共查询到20条相似文献,搜索用时 421 毫秒
1.
Deborah V. Robertson-Andersson Michelle Potgieter Joakim Hansen John J. Bolton Max Troell Robert J. Anderson Christina Halling Trevor Probyn 《Journal of applied phycology》2008,20(5):579-595
Land-based abalone aquaculture in South Africa, based on the local species Haliotis midae, started in the early 1990s and has grown rapidly in the last decade, with 13 commercial farms now producing over 850 t per
annum. Over 6,000 t per annum of kelp Ecklonia maxima are now harvested for this purpose, and some kelp beds are reaching maximum sustainable limits. Research into seaweed aquaculture
as feed (Ulva and some Gracilaria) for abalone started in the late 1990s on the southeast coast (where there are no kelp beds) using abalone waste water. A
growing body of evidence suggests that a mixed diet of kelp plus other seaweeds can give growth rates at least as good as
compound feed, and can improve abalone quality and reduce parasite loads. A pilot scale Ulva lactuca and abalone integrated recirculation unit using 25% recirculation was designed and built on the south west coast of South
Africa using one 12,000-L abalone tank containing 13,200 15 ± 2.5 g abalone, connected to two 3,000-L seaweed tanks containing
an initial starting biomass of 10 kg of seaweed, replicated 3 times. In an 18-month period, there were no significant differences
in abalone health or growth rates, sediment build up and composition, mobile macro fauna densities and species between the
recirculation or the flow-through units. Transfer of oxygen generated by the seaweeds to the abalone tanks was poor, resulting
in the recirculated abalone tanks having lower (33%) dissolved oxygen concentrations than a comparable flow-through abalone
unit. Seaweed nutrient content and specific growth rates in the units were comparable to seaweeds cultivated in fertilized
effluent (SGR = 3.2 ± 3.4%.day−1; Yield = 0.2 ± 0.19 kg.m2.day−1). Indications were that at this low recirculation ratio the seaweeds in the units were nutrient limited and that there were
no negative effects to the abalone being cultivated in such a recirculation unit at this recirculation ratio. 相似文献
2.
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
3.
Chris J. Hulatt Aino-Maija Lakaniemi Jaakko A. Puhakka David N. Thomas 《Bioenergy Research》2012,5(3):669-684
Mass culture of microalgae is a potential alternative to cultivation of terrestrial crops for bioenergy production. However, microalgae require nitrogen fertiliser in quantities much higher than plants, and this has important consequences for the energy balance of these systems. The effect of nitrogen fertiliser supplied to microalgal bubble-column photobioreactor cultures was investigated using different nitrogen sources (nitrate, urea, ammonium) and culture conditions (air, 12% CO2). In 20 L cultivations, maximum biomass productivity for Chlorella vulgaris cultivated using nitrate and urea was 0.046 and 0.053 g L−1 day−1, respectively. Maximum biomass productivity for Dunaliella tertiolecta cultivated using nitrate, urea and ammonium was 0.033, 0.038 and 0.038 g L−1 day−1, respectively. In intensive bubble-column photobioreactors using 12% CO2, maximum productivity reached 0.60 and 0.83 g L−1 day−1 for C. vulgaris and D. tertiolecta, respectively. Recycling of nitrogen within the photobioreactor system via algal exudation of nitrogenous compounds and bacterial activity was identified as a potentially important process. The energetic penalty incurred by supply of artificial nitrogen fertilisers, phosphorus, power and CO2 to microalgal photobioreactors was investigated, although analysis of all energy burdens from biomass production to usable energy carriers was not conducted. After subtraction of the power, nitrogen and phosphorus energy burdens, maximum net energy ratios for C. vulgaris and D. tertiolecta cultivated in bubble columns were 1.82 and 2.10. Assuming CO2 was also required from a manufactured source, the net energy ratio decreased to 0.09 and 0.11 for C. vulgaris and D. tertiolecta, so that biomass production in this scenario was unsustainable. Although supply of nitrogen is unlikely to be the most energetically costly factor in sparged photobioreactor designs, it is still a very significant penalty. There is a need to optimise both cultivation strategies and recycling of nitrogen in order to improve performance. Data are supported by measurements including biochemical properties (lipid, protein, heating value) and bacterial number by epifluorescence microscopy. 相似文献
4.
Sunil S. Adav Duu-Jong Lee Juin-Yih Lai 《Applied microbiology and biotechnology》2010,85(5):1601-1610
Aerobic sludge granules are compact, strong microbial aggregates that have excellent settling ability and capability to efficiently
treat high-strength and toxic wastewaters. Aerobic granules disintegrate under high organic loading rates (OLR). This study
cultivated aerobic granules using acetate as the sole carbon and energy source in three identical sequencing batch reactors
operated under OLR of 9–21.3 kg chemical oxygen demand (COD) m−3 day−1. The cultivated granules removed 94–96% of fed COD at OLR up to 9–19.5 kg COD m−3 day−1, and disintegrated at OLR of 21.3 kg COD m−3 day−1. Most tested isolates did not grow in the medium at >3,000 mg COD l−1; additionally, these strains lost capability for auto-aggregation and protein or polysaccharide productivity. This critical
COD regime correlates strongly with the OLR range in which granules started disintegrating. Reduced protein quantity secreted
by isolates was associated with the noted poor granule integrity under high OLR. This work identified a potential cause of
biological nature for aerobic granules breakdown. 相似文献
5.
Sorghum (Sorghum bicolor L. Moench) plants were grown in solution culture and stressed at three rates of decreasing leaf water potential (−0.123,
−0.068 and −0.029 MPa day−1) achieved by the incremental addition of an osmoticum, polyethylene glycol (PEG) 6000 to the solutions. Plants were also
grown in soil and given different amounts of water which resulted in rates of decreasing leaf water potentials of −0.130 and
−0.073 MPa day−1.
The rate of stress and the culture system influenced the accumulation of solutes in the cell, but not cell volume. A rapid
stress (−0.123 and −0.130 MPa day−1) to approximately −1.6 MPa leaf water potential resulted in 0.75 and 0.16 MPa of osmotic adjustment in the PEG and soil culture
respectively. At moderate stress (−0.068 and −0.073 MPa day−1) respective values were 1.68 and 0.58 MPa. There were some visual symptoms in the solution grown plants characteristic of
uptake of high molecular weight PEG. However the relative growth rates of these plants were equal to or greater than those
of the soil grown plants.
In view of the differences in plant water status of soil and PEG solution cultured plants it was concluded that the use of
the latter system would not be entirely suitable for some studies of drought resistance in sorghum, as related to crop performance
in the field. 相似文献
6.
K. P. Krishnan Rupesh Kumar Sinha Kiran Krishna Shanta Nair S. M. Singh 《Polar Biology》2009,32(12):1765-1778
The significance of freshwater systems in global manganese cycles is well appreciated. Yet, the polar systems, which encompass
the largest freshwater repository in the world, have been least studied for their role in manganese cycling. Here, we present
results from a study that was conducted in the brackish water lakes in the Larsemann Hills region (east Antarctica). The rate
of in situ manganese oxidation ranged from 0.04 to 3.96 ppb day−1. These lakes harbor numerous manganese-oxidizing bacteria (105 to 106 CFU l−1), predominantly belonging to genera Shewanella, Pseudomonas and an unclassified genus in the family Oxalobacteriaceae. Experiments were conducted with representatives of predominant
genera to understand their contribution to Mn cycling and also to assess their metabolic capabilities in the presence of this
metal. In general, the total and respiring cell counts were stimulated to a maximum when the growth medium was amended with
10 mM manganese. The addition of manganese promoted the use of d-mannitol, maltose, etc., but inhibited the use of maltotriose, l-serine and glycyl l-glutamic acid. The bacterial isolates were able to catalyze both the redox reactions in manganese cycling. In vitro manganese
oxidation rates ranged from 3 to 147 ppb day−1, while manganese reduction rates ranged from 35 to 213 ppb day−1. It was also observed that the maximum stimulation of manganese oxidation occurred in the presence of cobalt (81 ± 57 ppb day−1), rather than iron (37 ± 16 ppb day−1) and nickel (40 ± 47 ppb day−1). Our studies suggest that cobalt could have a more profound role in manganese oxidation, while nickel promoted manganese
reduction in polar aquatic systems. 相似文献
7.
Chia-Hung Su Liang-Jung Chien James Gomes Yu-Sheng Lin Yuan-Kun Yu Jhang-Song Liou Rong-Jhih Syu 《Journal of applied phycology》2011,23(5):903-908
Reserve lipids of microalgae are promising for biodiesel production. However, optimization of cultivation conditions for both
biomass yield and lipid production of microalgae is a contradictory problem because required conditions for both targets are
different. In this study, a two-stage cultivation strategy is proposed to enhance lipid production of the microalga Nannochloropsis oculata. Biomass growth and lipid production were carried out in two separate and non-interacting stages. In first-stage cultivation,
microalgae were cultivated in optimal conditions for cell growth. Then, microalgae were harvested and transferred into a growth-limited
environment, thus enhancing lipid production of microalgae. Here, optimization of the lipid production stage (second stage)
with respect to different levels of inoculum concentration, salinity of culture broth, and intensity of irradiance was performed.
The results show that irradiance exhibits a significant influence on lipid production. The highest lipid productivity of 0.324 g L−1 day−1 was obtained with an inoculum concentration of 2.3 g L−1, a salinity of 35 g L−1, and an irradiance of 500 μmol photons m−2 s−1. The final yield of lipid obtained from the two-stage process was 2.82-times higher than that from traditional single-stage
batch cultivation systems. 相似文献
8.
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
9.
Gang-Guk Choi Byung-Hyuk Kim Chi-Yong Ahn Hee-Mock Oh 《Journal of applied phycology》2011,23(6):1031-1037
The influence of nitrogen (N) deficiency on the cell growth and intracellular lipid production of the alga Botryococcus braunii UTEX 572 was investigated. Biomass concentration and lipid content of B. braunii cultivated in modified Chu-13 medium containing 0.04, 0.37, and 3.66 mM nitrate were 0.23–0.38 g L−1 and 36–63% of dry cell weight, respectively. The specific growth rate of B. braunii reached a constant of 0.185 day−1 during cultivation with an initial nitrate feed of 3.66 mM. The maximum lipid content of B. braunii was 63% with 0.04 mM nitrate. However, the maximum lipid productivity of 0.019 g L−1 day−1 was achieved with 0.37 mM nitrate. The level of oleic acid, an important component of biodiesel, was higher at 86% of the
total fatty acids under N-limited conditions (0.04 mM nitrate) compared to 69% under N-sufficient conditions (3.66 mM nitrate).
Furthermore, expression of the stearoyl-ACP desaturase gene (sad) encoding a stearoyl-ACP desaturase involved in the synthesis of oleic acid was 2.6-fold higher under N-limited conditions
than under N-sufficient conditions. 相似文献
10.
Biological breakdown of denitrifying sulfide removal process in high-rate expanded granular bed reactor 总被引:1,自引:0,他引:1
This work conducted a denitrifying sulfide removal (DSR) test in an expanded granular sludge bed (EGSB) reactor at sustainable
loadings of 6.09 kg m−3 day−1 for sulfide, 3.11 kg m−3 day−1 for nitrate–nitrogen, and 3.27 kg m−1 day−1 for acetate–carbon with >93% efficiency, which is significantly higher than those reported in literature. Strains Pseudomonas sp., Nitrincola sp., and Azoarcus sp. very likely yield heterotrophs. Strains Thermothrix sp. and Sulfurovum sp. are the autotrophs required for the proposed high-rate EGSB-DSR system. The EGSB-DSR reactor experienced two biological
breakdowns, one at loadings of 4.87, 2.13, and 1.82 kg m−3 day−1; reactor function was restored by increasing nitrate and acetate loadings. Another breakdown occurred at loadings of up to
8.00, 4.08, and 4.50 kg m−1 day−1; the heterotrophic denitrification pathway declined faster than the autotrophic pathway. The mechanism of DSR breakdown is
as follows. High sulfide concentration inhibits heterotrophic denitrifiers, and the system therefore accumulates nitrite.
Autotrophic denitrifiers are then inhibited by the accumulated nitrite, thereby leading to breakdown of the DSR process. 相似文献
11.
We investigated seasonal changes in dry mass and CO2 exchange rate in fruit and leaves of the evergreen tree Cinnamomum camphora with the aim of quantitatively determining the translocation balance between the two organs. The fruit dry mass growth peaked
in both August and October: the first increase was due to fruit pulp development and the second to seed development. Fruit
respiration also increased with the rapid increase in fruit dry mass. Therefore, the carbohydrates required for fruit development
showed two peaks during the reproductive period. Fruit photosynthesis was relatively high in early August, when fruit potentially
re-fixed 75% of respired CO2, indicating that fruit photosynthesis contributed 15–35% of the carbon requirement for fruit respiration. Current-year leaves
completed their growth in June when fruit growth began. Current-year leaves translocated carbohydrates at a rate of approximately
10–25 mg dry weight (dw) leaf−1 day−1 into other organs throughout the entire fruit growth period. This rate of translocation from current-year leaves was much
higher than the amount of carbohydrate required for reproduction (ca. 3 mg dw fruit−1 day−1). Given the carbon balance between fruit and current-year leaves, carbohydrates for reproduction were produced within the
current-year fruit-bearing shoots. C. camphora would be adaptive for steadily supplying enough amount of carbohydrate to the fruits, as there was little competition for
carbohydrates between the two organs. As assimilates by leaves are used for processes such as reproduction and the formation
of new shoots, photosynthesis by reproductive organs is considered to be important to compensate for reproductive cost. 相似文献
12.
During January/February 2006, we satellite-tracked two different ecotypes of killer whales (Orcinus orca) in McMurdo Sound, Ross Sea, Antarctica, using surface-mounted tags attached with sub-dermal darts. A single Type B whale
(pinniped prey specialist), tracked for 27 days, traveled an average net distance of 56.8 ± 32.8 km day−1, a maximum of 114 km day−1, and covered an estimated area of 49,351 km2. It spent several days near two large emperor penguin (Aptenodytes forsteri) colonies, a potential prey item for this form. By contrast, four Type C killer whales (fish prey specialists) tracked for
7–65 days, traveled an average net distance of 20 ± 8.3 km day−1, a maximum of 56 net km day−1, and covered an estimated area of only 5,223 km2. These movement patterns are consistent with those of killer whale ecotypes in the eastern North Pacific where mammal-eating
‘transients’ travel widely and are less predictable in their movements, and fish-eating ‘residents’ have a more localized
distribution and more predictable occurrence, at least during the summer months. 相似文献
13.
The tetrasporophyte of Asparagopsis armata has been previously established as a novel seaweed biofilter for integrated land-based mariculture. The species growth and
biofiltration rates were much higher than the values described in the literature for Ulva spp., the most common seaweed biofilter. However, a validation of the advantage of one species over the other requires a
study of the performances of these two species in the same system at the same time. In this work, we compared the biofiltration
performance and biomass yield of A. armata and Ulva rigida cultivated in the effluents of a fish farm in southern Portugal. Comparisons were performed at different water renewal rates
and in two seasons of the year. The maximum total ammonia nitrogen (TAN) removal rates were similar for both species in December
(2.7 and 2.8 g TAN m–2 day–1 for U. rigida and A. armata, respectively) and higher for A. armata (6.5 g TAN m–2 day–1) than for U. rigida (5.1 g TAN m–2 day–1) in May. Higher differences were observed when estimating the nitrogen biofiltration through the organic nitrogen yield (N
yield) of the biomass produced, particularly in May. This estimate is directly related with the biomass yield and the N content
in the tissue which were always higher for A. armata than for U. rigida. In December, the maximum biomass yields were 71 g dry weight (DW) m–2 day–1 for A. armata and 44 g DW m–2 day–1 for U. rigida, while in May, the yield of A. armata was 125 g DW m–2 day–1 and of U. rigida was 73 g DW m–2 day–1. This study confirmed that A. armata is indeed a more efficient biofilter than U. rigida. To the best of our knowledge, the production rates reported here are the highest ever reported for macroalgae cultivated
in tanks. 相似文献
14.
Cory J. D. Matthews Sebasti��n P. Luque Stephen D. Petersen Russel D. Andrews Steven H. Ferguson 《Polar Biology》2011,34(7):1091-1096
Killer whales (Orcinus orca) occur in the eastern Canadian Arctic during the open-water season, but their seasonal movements in Arctic waters and overall
distribution are poorly understood. During August 2009, satellite transmitters were deployed onto two killer whales in Admiralty
Inlet, Baffin Island, Canada. A whale tracked for 90 days remained in Admiralty and Prince Regent Inlets from mid-August until
early October, when locations overlapped aggregations of marine mammal prey species. While in Admiralty and Prince Regent
Inlets, the whale traveled 96.1 ± 45.3 km day−1 (max 162.6 km day−1) and 120.1 ± 44.5 km day−1 (max 192.7 km day−1), respectively. Increasing ice cover in Prince Regent Inlet in late September and early October was avoided, and the whale
left the region prior to heavy ice formation. The whale traveled an average of 159.4 ± 44.8 km day−1 (max 252.0 km day−1) along the east coast of Baffin Island and into the open North Atlantic by mid-November, covering over 5,400 km in approximately
one month. This research marks the first time satellite telemetry has been used to study killer whale movements in the eastern
Canadian Arctic and documents long-distance movement rarely observed in this species. 相似文献
15.
Leila Hayashi Alex A. Santos Gabriel S. M. Faria Beatriz G. Nunes Marina S. Souza Alessandra L. D. Fonseca Pedro L. M. Barreto Eurico C. Oliveira Zenilda L. Bouzon 《Journal of applied phycology》2011,23(3):337-343
Four strains of Kappaphycus alvarezii were cultivated in the subtropical waters of Florianópolis, Santa Catarina State, Brazil (27°29′19′′ S/48°32′28′′ W), from
February 2009 to February 2010. Seaweeds were cultivated on floating raft near of mussel farms. Salinity ranged from 29 to
36 psu and temperature from 17.1 to 28.5°C. Higher growth rates (5.12–4.29% day−1) were measured in summer and autumn, showing a positive correlation between growth rate and water temperature. Lower growth
rates (0.54–0.32% day−1) occurred in winter, resulted mainly by biomass loss. Significant differences were observed among the strains in spring and
the brown tetrasporophytic strain was the only one which failed to recover, being excluded of the experiments. The effect
of cultivation periods (36, 42, and 97 days) on carrageenan yield, gel strength, and viscosity were analyzed. Carrageenan
yields were higher for plants kept 42 days in the sea (28%), against 25% for 36 and 97 days. There were no significant differences
in carrageenan yield among the strains analyzed. Viscosity increased with the increase of cultivation period, while gel strength
seemed to vary at random. Tetrasporangia and cystocarps were not observed, and lost fragments did not attach outside the raft.
In general, dissolved inorganic nitrogen concentration decreased around the cultivation area as compared to the mussel farm.
Results show that cultivation of K. alvarezii is technically feasible in subtropical waters and can be associated with local mussel farms, mitigating the eutrophication
and, eventually, increasing the economic return of the farmers. 相似文献
16.
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
17.
A generic population model is formulated for radiation risk assessment of natural biota. The model demonstrates that effects
of radiation on the population survival do not follow directly the effects on individual organisms. Dose rates resulting in
population extinction can be analytically calculated. Besides individual radiosensitivity, two key parameters were found to
determine the survival potential of a population under chronic radiation stress: the ratio “biomass losses/biomass synthesis,”
and the lump amount of limiting resource in the environment. A benchmark scenario “Population response to chronic irradiation”
developed within the IAEA Programme EMRAS II was calculated for generic populations of mice, hare/rabbit, wolf/wild dog, and
deer/goat chronically exposed to different levels of ionizing radiation. In the conditions of the benchmark scenario, model
populations survived normally (>90% of the control value) at dose rates below the following levels: 3 mGy day−1 for wolf/wild dog; 10 mGy day−1 for deer/goat; 14 mGy day−1 for hare/rabbit; and 20 mGy day−1 for mice. The model predictions showed a relatively high survival potential of short-lived and productive species such as
mice. At the same time, populations of long-lived animals with slow and radiosensitive reproduction such as wolf/wild dog
were candidates to extinction at chronic exposures above 5 mGy day−1. Recovery of short-lived and productive species took a much shorter time compared with long-lived and slow reproductive species. 相似文献
18.
V. I. Kolmakov O. V. Anishchenko E. A. Ivanova M. I. Gladyshev N. N. Sushchik 《Journal of applied phycology》2008,20(3):289-297
Periphyton (epilithon) gross primary production (GPP) was estimated using the DCMU-fluorescence method in the Yenisei River.
In the unshaded littoral zone, chlorophyll a concentration (Chl a) and GPP value varied from 0.83 to 973.74 mg m−2and 2–304,425 O2 m−2 day−1 (0.64–95 133 mg C m−2 day−1), respectively. Positive significant correlation (r = 0.8) between daily GPP and periphyton Chl a was found. Average ratio GPP:Chl a for periphyton was 36.36 mg C mg Chl a m−2 day−1. The obtained GPP values for the Yenisei River have a high significant correlation with values predicted by a conventional
empirical model for stream periphyton. We concluded that the DCMU-fluorescence method can be successfully used for measuring
of gross primary production of stream phytoperiphyton at least as another useful tool for such studies. 相似文献
19.
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
20.
Sunil S. Adav Duu-Jong Lee Juin-Yih Lai 《Applied microbiology and biotechnology》2009,84(6):1181-1189
Efficient nitrification and denitrification of wastewater containing 1,700 mgl−1 of ammonium-nitrogen was achieved using aerobic granular sludge cultivated at medium-to-high organic loading rates. The cultivated
granules were tested in a sequencing batch reactor (SBR) fed with 6.4 or 10.2 kg NH4+-N m−3 day−1, a loading significantly higher than that reported in literature. With alternating 2 h oxic and 2 h anoxic operation (OA)
modes, removal rate was 45.5 mg NH4+-N g−1 volatile suspended solids−1 h−1 at 6.4 kg NH4+-N m−3 day−1 loading and 41.3 ± 2.0 at 10.2 kg NH4+-N m−3 day−1 loading. Following the 60 days SBR test, granules were intact. The fluorescence in situ hybridization and confocal laser
scanning microscopy results indicate that the SBR-OA granules have a distribution with nitrifers outside and heterotrophs
outside that can effectively expose functional strains to surrounding substrates at high concentrations with minimal mass
transfer limit. This microbial alignment combined with the smooth granule surface achieved nitrification–denitrification of
wastewaters containing high-strength ammonium using aerobic granules. Conversely, the SBR continuous aeration mode yielded
a distribution with nitrifers outside and heterotrophs inside with an unsatisfactory denitrification rate and floating granules
as gas likely accumulated deep in the granules. 相似文献