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1.
Two novel denitrifying bacteria were successfully isolated from industrial wastewater and soil samples. Using morphological,
biochemical/biophysical and 16S rRNA gene analyses, these two bacteria were identified as Stenotrophomonas sp. ZZ15 and Oceanimonas sp. YC13, respectively. Both of these two bacteria showed efficient NO3
−-N removing abilities under a semi-anaerobic condition without obvious accumulation of NO2
−-N, N2O-N and NH4
+-N. NO3
−-N removal from paper mill wastewater was also successful by treatments with either a denitrifier or an immobilization method.
Therefore, this study provides valuable denitrifying bacteria in biotreatment of industrial wastewater and other environmental
pollution caused by NO3
−/NO2
−. 相似文献
2.
Nitrogen (N) pollution is a problem in many large temperate zone rivers, and N retention in river channels is often small
in these systems. To determine the potential for floodplains to act as N sinks during overbank flooding, we combined monitoring,
denitrification assays, and experimental nitrate (NO3− -N) additions to determine how the amount and form of N changed during flooding and the processes responsible for these changes
in the Wisconsin River floodplain (USA). Spring flooding increased N concentrations in the floodplain to levels equal to the
river. As discharge declined and connectivity between the river and floodplain was disrupted, total dissolved N decreased
over 75% from 1.41 mg l−1, equivalent to source water in the Wisconsin River on 14 April 2001, to 0.34 mg l−1 on 22 April 2001. Simultaneously NO3− -N was attenuated almost 100% from 1.09 to <0.002 mg l−1. Unamended sediment denitrification rates were moderate (0–483 μg m−2 h−1) and seasonally variable, and activity was limited by the availability of NO
3− -N on all dates. Two experimental NO3− -N pulse additions to floodplain water bodies confirmed rapid NO3− -N depletion. Over 80% of the observed NO
3− -N decline was caused by hydrologic export for addition #1 but only 22% in addition #2. During the second addition, a significant
fraction (>60%) of NO3− -N mass loss was not attributable to hydrologic losses or conversion to other forms of N, suggesting that denitrification
was likely responsible for most of the NO3− -N disappearance. Floodplain capacity to decrease the dominant fraction of river borne N within days of inundation demonstrates
that the Wisconsin River floodplain was an active N sink, that denitrification often drives N losses, and that enhancing connections
between rivers and their floodplains may enhance overall retention and reduce N exports from large basins. 相似文献
3.
Floodplain restoration has been advocated as a means to restore several ecological services associated with floodplains: water
quality improvement, fish rearing habitat, wildlife habitat, flood control, and groundwater recharge. A history of agricultural
encroachment on the lower Cosumnes River has resulted in extensive channelization and levee construction. In fall 1998, an
experimental floodplain was established by breaching a levee in order to restore the connection between the main channel and
its historic floodplain. In this study, we examined how effective this newly restored floodplain was at processing nitrate
(NO
3
−
) before reentering the main channel downstream. Two methods were used to examine nitrate loss. In December 2001, we determined
denitrification potentials of the floodplain soils before seasonal flooding inundated the floodplain. Next, we conducted a
series of field soil column (mesocosm) experiments from March to June 2002 to study NO
3
−
-N loss from the overlying water in both sandy and clayey soils and at three levels of NO
3
−
-N (ambient, +1 mg N l−1, +5 mg N l−1). In addition, we examined NO
3
−
-N loss from mesocosms with water only to determine if loss was related primarily to soil or water column processes. Denitrification
potentials were highly variable ranging from 1.6 to 769 ng N2O–N cm−3 h−1. In addition, the denitrification potential was highly correlated with the amount of bioavailable carbon indicating that
carbon was a limiting factor for denitrification. Nitrate-N loss rates from mesocosms ranged from 2.9 to 21.0 μg N l−1 h−1 over all treatments and all 3 months examined. Significant loss of NO
3
−
-N (60–93%) from the water only treatment only occurred in June when warmer temperatures and solar radiation most likely increased
NO
3
−
-N uptake by phytoplankton. When scaled up, potential NO
3
−
-N loss from the restored floodplain represented 0.6–4.4% of the annual N load from the Lower Cosumnes River during a typical
wet year and ~24% during a dry year. During dry water years, the effectiveness of the floodplain for reducing nitrate is limited
by the amount of N supplied to the floodplain. Results from this study suggest that restored floodplains can be an effective
NO
3
−
sink. 相似文献
4.
A. M. Zyakun O. N. Lunina T. S. Prusakova N. V. Pimenov M. V. Ivanov 《Microbiology》2009,78(6):757-768
Fractionation of stable carbon isotopes 12C and 13C by three pure cultures of photoautotrophic purple sulfur bacteria (Ectothiorhodospira shaposhnikovii, Lamprocystis purpureus, and Thiocapsa sp.) (PSB) and the green sulfur bacterium Prosthecochloris sp. (GSB) was investigated in 13–15-day experiments. The cultivation was carried out in a luminostat (2000 lx) on mineral
media with 1–1.5 g/l NaHCO3 (inoculum) with the subsequent transfer to the medium with up to 10 g/l NaHCO3. For PSB, the difference in the quantitative characteristics of the isotopic composition of suspended carbon (including bacterial
cells) and mineral carbon of the medium (Δ13C = δ13Csubstrate − δ13Cbiomass) changed from 15.0 to 34.3‰. For GSB, the range of Δ13C changes was significantly less (18.3–22.7‰). These data suggested the possibility of a pool of soluble mineral carbon in
PSB cells. The pool of intracellular mineral carbon was calculated; depending on the PSB species and growth stage, it varied
from 0 to 68% of the total cell carbon. The α coefficients reflecting the carbon isotope fractionation by PSB and GBS and
calculated from the changes of the bicarbonate carbon isotopic composition in the medium depending on its consumption were
1.029 ± 0.003 and 1.019 ± 0.001, respectively. These α values did not depend on the growth rate. CO2 fixation on ribulose-bisphosphate was shown to be the major factor determining the carbon isotope fractionation by PSB; at
the stage of CO2 penetration into the cell, fractionation was insignificant. In GSB, fractionation occurred mostly at CO2 penetration into the cell, while it was insignificant at the stage of carbon dioxide fixation in the reverse TCA cycle. Analysis
of the isotopic data of the photosynthesis by PSB and GSB in meromictic lakes also revealed that in PSB-dominated natural
communities suspended organic matter was more enriched with light 13C (Δ13C = 23.4−24.6‰) than in the communities with more active GSB (Δ13C = 10.2−14.0‰) 相似文献
5.
Depletion of adenosine triphosphate inDesulfovibrio by oxyanions of group VI elements 总被引:1,自引:0,他引:1
Oxyanions of elements from group VI of the periodic table, i.e., analogs of SO4
2−, destroyed adenosine 5′-triphosphate (ATP) in cells of sulfate-respiring bacteria (Desulfovibrio spp.), probably via the ATP sulfurylase reaction. The approximate order of effectiveness was CrO4
2−> MoO4
2−=WO4
2−>SeO4
2−. Cultures of aerobically grown or nitrate-respiring bacteria were less susceptible and with fermentatively grownEscherichia coli the oxyanions even appeared to stimulate ATP levels. The selective depletion of ATP in sulfate-respiring bacteria might provide
the basis for a rapid and simple assay of their biomass in mixed cultures or environmental samples. 相似文献
6.
Spatial and Temporal Variability in Sediment Denitrification Within an Agriculturally Influenced Reservoir 总被引:2,自引:1,他引:1
Reservoirs are intrinsically linked to the rivers that feed them, creating a river–reservoir continuum in which water and
sediment inputs are a function of the surrounding watershed land use. We examined the spatial and temporal variability of
sediment denitrification rates by sampling longitudinally along an agriculturally influenced river–reservoir continuum monthly
for 13 months. Sediment denitrification rates ranged from 0 to 63 μg N2O g ash free dry mass of sediments (AFDM)−1 h−1 or 0–2.7 μg N2O g dry mass of sediments (DM)−1 h−1 at reservoir sites, vs. 0–12 μg N2O gAFDM−1 h−1 or 0–0.27 μg N2O gDM−1 h−1 at riverine sites. Temporally, highest denitrification activity traveled through the reservoir from upper reservoir sites
to the dam, following the load of high nitrate (NO3−-N) water associated with spring runoff. Annual mean sediment denitrification rates at different reservoir sites were consistently
higher than at riverine sites, yet significant relationships among theses sites differed when denitrification rates were expressed
per gDM vs. per gAFDM. There was a significant positive relationship between sediment denitrification rates and NO3−-N concentration up to a threshold of 0.88 mg NO3− -N l−1, above which it appeared NO3−-N was no longer limiting. Denitrification assays were amended seasonally with NO3−-N and an organic carbon source (glucose) to determine nutrient limitation of sediment denitrification. While organic carbon
never limited sediment denitrification, all sites were significantly limited by NO3−-N during fall and winter when ambient NO
3−-N was low. 相似文献
7.
Flores A Nisola GM Cho E Gwon EM Kim H Lee C Park S Chung WJ 《Bioprocess and biosystems engineering》2007,30(3):197-205
The performance of enriched sludge augmented with the B21 strain of Alcaligenes defragrans was compared with that of enriched sludge, as well as with pure Alcaligenes defragrans B21, in the context of a sulfur-oxidizing denitrification (SOD) process. In synthetic wastewater treatment containing 100–1,000 mg
NO3−-N/L, the single strain-seeded system exhibited superior performance, featuring higher efficiency and a shorter startup period,
provided nitrate loading rate was less than 0.2 kg NO3−-N/m3 per day. At nitrate loading rate of more than 0.5 kg NO3−-N/m3 per day, the bioaugmented sludge system showed higher resistance to shock loading than two other systems. However, no advantage
of the bioaugmented system over the enriched sludge system without B21 strain was observed in overall efficiency of denitrification.
Both the bioaugmented sludge and enriched sludge systems obtained stable denitrification performance of more than 80% at nitrate
loading rate of up to 2 kg NO3−-N/m3 per day. 相似文献
8.
Primary production of organic matter and phototrophic communities in the soda lakes of the Kulunda steppe (Altai krai) 总被引:1,自引:0,他引:1
E. I. Kompantseva A. V. Komova I. I. Rusanov N. V. Pimenov D. Yu. Sorokin 《Microbiology》2009,78(5):643-649
The rates of photosynthesis and dark CO2 fixation were determined in 12 soda lakes of the Kulunda steppe. Characterization of the phototrophic communities was given,
and the cell numbers of anoxygenic phototrophic bacteria (APB) were determined. The photosynthetic production in different
lakes was substantially different, constituting from 0.01 to 1.32 g C m−2 day−1. The main part of carbon dioxide was assimilated in the process of oxygenic photosynthesis. Anoxygenic photosynthesis was
recorded only in 5 of the 12 lakes studied. Its values varied between 0.06 and 0.42 g C m−2 day−1, constituting from 8 to 34% of the total photosynthetic activity. Anoxygenic photosynthesis was revealed in the lakes where
the number of APB reached 107–109 CFU cm−3. Dark CO2 fixation constituted 0.01–0.15 g C m−2 day−1. Positive correlation was observed between the primary production value and water alkalinity. No relationship between productivity
and water mineralization was revealed in the 30–200 g l−1 range, whereas an increase in salinity above 200 g l−1 suppressed the photosynthetic activity. The mechanisms of influence of the environmental factors on the rate of photosynthesis
are discussed. 相似文献
9.
The plant growth–promoting potentials, production of siderophore and solubilization of insoluble phosphorus (P) and zinc and
lead by the chromium (vi) -reducing Bacillus species, PSB 1, PSB 7, and PSB 10, was assessed both in the presence and absence of chromium under in vitro conditions. The Bacillus strains tolerated chromium up to the concentration of 500 (PSB1), 400 (PSB7), and 550 μg ml−1 (PSB10), respectively, on nutrient agar plates. Bacillus sp. PSB 10 reduced Cr (vi) by 87% at pH 7, which was followed by Bacillus sp. PSB 1 (83%) and PSB 7 (74%) in nutrient broth after 120 h of incubation. A concentration of 50 μg ml−1 of Cr (vi) was completely reduced by Bacillus sp. PSB 1 and PSB 10 (after 100 h) and PSB 7 (after 120 h). The Bacillus strains PSB 1, PSB 7, and PSB 10 produced 19.3, 17.7, and 17.4 μg ml−1 of indole acetic acid, respectively, in luria bertani broth at 100 μg ml−1 of tryptophan, which consistently decreased with an increase in chromium concentration. The Bacillus strains were positive for siderophore, HCN, and ammonia both in the absence and presence of chromium. The Bacillus strains solubilized 375 (PSB 1), 340 (PSB 7), and 379 (PSB 10) μg ml−1 P, respectively, in Pikovskaya broth devoid of chromium. In contrast, chromium at 150 μg ml−1 reduced the amount of P solubilized by 17 (PSB 1), 15 (PSB 7), and 9% (PSB 10) compared to control. The tested bacterial
strains solubilized a considerable amount of zinc and lead in nutrient broth both in the absence and presence of chromium.
Generally, the chromium reduction and the plant growth–promoting potentials of chromium-reducing Bacillus were strongly correlated at the tested concentration of chromium. The present observations demonstrated that the chromium-reducing,
metal-solubilizing, and plant growth–promoting potentials of the Bacillus strains PSB1, PSB 7, and PSB10 were not adversely affected by the chromium application and, hence, may be applied for raising
the productivity of crops under metal-contaminated soils. 相似文献
10.
V. D. Kreslavski I. R. Fomina A. A. Ivanov N. P. Tatarinzev A. A. Kosobryukhov K. Y. Biel S. K. Herbert 《Biophysics》2010,55(2):215-220
The joint effects of 0.5 M NaCl and light of different intensities on the activity of the photosynthetic apparatus and ATP
content in cells of the katG
− mutant of cyanobacterium Synechocystis sp. PCC 6803 have been studied. The mutant demonstrated a higher photoinhibition rate and a slower rate of recovery compared
with the wild type, as shown by measurements of the CO2-dependent O2 production and delayed fluorescence of Chl a. The presence of 0.5 M NaCl in the incubation medium caused equal photoinhibition of the photosynthetic apparatus at I = 1200 μE m−2 s−1 in the mutant and wild-type cells. At I = 2400 μE m−2 s−1, we observed stronger inhibition and slower recovery of the photosynthetic apparatus in the katG
− mutant than in wild-type cells. The data obtained evidence an important role of catalase-peroxidase in the system of reparation
of the photosynthetic apparatus damaged by high-intensity light, especially at the background of NaCl stress. 相似文献
11.
J. Alan Yeakley David C. Coleman Bruce L. Haines Brian D. Kloeppel Judy L. Meyer Wayne T. Swank Barry W. Argo James M. Deal Sharon F. Taylor 《Ecosystems》2003,6(2):0154-0167
We investigated the effects of removing near-stream Rhododendron and of the natural blowdown of canopy trees on nutrient export to streams in the southern Appalachians. Transects were instrumented
on adjacent hillslopes in a first-order watershed at the Coweeta Hydrologic Laboratory (35°03′N, 83°25′W). Dissolved organic
carbon (DOC), K+, Na+, Ca2+, Mg2+, NO3
−-N, NH4
+-N, PO4
3−-P, and SO4
2− were measured for 2 years prior to disturbance. In August 1995, riparian Rhododendron on one hillslope was cut, removing 30% of total woody biomass. In October 1995, Hurricane Opal uprooted nine canopy trees
on the other hillslope, downing 81% of the total woody biomass. Over the 3 years following the disturbance, soilwater concentrations
of NO3
−-N tripled on the cut hillslope. There were also small changes in soilwater DOC, SO4
2−, Ca2+, and Mg2+. However, no significant changes occurred in groundwater nutrient concentrations following Rhododendron removal. In contrast, soilwater NO3
−-N on the storm-affected hillslope showed persistent 500-fold increases, groundwater NO3
−-N increased four fold, and streamwater NO3
−-N doubled. Significant changes also occurred in soilwater pH, DOC, SO4
2−, Ca2+, and Mg2+. There were no significant changes in microbial immobilization of soil nutrients or water outflow on the storm-affected hillslope.
Our results suggest that Rhododendron thickets play a relatively minor role in controlling nutrient export to headwater streams. They further suggest that nutrient
uptake by canopy trees is a key control on NO3
−-N export in upland riparian zones, and that disruption of the root–soil connection in canopy trees via uprooting promotes
significant nutrient loss to streams.
Received 30 January 2001; accepted 25 July 2002. 相似文献
12.
Low Nitrification Rates in Acid Scots Pine Forest Soils Are Due to pH-Related Factors 总被引:1,自引:0,他引:1
In a previous study, ammonia-oxidizing bacteria (AOB)-like sequences were detected in the fragmentation layer of acid Scots
pine (Pinus sylvestris L.) forest soils (pH 2.9–3.4) with high nitrification rates (>11.0 μg g−1 dry soil week−1), but were not detected in soils with low nitrification rates (<0.5 μg g−1 dry soil week−1). In the present study, we investigated whether this low nitrification rate has a biotic cause (complete absence of AOB)
or an abiotic cause (unfavorable environmental conditions). Therefore, two soils strongly differing in net nitrification were
compared: one soil with a low nitrification rate (location Schoorl) and another soil with a high nitrification rate (location
Wekerom) were subjected to liming and/or ammonium amendment treatments. Nitrification was assessed by analysis of dynamics
in NH4
+-N and NO3
−-N concentrations, whereas the presence and composition of AOB communities were assessed by polymerase chain reaction–denaturing
gradient gel electrophoresis and sequencing of the ammonia monooxygenase (amoA) gene. Liming, rather than ammonium amendment, stimulated the growth of AOB and their nitrifying activity in Schoorl soil.
The retrieved amoA sequences from limed (without and with N amendment) Schoorl and Wekerom soils exclusively belong to Nitrosospira cluster 2. Our study suggests that low nitrification rates in acidic Scots pine forest soils are due to pH-related factors.
Nitrosospira cluster 2 detected in these soils is presumably a urease-positive cluster type of AOB. 相似文献
13.
P. Serrano-Ortiz A. S. Kowalski F. Domingo A. Rey E. Pegoraro L. Villagarcía L. Alados-Arboledas 《Photosynthetica》2007,45(1):30-35
Carbon and water fluxes in a semiarid shrubland ecosystem located in the southeast of Spain (province of Almería) were measured
continuously over one year using the eddy covariance technique. We examined the influence of environmental variables on daytime
(photosynthetically active photons, F
P >10 μmol m−2 s−1) ecosystem gas exchange and tested the ability of an empirical eco-physiological model based on F
P to estimate carbon fluxes over the whole year. The daytime ecosystem fluxes showed strong seasonality. During two solstitial
periods, summer with warm temperatures (>15 °C) and sufficient soil moisture (>10 % vol.) and winter with mild temperatures
(>5 °C) and high soil moisture contents (>15 % vol.), the photosynthetic rate was higher than the daytime respiration rate
and mean daytime CO2 fluxes were ca. −1.75 and −0.60 μmol m−2 s−1, respectively. Daytime evapotranspiration fluxes averaged ca. 2.20 and 0.24 mmol m−2 s−1, respectively. By contrast, in summer and early autumn with warm daytime temperatures (>10 °C) and dry soil (<10 % vol.),
and also in mid-winter with near-freezing daytime temperatures the shrubland behaved as a net carbon source (mean daytime
CO2 release of ca. 0.60 and 0.20 μmol m−2 s−1, respectively). Furthermore, the comparison of water and carbon fluxes over a week in June 2004 and June 2005 suggests that
the timing—rather than amount—of spring rainfall may be crucial in determining growing season water and carbon exchange. Due
to strongly limiting environmental variables other than F
P, the model applied here failed to describe daytime carbon exchange only as a function of F
P and could not be used over most of the year to fill gaps in the data. 相似文献
14.
Bacterial biofilters used in marine recirculation aquaculture systems need improvements to enhance nitrogen removal efficiency.
Relatively little is known about biofilter autochthonous population structure and function. The present study was aimed at
isolating and characterizing an autochthonous denitrifying bacterium from a marine biofilter installed at a recirculation
aquaculture system. Colonization of four different media in a marine fish farm was followed by isolation of various denitrifying
strains and molecular classification of the most promising one, strain T2, as a novel member of the Pseudomonas fluorescens cluster. This strain exhibits high metabolic versatility regarding N and C source utilization and environmental conditions
for growth. It removed nitrate through aerobic assimilatory metabolism at a specific rate of 116.2 mg NO3-N g dw−1 h−1. Dissimilatory NO3-N removal was observed under oxic conditions at a limited rate, where transient NO2-N formed represented 22% (0.17 mg L−1) of the maximum transient NO2-N observed under anoxic conditions. Dissimilatory NO3-N removal under anoxic conditions occurred at a specific rate of 53.5 mg NO3-N g dw−1 h−1. The isolated denitrifying strain was able to colonize different materials, such as granular activated carbon (GAC), Filtralite
and Bioflow plastic rings, which allow the development of a prototype bioreactor for strain characterization under dynamic
conditions and mimicking fish-farm operating conditions. 相似文献
15.
The impacts of various nitrogen sources, i.e. NO−
3, NH4
+ or NH4NO3 in combination with gaseous NH3, on nitrogen-, carbon- and water-use efficiency and 13C discrimination (δ13C) by plants of the C3 species Triticum aestivum L. (wheat) and the C4 species Zea mays L. (maize) were studied. Triticum aestivum and Z. mays were hydroponically grown with 2 mol · m−3 of N supplied as NO−
3, NH4
+ or NH4NO3 for 21 and 18 d, respectively, and thereafter exposed to gaseous NH3 at 320 μg · m−3 or to ambient air for 7 d. In T. aestivum and Z. mays over a 7-d growth period, nitrogen-use efficiency (NUE) values were influenced by N-sources in the decreasing order NH4NO3-N > NO−
3-N > NH4
+-N and NO−
3-N > NH4NO3-N > NH4
+-N, respectively. Fumigation with NH3 decreased the NUE values of plants grown with any of the N-forms. During 28- and 7-d growth periods, N-sources affected water-use
efficiency (WUE) values in the decreasing order of NH4
+-N > NO−
3-N≈NH4NO3-N in non-fumigated T. aestivum, while fumigation with NH3 increased the WUE of NO−
3-grown plants. There were insignificant effects of N-sources on WUE values of Z. mays over 25- and 7-d growth periods. Furthermore, δ13C values in plant tissues (leaves, stubble and roots) were higher (less negative) in NH4
+-grown plants of T. aestivum and Z. mays than in those supplied with NH4NO3 or NO−
3. Regardless of the N-form supplied to the roots of the plant species, exposure to NH3 caused more-positive δ13C values in the plant tissues. These results indicate that the variations in N-source were associated with small but significant
variations in δ13C values in plants of T. aestivum and Z. mays. These differences in δ13C values are in the direction expected from differences in WUE values over long or short growth periods and with differences
in the extent of non-Rubisco (ribulose-1,5-bisphosphate carboxylase-oxygenase, EC 4.1.1.39) carboxylate contribution to net
C acquisition, as a function of N-source.
Received: 12 September 1997 / Accepted: 13 January 1998 相似文献
16.
The concept of using higher plants to maintain a sustainable life support system for humans during long-duration space missions is dependent upon photosynthesis. The effects of extended exposure to microgravity on the development and functioning of photosynthesis at the leaf and stand levels were examined onboard the International Space Station (ISS). The PESTO (Photosynthesis Experiment Systems Testing and Operations) experiment was the first long-term replicated test to obtain direct measurements of canopy photosynthesis from space under well-controlled conditions. The PESTO experiment consisted of a series of 21–24 day growth cycles of Triticum aestivum L. cv. USU Apogee onboard ISS. Single leaf measurements showed no differences in photosynthetic activity at the moderate (up to 600 μmol m−2 s−1) light levels, but reductions in whole chain electron transport, PSII, and PSI activities were measured under saturating light (>2,000 μmol m−2 s−1) and CO2 (4000 μmol mol−1) conditions in the microgravity-grown plants. Canopy level photosynthetic rates of plants developing in microgravity at ∼280 μmol m−2 s−1 were not different from ground controls. The wheat canopy had apparently adapted to the microgravity environment since the CO2 compensation (121 vs. 118 μmol mol−1) and PPF compensation (85 vs. 81 μmol m−2 s−1) of the flight and ground treatments were similar. The reduction in whole chain electron transport (13%), PSII (13%), and PSI (16%) activities observed under saturating light conditions suggests that microgravity-induced responses at the canopy level may occur at higher PPF intensity. 相似文献
17.
Monthly field investigations were carried out at controlled low-tide in an estuarine intertidal sandflat of the Seto Inland
Sea (Japan) between January 1995 and April 1996. We assessed the spatial and temporal distribution of pore-water nutrient
[NH
4
+
-N, (NO
3
−
+ NO
2
−
)-N, PO
4
3−
-P and Si(OH)4-Si], chlorophyll a (chl a) and acid-volatile sulphide (AVS) concentrations in the uppermost 0–10 cm sediment horizon, and evaluated their relationships
with macrobenthic assemblages. Monthly hydrological data, nutrient and chl a concentrations in low-tide creek water adjacent to the flat were used as a complementary environmental characterisation of
the study area. All different pore-water nutrients showed a 10 to > 30-fold variability between different layers and periods.
NH
4
+
-N, PO
4
3−
-P and Si(OH)4-Si concentrations were lowest in winter, progressively increased throughout spring and summer, and were highest between September
and October, with a major increase at intermediate (4–8 cm) layers. In contrast, (NO
3
−
+ NO
2
−
)-N concentrations, correlated positively with chl a, peaked in winter and sharply decreased with depth in all different seasons and in most occasions. Depth-integrated NH
4
+
-N, PO
4
3−
-P and Si(OH)4-Si pools were correlated positively with biogenic nutrient flux calculated from the nutrient excretion rates of dominant
bivalves Ruditapes philippinarum and Musculista senhousia. These relationships indicated rapid removal pathways of P, Si and N (i.e., every 0.1, 0.24 and 0.34 day, respectively),
implying highly dynamic sediments. Based on the mass balance P = F + I, biogenic production (P) vs. diffusive flux (F) estimates suggested a predominant contribution of animal bioirrigation (I) to the upward flux of nutrients. AVS concentrations, correlated negatively with both (NO
3
−
+ NO
2
−
)-N and chl a, showed a progressive increase from late summer throughout winter, subsequent to that of NH
4
+
-N, PO
4
3−
-P and Si(OH)4-Si. The results indicate that in our study area the spatial and temporal distribution of pore-water nutrients, chl a and AVS in sediments are strongly interlinked and suggest that the metabolic processes (e.g., excretion, bio-deposition)
and behavioural activities (e.g., particle mixing, bioirrigation) of abundant macrobenthos play an important role in the year-round
biogeochemical processes occurring on this flat. 相似文献
18.
In this study, a bioassessment was conducted to determine the effectiveness of best management practices (BMPs) implemented
in farms in the Upper Delaware River watershed, NY (USA). Diatom and macroinvertebrate communities were analyzed across 17
low-order streams, designated as reference, BMP, or non-BMP. Streams lacking improvements (non-BMP) had significantly greater
specific conductance, pH, TDP, NH4
+-N, and NO3
−-N than did reference streams. Diatom model affinity (DMA) values were significantly greater in reference and BMP streams
than in non-BMP streams; non-BMP streams bordered on a “severely impacted” rating. The Trophic Diatom Index (TDI) varied two-fold
among stream classes, with non-BMP > BMP > reference. TDI and DMA values were highly correlated, and both varied significantly
with conductance, TDP, NH4
+-N, and NO3
−-N. Macroinvertebrate taxa, EPT richness, and Simpson’s diversity did not differ significantly among stream classes. Macroinvertebrate
metrics (HBI, Bioassessment Profile, Percent Model Affinity) varied by stream class, but none indicated greater water quality
in BMP sites. Nonetheless, each correlated significantly with conductance and TDP in the directions predicted by each model.
Our data suggest that diatoms are more sensitive to moderate increases in nutrients, conductivity, and pH in high-gradient
agricultural streams, and may be more useful in assessing stream management practices. 相似文献
19.
Murray T. Brown 《Journal of applied phycology》1995,7(4):427-432
Using vegetative propagules (ramuli) of the iota carrageenan producing red seaweed Solieria chordalis, a maximum growth rate of 6.8% d−1 was achieved when cultured at 20 °C and 100 μmol photon m−2 s−1 in seawater supplemented with 20 μM NO3-N or 10 μM NO3-N plus 10 μM NH4-N. Ramuli grew less well when nitrogen was supplied solely as NH
4
+
. Maximum carrageenan content was observed at the same temperature, irradiance and salinity as growth, but at lower nitrogen
concentrations. These findings are discussed in relation to results obtained from studies on other iota-carrageenan producing
carrageenophytes. 相似文献
20.
L. Dendooven C. Vega-Jarquin C. Cruz-Mondragon O. Van Cleemput R. Marsch 《Plant and Soil》2006,279(1-2):243-252
Induction of assimilatory NO
3
−
reduction through the application of an easily decomposable substrate in alkaline–saline soils of the former lake Texcoco
(Mexico) resulted in a fast immobilization of NO
3
−
in excess of N required for metabolic activity and the release of large concentrations of NO
2
−
and smaller amounts of NH
4
+
. We postulated that this was regulated by the amounts of NO
3
−
and glucose added, and affected by the specific characteristics of soil from the former lake Texcoco. This was investigated
by spiking soils of different electrolytic conductivity (EC) 56.0 dS m−1 (soil A of Texcoco) and 11.6 dS m−1 (soil B of Texcoco) with different concentrations of NO
3
−
and glucose while dynamics of CO2, NH
4
+
, NO
2
−
and NO
3
−
were monitored in an aerobic incubation for 7 days. For comparison reasons (control) an agricultural soil with low EC (0.3 dS
m−1) was included as well. In the agricultural soil, 67% of the added glucose mineralized within 7 days, but only 15% in soil
A of Texcoco and 20% in soil B of Texcoco. The application of NO
3
−
to the agricultural soil added with glucose increased cumulative production of CO2 1.2 times, 1.5 times in soil A of Texcoco and 1.8 times in soil B of Texcoco. Concentration of NO
2
−
increased to > 100 mg NO
2
−
-N kg−1 when 1000 mg glucose-C kg−1 and 500 mg NO
3
−
-N kg−1 were added to soil A and B of Texcoco, but remained < 3 mg NO
2
−
-N kg−1 in the agricultural soil. The ratio between the cumulative production of CO2 and the decrease in concentration of NO
3
−
was approximately one in soil A and B of Texcoco, but 10 in the agricultural soil after 3 days. It was found that micro-organisms
in the alkaline–saline soil of the former lake Texcoco were capable of immobilizing large quantities of NO
3
−
when an easy decomposable substrate was available in excess of what might be required for metabolic activity while producing
large concentrations of NO
2
−
, but these phenomena were absent in an agricultural soil. In soil of Texcoco, concentrations of NO
2
−
and NH
4
+
increased with increased salinity and availability of NO
3
−
. This ability to remove large quantities of NO
3
−
under these conditions and then utilize it at a later time might benefit micro-organisms of the N limited alkaline–saline
soils of Texcoco. 相似文献