共查询到20条相似文献,搜索用时 31 毫秒
1.
Nitrogen and phosphorus uptake by the Brazilian kelp Laminaria abyssalis (Phaeophyta) in culture 总被引:1,自引:1,他引:0
The uptake of ammonium, nitrate and phosphate by laboratory-grown young sporophytes of Laminaria abyssalis was measured in a perturbed system (batch mode) at 18 °C and 35 ± 5 µE m–2 s–1 photon flux density. Uptake of all appeared to follow saturation-type nutrient uptake kinetics. The NO
inf3
sup–
(K
s = 14.0 µM, V
max = 5.0 µmol h–1 g–1 dry wt) and NH
inf4
sup+
(K
s = 4.6 µM, V
max= 2.0 µmol h–1 g–1 dry wt) were taken up simultaneously, although NH
inf4
sup+
was taken up more rapidly. Values of K
3 and V
max for phosphate were, respectively, 2.21 µM and 0.83 µmol h–1 g–1 dry wt. Nitrate and phosphate were both consumed in similar rates (V
max /Ks 0.37) at low concentrations. NH
inf4
sup+
, thus, might be a more efficient form of N fertilizer if artificial enrichment of seawater is used. 相似文献
2.
Summary The effects of short- and long-term exposure to a range in concentration of sea salts on the kinetics of NH
inf4
sup+
uptake by Spartina alterniflora were examined in a laboratory culture experiment. Long-term exposure to increasing salinity up to 50 g/L resulted in a progressive increase in the apparent Km but did not significantly affect Vmax (mean Vmax=4.23±1.97 mole·g–1·h–1). The apparent Km increased in a nonlinear fashion from a mean of 2.66±1.10 mole/L at a salinity of 5 g/L to a mean of 17.56±4.10 mole/L at a salinity of 50 g/L. These results suggest that the long-term effect of exposure to total salt concentrations within the range 5–50 g/L was a competitive inhibition of NH
inf4
sup+
uptake in S. alterniflora. No significant NH
inf4
sup+
uptake was observed in S. alterniflora exposed to 65 g/L sea salts. Short-term exposure to rapid changes in salinity significantly affected both Vmax and Km. Reduction of solution salinity from 35 to 5 g/L did not change Vmax but reduced Km by 71%. However, exposing plants grown at 5 g/L salinity to 35 resulted in an decrease in Vmax of approximately 50%. Exposure of plants grown at 35 g/L to a total sea salt concentration of 50 g/L for 48h completely inhibited uptake of NH
inf4
sup+
. For both experiments, increasing salinity led to an increase in the apparent Km similar to that found in response to long-term exposure. Our data are consistent with a conceptual model of changes in the productivity of S. alterniflora in the salt marsh as a function of environmental modification of NH
inf4
sup+
uptake kinetics. 相似文献
3.
M. Daniel J. H. Choi J. H. Kim J. M. Lebeault 《Applied microbiology and biotechnology》1992,37(6):702-706
Summary
Pseudomonas 135, a facultative methylotroph, was cultivated on methanol as a sole carbon and energy source for the accumulation of poly--hydroxybutyric acid (PHB). The cells grew fairly well on minimal synthetic medium containing 0.5% (v/v) of methanol at pH 7.0 and 30° C. The maximum specific growth rate was determined to be 0.26–0.28 h–1 with a growth yield of 0.38 in the optimized growth medium. For stimulation of PHB accumulation in the cells, deficiency of nutrients such as NH
inf4
sup+
, Mg2+ and PO
inf4
sup3–
was crucial even though cell growth was significantly suppressed. The PHB content of a 40-h culture was determined to be 37% of the total cell mass in NH
inf4
sup+
-limited medium, 42.5% on Mg2+-deficient medium, and 34.5% on PO
inf4
sup3–
-deficient medium. The maximum content of PHB in the cells could reach 55% in NH
inf4
sup+
-limited fed-batch culture. The average relative molecular eight determined by gel permeation chromatography was 3.7 × 105 in NH
inf4
sup+
-limited culture, 2.5 × 105 in Mg2+-deficientmedium, and 3.1 × 105 in PO
inf4
sup3–
-deficient medium. Polydispersity determined in each culture was relatively high (about 10–11). The solid PHB had a melting temperature of 173° C.
Correspondence to: J. M. Lebeault 相似文献
4.
Nitrogen cycling in lake sediments bioturbated by Chironomus plumosus larvae, under different degrees of oxygenation 总被引:2,自引:1,他引:1
Sediment cores containing different densities of Chironomus plumosus, ranging from 0 to 12 000 ind. m–2, were incubated in the laboratory, with 100 and 39% O2 saturation in the overlying water. Rates of O2 uptake, and fluxes of the various inorganic N species were measured after addition of 15NO
inf3
su–
to the overlying water. The animals enhanced O2 and NO
inf3
su–
uptake, due to irrigation. Denitrification of NO
inf3
su–
coming from the overlying water (Dw) and dissimilatory NO
inf3
su–
reduction to NH
inf4
sup+
(DNRA) represented 20–30 and 4–10% of the NO
inf3
su–
uptake, respectively. Only 20–40% of the measured NH
inf4
sup+
effluxes corresponded to DNRA, the rest was probably due to animal excretion. Nitrite production, mostly from dissimilatory NO
inf3
sup–
reduction, was detected at both 39 and 100% oxygen saturation. Higher rates of NO
inf2
su–
production at the lower oxygen concentrations, were probably due to a thinner oxic layer, compared to fully oxygenated waters. The presence of Chironomus plumosus increased nitrification rates, relative to non-inhabited microcosms. However, nitrification rates were low compared to Dw, probably due to low numbers of nitrifiers in the sediment. At 39% oxygen saturation, rates of nitrification and denitrification of NO
inf3
su–
generated within the sediment were not measurable. 相似文献
5.
Ulva rigida was cultivated in 7501 tanks at different densities with direct and continuous inflow (at 2, 4, 8 and 12 volumes d–1) of the effluents from a commercial marine fishpond (40 metric tonnes, Tm, of Sparus aurata, water exchange rate of 16 m3 Tm–1) in order to assess the maximum and optimum dissolved inorganic nitrogen (DIN) uptake rate and the annual stability of the Ulva tank biofiltering system. Maximum yields (40 g DW m–2 d–1) were obtained at a density of 2.5 g FW 1–1 and at a DIN inflow rate of 1.7 g DIN m–2 d–1. Maximum DIN uptake rates were obtained during summer (2.2 g DIN M–2 d–1), and minimum in winter (1.1 g DIN m–2 d–1) with a yearly average DIN uptake rate of 1.77 g DIN m–2 d–1 At yearly average DIN removal efficiency (2.0 g DIN m–2 d–1, if winter period is excluded), 153 m2 of Ulva tank surface would be needed to recover 100% of the DIN produced by 1 Tm of fish.Abbreviations DIN=
dissolved inorganic nitrogen (NH
inf4
sup+
+ NO
inf3
sup–
+ NO
inf2
sup–
);
- FW=
fresh weight;
- DW=
dry weight;
- PFD=
photon flux density;
- V=
DIN uptake rate 相似文献
6.
Non-mycorrhizal uptake of amino acids by roots of the alpine sedge Kobresia myosuroides: implications for the alpine nitrogen cycle 总被引:5,自引:0,他引:5
Non-mycorrhizal plants of the alpine sedge, Kobresia myosuroides, take up the amino acid glycine from nutrient solutions at greater rates than NO
inf3
sup-
or NH
inf4
sup+
. The amino acids glutamate and proline were also taken up at high rates. Total plant biomass was twice as high after 4 months of growth on glycine, compared to NH4NO3, with significant increases in both root and leaf biomass. By taking advantage of differences in the 13C signature of air in the growth chamber and the glycine used for growth, a two-member mixing model was used to estimate that a significant amount of the glycine was taken up as intact molecules, enough to contribute 16% of the total carbon assimilation over a 4-month growing period. Glycine uptake was inhibited when roots were exposed to N2 in place of air, and when the protonophore carbonyl cyanide m-chlorophenylhydrazone (CCCP) was added to the root solution. From these results it is concluded that glycine uptake occurs through active transport. Glycine uptake exhibited a Q10 of 2.0 over the temperature range 5–15° C, with relatively high rates maintained at the lowest temperature measured (5° C). Roots of Kobreasia were not capable of taking up NH
inf4
sup+
at measureable rates. To our knowledge, this is the first report of a plant whose non-mycorrhizal roots cannot take up NH
inf4
sup+
. Measurements of three N fractions (NO
inf3
sup-
, NH
inf4
sup+
, and total amino acids) in the soil pore water were made over two growing seasons in two Kobresia dry meadows using microlysimeters. At the West Knoll site, which is characterized by soils with average amounts of organic matter, the dominant forms of N in the soil pore water were NO
inf3
sup-
and NH
inf4
sup+
(0–450 mol L-1). Amino acid concentrations were generally less than 20 mol L-1 at this site. At the East Knoll site, which is characterized by soils with higher than average amounts of organic matter, amino acids were generally present at higher concentrations (17–100 mol L-1), compared to NO
inf3
sup-
and NH
inf4
sup+
. The most abundant amino acids were glycine (10–100 mol L-1), glutamate (5–70 mol L-1), and late in the season cystein (5–15 mol L-1). The results demonstrate that this sedge, which dominates dry meadow communities in many alpine ecosystems, is capable of taking up intact amino acids as a principal N source, and has access to high amino acid concentrations in certain alpine soils. Such uptake of organic N may accommodate plant N demands in the face of slow alpine N mineralization rates due to cold soil temperatures. 相似文献
7.
Experiments conducted on samples collected from a large oligotrophic lake revealed the following: (1) excretion rates of PO
inf4
sup3–
by single Daphnia thorata were below detection (5 pmol animal–1 min–1) in 20 ml of oligotrophic lake water over a period of 10 min, (2) experimental addition of D. thorata to 20 ml aliquots of lake water decreased community-wide microbial uptake of PO
inf4
sup3–
on two occasions (as measured by 32PO
inf4
sup3–
incorporation), and (3) the presence of D. thorata increased uptake by organisms smaller than 1µm, and decreased uptake by large phytoplankton. The specific mechanism for these responses remains unclear, but the results imply that when phytoplankton larger than 1µm encounter cm scale patches of water recently occupied by Daphnia they may experience decreased PO
inf4
sup3–
availability rather than elevated concentrations of PO
inf4
sup3–
caused by excretion. We show that 32P uptake experiments using natural plankton assemblages can be influenced by the presence or absence of large zooplankton, and that neither grazing, turbulence, nor PO
inf4
sup3–
excretion can account for this influence. 相似文献
8.
The influence of different antecedent conditions on hydrochemical response during storm events was investigated in a small, south-western Cape mountain catchment. Winter and summer storms (four in total) were sampled both before and after the catchment was deliberately burnt. During winter storms, discharge responded rapidly to rainfall, and direct runoff represented the major component of streamflow. Marked lags were observed between rainfall and discharge peaks during the summer storms, and streamflow was dominated by delayed interflow. Chloride, PO
inf4
sup3–
-P and NO
inf3
sup–
-N exhibited variable response to discharge according to seasonal variations in soil-moisture levels, whereas the response of HCO
inf3
sup–
, H+ and NH
inf4
sup+
-N was not influenced by season. The movement of ions appears to be affected more by geochemical processes operating within the soil than by plant-uptake dynamics, as the prescribed burn appeared to have little effect on relationships between ionic concentration and discharge. The findings of the study highlight the complexity of relationships between solute concentration and discharge. 相似文献
9.
Jean-Claude Druart Olivier L. Reymond Jean Pierre Pelletier Françoise Gasse 《Hydrobiologia》1987,153(1):79-86
Intact sediment-water columns from a flowing cypress swamp receiving primary wastewater effluent were used to evaluate inorganic N removal and to determine the fate of 15NH
inf4
sup+
-N added to the floodwater. Treatments represented wetland sites which had received 0 (initial application), 2, and 50 years of primary wastewater application. The rate of inorganic-N decrease in the floodwater was greatest for the initial application columns, primarily due to sediment adsorption of NH
inf4
sup+
, followed by 2-year and 50-yr-columns. Maximum removal rates were 318, 296, and 148 mg N m–2 day–1, respectively. At the end of the 21-day study period, only 0.5 to 2.3% of applied 15N was recovered in the floodwater and 11.4 to 17.3% was recovered in the sediment, with the remaining 82.2 to 86.3% being lost from the sediment-water system. Results of the study indicated that N removal efficiency did not decrease with prolonged wastewater application, despite reduced sediment adsorption capacity, because of the significance of gaseous N losses (nitrification-denitrification, NH3 volatilization) as an N sink in the sediment-water system.Florida Agricultural Experiment Stations Journal Series No. 7712 相似文献
10.
Short-term variations in nutrient concentrations of water-masses have been studied in a Brittany estuary over several tidal cycles, during winter and summer. NH
inf4
sup+
, NO
inf2
su–
, NO
inf3
sup–
, SiO2 and PO
inf4
su3–
have been measured at a fixed station. The Dourduff estuary is characterized by a very low river discharge (80 l · s–1 during the minimum water runoff and 1 000 l · s–1 during the maximum) and an important tidal range (9 m at spring tides). SiO2 and NO
inf3
sup+
concentrations are directly related to freshwater flow whereas PO
inf4
su3–
is partially adsorbed by seston in the turbid ebb waters. NH
inf4
sup+
concentration seems to be, in part, dependent upon sediment resuspension: late ebb and onset of flood periods liberate NH
inf4
sup+
into the overlying water column. Nutrient concentrations are also related to seasons. Nutrient fluxes are insignificant or negative during summer periods, so the estuary imports nutrients for its own regulation whereas during winter periods it exports NO
inf3
sup–
and SiO2 (ca 50 kg NO
inf3
sup–
and ca 200 g SiO2 during a single spring tide). The NO3: PO4 ratio is always above 15:1 and can reach 300:1; moreover this ratio fluctuates during the tidal cycle. This imbalance originates in terrestrial discharges of nitrogen compounds.
Sels minéraux et cycles de marées dans un estuaire de Bretagne nord (Dourduff, France)相似文献
11.
This paper shows the importance of acid-base analyses and 13C measurements in the evaluation of the responses of Salvinia species' responses to different N sources. It also highlights the importance of these methodologies as potential tools in the study of differences between habitats and nutrient acquisition, particularly N. This study used three different species of Salvinia cultured in the absence of combined N or in the presence of either NO
inf3
sup–
or NH
inf4
sup+
as N sources. The interaction between NO
inf3
sup–
or NH
inf4
sup+
as N source and organic acid metabolism, and the information on diazotrophy from the organic acid measurements, were also examined. Nevertheless, the results presented may not be used per se to assign diazotrophy. Carboxylate (C-A) levels in the different Salvinia species are much lower than the norm for bryophytes and tracheophytes, consistent with previously published work on Azolla. This might be related to the aquatic life form of these plants, since they seem to have no potential to increase the availability of Fe or P by the acidification of their rooting medium (water) that a larger net synthesis of organic acids, with cation-H+ exchange, could achieve. 相似文献
12.
Diurnal variation in hydrological variables and dissolved inorganic nutrients such as PO
inf4
sup3–
-P, N O
inf2
sup–
-N, NO
inf3
sup–
-N and NH
inf4
sup+
-N were studied in three interconnected biotopes including freshwater, marine and mangrove brackish water of the Kakinada coastal zone, Andhra Pradesh. Samples were collected at intervals of 3 hours, for a period of 24 hours. In the marine environment salinity varied from 26 to 32 whereas in the mangrove waters it fluctuated from 12 to 20 and in both biotopes salinity showed bimodal type of oscillation. Dissolved oxygen content was high in the mangrove waters during day time but decreased rapidly during the night hours. In the marine environment POf4
p3–-P concentration varied from 0.345 to 1.195 g at l–1, NO
inf3
sup–
-N from 1.03 to 6.62 g at l–1 and NO
inf2
sup–
-N from 0.086 to 0.506 g at l–1. The highest and the lowest concentrations of PO
inf4
sup3–
-P, NO
inf3
sup–
-N, NO
inf2
sup–
-N recorded in the mangrove waters were 0.790 and 0.325 g at l–1, 7.10 and 1.60 g at l–1 and 0.278 and 0.060 g at l–1, respectively. The concentration of PO
inf4
sup3–
-P, NO
inf3
sup–
-N and NO
inf2
sup–
-N were high in the freshwater canal, the maximum and minimum values being 1.110 and 0.730 g at l–1, 26.40 and 9.98 g at l–1 and 0.520 and 0.252 g at l–1 respectively. The concentration of ammonia was relatively high in the mangrove water. Gross and net primary production in the mangrove water was 4 times higher than in the marine biotope. There was no export of dissolved nutrients from the mangrove environment to the adjacent marine waters. 相似文献
13.
Summary We compared ammonium and nitrate nutrition in Eriophorum scheuchzeri and E. vaginatum, two Alaskan sedges that are native to high- and low-fertility sites, respectively. When grown in solution culture, the two species were similar in their kinetics of NH
inf4
sup+
NO
inf3
sup-
absorption: at nitrogen concentrations below 50 M, net NH
inf4
sup+
and NO
inf3
sup-
were absorbed at similar rates, but at higher concentrations, net uptake of NO
inf3
sup-
was significantly faster than that of NH
inf4
sup+
. The two species also showed similar abilities to assimilate NO
inf3
sup-
. Growth of E. vaginatum under NO
inf3
sup-
nutrition was only slightly less than that under NH
inf4
sup+
. The observed similarities between these species from contrasting edaphic habitats indicate that factors other than tissue-specific rates of nitrogen acquisition and assimilation may underlie local adaptation to soil N fertility. Moreover, the capacity of these species to exploit NO
inf3
sup-
as a N source supports the view that NO
inf3
sup-
availability may be significant even in wet, acidic, arctic soils. 相似文献
14.
Geoffrey W. Garnham Geoffrey A. Codd Geoffrey M. Gadd 《Applied microbiology and biotechnology》1992,37(5):679-684
Summary Accumulation of [99Tc]pertechnetate ions (99TcO4
–) by the freshwater microalgae Chlorella emersonii, Chlamydomonas reinhardtii and Scenedesmus obliquus has been characterized. In all three species, accumulation consisted of a single rapid energy-independent phase (biosorption), and no energy-dependent accumulation was observed. Biosorption of 99TcO
inf4
sup–
by all three species was concentration dependent, followed a Freundlich adsorption isotherm, and was dependent on pH with increased accumulation by cells with decreasing external pH. Elevated external NaCl concentrations also caused increased accumulation of 99TcO
inf4
sup–
by the cells, as did increased external osmotic potential. Concentrations of K+, Mg2+ and Ca2+ increased accumulation of 99TcO
inf4
sup–
, but concentrations of HCO
inf3
sup–
, SO
inf4
sup2–
and CO
inf3
sup2–
decreased 99TcO
inf4
sup–
accumulation by the cells. Most of the 99TcO
inf4
sup–
accumulated by all three species was easily desorbed by 10 mm buffers at various pH values, 0.5 m NaCl, 10 mm Na2CO3 or 10 mm Na2SO4. No differences in the amount of desorption were observed between the various desorption agents used.
Correspondence to: G. M. Gadd 相似文献
15.
Cyanuric acid in high concentrations (15.5 mm) was degraded completely by Pseudomonas sp. NRRL B-12228 independently of glucose concentration. In the batch fermentations there was a relation between the glucose concentration, on the one hand, and the liberation of ammonia or production of protein, on the other. The greater the supply of carbon, the more biomass was produced, and fewer NH
inf4
sup+
ions were released. Continuous fermentations using adsorbed cells could be performed to degrade cyanuric acid. In spite of different glucose feeding there was only a negligible difference in residues of s-triazine. In a one-step continuous system with dilution rates between 0.021 h–1 and 0.035 h–1, even a ratio of 0.65 between glucose and cyanuric acid was not sufficient to degrade the cyanuric acid supplied (320–540 mol l–1 h–1) completely. When a continuous two-step system was applied with dilution rates between 0.035 h–1 and 0.056 h–1, the consumption of carbon source could be minimized while s-triazine degradation up to 860 mol l–1 h–1 was complete. In this way the ratio between glucose and cyanuric acid could be increased to 0.25 (molar C:N ratio = 0.33:1). Thereby the process was made considerably more economic. 相似文献
16.
Paul Golby Nicholas P. J. Cotton Mark Carver J. Baz Jackson 《Archives of microbiology》1992,157(2):125-130
Comparison of the rate of accumulation of 86Rb+ by intact cells of Rhodobacter capsulatus during short periods of illumination with the Rb+-dependent membrane ionic current measured by electrochromism supports the view that both activities reflect the operation of a low-affinity K+ transport system. In experiments performed under similar conditions the ratio of 86Rb+ uptake to charge uptake was approx. 1.0, suggesting that the transport system operates as a uniporter. The addition of NH
inf4
sup+
to a cell suspension led to an increase in membrane ionic current but failed to inhibit the accumulation of 86Rb+ during illumination. The presence of K+ and NH
inf4
sup+
inhibited the increase in cellular ATP levels at the onset of illumination. This effect was prevented by Cs+. The results are considered within the context of the hypothesis (Golby et al. Eur J Biochem 187: 589–597) that NH
inf4
sup+
can be transported by the K+ carrier and in the context of an alternative hypothesis that NH
inf4
sup+
increases the affinity of the K+ transport system for its natural substrate and for Rb+.Abbreviations pH
pH difference across the cytoplasmic membrane
-
electrical potential difference across the cytoplasmic membrane 相似文献
17.
Summary A method for removal of toxic hexavalent chromium (chlomate: CrO
inf4
sup2–
) was developed by use of dialysis-sac cultures of a chromate-reducing strain of Enterobacter cloacae (HO1). E. cloacae strain HO1 cells were put in dialysis (semipermeable membrane) sacs, and the sacs were submerged in water containing toxic CrO
inf4
sup2–
. The dialysis sacs allowed CrO
inf4
sup2–
to diffuse into the culture, and CrO
inf4
sup2–
was reduced anaerobically in the dialysis sacs by the E. cloacae cells. Because reduced chromium readily formed insoluble chromium hydroxides in the dialysis sacs, the greater part of reduced chromium was unable to diffuse out through the semipermeable membrane. Thus the dialysis culture of E. cloacae strain HO1 could successfully remove toxic chromium from the surrounding water. If the initial concentration of CrO
inf4
sup2–
was less than 4mM (208 ppm as chromium), about 90% of the total chromium could be removed from water by the described method.
Offprint requests to: H. Ohtake 相似文献
18.
Nitrate depletion in the riparian zone and stream channel of a small headwater catchment 总被引:30,自引:1,他引:29
A. Bryce Cooper 《Hydrobiologia》1990,202(1-2):13-26
A mass balance procedure was used to determine rates of nitrate depletion in the riparian zone and stream channel of a small New Zealand headwater stream. In all 12 surveys the majority of nitrate loss (56–100%) occurred in riparian organic soils, despite these soils occupying only 12% of the stream's border. This disproportionate role of the organic soils in depleting nitrate was due to two factors. Firstly, they were located at the base of hollows and consequently a disproportionately high percentage (37–81%) of the groundwater flowed through them in its passage to the stream. Secondly, they were anoxic and high in both denitrifying enzyme concentration and available carbon. Direct estimates ofin situ denitrification rate for organic soils near the upslope edge (338 mg N m–2 h–1) were much higher than average values estimated for the organic soils as a whole (0.3–2.1 mg N m–2 h–1) and suggested that areas of these soils were limited in their denitrification activity by the supply of nitrate. The capacity of these soils to regulate nitrate flux was therefore under-utilized. The majority of stream channel nitrate depletion was apparently due to plant uptake, with estimates of thein situ denitrification rate of stream sediments being less than 15% of the stream channel nitrate depletion rate estimated by mass balance.This study has shown that catchment hydrology can interact in a variety of ways with the biological processes responsible for nitrate depletion in riparian and stream ecosystems thereby having a strong influence on nitrate flux. This reinforces the view that those seeking to understand the functioning of these ecosystems need to consider hydrological phenomena. 相似文献
19.
Nitrate reduction in sediments of lowland tropical streams draining swamp forest in Costa Rica: An ecosystem perspective 总被引:2,自引:1,他引:1
Nitrate reduction and denitrification were measured in swamp forest streams draining lowland rain forest on Costa Rica's Atlantic slope foothills using the C2H2-block assay and sediment-water nutrient fluxes. Denitrification assays using the C2H2-block technique indicated that the full suite of denitrifying enzymes were present in the sediment but that only a small fraction of the functional activity could be expressed without adding NO3
–. Under optimal conditions, denitrification enzyme activity averaged 15 nmoles cm–3 sediment h–1. Areal NO3
– reduction rates measured from NO3
– loss in the overlying water of sediment-water flux chambers ranged from 65 to 470 umoles m–2 h–1. Oxygen loss rates accompanying NO3
– depletion averaged 750 umoles m–2 h–1. Corrected for denitrification of NO3
– oxidized from NH4
+ in the sediment, gross NO3
– reduction rates increase by 130 umoles m–2 h–1, indicating nitrification may be the predominant source of NO3
– for NO3
– reduction in swamp forest stream sediments. Under field conditions approximately 80% of the increase in inorganic N mass along a 1250-m reach of the Salto River was in the form of NO3
– with the balance NH4
+ . Scrutiny of potential inorganic N sources suggested that mineralized N released from the streambed was a major source of the inorganic N increase. Despite significant NO3
– reduction potential, swamp forest stream sediments appear to be a source of inorganic N to downstream communities. 相似文献
20.
Phosphorus and nitrogen mass balances of five wetlands (two beaver ponds, two conifer-Sphagnum swamps and one sedge fen) situated in three catchments in central Ontario, Canada, were measured. Monthly and annual input-output budgets of total phosphorus (TP), total nitrogen (TN), total organic nitrogen (TON), total inorganic nitrogen (TIN), ammonium ion (NH4
+ -N), nitrate (NO
3
–
-N) and dissolved organic carbon (DOC) were estimated for the five wetlands during the 1982–83 and 1983–84 water years. Except for the deepest beaver pond (3.2 m) which had annual TP retention of –44% (–0.030 ± 0.015 g m–2 yr–1), the wetlands retained < 0.001 to 0.015 g M–2 yr–1 ; however, this wasless than 20% of the inputs and the estimated budget uncertainties were equal to or greater than the retention rates. Annual TN retentions ranged from –0.44 to 0.56 g m–2 yr–1 (–12 to 4%) but were not significantly different from zero. The wetlands transformed nitrogen by retaining TIN (16 to 80% RT) and exporting an equivalent amount as TON (–7 to 102% RT). The beaver ponds, however, retained NO
3
–
while NH
4
+
was passed through or the outputs exceeded the inputs. In contrast, the conifer swamps retained both NH
4
+
and NO
3
–
. DOC fluxes into and out of the beaver ponds were equal (–18 and 4% RT) but output from the conifer swamps exceeded input by > 90%. Marked seasonal trends in nutrient retention were observed. Nutrient retention coincided with low stream flow, increased evapotranspiration and biotic uptake during the summer. Net nutrient export occurred during the winter and spring when stream flows were highest and biotic uptake was low. 相似文献