共查询到20条相似文献,搜索用时 46 毫秒
1.
To identify the controls on dissolved organic carbon (DOC) production, we incubated soils from 18 sites, a mixture of 52 forest
floor and peats and 41 upper mineral soil samples, at three temperatures (3, 10, and 22°C) for over a year and measured DOC
concentration in the leachate and carbon dioxide (CO2) production from the samples. Concentrations of DOC in the leachate were in the range encountered in field soils (<2 to >50 mg l−1). There was a decline in DOC production during the incubation, with initial rates averaging 0.03–0.06 mg DOC g−1 soil C day−1, falling to averages of 0.01 mg g−1 soil C day−1; the rate of decline was not strongly related to temperature. Cumulative DOC production rates over the 395 days ranged from
less than 0.01 to 0.12 mg g−1 soil C day−1 (0.5–47.6 mg g−1 soil C), with an average of 0.021 mg g−1 soil C day−1 (8.2 mg g−1 soil C). DOC production rate was weakly related to temperature, equivalent to Q10 values of 0.9 to 1.2 for mineral samples and 1.2 to 1.9 for organic samples. Rates of DOC production in the organic samples
were correlated with cellulose (positively) and lignin (negatively) proportion in the organic matter, whereas in the mineral
samples C and nitrogen (N) provided positive correlations. The partitioning of C released into CO2–C and DOC showed a quotient (CO2–C:DOC) that varied widely among the samples, from 1 to 146. The regression coefficient of CO2–C:DOC production (log10 transformed) ranged from 0.3 to 0.7, all significantly less than 1. At high rates of DOC production, a smaller proportion
of CO2 is produced. The CO2–C:DOC quotient was dependent on incubation temperature: in the organic soil samples, the CO2–C:DOC quotient rose from an average of 6 at 3 to 16 at 22°C and in the mineral samples the rise was from 7 to 27. The CO2–C:DOC quotient was related to soil pH in the organic samples and C and N forms in the mineral samples. 相似文献
2.
Masahiko Hirata Nobumi Hasegawa Maki Nomura Haruko Ito Kangoro Nogami Tatsunobu Sonoda 《Ecological Research》2009,24(1):119-125
This study monitored deposition and decomposition of cattle dung in a grazed young Chamaecyparis obtusa (an evergreen conifer) plantation in southwestern Japan, as a part of exploring the impacts of livestock in the forest grazing
system. Animals defecated 10–19 times hd−1 day−1, producing feces of 2.2–3.5 kg DM and 33–73 g N per animal per day. The DM and N concentrations of feces ranged from 157–207 g DM kg−1 and 14.8−23.1 g (kg DM)−1, respectively. Occurrence of defecation was spatially heterogeneous, with feces being concentrated mainly on areas for resting
(forest roads, ridges and valleys) and moving (forest roads and along fence lines). Decomposition of dung pats was considerably
slow, showing the rates of 1.37–3.05 mg DM (g DM)−1 day−1 as DM loss. Decomposition was further slower on the basis of N release, 0.51–1.63 mg N (g N)−1 day−1, resulting in steadily increased N concentrations of dung pats with time after deposition. The results show that introduction
of livestock into a forest (i.e., forest grazing) may limit nutrient availability to plants, by redistributing nutrients into
areas with no vegetation (bare land and streams) and by establishing a large N pool as feces due to an imbalance between deposition
and slow release, though further studies are necessary for investigating the occurrence of slow dung decomposition in other
forest situations. 相似文献
3.
The Ferrous Wheel Hypothesis (Davidson et al. 2003) postulates the abiotic formation of dissolved organic N (DON) in forest floors, by the fast reaction of NO2
− with dissolved organic C (DOC). We investigated the abiotic reaction of NO2
− with dissolved organic matter extracted from six different forest floors under oxic conditions. Solutions differed in DOC
concentrations (15–60 mg L−1), NO2
− concentrations (0, 2, 20 mg NO2
−-N L−1) and DOC/DON ratio (13.4–25.4). Concentrations of added NO2
− never decreased within 60 min, therefore, no DON formation from added NO2
− took place in any of the samples. Our results suggest that the reaction of NO2
− with natural DOC in forest floors is rather unlikely. 相似文献
4.
Permissible Value for Vanadium in Allitic Udic Ferrisols Based on Physiological Responses of Green Chinese Cabbage and Soil Microbes 总被引:2,自引:0,他引:2
Greenhouse experiments were conducted to study the permissible value of vanadium (V) based on the growth and physiological
responses of green Chinese cabbage (Brassica chinensis L.), and effects of V on microbial biomass carbon (MBC) and enzyme activities in allitic udic ferrisols were also studied.
The results showed that biomass of cabbage grown on soil treated with 133 mg V kg−1 significantly decreased by 25.1% compared with the control (P < 0.05). Vanadium concentrations in leaves and roots increased with increasing soil V concentration. Contents of vitamin
C (Vc) increased by 10.3%, while that of soluble sugar in leaves significantly decreased by 54.0% when soil V concentration
was 133 mg kg−1, respectively. The uptake of essential nutrient elements by cabbage was disturbed when soil V concentration exceeded 253 mg kg−1. Soil MBC was significantly stimulated by 15.5%, while dehydrogenase activity significantly decreased by 62.8% and urease
activity slightly changed at treatment of 133 mg V kg−1 as compared with the control, respectively. Therefore, the permissible value of V in allitic udic ferrisols is proposed as
130 mg kg−1. 相似文献
5.
Joshua Otieno Ogweno Wen Hai Hu Xing Shun Song Kai Shi Wei Hua Mao Yan Hong Zhou Jing Quan Yu 《Plant Growth Regulation》2010,60(3):175-182
Detached leaves of tomato (Lycopersicon esculentum Mill.) experienced photoinhibition associated with sharp reductions in net photosynthetic rate (Pn), quantum efficiency of
PSII (ΦPSII) and photochemical quenching (qP) even though they were exposed to mild light intensity (400 μmol m−2 s−1 PPFD) at 28°C. Photoinhibition and the reduction in Pn, ΦPSII and qP, however, were significantly alleviated by 1 mg l−1 ABA, 0.1 mg l−1
N-(2-chloro-4-pyridyl)-N′-phenylurea (CPPU) and 0.01 mg l−1 24-epibrassinolide (EBR). Higher concentrations, however, reduced the effects or even exacerbated the occurrence of photoinhibition.
Superoxide dismutase and ascorbate peroxidase activity in leaves increased with the increases in ABA concentration within
1–100 mg l−1, CPPU concentration within 0.1–10 mg l−1 and EBR concentration within 0.01–1.0 mg l−1. Catalase and guaiacol peroxidase activity also increased with the increase in EBR concentration but CPPU and ABA treatments
at higher concentrations caused a decrease. Malondialdehyde (MDA) content decreased with the increase in CPPU concentration.
ABA and EBR, however, decreased MDA concentration only at 1 and 0.01 mg l−1, respectively. In conclusion, detached leaves had increased sensitivity to PSII photoinhibition. Photoinhibition-induced
decrease in photosynthesis, however, was significantly alleviated by EBR, CPPU and ABA at a proper concentration. 相似文献
6.
Yoshioka T. Ueda S. Miyajima T. Wada E. Yoshida N. Sugimoto A. Vijarnsorn P. Boonprakub S. 《Limnology》2002,3(1):51-59
The distributions of organic matter in the tropical swamps in southern Thailand are reported. The concentrations of particulate
and dissolved organic carbon (POC and DOC) in the Bang Nara River, which drains swamp forests and nearby paddy fields, were
2.9 ± 2.0 and 6.2 ± 1.3 mg C l−1, respectively. Although the variation was large, DOC concentration in the Bang Nara River seemed to be higher than POC in
November 1992 (DOC/POC ratio, 2.8 ± 2.2). River waters from the upland areas were characterized by low POC and DOC concentrations
as compared with Bang Nara River water. The δ13C values of POC and river sediments were useful to distinguish between organic matter originating in upland and swamp areas.
It is suggested that the distributions of organic matter and its isotopic composition reflect the difference in drainage characteristics
between lowland swamp and upland areas. Isotopic analyses of plant leaves and soils revealed that the swamp forest ecosystems
were characterized by low δ13C and low δ15N values, which suggested low efficiency of water use by plants and large contributions of atmospheric deposition of nitrogen,
respectively. Although CO2 recycling in the forest might be an important factor determining the δ13C values of understory plants, the main process in carbon metabolism of tropical swamp forests would be CO2 exchange between the atmosphere and forest canopy.
Received: May 1, 2001 / Accepted: September 28, 2001 相似文献
7.
The cell cultures of Cayratia trifolia (Vitaceae) a tropical lianas, were maintained in Murashige and Skoog’s medium containing 0.25 mg l−1 naphthalene acetic acid, 0.2 mg l−1 kinetin and 250 mg l−1 casein hydrolysate. Cell suspension cultures of C. trifolia accumulate stilbenes (piceid, resveratrol, viniferin, ampelopsin) which on addition of 0.1–0.5 mg l−1 morphactin in the medium containing naphthalene acetic acid and kinetin declined. Morphactin or 2 isopentenyl adenine alone
at 0.1 mg l−1 concentration enhanced stilbenes which on combination markedly enhanced the yield to ~5 mg l−1 at 15th day. 相似文献
8.
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
9.
Masaru Akiyama Satoru Shimizu Toshiaki Sakai Seiichiro Ioka Yoji Ishijima Takeshi Naganuma 《Limnology》2011,12(1):1-9
Spatiotemporal variations in microbial gene abundances were investigated to identify potential zones of methanotroph and methanogen
biomass in a peat bog in Sarobetsu-genya wetland. The abundances of the bacterial and archaeal 16S rRNA genes, pmoA, and mcrA were 107–109, 107–108, 104–106, and 104–107 copies g−1 dry peat, respectively. Correlation analysis based on microbial gene abundances and environmental factors showed that the
spatiotemporal distributions of the abundances of the four microbial genes in peat layers were similar. The mcrA abundance showed a significant negative correlation with the dissolved organic carbon content and a significant positive
correlation with the peat temperature. The pmoA abundance was not detectable during the spring thaw when the lowest peat temperature at a depth of 50 cm was recorded. At
a depth of 200 cm, the peat temperature exceeded 6°C throughout the year, and the mcrA abundance exceeded 104 copies g−1 dry peat. These results indicate that the seasonal microbial activity related to methane should be evaluated in not only
the shallow but also the deep peat layers in order to elucidate the methane dynamics in boreal wetlands. 相似文献
10.
Understanding how the concentration and chemical quality of dissolved organic matter (DOM) varies in soils is critical because
DOM influences an array of biological, chemical, and physical processes. We used PARAFAC modeling of excitation–emission fluorescence
spectroscopy, specific UV absorbance (SUVA254) and biodegradable dissolved organic carbon (BDOC) incubations to investigate the chemical quality of DOM in soil water collected
from 25 cm piezometers in four different wetland and forest soils: bog, forested wetland, fen and upland forest. There were
significant differences in soil solution concentrations of dissolved organic C, N, and P, DOC:DON ratios, SUVA254 and BDOC among the four soil types. Throughout the sampling period, average DOC concentrations in the four soil types ranged
from 9–32 mg C l−1 and between 23–42% of the DOC was biodegradable. Seasonal patterns in dissolved nutrient concentrations and BDOC were observed
in the three wetland types suggesting strong biotic controls over DOM concentrations in wetland soils. PARAFAC modeling of
excitation–emission fluorescence spectroscopy showed that protein-like fluorescence was positively correlated (r
2 = 0.82; P < 0.001) with BDOC for all soil types taken together. This finding indicates that PARAFAC modeling may substantially improve
the ability to predict BDOC in natural environments. Coincident measurements of DOM concentrations, BDOC and PARAFAC modeling
confirmed that the four soil types contain DOM with distinct chemical properties and have unique fluorescent fingerprints.
DOM inputs to streams from the four soil types therefore have the potential to alter stream biogeochemical processes differently
by influencing temporal patterns in stream heterotrophic productivity. 相似文献
11.
Cell cultures of Cayratia trifolia (Vitaceae), a tropical lianas, were maintained in Murashige and Skoog’s medium containing 0.25 mg l−1 NAA, 0.2 mg l−1 kinetin and casein hydrolysate 250 mg l−1. Cell suspension cultures of C. trifolia accumulate stilbenes (piceid, resveratrol, viniferin, ampelopsin), which on elicitation by any of 500 μM salicylic acid,
100 μM methyl jasmonate, 500 μM ethrel and 500 mg l−1 yeast extract, added on the 7th day, were enhanced by 3- to 6-fold (5–11 mg l−1) by the 15th day. 相似文献
12.
Litter Decomposition and Nutrient Dynamics in a Phosphorus Enriched Everglades Marsh 总被引:3,自引:0,他引:3
A field study was conducted in a nutrient-impacted marsh in Water Conservation Area 2A (WCA-2A) of the Everglades in southern
Florida, USA, to evaluate early stages of plant litter (detritus) decomposition along a well-documented trophic gradient,
and to determine the relative importance of environmental factors and substrate composition in governing decomposition rate.
Vertically stratified decomposition chambers containing native plant litter (cattail and sawgrass leaves) were placed in the
soil and water column along a 10-km transect coinciding with a gradient of soil phosphorus (P) enrichment. Decomposition rate
varied significantly along the vertical water–soil profile, with rates typically higher in the water column and litter layer
than below the soil surface, presumably in response to vertical gradients of such environmental factors as O2 and nutrient availability. An overall decrease in decomposition rate occurred along the soil P gradient (from high- to low-impact).
First-order rate constant (k) values for decomposition ranged from 1.0 to 9.2 × 10−3 day−1 (mean = 2.8 ×10−3 day−1) for cattails, and from 6.7 × 10−4 to 3.0 × 10−3 day−1 (mean = 1.7 × 10−3 day−1) for sawgrass. Substantial N and P immobilization occurred within the litter layer, being most pronounced at nutrient-impacted
sites. Nutrient content of the decomposing plant tissue was more strongly correlated to decomposition rate than was the nutrient
content of the surrounding soil and water. Our experimental results suggest that, although decomposition rate was significantly
affected by initial substrate composition, the external supply or availability of nutrients probably played a greater role
in controlling decomposition rate. It was also evident that nutrient availability for litter decomposition was not accurately
reflected by ambient nutrient concentration, e.g., water and soil porewater nutrient concentration. 相似文献
13.
Alchichica is a warm-monomictic, oligotrophic lake whose phytoplanktonic biomass is dominated by large size (average ca. 55 μm) diatoms. The fast sinking phytoplankton leads to silica, and other nutrient exportation out of the productive zone
of the lake. The aim of the present study was to identify and measure the sedimentation fluxes of the diatom species and their
temporal dynamics to better understand the magnitude of silica and carbon fluxes. Sediment-traps were exposed at three different
depths and collected monthly. A total of 13 diatom species were observed in the traps. The maximum diatom flux was in February
(304 × 106 cells m−2 day−1) related to the winter diatom bloom. The diatom silica (DSi) fluxes varied from 2.2 to 2,997 mg m−2 day−1 and the diatom carbon (DC) fluxes from 1.2 to 2,918 mg m−2 d−1. Cyclotella alchichicana was the main contributor (>98%) to the total DSi and DC fluxes. The annual diatom (15 × 109 cells m−2 year−1), DSi (147 g m−2 year−1) and DC (92 g m−2 year−1) fluxes are higher than in other aquatic ecosystems of similar or even higher trophic conditions. Our findings in Alchichica
are indicative of the relevance of the phytoplankton type and size in understanding the role tropical and oligotrophic lakes
play regarding silica and carbon fluxes. In addition, our results support previous findings suggesting that inland aquatic
ecosystems are more important than formerly thought in processing carbon, and can, therefore, affect regional carbon balances. 相似文献
14.
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
15.
Ecosystem restoration by rewetting of degraded fens led to the new formation of large-scale shallow lakes in the catchment
of the River Peene in NE Germany. We analyzed the biomass and the nutrient stock of the submersed (Ceratophyllum demersum) and the floating macrophytes (Lemna minor and Spirodela polyrhiza) in order to assess their influence on temporal nutrient storage in water bodies compared to other freshwater systems. Ceratophyllum demersum displayed a significantly higher biomass production (0.86–1.19 t DM = dry matter ha−1) than the Lemnaceae (0.64–0.71 t DM ha−1). The nutrient stock of submersed macrophytes ranged between 28–44 kg N ha−1 and 8–12 kg P ha−1 and that of floating macrophytes between 14–19 kg N ha−1 and 4–5 kg P ha−1 which is in the range of waste water treatment plants. We found the N and P stock in the biomass of aquatic macrophytes being
20–900 times and up to eight times higher compared to the nutrient amount of the open water body in the shallow lakes of rewetted
fens (average depth: 0.5 m). Thereafter, submersed and floating macrophytes accumulate substantial amounts of dissolved nutrients
released from highly decomposed surface peat layers, moderating the nutrient load of the shallow lakes during the growing
season from April to October. In addition, the risk of nutrient loss to adjacent surface waters becomes reduced during this
period. The removal of submersed macrophytes in rewetted fens to accelerate the restoration of the low nutrient status is
discussed. 相似文献
16.
Le Dinh Hung Kanji Hori Huynh Quang Nang Tran Kha Le Thi Hoa 《Journal of applied phycology》2009,21(3):265-272
The three color morphotypes of the red alga Kappaphycus alvarezii (brown, red and green) were cultured in Camranh Bay, Vietnam, using the fixed off-bottom monoline culture method to evaluate
the growth rate, carrageenan yield, 3,6-anhydrogalactose, gel strength and lectin content. The brown morphotype was cultivated
over a 12-month period; the red and green morphotypes were over a 6-month period. At the 60-day culture timepoint, the brown
morphotype showed a higher growth rate (3.5–4.6% day−1) from September to February, and lower growth rate (1.6–2.8% day−1) from March to August. Significant (P < 0.05) differences in growth rate between culture months were found with the brown morphotype. High growth rates for the
red (3.6–4.4% day−1) and green (3.7–4.2% day−1) morphotypes were obtained from September to February. The carrageenan yield, 3,6-anhydrogalactose and gel strength of the
three morphotypes showed little variation, with the highest values obtained in November–December. At the 30-day sampling point,
the brown morphotype had a higher lectin content (167–302 μg g−1 dry alga) from August to March and a lower lectin content (23–104 μg g−1 dry alga) from April to July. High lectin contents were recorded for the red (139–338 μg g−1 dry alga) and green (124–259 μg g−1 dry alga) morphotypes from September to February. This study shows that the different morphotypes of K. alvarezii can be grown in the tropical waters of the Camranh during the northeast monsoon, and part of the southwest monsoon, especially
the brown morphotype, which can be grown during any season. 相似文献
17.
Tsuyoshi Kobayashi Darren S. Ryder Geoff Gordon Ian Shannon Timothy Ingleton Max Carpenter Stephen J. Jacobs 《Aquatic Ecology》2009,43(4):843-858
Environmental flows were released to the Macquarie Marshes (~210,000 ha) in north-west NSW of Australia between October and
December 2005, inundating an estimated 24,600 ha of floodplain area. According to the flood pulse concept, the marsh floodplains
would have stored large amounts of nutrients and carbon during dry antecedent conditions, which would be released into the
overlaying flood water. Field studies were conducted in mid-December 2005 at two sites, one on open floodplain woodland with
a sparse canopy of River Red Gum and ground cover dominated by saltbushes and the other on open floodplain with black roly-poly.
At each site, nutrients, dissolved organic carbon (DOC), planktonic bacteria and phytoplankton were monitored daily for a
6-day period from the overlaying water of a floodplain inundated by the environmental water release. Those in mesocosms deployed
in situ, containing marsh floodplain sediments that had been inundated artificially, were also monitored. The mesocosm results
from both the sites showed that release of nitrogen was rapid, attaining mean concentrations of total nitrogen of 3.7–14.8 mg l−1, followed by more gradual increases in total phosphorus (mean concentrations 0.6–0.8 mg l−1) and DOC (26.1–50.2 mg l−1) within the 6-day experiment; planktonic microbial communities developed concomitantly with the increasing concentrations
of nutrients and DOC, attaining mean densities of (6.0–6.9) × 106 cells ml−1 of planktonic bacteria and (80.7–81.4) × 103 cells ml−1 of phytoplankton; and for each site the overall measured condition of the mesocosm tended to approach that of the Marshes,
over the course of the 6-day experiment. The present study (both observational and experimental) demonstrates that the floodplain
sediments in the Marshes, which have been exposed to dry antecedent conditions, release nutrients and carbon to the overlaying
flood water following inundation. These resources are thought to have been stored during the dry antecedent phase in accord
with the flood pulse concept. Based on the mesocosm experiment, the released nutrients and carbon are in turn most likely
to be used by microbial components, such as bacteria and algae, which develop within days of inundation of the floodplain
sediments. Thus, environmental flow release provides potential for floodplains to attain a series of ecological responses
including initial release of inorganic nutrients and dissolved organic matter and increase in planktonic bacteria and phytoplankton. 相似文献
18.
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
19.
The effects of nutrient enrichment on the release of dissolved organic carbon and nitrogen (DOC and DON, respectively) from
the coral Montipora digitata were investigated in the laboratory. Nitrate (NO3
−) and phosphate (PO4
3−) were supplied to the aquarium to get the final concentrations of 10 and 0.5 μmol l−1, respectively, and the corals were incubated for 8 days. The release rate of DON per unit coral surface area significantly
decreased after the nutrient enrichment, while the release rate of DOC was constant. Because the chlorophyll a (chl a) content of zooxanthellae per unit surface area increased, the release rate of DOC significantly decreased when normalized
to unit chl a. These results suggested that the incorporation of NO3
− and PO4
3− stimulated the synthesis of new cellular components in the coral colonies and consequently, reduced extracellular release
of DOC and DON. Actually, significant increase in N and P contents relative to C content was observed in the coral’s tissue
after the nutrient enrichment. The present study has concluded that inorganic nutrient enrichment not only affects coral-algal
metabolism inside the colony but also affects a microbial community around the coral because the organic matter released from
corals functions as energy carrier in the coral reef ecosystem. 相似文献
20.
María Fernanda Adame Ruth Reef Jorge A. Herrera-Silveira Catherine E. Lovelock 《Hydrobiologia》2012,691(1):239-253
Poor water quality affects the biogeochemistry functions and the biological community structure of coastal ecosystems. In this study we investigated the effect of water quality on: (a) The exchange of dissolved organic carbon (DOC) between floodwater and mangrove forests, (b) the abundance of sediment bacteria, (c) the microbial community composition, and (d) the microbial catabolic activity. We selected six mangrove forests that were flooded by creeks with differing water qualities to test for thresholds of nutrient concentrations associated with changes in DOC dynamics and the microbial community. Our results show that in sites flooded by water high in soluble reactive phosphorus (SRP) (>20 μg l−1) and NH4 + (>30 μg l−1) the DOC concentrations in the floodwater were higher than in ebb water, suggesting DOC import by the mangroves. In contrast, in sites flooded by water low in SRP (<20 μg l−1) and NH4 + (<30 μg l−1), DOC concentrations in the floodwater were lower than in the ebb water, suggesting DOC export by the mangroves. Bacterial abundance was higher in sediments with low bulk density, high organic carbon and when flooded by water with low N:P (1–2), but the microbial composition and total catabolic activity assessed using Biolog Ecoplates™ did not differ among sites. The relationship between water quality, microbial communities and DOC exchange suggests that, at least during some periods of the year, poor water quality increases bacterial abundance and modifies DOC exchange of mangrove forests with floodwater and thus, their role in supporting near-shore productivity. 相似文献