in determining
the fate of freshwater and associated loads entering Liverpool Bay. 相似文献
7.
8.
Young-Joo Lee 《中国科学D辑(英文版)》2006,49(8):872-880
Serious interest has been directed toward natural gas hydrate as a potential energy resource; factor in global climate change, and submarine geohazard since naturally occurring gas-hydrate deposits were found in the 1960s. Hydrate Ridge, Cascadia convergent mar- gin, is characterized by abundant methane hydrates at and below the seafloor, active venting of fluids and gases, chemosynthetic communities, and some of the highest methane oxidation rates ever found in the ma-rine environment. All of… 相似文献
9.
Giuseppe Crosa Elena Castelli Gaetano Gentili Paolo Espa 《Aquatic Sciences - Research Across Boundaries》2010,72(1):85-95
The downstream ecological consequences of two controlled “free flow” flushing operations designed to remove sediments accumulated
in an alpine reservoir are described. The main objectives of the study were (a) to verify to what extent the suspended solid
concentration (SSC) in the receiving water course can be controlled by flushing operations, (b) to determine the biological
consequences of flushing operations, and (c) to produce technical guidelines for the future planning and monitoring of these
activities. We found that the flushing of large volumes of accumulated sediment had clear effects on the stream ecosystem
due to the unpredictability of short duration SSC peaks (70–80 g L−1) and the high average SSC (4–5 g L−1) within flushing periods. The main impacts were decreased fish densities (up to 73%) and biomass (up to 66%). A greater mortality
recorded for juveniles will likely result in long-term impairment of the age-structures of future fish populations. The zoobenthic
assemblages, despite exhibiting a drastic reduction in abundance following the first floods, showed substantial recovery within
3 months of the beginning of flushing operations. Regular sediment removal by yearly flushing is recommended in order to avoid
SSC peaks and to facilitate the control of scouring effects caused by the water used to wash out sediments. We also recommend
maximum allowable SSCs of 10 g L−1 (daily average) and 5 g L−1 (overall average) for flushing operations carried out in similar environmental contexts. 相似文献
10.
Agnes Mazot Dmitri Rouwet Yuri Taran Salvatore Inguaggiato Nick Varley 《Bulletin of Volcanology》2011,73(4):423-441
During 2007–2008, three CO2 flux surveys were performed on El Chichón volcanic lake, Chiapas, Mexico, with an additional survey in April 2008 covering
the entire crater floor (including the lake). The mean CO2 flux calculated by sequential Gaussian simulation from the lake was 1,190 (March 2007), 730 (December 2007) and 1,134 g m−2 day−1 (April 2008) with total emission rates of 164 ± 9.5 (March 2007), 59 ± 2.5 (December 2007) and 109 ± 6.6 t day−1 (April 2008). The mean CO2 flux estimated from the entire crater floor area was 1,102 g m−2 day−1 for April 2008 with a total emission rate of 144 ± 5.9 t day−1. Significant change in CO2 flux was not detected during the period of survey, and the mapping of the CO2 flux highlighted lineaments reflecting the main local and regional tectonic patterns. The 3He/4He ratio (as high as 8.1 R
A) for gases in the El Chichón crater is generally higher than those observed at the neighbouring Transmexican Volcanic Belt
and the Central American Volcanic Arc. The CO2/3He ratios for the high 3He/4He gases tend to have the MORB-like values (1.41 × 109), and the CO2/3He ratios for the lower 3He/4He gases fall within the range for the arc-type gases. The high 3He/4He ratios, the MORB-like CO2/3He ratios for the high 3He/4He gases and high proportion of MORB-CO2 (M = 25 ±15%) at El Chichón indicate a greater depth for the generation of magma when compared to typical arc volcanoes. 相似文献
11.
Paula Sardiña Daniel H. Cataldo Demetrio Boltovskoy 《Aquatic Sciences - Research Across Boundaries》2009,71(4):479-486
We conducted a field experiment to assess the influence of conspecific adults on recruitment success of the golden mussel
Limnoperna fortunei. Tiles, 225 cm2 surface area, were used as artificial substrates in four treatments: control (blank tiles), low (800 mussels m−2), medium (4,000 mussels m−2) and high (12,000 mussels m−2) density treatments. Results indicated that recruitment was strongly affected by the presence and density of conspecifics.
After one and 3 months of exposure, numbers of recruits were significantly higher on tiles with conspecific adults than on
blank tiles, and there was a positive and significant relationship between the number of recruits and the number of adults
in the three treatments assayed. Also, after 3 months of exposure, recruits in all treatments with adults present were larger
than recruits in the control treatment. Our results suggest that conspecific adults have a positive effect on recruitment
success and growth of newly settled juveniles through factors that enhance larval settling or that contribute to the survival
of settlers in areas colonized by adult conspecifics. 相似文献
12.
Tonalites from the island arc rock assemblage in the Zêtang segment of the Yarlung Zangbo suture zone were analyzed for major, trace elements (including REE) and Sr-Nd isotope. The experimental datademonstrate that the tonalites have the adakite-like characteristics, including high SiO2 (58%-63%),Al2O3 (18.4%-22.4%), Sr (810×10-6-940×10-6), Sr/Y (77-106), low HREE (Y=9×10-6-11×10-6, Yb=1×10-6-1.3×10-6), with LREE enrichment and faint Eu positive anomaly. Isr (0.70421-0.70487) is relatively low whereas 143Nd/144Nd (0.512896-0.512929) and εNd(t) values ( 6.7- 7.3) are high. These feainvolvement of a small amount of oceanic sediments. The identification of Z(e)tang adakites, derived from slab melting, presents new evidence for the intra-Tethyan subduction and the previous suggestion about the existence of intra-oceanic island arc within Tethys. 相似文献
13.
D. M. Imboden B. S. F. Eid T. Joller M. Schurter J. Wetzel 《Aquatic Sciences - Research Across Boundaries》1979,41(2):177-189
In a limno-corral (diameter 12 m, depth to sediments 10 m), located in Baldeggersee (Switzerland), vertical mixing has been
measured during more than one year and compared to the conditions in the open lake (maximum depth 65 m, surface area 5.3 km2). The temperature method by McEwen and Hutchinson yields Kz values between 5×10−2 cm2s−1 at the upper boundary of the thermocline and 2×10−3 cm2s−1 at the bottom, a value near the molecular diffusion of heat at 4°C (1.36×10−3 cm2s−1). Kz calculated from profiles of excess radon-222 generally agree with those from the temperature data. Compared to the open lake,
the corral has a more shallow epilimnion. However, during calm meteorological conditions, vertical mixing in the upper 10
m is similar outside and inside the corral.
Supported by the Swiss National Science Foundation within the framework for its National Research Program on ‘Lake Currents.’ 相似文献
14.
Paul A. Bukaveckas Amy MacDonald Anthony Aufdenkampe John H. Chick John E. Havel Richard Schultz Ted R. Angradi David W. Bolgrien Terri M. Jicha Debra Taylor 《Aquatic Sciences - Research Across Boundaries》2011,73(3):419-436
Main channel habitats of the Ohio, Missouri, and Upper Mississippi Rivers were surveyed during the summers of 2004, 2005 and
2006 using a probability-based sampling design to characterize inter-annual and inter-river variation in suspended chlorophyll
a (CHLa) and related variables. Large (fivefold) differences in CHLa were observed with highest concentrations in the Upper
Mississippi (32.3 ± 1.8 μg L−1), intermediate values in the Missouri (19.7 ± 1.1 μg L−1) and lowest concentrations in the Ohio (6.8 ± 0.5 μg L−1). Inter-annual variation was small in comparison to inter-river differences suggesting that basin-specific factors exert
greater control over river-wide CHLa than regional-scale processes influencing climate and discharge. The rivers were characterized
by variable but generally low light conditions as indicated by depth-averaged underwater irradiance <4 E m−2 day−1 and high ratios of channel depth to euphotic depth (>3). Despite poor light conditions, regression analyses revealed that
TP was the best single predictor of CHLa (R
2 = 0.40), though models incorporating both light and TP performed better (R
2 = 0.60). Light and nutrient conditions varied widely within rivers and were inversely related, suggesting that riverine phytoplankton
may experience shifts in resource limitation during transport. Inferred grazing and sedimentation losses were large yet CHLa
concentrations did not decline downriver indicating that growth and loss processes were closely coupled. The contribution
by algae to suspended particulate organic matter in these rivers (mean = 41%) was similar to that of lakes (39%) but lower
relative to reservoirs (61%). 相似文献
15.
Genrietta A. Pospelova Elżbieta Król Galina M. Levkovskaya Jadwiga Kruczyk Magdalena Kądziałko-Hofmokl Sergey A. Kulakov 《Acta Geophysica》2007,55(4):619-639
The paper presents the results of experimental rock-magnetic, paleomagnetic and palynologic study of Paleolithic sediments
sampled along two profiles in the Akhshtyrskaya cave, situated in the vicinity of Black Sea shore. In the upper part of profiles,
some magnetite was observed; in the middle and lower parts, strongly oxidized non-stoichiometric magnetite and hematite prevail.
Thin maghemite covers on the surface of fine magnetite grains are present in the majority of specimens. Natural remanence
has one characteristic component (CHRM), mostly of chemical origin, although in few specimens containing magnetite it may
be sedimentary. Directions of CHRM obtained by standard paleomagnetic methods revealed anomalous pattern only in layer 3/2,
which is slightly older than the overlying layer 3/1 whose age was established as (35±2)×103 years BP by the U-Th method. This suggests that this paleomagnetic anomaly (PMA) can be correlated with Kargapolovo excursion
dated on about (45−39)×103 years BP. In the remaining overlying and underlying layers, directions of CHRM are grouped around the present geomagnetic
field. Depth distributions of scalar magnetic parameters generally coincide with the lithological division of the profiles.
Palynologic study revealed the presence of 22 pollen zones. Five thermomers separated with colder periods were found in the
middle and lower parts of profile. The non-magnetite composition of magnetic fraction of the majority of studied sediments
— oxidized nonstoichiometric magnetite and hematite — resulted in the lack of correlations between paleoclimatic and scalar
magnetic characteristics. 相似文献
16.
Matthew Robert Palmer 《Ocean Dynamics》2010,60(2):219-226
Understanding the fate of freshwater runoff and corresponding nutrient and pollution loads is of critical importance for the
development of accurate predictive models and coastal management tools. A key element of such studies is the identification
and understanding of the interaction between stratification and current structure. This paper presents a new series of measurements
made in the Liverpool Bay region of freshwater influence (ROFI) during spring 2004 where freshwater-maintained horizontal
density gradients and strong tidal currents interact to produce strain-induced periodic stratification (SIPS). During stratification,
tidal current profiles are significantly modified such that the tidal flow deviates from the otherwise rectilinear E–W axis
generating counter rotating upper and lower mixed layers. This feature has often been reported for the Rhine ROFI but not
previously identified in Liverpool Bay despite previous investigation at this site. Investigation of an ongoing long-term
dataset collected nearby reveals this process to be a common feature throughout the year. Liverpool Bay is shown to maintain
three different regimes, long term mixed, long term stratified, and a transitional state when SIPS occurs. The phase of SIPS
relative to the tide results in a residual flow away from the Welsh coastline in the upper water column of 2.3–3.6 cm s−1 with a counterflow in the lower layer of 2.8–3.1 cm s−1 towards the coast. 相似文献
17.
18.
Detlev Ingendahl Dietrich Borchardt Nicole Saenger Peter Reichert 《Aquatic Sciences - Research Across Boundaries》2009,71(4):399-410
To quantify the contribution of hyporheic community respiration to whole running-water ecosystem respiration in a cultural
landscape setting, we studied the vertical hydraulic exchange in riffle–pool sequences of the River Lahn (Germany). We used
flow through curves from four tracer experiments to estimate flow velocities in the surface and subsurface water. Generally,
vertical exchange velocities were higher in riffle sections and a high temporal variability was observed (range of values
0.11–1.08 m day−1). We then used (1) the exchange velocities and (2) time series of dissolved oxygen concentration in surface and subsurface
water to calculate hyporheic respiration. Hyporheic respiration was estimated in a range of 10–50 mg O2 m−3 day−1 for the upper sediment layer (first 20 cm). It was much lower in the deeper sediment layer (20–40 cm), ranging from 0 to
10 mg O2 m−3 day−1 (volumes are volumes of interstitial water; the average porosity was 20%). We determined primary production and respiration
of the biofilm growing on the sediment by modelling dissolved oxygen concentration time series for a 2,450 m long stream reach
(dissolved oxygen concentrations with diurnal variations from 8 to 16 mg L−1). Modelled respiration rates ranged from 2 to 21 g O2 m2 day−1. All information was integrated in a system analysis with numerical simulations of respiration with and without sediments.
Results indicated that hyporheic respiration accounted for 6 to 14% of whole ecosystem respiration. These values are much
lower than in other whole system respiration studies on more oligotrophic river systems. 相似文献
19.
M. Díaz-Asencio C.M. Alonso-Hernndez Y. Bolanos-lvarez M. Gmez-Batista V. Pinto R. Morabito J.I. Hernndez-Albernas M. Eriksson J.A. Sanchez-Cabeza 《Marine pollution bulletin》2009,59(4-7):108
The vertical distribution of Hg and Pb were determined in a sediment core collected from the Sagua estuary (North Cuba) that receives input from the Sagua river, one of the most polluted rivers discharging into the Cuban coastal environment. Depth profiles of metal concentrations were converted to time-based profiles using the 210Pb dating method and confirmed with the 137Cs fallout peak. The mean mass accumulation rate was estimated to be 0.17 ± 0.04 g cm−2 y−1 (mean sediment accumulation rate 0.52 ± 0.13 cm y−1) and the core bottom was estimated to date back about 130 years. The historical sedimentary record showed a strong enrichment of mercury concentrations in the past decades, caused by the incomplete treatment of industrial wastes from a chlor-alkali plant with mercury-cell technology in the Sagua river basin. Lead fluxes to sediments showed a gradual increase from the 1920s to present, which agrees with a population increase in Sagua la Grande City. Fluxes of both metals have increased the past 25 years, with values reaching a maximum of 0.5 and 3.9 μg cm−2 y−1 for Hg and Pb, respectively. 相似文献
20.
The results from Raman spectroscopy analysis of salt aqueous solutions at −170°C demonstrate that for those clearly sharp
iron peaks whose Raman wavenumber is close to each other such as NO
3
−
and CO
3
2−
, their original shape could be restorable by the stripping technique, and that ice’s sharp characteristic peak 3090–3109
cm−1) is steady, while the spectrum band of the complex compound (nCl−-[H+-OH−]n) chlorine ion combined chemically with water molecule is 3401–3413 cm−1. On the other hand, the research shows that the higher the negative iron concentration, the stronger its Raman characteristic
peak intensity and the smaller the ice’s. Based on the number of data and theoretical work, the strong correlation of the
molar concentration of negative ion with the S
i/S
H
2O band area ratio is built up. Moreover, the developed Raman method is successfully used in the component analysis of the
field fluid inclusions from Silurian sandstone in Tarim basin. 相似文献