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1.
Blue-green algal blooms formed by Microcystis and Oscillatoria often occur in shallow eutrophic lakes, such as Lake Taihu (China) and Lake Kasumigaura (Japan). Growth characteristics
and competitions between Microcystis aeruginosa and Oscillatoria mougeotii were investigated using lake simulator systems (microcosms) at various temperatures. Oscillatoria was the superior competitor, which suppressed Microcystis, when temperature was <20°C, whereas the opposite phenomenon occurred at 30°C. Oscillatoria had a long exponential phase (20 day) and a low growth rate of 0.22 day−1 and 0.20 day−1 at 15°C and 20°C, respectively, whereas Microcystis had a shorter exponential phase (2–3 days) at 30°C and a higher growth rate (0.86 day−1). Interactions between the algae were stronger and more complex in the lake simulator system than flask systems. Algal growth
in the lake simulator system was susceptible to light attenuation and pH change, and algae biomasses were lower than those
in flasks. The outcome of competition between Microcystis and Oscillatoria at different temperatures agrees with field observations of algal communities in Lake Taihu, indicating that temperature
is a significant factor affecting competition between Microcystis and Oscillatoria in shallow, eutrophic lakes. 相似文献
2.
Effects of the burrowing mayfly,Hexagenia, on nitrogen and sulfur fractions in lake sediment microcosms 总被引:1,自引:1,他引:0
Effects of the burrowing mayfly, Hexagenia, on nitrogen and sulfur fractions of sediment, and overlying water were determined. Laboratory microcosms were used to reproduce
the benthic environment. The activities of Hexagenia increased sediment Eh (1.98 ± 0.486 (22) mV · day −1), and decreased pH in sediment (−0.007 ± 0.001 (22) day −1) and overlying water(-0.024 ± 0.004 (10) day−1). In the control, Eh decreased and pH did not change. The presence of Hexagenia also markedly increased ammonia in sediment (5.46 ± 0.14 (22) ppm N · day−1) and overlying water (0.792 ± 0.154 (10) ppm N · day−1), while the control did not change. In addition, the sulfate fraction of sediment (0.177 ± 0.006 (17)% dry mass) and water
(50.0 ± 4.9 (5) mg · I−1) in microcosms with Hexagenia was greater than that of the control (0.151 ± 0.005 (16)% dry mass; 14.7 ± 1.71 (3) mg · 1−1) at the termination of the experiment. Hexagenia may also stimulate the mineralization of carbon-bonded sulfur. The general role of Hexagenia in altering sediment chemistry is discussed. 相似文献
3.
William Y. B. Chang 《Hydrobiologia》1982,87(3):193-200
Lake Monroe is the largest body of water in Indiana with a daily mean productivity of 220 mg · C · m−2 · day−1 in an observed range from 26 to 714 m · C · M−2 day−1. It is a medium soft reservoir; the acid combining capacity varies from 0.28 to 0.71 meq · l−1 with a mean slightly above 0.5 meq · l−1. The results of diurnal changes in major nutrients, the C, N, and P ratios, and bioassay experiments indicated that phosphorus
is the major limiting nutrient on algal photosynthesis in this lake. Surface photo-inhibition may be used to indicate the
sufficiency of light for the species of algae in the water. The low productivity in December, January, February, and early
March can be attributed to light limitation due to low water transparency.
Contribution no. 312 of the Great Lakes Research Division, University of Michigan.
Contribution no. 312 of the Great Lakes Research Division, University of Michigan. 相似文献
4.
J. Hall I. A. Macdonald P. J. Maddison J. P. O''Hare 《European journal of applied physiology and occupational physiology》1998,77(3):278-284
This study compared the cardiorespiratory responses of eight healthy women (mean age 30.25 years) to submaximal exercise
on land (LTm) and water treadmills (WTm) in chest-deep water (Aquaciser). In addition, the effects of two different water
temperatures were examined (28 and 36°C). Each exercise test consisted of three consecutive 5-min bouts at 3.5, 4.5 and 5.5 km · h−1. Oxygen consumption (V˙O2) and heart rate (HR), measured using open-circuit spirometry and telemetry, respectively, increased linearly with increasing
speed both in water and on land. At 3.5 km · h−1
V˙O2 was similar across procedures [χ = 0.6 (0.05) l · min−1]. At 4.5 and 5.5 km · h−1
V˙O2 was significantly higher in water than on land, but there was no temperature effect (WTm: 0.9 and 1.4, respectively; LTm:
0.8 and 0.9 l · min−1, respectively). HR was significantly higher in WTm at 36°C compared to WTm at 28°C at all speeds, and compared to LTm at
4.5 and 5.5 km · h−1 (P ≤ 0.003). The HR-V˙O2 relationship showed that at a V˙O2 of 0.9 l · min−1, HR was higher in water at 36°C (115 beats · min−1) than either on land (100 beats · min−1) or in water at 28°C (99 beats · min−1). The Borg scale of perceived exertion showed that walking in water at 4.5 and 5.5 km · h−1 was significantly harder than on land (WTm: 11.4 and 14, respectively; LTm: 9.9 and 11, respectively; P ≤ 0.001). These cardiorespiratory changes occurred despite a slower cadence in water (the mean difference at all speeds was
27 steps/min). Thus, walking in chest-deep water yields higher energy costs than walking at similar speeds on land. This data
has implications for therapists working in hydrotherapy pools.
Accepted: 3 September 1997 相似文献
5.
Moro D Bradshaw SD 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1999,169(8):538-548
A laboratory study investigated the metabolic physiology, and response to variable periods of water and sodium supply, of
two arid-zone rodents, the house mouse (Mus domesticus) and the Lakeland Downs short-tailed mouse (Leggadina lakedownensis) under controlled conditions. Fractional water fluxes for M. domesticus (24 ± 0.8%) were significantly higher than those of L. lakedownensis (17 ± 0.7%) when provided with food ad libitum. In addition, the amount of water produced by M. domesticus and by L. lakedownensis from metabolic processes (1.3 ± 0.4 ml · day−1 and 1.2 ± 0.4 ml · day−1, respectively) was insufficient to provide them with their minimum water requirement (1.4 ± 0.2 ml · day−1 and 2.0 ± 0.3 ml · day−1, respectively). For both species of rodent, evaporative water loss was lowest at 25 °C, but remained significantly higher
in M. domesticus (1.1 ± 0.1 mg H2O · g−0.122 · h−1) than in L. lakedownensis (0.6 ± 0.1 mg H2O · g−0.122 · h−1). When deprived of drinking water, mice of both species initially lost body mass, but regained it within 18 days following
an increase in the amount of seed consumed. Both species were capable of drinking water of variable saline concentrations
up to 1 mol · l−1, and compensated for the increased sodium in the water by excreting more urine to remove the sodium. Basal metabolic rate
was significantly higher in M. domesticus (3.3 ± 0.2 mg O2 · g−0.75 · h−1) than in L. lakedownensis (2.5 ± 0.1 mg O2 · g−0.75 · h−1). The study provides good evidence that water flux differences between M. domesticus and L. lakedownensis in the field are due to a requirement for more water in M. domesticus to meet their physiological and metabolic demands. Sodium fluxes were lower than those observed in free-ranging mice, whose
relatively high sodium fluxes may reflect sodium associated with available food.
Accepted: 16 August 1999 相似文献
6.
In winter of 2009/2010, Aphanizomenon flos-aquae bloomed in the ice and snow covered oligo-mesotrophic Lake Stechlin, Germany. The photosynthesis of the natural population was measured at eight temperatures in the range of 2–35°C, at nine different irradiance levels in the range of 0–1,320 μmol m−2 s−1 PAR at each applied temperature. The photoadaptation parameter (I k) and the maximum photosynthetic rate (P max) correlated positively with the temperature between 2 and 30°C, and there was a remarkable drop in both parameters at 35°C. The low I k at low temperatures enabled the active photosynthesis of overwintering populations at low irradiance levels under ice and snow cover. The optimum of the photosynthesis was above 20°C at irradiances above 150 μmol m−2 s−1. At lower irradiance levels (7.5–30 μmol m−2 s−1), the photosynthesis was the most intensive in the temperature range of 2–5°C. The interaction between light and temperature allowed the proliferation of A. flos-aquae in Lake Stechlin resulting in winter water bloom in this oligo-mesotrophic lake. The applied 2°C is the lowest experimental temperature ever in the photosynthesis/growth studies of A. flos-aquae, and the results of the P–I and P–T measurements provide novel information about the tolerance and physiological plasticity of this species. 相似文献
7.
M. J. Tipton F. S. C. Golden C. Higenbottam I. B. Mekjavic C. M. Eglin 《European journal of applied physiology and occupational physiology》1998,78(3):253-257
The initial responses to cold-water immersion, evoked by stimulation of peripheral cold receptors, include tachycardia, a
reflex inspiratory gasp and uncontrollable hyperventilation. When immersed naked, the maximum responses are initiated in water
at 10°C, with smaller responses being observed following immersion in water at 15°C. Habituation of the initial responses
can be achieved following repeated immersions, but the specificity of this response with regard to water temperature is not
known. Thirteen healthy male volunteers were divided into a control (C) group (n = 5) and a habituation (H) group (n = 8). Each subject undertook two 3-min head-out immersions in water at 10°C wearing swimming trunks. These immersions took
place at a corresponding time of day with 4 days separating the two immersions. In the intervening period the C group were
not exposed to cold water, while the H group undertook another six, 3-min, head-out immersions in water at 15°C. Respiratory
rate (f
R), inspiratory minute volume (V˙
I) and heart rate (f
H) were measured continuously throughout each immersion. Following repeated immersions in water at 15°C, the f
R, V˙
I and f
H responses of the H group over the first 30 s of immersion were reduced (P < 0.01) from 33.3 breaths · min−1, 50.5 l · min−1 and 114 beats · min−1 respectively, to 19.8 breaths · min−1, 26.4 l · min−1 and 98 beats · min−1, respectively. In water at 10°C these responses were reduced (P < 0.01) from 47.3 breaths · min−1, 67.6 l · min−1 and 128 beats · min−1 to 24.0 breaths · min−1, 29.5 l · min−1 and 109 beats · min−1, respectively over a corresponding period of immersion. Similar reductions were observed during the last 2.5 min of immersions.
The initial responses of the C group were unchanged. It is concluded that habituation of the cold shock response can be achieved
by immersion in warmer water than that for which protection is required. This suggests that repeated submaximal stimulation
of the cutaneous cold receptors is sufficient to attenuate the responses to more maximal stimulation.
Accepted: 6 February 1998 相似文献
8.
Redox Changes of Iron Caused by Erosion,Resuspension and Sedimentation in Littoral Sediment of a Freshwater Lake 总被引:1,自引:0,他引:1
Depth profiles of oxygen concentration and the redox status of acid-extractable iron were measured in littoral sediment cores
of Lake Constance after mechanical removal of surface sediment, mixing, and re-deposition. In undisturbed sediment cores,
oxygen penetrated down to 2.9±0.4 mm or 4.6±0.4 mm depth, respectively, after 12 h of incubation in the dark or light; causing
a net diffusive flux of 108±20 nmol cm−2 h−1 oxygen into or 152±35 nmol cm−2 h−1 out of the sediment. The uppermost 20 mm layer of the undisturbed sediment cores contained 10.2± 0.7 μmol cm−3 ferrous and 3.8±1.1 μmol cm−3 ferric iron. After erosion, the oxic–anoxic interface in the newly exposed sediment was shifted to about 2 mm depth within
30 min, causing an oxygen flow into the sediment. During the following 12 h, oxygen penetrated deeper into the sediment, and
in the light oxygen was produced photosynthetically. Ferrous iron was largely oxidized within two days after erosion. The
oxidation rates were higher in oxic than in anoxic sediment layers, and decreased with time. This oxidation process took the
longer and was confined closer to the surface the more reduced the exposed sediment had been before. Resuspension of eroded
sediment in aerated lake water did not cause a significant oxidation or reduction of iron. After re-deposition, the oxic–anoxic
interface in the re-sedimented material shifted to about 2 mm depth within 30 min, causing an oxygen flow into the sediment.
During the following 12 h, the oxygen penetration depth and the oxygen flow rate into the re-deposited sediment did not change
any further, and no oxygen was produced in the light. Ferric iron was reduced during the first day after re-deposition, and
partly re-oxidized during the second day. The extent of reduction was stronger and the extent of oxidation weaker the more
reduced the resuspended sediment was before. Oxic conditions in the sediment surface were established faster and ferrous iron
was oxidized to a larger extent after erosion of sediment than after resuspension and sedimentation. 相似文献
9.
A multilayer sediment-water exchange model was used to evaluate the importance of bioturbation in the profundal sediments
of L. Esrom. The temporal variation of the vertical distribution of sedimentary phosphorus fractions was modelled with an
objective function of 1.50. Deviations between measured and simulated values occurred in the spring, where the measured pool
of sedimentary phosphorus sharply declined in the surface sediments. The application of a model for the activity ofChironomus anthracinus based on biomass, oxygen consumption and temperature improved the model in the spring period. The downwards transport of
easy-degradable surface sediments reduced the average release of sedimentary phosphorus from 12 mg P · m−2 · day−1 to 11 mg P · M−2 · day−1. The introduction of a similar model for the other important burrowing species in L. Esrom,Potamothrix hammoniensis, lowered the objective function to 1.37 and increased the average release to 12.5 mg P · m−2 · day−1. The minor role of bioturbation in sediment processes is discussed. 相似文献
10.
Han Gil Choi Ki Hoon Lee Hyun Il Yoo Pil Jun Kang Young Sik Kim Ki Wan Nam 《Journal of applied phycology》2008,20(5):729-735
The effects of temperature, irradiance, and daylength on Sargassum horneri growth were examined at the germling and adult stages to discern their physiological differences. Temperature–irradiance
(10, 15, 20, 25, 30°C × 20, 40, 80 μmol photons m−2s−1) and daylength (8, 12, 16, 24 h) experiments were carried out. The germlings and blades of S. horneri grew over a wide range of temperatures (10–25°C), irradiances (20–80 μmol photons m−2s−1), and daylengths (8–24 h). At the optimal growth conditions, the relative growth rates (RGR) of the germlings were 21% day−1 (25°C, 20 μmol photons m−2s−1) and 13% day−1 (8 h daylength). In contrast, the RGRs of the blade weights were 4% day−1 (15°C, 20 μmol photons m−2s−1) and 5% day−1 (12 h daylength). Negative growth rates were found at 20 μmol photons m−2s−1 of 20°C and 25°C treatments after 12 days. This phenomenon coincides with the necrosis of S. horneri blades in field populations. In conclusion, we found physiological differences between S. horneri germlings and adults with respect to daylength and temperature optima. The growth of S. horneri germlings could be enhanced at 25°C, 20 μmol photons m−2s−1, and 8 h daylength for construction of Sargassum beds and restoration of barren areas. 相似文献
11.
Salo-Zieman VL Sivonen T Plumb JJ Haddad CM Laukkanen K Kinnunen PH Kaksonen AH Franzmann PD Puhakka JA 《Journal of industrial microbiology & biotechnology》2006,33(12):984-994
A thermoacidophilic elemental sulfur and chalcopyrite oxidizing enrichment culture VS2 was obtained from hot spring run-off sediments of an underground mine. It contained only archaeal species, namely a Sulfolobus metallicus-related organism (96% similarity in partial 16S rRNA gene) and Thermoplasma acidophilum (98% similarity in partial 16S rRNA gene). The VS2 culture grew in a temperature range of 35–76°C. Sulfur oxidation by VS2 was optimal at 70°C, with the highest oxidation rate being 99 mg S0 l−1 day−1. At 50°C, the highest sulfur oxidation rate was 89 mg l−1 day−1 (in the presence of 5 g Cl− l−1). Sulfur oxidation was not significantly affected by 0.02–0.1 g l−1 yeast extract or saline water (total salinity of 0.6 M) that simulated mine water at field application sites with availability of only saline water. Chloride ions at a concentration above 10 g l−1 inhibited sulfur oxidation. Both granular and powdered forms of sulfur were bioavailable, but the oxidation rate of granular sulfur was less than 50% of the powdered form. Chalcopyrite concentrate oxidation (1% w/v) by the VS2 resulted in a 90% Cu yield in 30 days. 相似文献
12.
Brandon K. Swan James M. Watts Kristen M. Reifel Stuart H. Hurlbert 《Hydrobiologia》2007,576(1):111-125
The Salton Sea currently suffers from several well-documented water quality problems associated with high nutrient loading.
However, the importance of phosphorus regeneration from sediments has not been established. Sediment phosphorus regeneration
rates may be affected by benthic macroinvertebrate activity (e.g. bioturbation and excretion). The polychaete Neanthes
succinea (Frey and Leuckart) is the dominant benthic macroinvertebrate in the Salton Sea. It is widely distributed during periods
of mixing (winter and spring), and inhabits only shallow water areas following development of anoxia in summer. The contribution
of N. succinea to sediment phosphorus regeneration was investigated using laboratory incubations of cores under lake temperatures and dissolved
oxygen concentrations typical of the Salton Sea. Regeneration rates of soluble reactive phosphorus (SRP) were lowest (−0.23–1.03
mg P m−2 day−1) under saturated oxygen conditions, and highest (1.23–4.67 mg P m−2 day−1) under reduced oxygen levels. N. succinea most likely stimulated phosphorus regeneration under reduced oxygen levels via increased burrow ventilation rates. Phosphorus
excretion rates by N. succinea were 60–70% more rapid under reduced oxygen levels than under saturated or hypoxic conditions. SRP accounted for 71–80% of
the dissolved phosphorus excreted under all conditions. Whole-lake SRP regeneration rates predicted from N. succinea biomass densities are highest in early spring, when the lake is mixing frequently and mid-lake phytoplankton populations
are maximal. Thus, any additional phosphorus regenerated from the sediments at that time has potential for contributing to
the overall production of the lake.
Guest Editor: John M. Melack
Saline Water and their Biota 相似文献
13.
Delorme M Thomas DW 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1999,169(2):123-132
Nitrogen (N) and energy (E) requirements of the phyllostomid fruit bat, Artibeus jamaicensis, and the pteropodid fruit bat Rousettus aegyptiacus, were measured in adults that were fed on four experimental diets. Mean daily food intake by A. jamaicensis and R. aegyptiacus ranged from 1.1–1.6 times body mass and 0.8–1.0 times body mass, respectively. Dry matter digestibility and metabolizable
E coefficient were high (81.1% and 82.4%, respectively) for A. jamaicensis and (77.5% and 78.0%, respectively) for R. aegyptiacus. Across the four diets, bats maintained constant body mass with mean metabolizable E intakes ranging from 1357.3 kJ · kg−0.75 · day−1 to 1767.3 kJ · kg−0.75 · day−1 for A. jamaicensis and 1282.6–1545.2 kJ · kg−0.75 · day−1 for R. aegyptiacus. Maintenance E costs were high, in the order of 3.6–5.4 times the basal metabolic rate (BMR). It is unlikely that the E intakes
that we observed represent a true measure of maintenance E requirements. All evidence seems to indicate that fruit bats are
E maximizers, ingesting more E than required and regulating storage by adjusting metabolic output. We suggest that true maintenance
E requirements are substantially lower than what we observed. If it follows the eutherian norm of two times the BMR, fruit
bats must necessarily over-ingest E on low-N fruit diet. Dietary E content did affect N metabolism of A. jamaicensis. On respective low- and high-E diets, metabolic fecal N were 0.492 mg N · g−1 and 0.756 mg N · g−1 dry matter intake and endogenous urinary N losses were 163.31 mg N · kg−0.75 · day−1 and 71.54 mg N · kg−0.75 · day−1. A. jamaicensis required 332.3 mg · kg−0.75 · day−1 and 885.3 mg · kg−0.75 · day−1 of total N on high- and low-E diets, respectively, and 213.7 mg · kg−0.75 · day−1 of truly digestible N to achieve N balance. True N digestibilities were low (29% and 49%) for low- and high-E diets, respectively.
For R. aegyptiacus, metabolic fecal N and endogenous urinary N losses were 1.27 mg N · g−1 dry matter intake and 96.0 mg N · kg−0.75 · day−1, respectively, and bats required 529.8 mg · kg−0.75 · day−1 (total N) or 284.0 mg · kg−0.75 · day−1 (truly digestible N). True N digestibility was relatively low (50%). Based on direct comparison, we found no evidence that
R. aegyptiacus exhibits a greater degree of specialization in digestive function and N retention than A. jamaicensis. When combined with results from previous studies, our results indicate that all fruit bats appear to be specialized in their
ability to retain N when faced with low N diet.
Accepted: 24 November 1998 相似文献
14.
Jana Woelfel Rhena Schumann Florian Peine Anita Flohr Aleksandra Kruss Jaroslaw Tegowski Philippe Blondel Christian Wiencke Ulf Karsten 《Polar Biology》2010,33(9):1239-1253
During summer 2007, Arctic microphytobenthic potential primary production was measured at several stations around the coastline
of Kongsfjorden (Svalbard, Norway) at ≤5 m water depth and at two stations at five different water depths (5, 10, 15, 20,
30 m). Oxygen planar optode sensor spots were used ex situ to determine oxygen exchange in the overlying water of intact sediment
cores under controlled light (ca. 100 μmol photons m−2 s−1) and temperature (2–4°C) conditions. Patches of microalgae (mainly diatoms) covering sandy sediments at water depths down
to 30 m showed high biomass of up to 317 mg chl a m−2. In spite of increasing water depth, no significant trend in “photoautotrophic active biomass” (chl a, ratio living/dead cells, cell sizes) and, thus, in primary production was measured at both stations. All sites from ≤5 to
30 m water depth exhibited variable rates of net production from −19 to +40 mg O2 m−2 h−1 (−168 to +360 mg C m−2 day−1) and gross production of about 2–62 mg O2 m−2 h−1 (17–554 mg C m−2 day−1), which is comparable to other polar as well as temperate regions. No relation between photoautotrophic biomass and gross/net
production values was found. Microphytobenthos demonstrated significant rates of primary production that is comparable to
pelagic production of Kongsfjorden and, hence, emphasised the importance as C source for the zoobenthos. 相似文献
15.
Thorén AK 《Microbial ecology》2007,53(2):221-232
Transformation of urea to ammonium is an important link in the nitrogen cycle in soil and water. Although microbial nitrogen
transformations, such as nitrification and denitrification, are well studied in freshwater sediment and epiphytic biofilm
in shallow waters, information about urea transformation in these environments is scarce. In this study, urea transformation
of sedimentary, planktonic, and epiphytic microbial communities was quantified and urea transformation of epiphytic biofilms
associated with three different common wetland macrophyte species is compared. The microbial communities were collected from
a constructed wetland in October 2002 and urea transformation was quantified in the laboratory at in situ temperature (12°C) with the use of the 14C-urea tracer method, which measures the release of 14CO2 as a direct result of urease activity. It was found that the urea transformation was 100 times higher in sediment (12–22 mmol
urea-N m−2 day−1) compared with the epiphytic activity on the surfaces of the submerged plant Elodea canadensis (0.1–0.2 mmol urea-N m−2 day−1). The epiphytic activity of leaves of Typha latifolia was lower (0.001–0.03 mmol urea-N m−2 day−1), while urea transformation was negligible in the water column and on the submerged leaves of the emergent plant Phragmites australis. However, because this wetland was dominated by dense beds of the submerged macrophyte E. canadensis, this plant provided a large surface area for epiphytic microbial activity—in the range of 23–33 m2 of plant surfaces per square meter of wetland. Thus, in the wetland system scale at the existing plant distribution and density,
the submerged plant community had the potential to transform 2–7 mmol urea-N m−2 day−1 and was in the same magnitude as the urea transformation in the sediment. 相似文献
16.
Cappenberg Thom E. Hordijk Kees A. Jonkheer Gert J. Lauwen Jos P. M. 《Hydrobiologia》1982,91(1):161-168
The turnover and exchange rates, as well as the diffusion processes, concerning the input and output of carbon compounds at
the mud-water interface, were studied. The carbon input rates were derived from the annual sedimentation rates of particulate
organic matter (about 1 100 kg C · yr−1). The nature of the sedimented POC, and its breakdown pathways and turnover rates towards important metabolic intermediates
in methanogenesis, were examined. The breakdown kinetics ofChlorella cell walls, a dominant green alga in Lake Vechten, was studied using U-14C-labelled cell walls. The breakdown of the cell walls appears to the rate-limiting step in anaerobic mineralization.
Using first order kinetic equations, and HPLC and GLC and radio-chemical methods, turnover rate constants (k-values) of between
0.18 and 0.32 day−1 and pool sizes of algal cell walls of 37 to 80 μg · g−1 wet mud were found, giving turnover rates of 7.7 to 25.6 μg · g−1 · day−1 of cell wall material. The turnover rates (k-values between 0.07 and 0.31 h−1) of acetate, the most important breakdown product, and its concentration gradients (between 5 and 30 μmol) and diffusion
coefficient (Ds = 2.2 × 10−6 cm2 · s−1) just in and above mud-water interface, was quantified. The diffusion of acetate, within the sediments, could not account
for the turnover rates observed.
Finally, from acetate flux data and from those on the rates of formation of carbon dioxide and methane, the output of carbon
and its cycling in Lake Vechten are discussed. 相似文献
17.
G. Selvakumar S. Kundu Piyush Joshi Sehar Nazim A. D. Gupta H. S. Gupta 《Indian journal of microbiology》2010,50(1):50-56
Exiguobacterium acetylicum strain 1P (MTCC 8707) is a gram-positive, rod-shaped, yellow pigmented bacterium isolated from soil on nutrient agar plates
at 4°C. The identity of the bacterium was arrived on the basis of the biochemical characterization, BIOLOG sugar utilization
pattern and sequencing of the 16S rRNA gene. It grew at temperatures ranging from 4 to 42°C, with temperature optima at 30°C.
It expressed multiple plant growth promotion attributes such as phosphate solubilization, indole acetic acid (IAA), siderophore
and hydrogen cyanide (HCN) production, differentially at suboptimal growth temperatures (15 and 4°C). At 15°C it solubilized
phosphate (21.1 μg of P ml−1 day−1), and produced IAA (14.9 μg ml−1 day−1) in tryptophan amended media. Qualitative detection of siderophore production and HCN were possible at 15°C. At 4°C it retained
all the plant growth promotion attributes. Seed bacterization with the isolate, positively influenced the growth and nutrient
uptake parameters of wheat seedlings in glass house studies at suboptimal cold growing temperatures. 相似文献
18.
Denitrification Potential in Lake Sediment Increases Across a Gradient of Catchment Agriculture 总被引:1,自引:0,他引:1
Intensification of catchment agriculture has increased nutrient loads and accelerated eutrophication in some lakes, often
resulting in episodic harmful algal blooms or prolonged periods of anoxia. The influence of catchment agriculture on lake
sediment denitrification capacity as a nitrogen (N) removal mechanism in lakes is largely unknown, particularly in contrast
to research on denitrification in agricultural streams and rivers. We measured denitrification enzyme activity (DEA) to assess
sediment denitrification potential in seven monomictic and three polymictic lakes that range in the proportion of agriculture
in the catchment from 3 to 96% to determine if there is a link between agricultural land use in the lake catchment and sediment
denitrification potential. We collected sediment cores for DEA measurements over 3 weeks in austral spring 2008 (October–November).
Lake Okaro, with 96% catchment agriculture, had approximately 15 times higher DEA than Lake Tikitapu, with 3% catchment agriculture
(232.2 ± 55.9 vs. 15.9 ± 4.5 μg N gAFDM−1 h−1, respectively). Additionally, sediment denitrification potential increased with the proportion of catchment in agriculture
(R
2 = 0.85, P < 0.001). Our data suggest that lakes retain a high capacity to remove excess N via denitrification under increasing N loads
from higher proportions of catchment agriculture. However, evidence from the literature suggests that despite a high capacity
for denitrification and longer water residence times, lakes with high N loads will still remove a smaller proportion of their
N load. Lakes have a denitrification potential that reflects the condition of the lake catchment, but more measurements of
in situ denitrification rates across lake catchments is necessary to determine if this capacity translates to high N removal
rates. 相似文献
19.
V. B. Dambaev G. G. Gonchikov S. P. Buryukhaev B. S. Tsyrenov A. M. Zyakun B. B. Namsaraev 《Microbiology》2011,80(6):857-866
The rates of microbial processes in the sor solonchaks and the silts of the Western Transbaikalean saline lakes were investigated.
The rate of deep CO2 fixation in the silt of Lake Beloe was as high as 0.19 mg C dm−3 day−1. The content of cellulose and protein in the sor solonchaks (for air-dry material) were up to 5.0 and 0.42 mg g−1, respectively. The rates of cellulose decomposition and proteolysis in the silt were 1.08 and 0.96 % day−1, respectively. Sulfate reduction (up to 1.82 mg S dm−3 day−1) prevails at the terminal stages of anaerobic decomposition of organic matter in the silt. During the flooding period, methanogenesis
producing isotopically light CH4 probably prevails in the sor solonchaks and arid soils of the region. This suggestion is supported by the surface foaming
of the local arid soils after abundant monsoon rains, an increase in the δ13C value for soil carbonates to -5.94‰ along the solonchak profile, and a decrease in the ·13C value for the soil carbonates formed by methane-oxidizing bacteria to −11.41‰. The seasonal peaks of isotopically heavier
(to −16.60‰) organic matter in the bottom sediments of the lake may be explained as the result of activity of heterotrophic
sulfate reducers, which exhibited the highest growth rates at the peak sulfate concentrations in the silt. 相似文献
20.
Sediment in the littoral zone of lakes is frequently disturbed by wave action or bioturbation, resulting in sediment resuspension.
In undisturbed sediment, methanotrophic bacteria efficiently reduce the diffusive flux of methane into the water column. In
a microcosm study, the resuspension of littoral sediment was simulated in sediment cores for a winter (n = 3) and a summer situation (n = 3). The erosion of surface sediment resulted in a large flux of methane into the overlying water (207 ± 176 μmol h−1 m−2 in winter and 73 ± 18 μmol h−1 m−2 in summer). Only a minor part (16 ± 7%) of the methane released was oxidized by methanotrophic bacteria, whereas the major
part escaped into the water column. Only 6–16% of the littoral zone has to be resuspended to reach the same flux as from undisturbed
littoral sediment. For the daily flux, a sediment resuspension has to last 1–4 h to reach the undisturbed daily flux. The
study reveals the important role of sediment resuspension in the littoral methane cycle as an intense but variable source
of methane of largely unknown magnitude. 相似文献