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1.
Short-term sediment deposition was studied at four salt marsh areas in the Tagus estuary. In areas covered with Sarcocornia perennis, Sarcocornia fruticosa, Halimione portulacoides and Spartina maritima and also in the non-vegetated areas, sedimentation was measured as the monthly accumulation of sediments on nylon filters
anchored on the soil surface, from August 2000 to May 2001. Our experiments were used also to determine the influence of the
different plant species in vertical accretion rates. Short-term sedimentation rates (from 2.8 to 272.3 g m−2 d−1) did show significant differences when the four salt marshes studied in the Tagus estuary were compared to each others. Salt
marshes closer to the sediment sources had higher sedimentation rates. Our results suggest that the salt marsh type and surface
cover may provide small-scale variations in sedimentation and also that sediment deposition values do change according to
the position of the different plant species within the salt marsh. Sedimentation is an essential factor in salt marsh vertical
accretion studies and our investigation may provide support to help forecast the adaptative response of the Tagus estuary
wetlands to future sea level rise. 相似文献
2.
Temporal changes in α-and β-glucosidase activities, dissolved organic matter content, and bacterial biomass were studied in
the superficial sediment layer of a eutrophic lake during the period of anoxia. The mean α-and β-glucosidase activities were
30.7±11.0 and 15.1±6.2 nmol h−1 g−1 of dry sediment, respectively. The specifc β-glucosidase activity seemed to be stimulated by carbohydrates (r=0.80, P<0.05), whereas the specifc α-glucosidase activity was negatively correlated with the dissolved protein concentration (r=−0.72, P<0.10). To test the effect of organic matter on hydrolytic activities under controlled conditions, changes in specific activities
were studied in relation to the concentrations of different types of organic matter: phytoplankton, polymers (proteins, cellobiose,
and starch) and monomers (glucose and amino acids). The specifc α-and β-glucosidase activities were strongly induced by their
natural substrates (starch and cellobiose, respectively) (P<0.05) and were not inhibited by glucose. Proteins inhibited these activities (P<0.05), whereas supplementation with amino acids had no effect on specifc glycolytic activities. 相似文献
3.
The role of salt marshes as nitrogen sink is examined taking into consideration the seasonal variation of above and belowground
biomass of Spartina martima and Halimione portulacoides in two marshes from Tagus estuary, Pancas and Corroios, and the degradation rates of belowground litter. Total nitrogen was
determined in plant components, decomposing litter and sediment. Biomass was higher in Corroios, the saltier marsh, with 7190
g m−2 y−1 dw of S. maritima and 6593 g m−2 y−1 dw of H. portulacoides and the belowground component contributed to 96% and 90% of total biomass, respectively. In the other marsh, Pancas, belowground
biomass contributed to 56% and 76% of total biomass for S. maritima and H. portulacoides, respectively. Litterbag experiment showed that between 25% and 50% of nitrogen is lost within the first month and remained
relatively constant in the next four months. Slower decomposition is observed in sediments with higher nitrogen concentration
(max. 0.7% N in the saltier marsh). Higher concentrations of N were found in the sediment upper layers. Considering the sediment-root
system, most of the nitrogen is stored in the sediment compartment and only about 1–4% of the total N was found in the roots.
Considering these results, Tagus salt marshes act as a sink for nitrogen. 相似文献
4.
Jorge L. Gutiérrez Clive G. Jones Peter M. Groffman Stuart E. G. Findlay Oscar O. Iribarne Pablo D. Ribeiro C. Martín Bruschetti 《Ecosystems》2006,9(4):647-658
Geomorphology, vegetation and tidal fluxes are usually identified as the factors introducing variation in the flushing of
particulate organic matter (POM) from tidal marshes to adjacent waters. Such variables may, however, be insufficient to explain
export characteristics in marshes inhabited by ecosystem engineers that can alter the quantity and quality of POM on the marsh
surface that is subject to tidal flushing. In this study we evaluated the balance between transfer of buried sedimentary organic
carbon (C) to the marsh surface due to crab excavation (measured from the mounds of sediment excavated from burrows) and outputs
of C from the surface due to sediment deposition within crab burrows (estimated from sediment deposited within PVC burrow
mimics), in a Southwestern Atlantic salt marsh supporting dense (approximately 70 ind m−2) populations of the crab Chasmagnathus granulatus. C excavation by crabs was much greater than deposition of C within crab burrow mimics. Per area unit estimates of the balance
between these two processes indicated that crabs excavated 5.98 g m−2 d−1 and 4.80 mg m−2 d−1 of total and readily (10 d) labile C, respectively. However, sediments excavated by crabs showed a significantly lower content
of both total and readily-labile C than sediment collected in burrow mimics. This indicates that ecosystem engineering by
burrowing crabs causes a net decrease in the concentration of C in the superficial sediment layers and, thus, an overall decrease
in the amount of C that can be washed out of the marsh by tidal action. Incorporating the in situ activities of ecosystem
engineers in models of marsh export should enhance understanding of the function of marshes in estuarine ecosystems. 相似文献
5.
Dynamics of biogenic Si in freshwater tidal marshes: Si regeneration and retention in marsh sediments (Scheldt estuary) 总被引:1,自引:0,他引:1
The sequestration and recycling of biogenic silica (BSi) in freshwater tidal marshes was modelled through the combination
of short-term year round sediment trap data with a long-term sedimentation model, MARSED. The modelling was implemented through
the complete evolution from a young rapidly rising marsh to a marsh with an elevation close to mean high water. BSi in imported
suspended matter was higher in summer (10.9 mg BSi g−1 sediment) than winter (7.6 mg BSi g−1 sediment). However, the deposition of BSi on the marsh surface was higher in winter compared to summer, due to the higher
sedimentation rates. Deposition of BSi was correlated to the suspended matter deposition. In the old marsh, yearly about 40 g
BSi m−2 was deposited, while in the young marsh deposition could rise up to 300 g m−2. Young marshes retained up to 85% of the imported biogenic silica. Recycling efficiency (60%) increased drastically for older
marshes. The study shows that marshes act as important sinks for BSi along estuaries. The recycling of the imported BSi to
DSi in summer and spring is most likely an essential factor in the buffering role of tidal marshes for estuarine DSi concentrations. 相似文献
6.
Variations of soil enzyme activities in a temperate forest soil 总被引:3,自引:0,他引:3
Soil enzyme activities (dehydrogenase, urease, phosphatase, and arylsulfatase) in a temperate forest soil were determined
in relation to landscape position and seasons. Overstory of the area is dominated by Quercus mongolica, Kalopanax pictus, Carpicus cordata, and Acer pseudo-sieboldianum. The activities were measured in three patches, namely a north-facing backslope, a ridge, and a south-facing backslope in
autumn and spring over 2 years. In addition, spatially more detailed analysis for phosphatase was conducted before and after
litterfall production in six patches. Dehydrogenase, urease, phosphatase, and arylsulfatase activities varied 1.8–18.5 μg
INT-formazan g−1 h−1, 45.4–347.0 μg NH4
+ g−1 h−1, 0.9–4.5 mmol pNP g−1 h−1, and 0.7–2.6 mmol pNP g−1 h−1, respectively. In general, higher enzyme activities were found in the northern aspect than in the southern aspect. This variation
appears to be related to differences in chemical properties (e.g., Fe, Al, and Mg) of soil as well as distribution of leaf
litter. Two patterns were discernible in relation to seasonal variations. Dehydrogenase and urease exhibited a positive correlation
with mean air temperature, suggesting that temperature would be a major controlling variable for those enzymes. In contrast,
higher activities were detected in autumn for phosphatase and arylsulfatase activities, which appeared to be closely related
to litter production and distribution. Overall results of this study indicate that soil enzyme activities in a forest floor
are influenced by several variables such as temperature, nutrient availability, and input of leaf litter, which are closely
related to landscape position. 相似文献
7.
Bioturbation of Burrowing Crabs Promotes Sediment Turnover and Carbon and Nitrogen Movements in an Estuarine Salt Marsh 总被引:1,自引:0,他引:1
Jin Qing Wang Xiao Dong Zhang Li Fen Jiang Mark D. Bertness Chang Ming Fang Jia Kuan Chen Toshihiko Hara Bo Li 《Ecosystems》2010,13(4):586-599
Ecological functions of bioturbation in ecosystems have received increasing attention over the recent decades, and crab burrowing
has been considered as one of the major bioturbations affecting the physical and chemical processes in salt marshes. This
study assessed the integrated effects of crab excavating and burrow mimic trapping on sediment turnover and vertical C and
N distributions in a Chinese salt marsh in the Yangtze River estuary. Crab burrowing increased soil water content and the
turnover of carbon and nitrogen and decreased bulk soil density. Vertical movement of materials, nutrient cycling and reuse
driven by crab burrowing might be obstructed by vegetation (Phragmites
australis and Spartina
alterniflora communities). The amount of soil excavated by crab burrowing was higher than that deposited into burrow mimics. In Phragmites marshes, Spartina marshes and unvegetated mudflats, net transport of soil to the marsh surface was 171.73, 109.54, and 374.95 g m−2 d−1, respectively; and the corresponding estimated soil turnover time was 2.89, 4.07 and 1.83 years, respectively. Crab burrowing
in salt marshes can mix surface and deeper soil over a period of years, accelerating litter decomposition and promoting the
efficient reuse of nutrients by plants. Therefore, bioturbation affects soil physical processes and functioning of ecosystems,
and needs to be addressed in ecosystem management. 相似文献
8.
Ana Isabel Lillebø J. P. Coelho M. R. Flindt H. S. Jensen J. C. Marques C. B. Pedersen M. A. Pardal 《Hydrobiologia》2007,583(1):195-204
During the last decades the Mondego estuary has been under severe ecological stress mainly caused by eutrophication. In this
salt march system, Spartina maritima covers about 10.5 ha of the intertidal areas. The objective of the present study was to evaluate the effect of Spartina maritima marshes on the dynamics of phosphorus (P) binding in the surface sediment. We compare phosphate and oxygen fluxes, P-adsorption
capacity, phosphate concentrations and total amount, and the extractable P forms in the upper 20 cm of sediment in vegetated
sediment with adjacent mudflats without vegetation. Sediment pore-water profiles followed a clear trend, with lower P concentrations
in more superficial layers, and increasing with depth. The vegetated mudflats presented lower concentrations of dissolved
inorganic phosphorus than adjacent bare bottom mudflats, lower phosphate total amount, as well as higher P-adsorption capacity.
Results from the extraction procedure show that the superficial layers are the most important for estuarine phosphorus dynamics,
since maximum concentrations of labile P pools are present here. In contrast, higher proportions of refractory P pool are
found in deeper layers. Spartina marsh sediments had less total P, less iron bound P, and less exchangeable P than adjacent bare bottom mudflats. Also the
pool of loosely sorbed P is lower in the Spartina marsh. Phosphate regeneration from the sediment to the overlying water was only 11.8 kg ha−1 year−1 in vegetated sediment while 25.8 kg ha−1 year−1 in the bare mud flat. Plant uptake for growth combined with an enhanced P-adsorption capacity of the sediment, may explain
these differences. Therefore, Spartina marshes are very important agents in the sedimentary P cycle worldwide, and can be considered a useful management tool in
estuarine ecosystem recovery efforts. 相似文献
9.
M. I. Rajoka 《World journal of microbiology & biotechnology》2005,21(6-7):1063-1066
Summary Deoxyglucose-resistant mutants of Cellulomonas biazotea secreted elevated levels of cellulases and xylanases. The production of β-glucosidase in the constitutive mutant was increased 5-fold over its parent strain. This mutant showed an approximately 1.6-fold
enhanced productivity of extracellular endo-glucanase following growth on Leptochloa fusca over the mutant parent. Extracellular production of xylanase, filter-paper cellulase (FPase) and endo-glucanase (CMCase)
were also altered in the mutant. Maximum volumetric productivities for xylanase, β-xylosidase, FPase, β-glucosidase and endo-glucosidase were 451, 98, 80, 95, and 143 IU l−1 h−1 which were significantly more than their respective values from the parental strains. The enzyme preparation of the mutants
exhibited improved saccharification of kallar grass straw. 相似文献
10.
Catherine E. Lovelock Vicki Bennion Alistair Grinham Donald R. Cahoon 《Ecosystems》2011,14(5):745-757
Increases in the elevation of the soil surfaces of mangroves and salt marshes are key to the maintenance of these habitats
with accelerating sea level rise. Understanding the processes that give rise to increases in soil surface elevation provides
science for management of landscapes for sustainable coastal wetlands. Here, we tested whether the soil surface elevation
of mangroves and salt marshes in Moreton Bay is keeping up with local rates of sea level rise (2.358 mm y−1) and whether accretion on the soil surface was the most important process for keeping up with sea level rise. We found variability
in surface elevation gains, with sandy areas in the eastern bay having the highest surface elevation gains in both mangrove
and salt marsh (5.9 and 1.9 mm y−1) whereas in the muddier western bay rates of surface elevation gain were lower (1.4 and −0.3 mm y−1 in mangrove and salt marsh, respectively). Both sides of the bay had similar rates of surface accretion (~7–9 mm y−1 in the mangrove and 1–3 mm y−1 in the salt marsh), but mangrove soils in the western bay were subsiding at a rate of approximately 8 mm y−1, possibly due to compaction of organic sediments. Over the study surface elevation increments were sensitive to position
in the intertidal zone (higher when lower in the intertidal) and also to variation in mean sea level (higher at high sea level).
Although surface accretion was the most important process for keeping up with sea level rise in the eastern bay, subsidence
largely negated gains made through surface accretion in the western bay indicating a high vulnerability to sea level rise
in these forests. 相似文献
11.
The culture-medium composition was optimised, on a shake-flask scale, for simultaneous production of high activities of endoglucanase
and β-glucosidase by Thermoascus aurantiacus using statistical factorial designs. The optimised medium containing 40.2 g l−1 Solka Floc as the carbon source and 9 g l−1 soymeal as the organic nitrogen source yielded 1130 nkat ml−1 endoglucanase and 116 nkat ml−1β-glucosidase activities after 264 h as shake cultures. In addition, good levels of β-xylanase (3479 nkat ml−1) and low levels of filter-paper cellulase, β-xylosidase, α-l-arabinofuranosidase, β-mannanase, β-mannosidase, α-galactosidase and β-galactosidase were detected. Batch fermentation in
a 5-l laboratory fermentor using the optimised medium allowed the production of 940 nkat ml−1 endoglucanase and 102 nkat ml−1β-glucosidase in 192 h. Endoglucanase and β-glucosidase showed optimum activity at pH 4.5 and pH 5, respectively, and they
displayed optimum activity at 75 °C. Endoglucanase and β-glucosidase showed good stability at pH values 4–8 and 4–7, respectively,
after a prolonged incubation (48 h at 50 °C). Endoglucanase had half-lives of 98 h at 70 °C and 4.1 h at 75 °C, while β-glucosidase
had half-lives of 23.5 h at 70 °C and 1.7 h at 75 °C. Alkali-treated bagasse, steam-treated wheat straw, Solka floc and Sigmacell
50 were 66, 48.5, 33.5 and 14.4% hydrolysed by a crude enzyme complex of T. aurantiacus in 50 h.
Received: 12 November 1999 / Accepted: 14 November 1999 相似文献
12.
Launen LA Dutta J Turpeinen R Eastep ME Dorn R Buggs VH Leonard JW Häggblom MM 《Biodegradation》2008,19(3):347-363
The aerobic polyaromatic hydrocarbon (PAH) degrading microbial communities of two petroleum-impacted Spartina-dominated salt marshes in the New York/New Jersey Harbor were examined using a combination of microbiological, molecular
and chemical techniques. Microbial isolation studies resulted in the identification of 48 aromatic hydrocarbon-degrading bacterial
strains from both vegetated and non-vegetated marsh sediments. The majority of the isolates were from the genera Paenibacillus and Pseudomonas. Radiotracer studies using 14C-phenanthrene and 14C-pyrene were used to measure the PAH-mineralization activity in salt marsh sediments. The results suggested a trend towards
increased PAH mineralization in vegetated sediments relative to non-vegetated sediments. This trend was supported by the enumeration
of PAH-degrading bacteria in non-vegetated and vegetated sediment using a Most Probable Numbers (MPN) technique, which demonstrated
that PAH-degrading bacteria existed in non-vegetated and vegetated sediments at levels ranging from 102 to 105 cells/g sediment respectively. No difference between microbial communities present in vegetated versus non-vegetated sediments
was found using terminal restriction fragment length polymorphism (of the 16S rRNA gene) or phospholipid fatty acid analysis.
These studies provide information on the specific members and activity of the PAH-degrading aerobic bacterial communities
present in Spartina-dominated salt marshes in the New York/New Jersey Harbor estuary. 相似文献
13.
M. S. Umikalsom A. B. Ariff Z. H. Shamsuddin C. C. Tong M. A. Hassan M. I. A. Karim 《Applied microbiology and biotechnology》1997,47(5):590-595
Studies on the feasibility of using delignified oil palm empty-fruit-bunch (OPEFB) fibres as a substrate for cellulase production
by Chaetomium globosum strain 414 were carried out in shake-flask cultures containing different types and concentrations of nitrogen source. Peptone,
as nitrogen source, gave maximum production of all the three main components of the cellulase complex (endoglucanase or carboxymethylcellulase,
cellobiohydrolase or filter-paper-hydrolysing enzyme and β-glucosidase), followed by yeast extract, urea, KNO3 and (NH4)2SO4. The maximum specific growth rate (μmax) of C. globosum strain 414 grown in medium containing OPEFB and peptone was 0.038 h−1. In all the fermentations, the fungus was able to produce all the three cellulases with significant amounts of β-glucosidase,
except when using (NH4)2SO4 as nitrogen source, where β-glucosidase was not produced. With 6 g/l peptone and 10 g/l delignified OPEFB fibres, the fungus
produced maximum concentrations of FPase, carboxymethylcellulase and β-glucosidase: 1.4, 30.8 and 9.8 U/ml, giving productivities
of 10, 214 and 24 U l−1h−1, respectively. The cellulase mixture, partially purified by ammonium sulphate precipitation, was able to hydrolyse delignified
OPEFB fibres, converting about 68 % of the cellulosics to reducing sugars after 5 days.
Received: 17 June 1996 / Received revision: 18 November 1996 / Accepted: 23 November 1996 相似文献
14.
Temporary rivers are characterized by recurrent dry phases, and global warming will stress their hydrology by amplifying extreme
events. Microbial degradation and transformation of organic matter (OM) in riverbed sediment are key processes with regard
to carbon and nutrient fluxes. In this study, we describe structural and functional changes of benthic microbial communities
in a riverine environment subject to hydrological fluctuation. Sampling was carried out in the outlet section of the Mulargia
River (Sardinia, Italy) under various water regimes, including one flood event. Overall, sediments were characterized by low
bacterial cell abundance (range 0.6–1.8 × 109 cell g−1) as a consequence of their low nutrient and OM concentrations. No major differences were found in the community composition.
Alpha-Proteobacteria dominated during the whole year (range 21–30%) followed by Beta-Proteobacteria, Gamma-Proteobacteria, and Cytophaga-Flavobacteria which always contributed <18%. Planctomycetes and Firmicutes were found in smaller amounts (<7%). In spring, when the highest total organic carbon content was also detected (0.42% w/w),
both bacterial abundance and C production (BCP, 170 nmol C h−1 g−1) reached relatively high values. During the flood event, an increase in BCP and the highest values of community respiration
(CR, 74 nmol C h−1 g−1) were observed. Moreover, most of the extracellular enzyme activities (EEA) changed significantly during the flood. The variation
of the water flow itself can explain part of these changes and other factors also come into play. The presence of different
patterns of functional parameters could suggest that the quality of the OM could be the major driving force in nutrient flux. 相似文献
15.
Many authors have referred to the important role of vegetation in the consolidation of salt marsh sediments, but experiments
previously carried out by us have shown results that do not always agree with these statements. In other words, the type of
salt marsh surface coverage is not the main factor that contributes to the consolidation of sediments. To test this hypothesis
different Portuguese salt marsh stations (species/unvegetated areas) from two sites, Tagus estuary (Corroios and Pancas) and
Ria de Aveiro (Barra and Verdemilho), were compared to evaluate their influence on suspended matter deposition on the salt
marsh surface. A short-term sedimentation study was performed within stands of Spartina maritima, Halimione portulacoides, Sarcocornia perennis subsp. perennis and unvegetated areas, by analysing the deposition of sediment material on nylon filters anchored to the marsh surface. Numerical
results obtained from hydrodynamic models coupled to a Lagrangean module implemented for the Ria de Aveiro and the Tagus Estuary,
namely the root-mean square velocity (V
rms) and residual velocity of tides, were also used.
Average sedimentation rates (mean value between the different surface cover in a salt marsh) showed a seasonal trend more
or less defined but with significantly different values between sites and salt marshes. Sedimentation rates varied between
marshes: there are significant differences between Pancas and the other three marshes, but only significant differences in
sedimentation rates between Spartina and Sarcocornia.
Despite the important role of vegetation in the consolidation of salt marsh sediments, our results suggest that, the position
of stations and related abiotic conditions in the salt marshes are determining factors of variation to take into account in
the studies related with the stabilization and survival of salt marshes facing sea level rise.
Handling editor: P. Viaroli 相似文献
16.
Gabriel Vigueras Sonia Arriaga Keiko Shirai Marcia Morales Sergio Revah 《Biotechnology letters》2009,31(8):1203-1209
Rhinocladiella similis biodegraded volatile organic compounds (VOCs) of different polarity in gas-phase biofilters. Elimination capacities, (EC)
of 74 ghexane m−3 h−1, 230 gethanol m−3 h−1, 85 gtoluene m−3 h−1 and 30 gphenol m−3 h−1 were obtained. EC values correlated with the solubility of the VOCs. R. similis grown with n-hexane or ethanol in biofilters packed with Perlite showed that the surface hydrophobicity was higher with n-hexane
than ethanol. The hydrophobin-like proteins extracted from the mycelium produced with n-hexane (15 kDa) were different from
those in the ethanol biofilter (8.5 kDa and 7 kDa). 相似文献
17.
18.
The influence of environmental pH on biological activity of Bifidobacterium longum CRL 849 grown in MRS-raffinose was evaluated. At pH 6.0, 5.5 and 5.0, raffinose was completely consumed by this microorganism,
showing different consumption rates at each pH value (between 3.03 and 0.76 mmol l−1 h−1). At pH 4.5, the growth was lowest. The removal of raffinose was due to the α-galactosidase (α-gal) activity of this bifidobacteria,
which was highest at pH 6.0–5.5 (1,280–1,223 mU ml−1). The production of β-glucosidase (β-glu) showed a similar pattern to α-gal activity with major values. The yield of organic
acids produced during raffinose consumption was also highest at pH 6.0–5.5. The results of this study will allow the selection
of the optimum growth conditions of B. longum CRL 849, with elevated levels of α-gal to be used in the reduction of nondigestible α-oligosaccharide in soy products and
β-glu activities involved in isoflavone conversion to bioactive forms when used as starter culture. 相似文献
19.
This work studied the effect of two cell-surface lectins isolated from the nitrogen-fixing soil bacterium Azospirillum brasilense Sp7 and from its mutant defective in hemagglutinating activity, A. brasilense Sp7.2.3, on the activities of α-glucosidase, β-glucosidase and β-galactosidase in the exocomponent, membrane and apoplast
fractions of wheat-seedling roots. Lectin (40 μg mL−1) incubation for 1 h of the plant fractions increased the enzymes’ activities; both wild-type and mutant lectins were most
stimulatory to the activities of all the exocomponent-fraction enzymes studied and to the apoplast-fraction β-glucosidase.
Pretreatment of the lectins with their carbohydrate hapten, L-fucose, lowered the effect. The observed differences in the lectins’ ability to influence enzyme catalytic activity are explained
by change in the antigenic properties of the mutant lectin. 相似文献
20.
Macrophyte presence is an indicator of enhanced denitrification and nitrification in sediments of a temperate restored agricultural stream 总被引:1,自引:0,他引:1
Stream macrophytes are often removed with their sediments to deepen stream channels, stabilize channel banks, or provide habitat
for target species. These sediments may support enhanced nitrogen processing. To evaluate sediment nitrogen processing, identify
seasonal patterns, and assess sediment processes relative to stream load, we measured denitrification and nitrification rates
in a restored third- to fourth-order agricultural stream, Black Earth Creek, Wisconsin, and estimated processing over a 10 km
reach. Our results show that sediments with submerged and emergent macrophytes (e.g., Potomageton spp. and Phalaris arudinacea) support greater denitrification rates than bare sediments (1.12 μmol N g−1 h−1 vs. 0.29). Sediments with macrophytes were not carbon limited and organic matter fraction was weakly correlated to denitrification.
The highest denitrification potential occurred in macrophyte beds (5.19 μmol N g−1 h−1). Nitrification rates were greater in emergent beds than bare sediments (1.07 μg N ml−1day−1 vs. 0.35) with the greatest nitrification rates during the summer. Total denitrification removal in sediments with macrophytes
was equivalent to 43% of the nitrate stream load (463.7 kg N day−1) during spring and nitrification in sediments with macrophytes was equivalent to 247% of summer ammonium load (3.5 kg N day−1). Although the in-channel connectivity to nitrogen rich water was limited, actual stream nitrogen loads could increase with
removal of macrophytes. Macrophyte beds and supporting fringing wetted areas are important if nitrogen management is a concern
for riparian stream restoration efforts. 相似文献