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1.
Laminated sediment is deposited in the deep areas (> 30 m) of Lake Pääjärvi. In the diatom microstratigraphy a regular alteration of planktonic and littoral floras, which goes in pace with the visual structure, reflects the yearly cycle of sedimentation. Considerable variation in sedimentation was found to have occurred during the past two decades. A sequence, dated to the early 1960's, in which the organic content was exceptionally high, could be identified in the sediment at 6–14 cm depth even in shallower areas where laminations are not formed. This level was used as a marker horizon when determining the recent distribution of sediment by means of 19 cores taken from different parts of the lake. The average annual sediment accumulation in the profundal zone of the lake is 340 g m?2a?1 dry weight, of which 25 g m?2 a?1 (1100 kJ m?2 a?1) is organic carbon. 相似文献
2.
Annual cycles of benthic community oxygen uptake in a deep oligotrophic lake (Attersee,Austria) 总被引:1,自引:1,他引:0
Peter Newrkla 《Hydrobiologia》1982,94(2):139-147
Benthic community oxygen uptake of Lake Attersee sediments was measured between 1976 and 1979, along two profiles at 25, 50
and 100 m depth. Profile I was situated in the bay of Unterach into which the main tributary, Mondsee-Ache, discharges a high
load of organic matter. Profile II was chosen at Weyregg to avoid the eutrophying effect of Mondsee-Ache. Oxygen uptake rates
of Unterach sediments at 25 and 50 m depth were found to be higher when compared to the other sites (mean rates: Unterach
25 m = 15.56, 50 m = 11.05 mg O2 · m−2 · h−1; Weyregg 25 m = 6.43, 50 m = 5.14 mg O2 · m−2 · h−1). Organic content of the uppermost sediment layer was also higher in the bay of Unterach than at Weyregg.
Oxygen uptake rates of undisturbed sediment cores vary considerably throughout the year, but no simple correlation existed
with variations in organic content of the sediments. Peaks of organic matter were found to concur with following peaks of
oxygen uptake rates, which implies that a certain time span is necessary for transforming freshly sedimented organic matter
into a state digestable for the benthic community. The retardation between increasing organic matter of the sediment and the
corresponding increase of benthic oxygen uptake was different at Unterach and Weyregg respectively, which is explained by
the different quality of sedimenting material. 相似文献
3.
Fixation of phosphorus in lake sediments using iron(III)chloride: experiences,expectations 总被引:5,自引:5,他引:0
Paul Boers Joop Van der Does Marinus Quaak Jo Van der Vlugt Paddy Walker 《Hydrobiologia》1992,233(1-3):211-212
After a reduction of the external phosphorus loading to a lake, an internal loading from the sediments may delay the improvement of the water quality. The accepted method to combat internal loading is careful dredging of the upper sediment layers (Cooke et al., 1986), but this method is costly and time consuming. Addition of phosphorus binding agents to the sediments might offer an alternative. In the Netherlands the use of aluminum compounds, the most common phosphorus binding agent, for water quality improvement purposes is not favoured. Therefore a sediment treatment with a solution of iron(III)chloride was tested. Iron was chosen because it is considered to be a natural binder of phosphate. 100 g m–2 of Fe3+ were added to the sediments of the shallow (1.75 m average depth) and eutrophic Lake Groot Vogelenzang (The Netherlands) in October and November 1989. The iron(III)chloride solution was diluted 100 times with lake water and mixed with the surface sediments with a water jet.Following the addition the concentrations of total phosphorus (Fig. 1), chlorophyll-a and suspended solids decreased. This improvement of the water quality lasted for three months. After this time the total phosphorus concentration increased again, but remained at a lower level than in spring and summer of 1989. The phosphorus release rate from the sediments as measured from intact sediment cores decreased from 4 to 1.2 mg P m–2 d–1 (n = 5), and the bioavailability of the sediment phosphorus, as measured with bioassays, decreased from 34 to 23% (n = 5) shortly after the treatment. One year after the treatment the release rate was increased to 3 mg P m–2 d–1 (n = 5). Before treatment, the lake was thought to have a residence time of over one year. However, the chloride added to the lake disappeared according to a dilution rate of 0.03 d–1 or a retention time of about 35 days. A high external loading due to rapid flushing with phosphorus-rich water from surrounding lakes possibly prevented a more durable improvement in water quality. Another possibility is that the iron addition has lost its phosphate binding capacity due to reduction or binding with other anions like carbonate or sulphide. Therefore the suitability of the method to reduce internal loading and especially the long term availability of added iron to bind phosphorus needs additional proof.The treatment of the 18 ha area of Lake Groot Vogelenzang took three weeks. The operational costs were about US$ 125000. This is fast and cheap compared to dredging. Application of the technique is limited to those cases where the sediments are not polluted with micro-pollutants and the water depth need not be increased. 相似文献
4.
Temperature dependence of sediment-water exchange in Lake Grevelingen,SW Netherlands 总被引:1,自引:1,他引:0
Extended abstract Lake Grevelingen is a brackish water lake in the SW Netherlands. The lake has an area of 108 km2, a mean depth of 5.3 m (maximum 48 m), a mean chlorinity of 13 to 16%0 Cl−, and a hydraulic residence time of about 8 years.
Mass budget studies have shown a consistent seasonal pattern in the phosphorus sediment-water exchange in Lake Grevelingen
(Kelderman 1980). From May to August a P mobilization from the sediment takes place, estimated atca. 12.5 mg P · m−2 · day−1. The sediment accumulatesca. 5.5 mg P · m−2 · day−1 during the rest of the year. Temperature may be an important factor in establishing this pattern.
Sediment-water exchange was studied by means of laboratory experiments under specified conditions. Sediment cores (30 cm depth,
11 cm diameter) were taken at four stations in the lake, with sediment types varying from medium- to muddy sand (Fig. 1).
The cores with overlying water (ca. 21) were placed in the dark at 5 °C in thermostatically controlled water baths. After a week's incubation time the temperature
was slowly raised, such that after three weeks eight cores (four sediment types, duplicates) were at 5 °C, eight were at 10
°C, eight at 15 °C and eight at 20 °C. The same procedure was applied to the four control cores, containing lake water. 相似文献
5.
Microbial community structure and biomass estimates of a methanogenic Antarctic Lake ecosystem as determined by phospholipid analyses 总被引:3,自引:0,他引:3
Phospholipid analyses were performed on water column particulate and sediment samples from Ace Lake, a meromictic lake in the Vestfold Hills, Antarctica, to estimate the viable microbial biomass and community structure in the lake. In the water column, methanogenic bacterial phospholipids were present below 17 m in depth at concentrations which converted to a biomass of between 1 and 7×108 cells/liter. Methanogenic biomass in the sediment ranged from 17.7×109 cells/g dry weight of sediment at the surface to 0.1×109 cells/g dry weight at 2 m in depth. This relatively high methanogenic biomass implies that current microbial degradation of organic carbon in Ace Lake sediments may occur at extremely slow rates. Total microbial biomass increased from 4.4×108 cells/ liter at 2 m in depth to 19.4×108 cells/liter at 23 m, near the bottom of the water column. Total nonarchaebacterial biomass decreased from 4.2 ×109 cells/g dry weight in the surface sediment (1/4 the biomass of methanogens) to 0.06×108 cells/g dry weight at 2 m in depth in the sediment. Phospholipid fatty acid profiles showed that microeukaryotes were the major microbial group present in the oxylimnion of the lake, while bacteria dominated the lower, anoxic zone. Sulfate-reducing bacteria (SRB) comprised 25% of the microbial population at 23 m in depth in the water column particulates and were present in the surface sediment but to a lesser extent. Biomass estimates and community structure of the Ace Lake eco-system are discussed in relation to previously measured metabolic rates for this and other antarctic and temperate ecosystems. This is the first instance, to our knowledge, in which the viable biomass of methanogenic and SRB have been estimated for an antarctic microbial community. 相似文献
6.
Thomas Smayda 《Hydrobiologia》1990,192(2-3):191-203
The addition of powdered limestone to intact sediment cores from oligotrophic, acid Lake Hovvatn caused pH to increase, redox potential (E7) to drop, and permitted net precipitation of phosphorous (P) from the water column. Significant pH increase was found to a sediment depth of 6 cm and a maximum increase in pH from 4.9 to 6.5 was found at a depth of 0.5 cm when dosed with 36 g m–2 of lime. Such pH increase creates important changes in sediment equilibrium chemistry and enhances habitat suitability. In the case of Hovvatn, however, sediments would consume only 5 kg of the 91 tons of applied limestone. Superficial sediments remained oxidized, but below 0.5 cm, E7 in limed sediment declined significantly more than in unlimed sediments, with a maximum difference of 102 mV versus –66 mV at a depth of 6 cm in unlimed and limed cores, respectively. Abiotic reactions account for 82 ± 54% of this reduction and the remainder is due to the oxidation of organic matter by bacteria. Precipitation of CaSO4, reduction of the sediments by organic compounds at elevated pH and inhibition of the downward diffusion of O2 by the limestone powder are potential abiotic mechanisms which could drive E7 down. Enhanced P release was not found at lowered E7, and supernatent TP concentrations dropped from 11.7 to 4.4 µg P l–1. More P was swept from solution in cores which recieved larger lime doses. The presence of chironomids caused sediment pH to increase by as much as 1.2 pH units, presumably due to NH4 release, reduced sediment E7 by as much as 171 mV and facilitated TP release during the first 17 d of core incubation. Field measurements of vertical distributions of sediment pH and E7 before and after the liming of Hovvtn corroborated laboratory findings. 相似文献
7.
Frederick M. Soster David T. Harvey Michelle R. Troksa Travis Grooms 《Hydrobiologia》1992,248(3):249-258
A laboratory experiment was conducted to determine the effect of tubificid worms on the flux of zinc into lake sediments. Forty-six cores of Lake Erie sediment, with and without (control) tubificid worm populations, were exposed to aquarium water with a zinc concentration of about 5 mg 1–1 for 139 days. Pore water and exchangeable particulate zinc concentrations in the top 12 cm of sediment were periodically determined in pairs of cores — one with worms and one without worms — at 1 cm depth increments. After 139 days, pore water zinc concentrations in sediments with and without worms were nearly identical in the 0–1 cm interval (4.1 and 4.3 mg 1–1 respectively), but were significantly greater in the sediments with worms in the 1–2 cm (4.4 vs. 0.3 mg1–1) and the 2–3 cm (1.3 vs. 0.3 mg 1–1) intervals. Exchangeable particulate zinc concentrations in the 0–1, 1–2, and 2–3 cm intervals in sediments with worms were 612.3, 750.7, and 191.5 µg g–1 dry sediment respectively, whereas in sediments without worms, concentrations were 375.4, 5.9, and 3.2 µg g–1 dry sediment. The increased flux of zinc into tubificid-inhabited sediments was caused by the conveyor belt feeding activity of the worms, which continuously exposed sedimentary particles to the overlying water. Movement of zinc into sediments with worms was dominated by adsorption and by particle movement, whereas movement of zinc into control sediments was by adsorption at the sediment-water interface and diffusion. The increased concentration of zinc in tubificid-inhabited sediments has important implications with respect to the trophic transfer of zinc through the aquatic food chain. 相似文献
8.
Pore water and solid phase distributions of C, N, P and Si in sediments of the Arctic Ocean (Svalbard area) have been investigated.
Concentrations of organic carbon (Corg) in the solid phase of the sediment varied from 1.3 to 2.8% (mean 1.9%), with highest concentrations found at shallow stations
south/southwest of Svalbard. Relatively low concentrations were obtained at the deeper stations north/northeast of Svalbard.
Atomic carbon to nitrogen ratios in the surface sediment ranged from below 8 to above 10. For some stations, high C/N ratios
together with high concentrations of Corg suggest that sedimentary organic matter is mainly of terrigenous origin and not from overall biological activity in the water
column. Organic matter reactivity (defined as the total sediment oxygen consumption rate normalized to the organic carbon
content of the surface sediment) correlated with water depth at all investigated stations. However, the stations could be
divided into two separate groups with different reactivity characteristics, representing the two most dominant hydrographic
regimes: the region west of Svalbard mainly influenced by the West Spitsbergen Current, and the area east of Svalbard where
Arctic polar water set the environmental conditions. Decreasing sediment reactivity with water depth was confirmed by the
partitioning between organic and inorganic carbon of the surface sediment. The ratio between organic and inorganic carbon
at the sediment-water interface decreased exponentially with water depth: from indefinite values at shallow stations in the
central Barents Sea, to approximately 1 at deep stations north of Svalbard. At stations east of Svalbard there was an inverse
linear correlation between the organic matter reactivity (as defined above) and concentration of dissolved organic carbon
(DOC) in the pore water. The more reactive the sediment, the less DOC existed in the pore water and the more total carbonate
(Ct or ΣCO2) was present. This observation suggests that DOC produced in reactive sediments is easily metabolizable to CO2. Sediment accumulation rates of opaline silica ranged from 0.35 to 5.7 μmol SiO2 m−2d−1 (mean 1.3 μmol SiO2 m−2d−1), i.e. almost 300 times lower than rates previously reported for the Ross Sea, Antarctica. Concentrations of ammonium and
nitrate in the pore water at the sediment-water interface were related to organic matter input and water depth. In shallow
regions with highly reactive organic matter, a pool of ammonium was present in the pore water, while nitrate conoentrations
were low. In areas where less reactive organic matter was deposited at the sediment surface, the deeper zone of nitrification
caused a build-up of nitrate in the pore water while ammonium was almost depleted. Nitrate penetrated from 1.8 to ≥ 5.8 cm
into the investigated sediments. Significantly higher concentrations of “total” dissolved nitrogen (defined as the sum of
NO3, NO2, NH4 and urea) in sediment pore water were found west compared to east of Svalbard. The differences in organic matter reactivity,
as well as in pore water distribution patterns of “total” dissolved nitrogen between the two areas, probably reflect hydrographic
factors (such as ice coverage and production/import of particulate organic material) related to the dominant water mass (Atlantic
or Arctic Polar) in each of the two areas.
The data presented were collected during the European “Polarstern” Study (Arctic EPOS) sponsored by the European Science Foundation 相似文献
9.
湛江高桥红树林湿地有机碳分布及埋藏特征 总被引:3,自引:0,他引:3
红树林是世界上单位生产力最高的生态系统之一,其能够持续地固定有机碳,对全球碳平衡和生物地球化学循环有着深远影响。以广东湛江国家级红树林自然保护区高桥核心区为研究区,旨在分析我国典型红树林湿地的固碳潜力,为红树林湿地碳计量提供依据。在垂直于海岸线的两条样线上选取6个不同潮位的样点进行沉积柱取样分析,通过重铬酸钾氧化-外加热法测定有机碳含量,基于放射性同位素~(210)Pb定年推演沉积率,并对湿地有机碳密度和埋藏率进行计算。结果表明:研究区红树林湿地有机碳含量2.14—36.94 g/kg,平均(12.79±9.91)g/kg。红树林湿地有机碳密度为(0.0100±0.0056)g/cm3,空间上差异显著显著,水平方向上两条样线均以中带样点的有机碳密度最大,近陆侧(内带)样点的有机碳密度高于近海侧(外带);垂直方向上,内带和外带样柱的有机碳密度均以表层最高,而且随深度增加而减小。研究区红树林湿地百年尺度上沉积率为6.5—11mm/a,且外带样点沉积速率显著快于内带样点。有机碳埋藏率空间差异大,外带样点为(34.58±7.67)g m-2a-1,而中带样点可达150.56 g m-2a-1。红树林湿地有机碳的分布受潮位的影响大,更高潮位点和表层的有机碳含量和密度更高,而处于低潮位的外带样点的有机碳沉积更快。研究区红树林湿地有机碳含量和密度比更低纬度带低,但均高于地带性陆地植被,且其能够通过持续的沉积过程来捕捉和固定有机碳,固碳潜力大。 相似文献
10.
The offshore displacement of commercial bottom trawling has raised concerns about the impact of this destructive fishing practice on the deep seafloor, which is in general characterized by lower resilience than shallow water regions. This study focuses on the flanks of La Fonera (or Palamós) submarine canyon in the Northwestern Mediterranean, where an intensive bottom trawl fishery has been active during several decades in the 400–800 m depth range. To explore the degree of alteration of surface sediments (0–50 cm depth) caused by this industrial activity, fishing grounds and control (untrawled) sites were sampled along the canyon flanks with an interface multicorer. Sediment cores were analyzed to obtain vertical profiles of sediment grain-size, dry bulk density, organic carbon content and concentration of the radionuclide 210Pb. At control sites, surface sediments presented sedimentological characteristics typical of slope depositional systems, including a topmost unit of unconsolidated and bioturbated material overlying sediments progressively compacted with depth, with consistently high 210Pb inventories and exponential decaying profiles of 210Pb concentrations. Sediment accumulation rates at these untrawled sites ranged from 0.3 to 1.0 cm y−1. Sediment properties at most trawled sites departed from control sites and the sampled cores were characterized by denser sediments with lower 210Pb surface concentrations and inventories that indicate widespread erosion of recent sediments caused by trawling gears. Other alterations of the physical sediment properties, including thorough mixing or grain-size sorting, as well as organic carbon impoverishment, were also visible at trawled sites. This work contributes to the growing realization of the capacity of bottom trawling to alter the physical properties of surface sediments and affect the seafloor integrity over large spatial scales of the deep-sea. 相似文献
11.
Miralles G Nérini D Manté C Acquaviva M Doumenq P Michotey V Nazaret S Bertrand JC Cuny P 《Microbial ecology》2007,54(4):646-661
The effects of spilled oil on sedimentary bacterial communities were examined in situ at 20 m water depth in a Mediterranean coastal area. Sediment collected at an experimental site chronically subjected to
hydrocarbon inputs was reworked into PVC cores with or without a massive addition of crude Arabian light oil (∼20 g kg−1 dry weight). Cores were reinserted into the sediment and incubated in situ at the sampling site (20 m water depth) for 135 and 503 days. The massive oil contamination induced significant shifts in
the structure of the indigenous bacterial communities as shown by ribosomal intergenic spacer analysis (RISA). The vertical
heterogeneity of the bacterial communities within the sediment was more pronounced in the oiled sediments particularly after
503 days of incubation. Response to oil of the deeper depth communities (8–10 cm) was slower than that of superficial depth
communities (0–1 and 2–4 cm). Analysis of the oil composition by gas chromatography revealed a typical microbial alteration
of n-alkanes during the experiment. Predominant RISA bands in oiled sediments were affiliated to hydrocarbonoclastic bacteria
sequences. In particular, a 395-bp RISA band, which was the dominant band in all the oiled sediments for both incubation times,
was closely related to hydrocarbonoclastic sulfate-reducing bacteria (SRB). These bacteria may have contributed to the main
fingerprint changes and to the observed biodegradation of n-alkanes. This study provides useful information on bacterial dynamics in anoxic contaminated infralittoral sediments and
highlights the need to assess more precisely the contribution of SRB to bioremediation in oil anoxic contaminated areas. 相似文献
12.
Viral Density and Virus-to-Bacterium Ratio in Deep-Sea Sediments of the Eastern Mediterranean 总被引:10,自引:6,他引:4
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Viruses are now recognized as a key component in pelagic systems, but their role in marine sediment has yet to be assessed. In this study bacterial and viral densities were determined at nine deep-sea stations selected from three main sites (i.e., the Sporades Basin, the Cretan Sea, and the Ierapetra Trench at depths of 1,232, 1,840, and 4,235 m, respectively) of the Eastern Mediterranean. The three areas were characterized by different phytopigment and biopolymeric carbon concentrations and by changes in the protein and carbohydrate pools. A gradient of increasing trophic conditions was observed from the Sporades Basin (North Aegean) to the Ierapetra Trench (South Aegean). Viral densities (ranging from 1 × 109 to 2 × 109 viruses ml of sediment−1) were significantly correlated to bacterial densities (n = 9, r2 = 0.647) and reached values up to 3 orders of magnitude higher than those generally reported for the water column. However, the virus-to-bacterium density ratio in deep-sea sediments was about 1 order of magnitude lower (range of 2 to 5, with a modal value of 2.6) than in pelagic environments. Virus density decreased vertically with depth in sediment cores at all stations and was below detection limits at the 10-cm depth of the abyssal sediments of the Ierapetra Trench. Virus density in the sediment apparently reflected a gradient of particle fluxes and trophic conditions, displaying the highest values in the Sporades Basin. The low virus-to-bacterium ratios and their inverse relationship with station depth suggest that the role played by viruses in controlling deep-sea benthic bacterial assemblages and biogeochemical cycles is less relevant than in pelagic systems. 相似文献
13.
High resolution measurements of sediment resuspension above an accumulation bottom in a stratified lake 总被引:6,自引:3,他引:3
A detailed record of suspended particulate matter (SPM) concentrations in the benthic boundary layer (BBL) 1.5 m above an accumulation bottom and 13.5 m below the surface was obtained from frequent (30 min interval) beam attenuation measurements made with a Sea Tech transmissometer in the main basin of Lake Erken, a moderately deep (mean depth 9 m, maximum depth 21 m) dimictic lake in central Sweden. Concentrations of SPM (g m–3) were not as strongly correlated to the beam attenuation coefficient (c, [m–1]), as were concentrations of the inorganic SPM fraction. Apparently, this was caused by large optically inactive organic particles which significantly affected the measurements of SPM, but had little effect on the attenuation of light.When the water column was thermally stratified, SPM concentrations in the BBL showed a seasonal increase which was related to an increase in the thermocline depth. As the epilimnion deepened, there was also a marked increase in the occurrence of rapid and large changes in SPM concentration. After the loss of stratification, the amount of SPM and the temporal variability in its concentration was reduced. Since surface waves could not influence sediment resuspension at the depth of measurement, these data show the importance of internal waves in promoting sediment resuspension in areas of sediment accumulation. The relatively short period in each summer, when the thermocline reaches a sufficient depth to allow for resuspension over accumulation bottoms, can have important consequences for both the redistribution of lake sediments and the internal loading of phosphorus. 相似文献
14.
Natalia V. Ignatieva 《Hydrobiologia》1996,322(1-3):129-136
Sedimentary phosphorus fractions and phosphorus release from the sediments were studied in Lake Ladoga at altogether 46 sampling sites, representing the full range of sediment types encountered in the lake. Determination of P fractions and physico-chemical analyses were made of surface sediment cores (10–20 cm long, each sampled at 3–4 levels) and in the overlying water. The range of total phosphorus per dry weight of sediment was 0.2–3.3 mg g–1, and that of inorganic P 0.1–2.5 mg g–1. The levels of interstitial soluble phosphorus, range 2–613 µg 1–1 for total P and 1–315 µg 1–1 for inorganic P, were higher than those of dissolved P concentrations in the overlying water. Diffusive fluxes of phosphate from sediment to the overlying water were estimated using three independent methods. The estimated range was 4–914 µg P m–2 d–1; the mean value for the whole bottom area, 0.1 mg P m–2 d–1, is lower than previously published estimates. The estimated annual contribution of sedimentary inorganic P flux to Lake Ladoga water is equal to 620 tons of P per year, which amounts to more than 10% of the estimated external P load into the lake. 68% of the total diffusive flux emanates from deep water sediments, which are not exposed to seasonal variation of conditions. In deep lakes, such as Lake Ladoga, phosphorus release from the sediments is controlled primarily by diffusive mechanisms. Wave action and currents as well as bioturbation are probably of importance mainly in shallow near-shore areas. Phosphorus release by gas ebullition and macrophytes is considered negligible. 相似文献
15.
Sulphate,dissolved organic carbon,nutrients and terminal metabolic products in deep pore waters of an intertidal flat 总被引:6,自引:0,他引:6
Melanie Beck Olaf Dellwig Jan M. Holstein Maik Grunwald Gerd Liebezeit Bernhard Schnetger Hans-Jürgen Brumsack 《Biogeochemistry》2008,89(2):221-238
This study addresses deep pore water chemistry in a permeable intertidal sand flat at the NW German coast. Sulphate, dissolved
organic carbon (DOC), nutrients, and several terminal metabolic products were studied down to 5 m sediment depth. By extending
the depth domain to several meters, insights into the functioning of deep sandy tidal flats were gained. Despite the dynamic
sedimentological conditions in the study area, the general depth profiles obtained in the relatively young intertidal flat
sediments of some metres depth are comparable to those determined in deep marine surface sediments. Besides diffusion and
lithology which control pore water profiles in most marine surface sediments, biogeochemical processes are influenced by advection
in the studied permeable intertidal flat sediments. This is supported by the model setup in which advection has to be implemented
to reproduce pore water profiles. Water exchange at the sediment surface and in deeper sediment layers converts these permeable
intertidal sediments into a “bio-reactor” where organic matter is recycled, and nutrients and DOC are released. At tidal flat
margins, a hydraulic gradient is generated, which leads to water flow towards the creekbank. Deep nutrient-rich pore waters
escaping at tidal flat margins during low tide presumably form a source of nutrients for the overlying water column in the
study area. Significant correlations between the inorganic products of terminal metabolism (NH4
+ and PO4
3−) and sulphate depletion suggest sulphate reduction to be the dominant pathway of anaerobic carbon remineralisation. Pore
water concentrations of sulphate, ammonium, and phosphate were used to elucidate the composition of organic matter degraded
in the sediment. Calculated C:N and C:P ratios were supported by model results. 相似文献
16.
Microbial Diversity in Sediments of Saline Qinghai Lake, China: Linking Geochemical Controls to Microbial Ecology 总被引:2,自引:0,他引:2
Saline lakes at high altitudes represent an important and extreme microbial ecosystem, yet little is known about microbial
diversity in such environments. The objective of this study was to examine the change of microbial diversity from the bottom
of the lake to sediments of 40 cm in depth in a core from Qinghai Lake. The lake is saline (12.5 g/L salinity) and alkaline
(pH 9.4) and is located on the Qinghai–Tibetan Plateau at an altitude of 3196 m above sea level. Pore water chemistry of the
core revealed low concentrations of sulfate and iron (<1 mM), but high concentrations of acetate (40–70 mM) and dissolved
organic carbon (1596–5443 mg/L). Total organic carbon and total nitrogen contents in the sediments were ∼2 and <0.5%, respectively.
Acridine orange direct count data indicated that cell numbers decreased from 4 × 109 cells/g at the water–sediment interface to 6× 107 cells/g wet sediment at the 40-cm depth. This change in biomass was positively correlated with acetate concentration in pore
water. Phospholipid fatty acid (PLFA) community structure analyses determined decrease in the proportion of the Proteobacteria and increase in the Firmicutes with increased depth. Characterization of small subunit (SSU) rRNA genes amplified from the sediments indicated a shift in
the bacterial community with depth. Whereas the α-, β-, and γ-Proteobacteria and the Cytophaga/Flavobacterium/Bacteroides (CFB) were dominant at the water–sediment interface, low G + C gram-positive bacteria (a subgroup of Firmicutes) became the predominant group in the anoxic sediments. Both PLFA and the sequence data showed similar trend. The Proteobacteria, CFB, and gram-positive bacteria are present in other saline lakes, but thepresence of Actinobacteria and Acidobacteria/Holophaga in significant proportions in the Qinghai Lake sediments appears to be unique. The archaeal diversity was much lower, and
clone sequences could be grouped inthe Euryarchaeota and Crenarchaeota domains. The archaeal clones were not related to any known cultures but to sequences previously found in methane-rich sediments.
Acetate-utilizing methanogens were isolated from sediment incubations, and α- and γ-proteobacterial isolates were obtained
from a water sample from the lakebottom (23 m). Our data collectively showed that the observed diversity and shift in the
community structure with depth was correlated with geochemical parameters (the redox state and availability of electron acceptor
and donor). Heterotrophic methanogenesis is possibly adominant metabolic process in the Qinghai Lake sediments. These results
reinforce the importance of geochemical controls on microbial ecology in saline and alkaline lake environments. 相似文献
17.
Understanding the dynamics of fine sediment transport across the upper intertidal zone is critical in managing the erosion and accretion of intertidal areas, and in managed realignment/estuarine habitat recreation strategies. This paper examines the transfer of sediments between salt marsh and mudflat environments in two contrasting macrotidal estuaries: the Seine (France) and the Medway (UK), using data collected during two joint field seasons undertaken by the Anglo-French RIMEW project (Rives-Manche Estuary Watch). High-resolution ADCP, Altimeter, OBS and ASM measurements from mudflat and marsh surface environments have been combined with sediment trap data to examine short-term sediment transport processes under spring tide and storm flow conditions. In addition, the longer-term accumulation of sediment in each salt marsh system has been examined via radiometric dating of sediment cores. In the Seine, rapid sediment accumulation and expansion of salt marsh areas, and subsequent loss of open intertidal mudflats, is a major problem, and the data collected here indicate a distinct net landward flux of sediments into the marsh interior. Suspended sediment fluxes are much higher than in the Medway estuary (averaging 0.09 g/m3/s), and vertical accumulation rates at the salt marsh/mudflat boundary exceed 3 cm/y. Suspended sediment data collected during storm surge conditions indicate that significant in-wash of fine sediments into the marsh interior can occur during (and following) these high-magnitude events. In contrast to the Seine, the Medway is undergoing erosion and general loss of salt marsh areas. Suspended sediment fluxes are of the order of 0.03 g/m3/s, and the marsh system here has much lower rates of vertical accretion (sediment accumulation rates are ca. 4 mm/y). Current velocity data for the Medway site indicate higher velocities on the ebb tide than occur on the flood tide, which may be sufficient to remobilise sediments deposited on the previous tide and so force net removal of material from the marsh. 相似文献
18.
Laila Bodbacka 《Hydrobiologia》1986,143(1):337-342
X-ray radiography is a superior method of showing structures in recently deposited sediments. Annually laminated sediments have been proved to exist in Lakes Lilla Ullfjärden and Stora Ullfjärden using this method.From X-ray radiographs of laminated sediment cores sampled nearly every year since 1977 in Lake Lilla Ullfjärden and since 1978 in Lake Stora Ullfjärden, it is possible to distinguish the seasonal variation in sediment deposition in the lakes. The variation in time and space in sediment accumulation is possible to estimate. The rate of sediment accumulation has been calculated to be 320 g solids/m2 · y–1 for the deepest part of Lake Lilla Ullfjärden and 920 g solids/m2 · y–1 for the central part of Lake Stora Ullfjärden for the period 1978 to 1983. It is also possible to trace the effect of eutrophication in time and space. An estimation of the appearance of the oxygen deficit in Lilla Ullfjärden gives a time around 1885. 相似文献
19.
Mangroves represent a major environment of tropical coasts. They are highly productive, and act both as a source and a sink of organic carbon. Concentrations and characteristics (fluorescence and hydrophobic–hydrophilic fractions) of dissolved organic matter (DOM) were investigated in relation to the organic content of sediments and to the chemistry of pore waters along the coastline of French Guiana. The pore waters studied were extracted (centrifugation, soil moisture sampler) from sediments cored beneath A. germinans mangrove stands representative of development stages: pioneer, mature and senescent. In order to asses the effects of seasonal changes, two cores were performed in each location, just after dry and wet seasons, respectively. Dissolved organic carbon (DOC) concentrations in pore waters of the upper sediment were found to increase, from 0.7 mmol l−1 under the pioneers to 9 under senescent mangroves. The evolution of sedimentary organic carbon (SedOC) in the same sediment paralleled that of DOC, increasing from 0.7 to 28%. On the contrary, in the lower parts of sediment cores SedOC and DOC displayed contrasting vertical trends: SedOC decreased sharply with depth while DOC increased, reaching concentrations up to 30 mmol l−1 at 50 cm in the older, senescent mangroves. In addition, the Fluorescence/DOC ratios and the hydrophobic contents of DOC were higher at greater depths in most cores, expressing changes in the DOC composition. These results suggest that the DOC of the upper layers originated directly from the SedOC of the enclosing sediment, while the hydrophobic and fluorescent DOC accumulated in the anoxic bottom layer. The mechanisms responsible for this accumulation at depth requires additional research to be fully understood. However, the anoxic conditions and high pH values prevailing in the lower sediment, by lessening DOM sorption and enhancing SedOC dissolution, may be partly responsible for the high DOC concentrations and fluorescences at depth. In addition, seasonal variation may be involved. During the rainy season, water sources were mixed resulting in lower DOC concentrations in the upper sediment, whereas during the dry season, increased evapotranspiration concentrate salts and DOC, which are transported vertically with percolating water. 相似文献
20.
Judith Z. Drexler Isa Woo Christopher C. Fuller Glynnis Nakai 《Restoration Ecology》2019,27(5):1117-1127
Few comparisons exist between vertical accretion (VA) and carbon accumulation rates (CARs) in restored versus historic (i.e. reference) marshes. Here, we compare these processes in a formerly diked, sparsely vegetated, restored salt marsh (Six Gill Slough, SG), whose surface is subsided relative to the tidal frame, to an adjacent, relatively pristine, historic salt marsh (Animal Slough, AS). Six sediment cores were collected at both AS and SG approximately 6 years after restoration. Cores were analyzed for bulk density (BD), % loss of ignition, % organic carbon, and 210Pb. We found that sharp changes in BD in surface layers of SG cores were highly reliable markers for the onset of restoration. The mean VA since restoration at SG (0.79 [SD = 0.29] cm/year) was approximately twice that of AS (0.41 [SD = 0.16] cm/year). In comparison, the VA at AS over 50 years was 0.30 (SD = 0.09) cm/year. VA consisted almost entirely of inorganic sediment at SG whereas at AS it was approximately 55%. Mean CARs at SG were somewhat greater than at AS, but the difference was not significant due to high variability (SG: 81–210 g C m?2 year?1; AS: 115–168 g C m?2 year?1). The mean CAR at AS over the past 50 years was 118 (SD = 23) g C m?2 year?1. This study demonstrates that a sparsely vegetated, restored salt marsh can quickly begin to accumulate carbon and that historic and restored marshes can have similar CARs despite highly divergent formation processes. 相似文献