共查询到20条相似文献,搜索用时 15 毫秒
1.
2.
Phototrophic primary production is a fundamental ecosystem process, and it is ultimately constrained by access to limiting
nutrients. Whereas most research on nutrient limitation of lacustrine phytoplankton has focused on phosphorus (P) and nitrogen
(N) limitation, there is growing evidence that iron (Fe) limitation may be more common than previously acknowledged. Here
we show that P was the nutrient that stimulated phytoplankton primary production most strongly in seven out of nine bioassay
experiments with natural lake water from oligotrophic clearwater lakes. However, Fe put constraints on phytoplankton production
in eight lakes. In one of these lakes, Fe was the nutrient that stimulated primary production most, and concurrent P and Fe
limitation was observed in seven lakes. The effect of Fe addition increased with decreasing lake water concentrations of total
phosphorus and dissolved organic matter. Possible mechanisms are low import rates and low bioavailability of Fe in the absence
of organic chelators. The experimental results were used to predict the relative strength of Fe, N, and P limitation in 659
oligotrophic clearwater lakes (with total phosphorus ≤ 0.2 μM P and total organic carbon < 6 mg C l−1) from a national lake survey. Fe was predicted to have a positive effect in 88% of these lakes, and to be the nutrient with
the strongest effect in 30% of the lakes. In conclusion, Fe, along with P and N, is an important factor constraining primary
production in oligotrophic clearwater lakes, which is a common lake-type throughout the northern biomes.
This paper is dedicated to the memory of Prof. Peter Blomqvist (deceased 2004). 相似文献
3.
We assessed the effect of whole-stream nitrate enrichment on decomposition of three substrates differing in nutrient quality
(alder and oak leaves and balsa veneers) and associated fungi and invertebrates. During the 3-month nitrate enrichment of
a headwater stream in central Portugal, litter was incubated in the reference site (mean NO3-N 82 μg l−1) and four enriched sites along the nitrate gradient (214–983 μg NO3-N l−1). A similar decomposition experiment was also carried out in the same sites at ambient nutrient conditions the following
year (33–104 μg NO3-N l−1). Decomposition rates and sporulation of aquatic hyphomycetes associated with litter were determined in both experiments,
whereas N and P content of litter, associated fungal biomass and invertebrates were followed only during the nitrate addition
experiment. Nitrate enrichment stimulated decomposition of oak leaves and balsa veneers, fungal biomass accrual on alder leaves
and balsa veneers and sporulation of aquatic hyphomycetes on all substrates. Nitrate concentration in stream water showed
a strong asymptotic relationship (Michaelis–Menten-type saturation model) with temperature-adjusted decomposition rates and
percentage initial litter mass converted into aquatic hyphomycete conidia for all substrates. Fungal communities did not differ
significantly among sites but some species showed substrate preferences. Nevertheless, certain species were sensitive to nitrogen
concentration in water by increasing or decreasing their sporulation rate accordingly. N and P content of litter and abundances
or richness of litter-associated invertebrates were not affected by nitrate addition. It appears that microbial nitrogen demands
can be met at relatively low levels of dissolved nitrate, suggesting that even minor increases in nitrogen in streams due
to, e.g., anthropogenic eutrophication may lead to significant shifts in microbial dynamics and ecosystem functioning.
Electronic Supplementary Material Supplementary material is available to authorised users in the online version of this article at . 相似文献
4.
Effects of temperature, and availability of nitrogen and phosphorus on the abundance of Anabaena and Microcystis in Lake Biwa, Japan: an experimental approach 总被引:23,自引:0,他引:23
Under optimal nutrient conditions, both Microcystis sp. and Anabaena sp. isolated from Lake Biwa grew optimally at 28–32°C but differed in maximal growth rates, phosphate uptake kinetics, maximal
phosphorus quotas, and growth responses to nitrogen and phosphorus limitation. The maximal growth rates of Microcystis and Anabaena were 1.6 and 1.25 divisions day−1, respectively. With phosphate and nitrate in the growth-limiting range, the growth of Microcystis was optimal at an N : P ratio of 100 : 1 (by weight) and declined at lower (nitrogen limitation) and higher (phosphorus limitation)
ratios. In contrast, Anabaena growth rates did not change at N : P ratios from 1000 : 1 to 10 : 1. Starting with cells containing the maximal phosphorus
quota, Microcystis growth in minus-phosphorus medium ceased in 7–9 days, compared with 12–13 days for Anabaena. The phosphate turnover time in cultures starved to their minimum cell quotas was 7.9 min for Microcystis and 0.6 min for Anabaena. Microcystis had a higher K
s (0.12 μg P l−1 10−6 cells) and lower V
max (9.63 μg P l−1 h−1 10−6 cells), than Anabaena (K
s 0.02 μg P l−1 h−1 10−6 cells; V
max 46.25 63 μg P l−1 h−1 10−6 cells), suggesting that Microcystis would not be able to grow well in phosphorus-limited waters. We conclude that in spite of the higher growth rate under ideal
conditions, Microcystis does not usually bloom in the North Basin because of low availability of phosphorus and nitrogen. Although Anabaena has an efficient phosphorus-uptake system, its main strategy for growth in low-phosphorus environments may depend on storage
of phosphorus during periods of abundant phosphorus supply, which are rare in the North Basin.
Received: July 31, 2000 / Accepted: October 18, 2000 相似文献
5.
Characterization of phosphorus fractions in the sediments of a tropical intertidal mangrove ecosystem 总被引:2,自引:0,他引:2
Solid phases of phosphorus fractions in the surface and core sediments were studied to understand the biogeochemical cycling
and bioavailability of phosphorus in the Pichavaram intertidal mangrove sediments of India. Total P in surface and core sediments
ranged between 451–552 and 459–736 μg g−1 respectively and Fe bound P was the dominant fraction. Low levels of Fe bound P in the mangrove zone than the two estuarine
zones may be because of high salinity inhibition of phosphate adsorption onto the Fe-oxides/hydroxides. Post-depositional
reorganization of P was observed in surface sediments, converting organic P and Fe bound P into the authigenic P. High levels
of organic P in the mangrove zone is primarily due to intensive cycling and degradation of organic matter and adsorption of
phosphate on the organic molecules. The burial rates and regeneration efficiency of P in the intertidal mangrove ecosystem
ranged from 5.41 to 7.27 μmol P cm−2 year−1 and 0.122 to 0.233 μmol P cm−2 year−1, respectively. High burial efficiency (≈99%) of P proves the earlier observation of limiting nature of P for the biological
productivity. Further, bioavailable P (exchangeable P + Fe bound P + organic P) constituted a considerable proportion of sedimentary
P pool of which an average accounted for 55 and 50% in surface and core sediments respectively. The results indicate that
significant amount of P is locked in sediments in the form of authigenic P and detrital P which makes P as a limiting nutrient
for the biological productivity. 相似文献
6.
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
7.
Tetraspores of Sarcothalia crispata from San Juan Bay, Strait of Magellan, Chile, were cultivated under different combinations of photon flux densities and agricultural
fertilizers in the laboratory. In the experiment, the S. crispata specimens were cultured in combinations of different photon flux densities (50, 100, 150 μmol photons m-2 s-1) and enriched seawater solutions (sodium nitrate + monocalcium phosphate, urea + monocalcium phosphate, ammonium nitrate
+ monocalcium phosphate), always adjusting the N and P concentrations to 10 and 3 mg L-1, and in sea water as control. After 45 days, the tetrasporeling plants were found to be larger at photon flux densities of
50 and 100 μmol photons m-2 s-1 in the nutrient enrichment experiments; growth was greatest in the sea water enriched with ammonium nitrate and urea. An
analysis of the combined effect of the photon flux density and nutrients revealed that the best combination for sporeling
growth was the ammonium nitrate and urea solution at 50–100 μmol photons m-2 s-1. 相似文献
8.
Dalila Serpa Manuela Falcão Pedro Duarte Luís Cancela da Fonseca Carlos Vale 《Biogeochemistry》2007,82(3):291-304
During an annual cycle, overlying water and sediment cores were collected simultaneously at three sites (Tavira, Culatra and
Ramalhete) of Ria Formosa’s intertidal muddy and subtidal sandy sediments to determine ammonium, nitrates plus nitrites and
phosphate. Organic carbon, nitrogen and phosphorus were also determined in superficial sediments. Ammonium and phosphate dissolved
in porewater were positively correlated with temperature (P < 0.01) in muddy and sandy sediments, while the nitrogen-oxidized forms had a negative correlation (P < 0.02) in muddy sediments probably because mineralization and nitrification/denitrification processes vary seasonally. Porewater
ammonium profiles evidenced a peak in the top-most muddy sediment (380 μM) suggesting higher mineralization rate when oxygen
is more available, while maximum phosphate concentration (113 μM) occurred in the sub-oxic layer probably due to phosphorus
desorption under reduced conditions. In organically poor subtidal sandy sediments, nutrient porewater concentrations were
always lower than in intertidal muddy sediments, ranging annually from 20 μM to 100 μM for ammonium and from 0.05 μM to 16 μM
for phosphate. Nutrient diffusive fluxes predicted by a mathematical model were higher during summer, in both muddy (104 nmol cm−2 d−1––NH4+; 8 nmol cm−2 d−1––HPO4−2) and sandy sediments (26 nmol cm−2 d−1––NH4+; 1 nmol cm−2 d−1––HPO4−2), while during lower temperature periods these fluxes were 3–4 times lower. Based on simulated nutrient effluxes, the estimated
annual amount of ammonium and phosphate exported from intertidal areas was three times higher than that released from subtidal
areas (22 ton year−1––NH4+; 2 ton year−1––HPO4−2), emphasizing the importance of tidal flats to maintain the high productivity of the lagoon. Global warming scenarios simulated
with the model, revealed that an increase in lagoon water temperature only produces significant variations (P < 0.05) for NH4+ in porewater and consequent diffusive fluxes, what will probably affect the system productivity due to a N/P ratio unbalance. 相似文献
9.
U. H. Brockmann 《Aquatic Ecology》1994,28(3-4):371-381
In the low salinity region of the Elbe estuary in March–April 1992 the turbidity zone was characterized by high loads of suspended
matter, 7% of which was organic material (750 μM C) at the surface. Particulate nitrogen, phosphorus and carbohydrates concentrations
reached 55 μM N, 10 μM P and more than 15 μM glc. eq., corresponding to 13% of total C, at the surface and increasing threefold
near the bottom.
In spite of the peaking of particulate organic material levels in the maximum turbidity zone, there were only consistent qualitative
changes in total particulate C, N, P, and carbohydrates along the Elbe estuary. Downstream, both the percentage of particulate
organic material and the turbidity: organic material ratio decreased, indicating decomposition in the upper estuary and dilution
with inorganic suspended matter from the lower estuary.
Diatoms, the dominant phytoplankton group, decreased from the upper reaches towards the turbidity zone by 0.3 (surface) and
1.5 mg C l−1 (bottom). This corresponded to 12 and 60% of the decrease in total particulate carbon. Estimated local input of organic carbon
by primary production (21 μg Cl−1d−1) was almost compensated by calculated minimum grazing (14 μg C l−1d−1). Considering net primary production and grazing, the dissimilation by zooplankton (5 μg C l−1d−1) and heterotrophic bacterial decomposition (48 μg C l−1d−1), when summed over the estimated flushing time (12 days) represented a loss of suspended organic matter of 0.6 mg Cl−1. Since this was only 20% of the observed decrease in particulate carbon, significant dilution processes must be assumed.
Dissolved organic nitrogen decreased from 35 to 10 μM N and dissolvd organic phosphorus from 0.6 to 0.1 μM P towards the sea,
mainly due to dilution. The distribution of phosphate, with highest loads in the turbidity maximum of 2.4 μM, suggested an
interaction with the accumulated load of particulate material. 相似文献
10.
Nannochloropsis sp. was grown to the exponential phase and transferred to the high CO2 (2,800 μl l−1) and irradiance (100 μmol photons m−2 s−1) condition with different levels of nitrate and phosphate for 72 h, then the photosynthetic activity and inorganic carbon
acquisition of the alga were measured. The apparent photosynthetic efficiency (α) of Nannochloropsis sp. decreased with increasing NO3
− concentration from 150 to 3,000 μM, and the high nitrate-grown cells showed the lowest levels of light-saturated photosynthetic
rate (P
m), while the low nitrate-grown cells showed the highest levels of dark respiration rate (R
d). The maximal light-saturated photosynthetic rate and the minimal dark respiration rate were seen under the middle nitrate
condition. When the nitrate concentration ranged from 150 to 3,000 μM, the affinity for inorganic carbons of Nannochloropsis sp. increased sharply with the increasing NO3
− concentration to 300 μM and then decreased significantly. The middle phosphate-grown cells exhibited the highest light-saturated
photosynthetic rate and apparent photosynthetic efficiency, however, the affinity for inorganic carbons of Nannochloropsis sp. was the maximum under the low phosphate condition. It was shown that the appropriate nitrogen and phosphorus levels were
of vital importance to the photosynthesis of cells. 相似文献
11.
R. Jan Stevenson Steven T. Rier Catherine M. Riseng Richard E. Schultz Michael J. Wiley 《Hydrobiologia》2006,561(1):149-165
Responses of stream algal biomass to nutrient enrichment were studied in two regions where differences in hydrologic variability
cause great differences in herbivory. Around northwestern Kentucky (KY) hydrologic variability constrains invertebrate biomass
and their effects on algae, but hydrologic stability in Michigan (MI) streams permits accrual of high herbivore densities
and herbivory of benthic algae. Multiple indicators of algal biomass and nutrient availability were measured in 104 streams
with repeated sampling at each site over a 2−month period. Many measures of algal biomass and nutrient availability were positively
correlated in both regions, however the amount of variation explained varied with measures of biomass and nutrient concentration
and with region. Indicators of diatom biomass were higher in KY than MI, but were not related to nutrient concentrations in
either region. Chl a and % area of substratum covered by Cladophora were positively correlated to nutrient concentrations in both regions. Cladophora responded significantly more to nutrients in MI than KY. Total phosphorus (TP) and total nitrogen (TN) explained similar
amounts of variation in algal biomass, and not significantly more variation in biomass than dissolved nutrient concentrations.
Low N:P ratios in the benthic algae indicated N as well as P may be limiting their accrual. Most observed responses in benthic
algal biomass occurred in nutrient concentrations between 10 and 30 μg TP l−1 and between 400 and 1000 μg TN l−1. 相似文献
12.
Effects of nutrients and fish on periphyton and plant biomass across a European latitudinal gradient
Eloy Bécares Joan Gomá Margarita Fernández-Aláez Camino Fernández-Aláez Susana Romo Maria R. Miracle Anika Ståhl-Delbanco Lars-Anders Hansson Mykael Gyllström Wouter J. Van de Bund Ellen Van Donk Timo Kairesalo Jaana Hietala Debbie Stephen David Balayla Brian Moss 《Aquatic Ecology》2008,42(4):561-574
Replicated, factorial mesocosm experiments were conducted across Europe to study the effects of nutrient enrichment and fish
density on macrophytes and on periphyton chlorophyll a (chl-a) with regard to latitude. Periphyton chl-a densities and plant decline were significantly related to nutrient loading in all countries. Fish effects were significant
in a few sites only, mostly because of their contribution to the nutrient pool. A saturation-response type curve in periphyton
chl-a with nutrients was found, and northern lakes achieved higher densities than southern lakes. Nutrient concentration and phytoplankton
chl-a necessary for a 50% plant reduction followed a latitudinal gradient. Total phosphorus values for 50% plant disappearance
were similar from Sweden (0.27 mg L−1) to northern Spain (0.35 mg L−1), but with a sharp increase in southern Spain (0.9 mg L−1). Planktonic chl-a values for 50% plant reduction increased monotonically from Sweden (30 μg L−1) to València (150 μg L−1). Longer plant growing-season, higher light intensities and temperature, and strong water-level fluctuations characteristic
of southern latitudes can lead to greater persistence of macrophyte biomass at higher turbidities and nutrient concentration
than in northern lakes. Results support the evidence that latitudinal differences in the functioning of shallow lakes should
be considered in lake management and conservation policies. 相似文献
13.
Raoul Henry Kozo Hino Jos Geraldo Gentil Jos Galazia Tundisi 《International Review of Hydrobiology》1985,70(4):561-573
Primary productivity of the phytoplankton was evaluated by the 14C and dissolved oxygen methods in December 1981 at the Barra Bonita Reservoir (São Paulo State, Brazil). The primary production varied between 0.17 to 14.51 mg C m−3h−1 at 4 and 0 m depth, respectively. About 57 to 94% of the photosynthetic activity was due to phytoplankton > 50 μm. The highest value of assimilation rate (3.36 mg C mg Chl−1h−1) was found in the surface water. Dissolved nutrient concentrations were very high and consisted mainly of nitrate. Light penetration was low, the aphotic zone accounting for about 90% of the water column. Enrichment with nitrate and phosphate showed that both N and P stimulated the production of biomass (chlorophyll a), mainly due to the addition of phosphate. The enrichment experiment also indicated that phosphate addition has a significant stimulatory effect on the growth of Melosira sp. The limiting effect of light penetration on photosynthetic activity is more severe than that of nutrients. 相似文献
14.
Seasonality and controls of phytoplankton productivity in the middle Cape Fear River, USA 总被引:1,自引:0,他引:1
Our 1 year study was aimed at assessing seasonal patterns and controls on phytoplankton primary production (PPR) and biomass
(chlorophyll a) in a fourth order section of the middle Cape Fear River in North Carolina, USA, and to determine the impact of three low-head
lock and dam (LD) structures on these variables within the 70 km study reach of this coastal river. Mean concentrations of
NO3
−–N, NH4
+–N and soluble reactive phosphorus (SRP) averaged 52.9, 6.0, and 3.6 μmol l−1 in monthly sampling, while the average light attenuation coefficient was 2.4 m−1. The average euphotic depth was 2.1 m. Nutrient concentrations and attenuation coefficients were not significantly different
above versus below each LD, or along the entire study reach. Significantly higher concentrations of dissolved O2 below versus above each LD were attributed to re-aeration during spillway transit. No seasonal pattern in physicochemical
properties was apparent. Phytoplankton chlorophyll a concentrations ranged from <1 to 36 μg l−1, while rates of primary production ranged from 18 to 2,580 mg C m−2 day−1, with values for both variables peaking in the spring and early summer. Chlorophyll a and primary productivity values were consistently higher above versus below each LD in May and June suggesting a seasonal
effect, but values were otherwise similar such that overall means were not significantly different. Several factors point
to light as the primary control on phytoplankton in the middle Cape Fear River: high nutrient concentrations; a low ratio
of euphotic : mixing depth (0.46); progressive increases in chlorophyll a and radiocarbon uptake in all treatments in quarterly nutrient enrichment bioassays conducted at levels of irradiance elevated
relative to in situ river values; and consistently low quarterly values of
(maximum rate of chlorophyll-normalized C uptake; ≤3.7 mg C mg chl a−1 h−1) and I
k (light saturation parameter; ≤104 μmol photons m−2 s−1) for photosynthetic light–response (P–I) curves.
Handling editor: L. Naselli-Flores 相似文献
15.
Jes Jessen Rasmussen Annette Baattrup-Pedersen Tenna Riis Nikolai Friberg 《Aquatic Ecology》2011,45(2):231-242
We surveyed macrophyte community structure and measured community metabolism and nutrient uptake along a temperature gradient
(9.7–17.4°C) in four Icelandic streams influenced by geothermal heating. The study streams are part of the geothermal area
in Hengill that is uniquely characterised by streams with comparable water chemistry despite the geothermal influence. Stream
metabolism was studied applying the diurnal upstream–downstream dissolved oxygen change technique. Nutrient uptake was studied
by adding solutions of nitrogen and phosphorus together with a conservative tracer. Rates of primary production (GPP) and
uptake of nitrate–N and phosphate-P increased with increasing stream temperature. GPP was 20 times higher (up to 12.99 g O2 m−2 day−1) and rates of nutrient uptake were up to 30-times higher (up to 22.99, 13.31 and 7.94 mg m−2 h−1 for ammonium, nitrate and phosphate, respectively) in the warmest streams compared with the coldest. Furthermore, macrophytes,
when present, were strongly controlling ecosystem processes. Our study implies that temperature may affect stream ecosystem
processes both directly (i.e. physiologically) and indirectly (i.e. by changing other structural parameters). 相似文献
16.
Evelin Carlier Marisa Rovera Alberto Rossi Jaume Susana B. Rosas 《World journal of microbiology & biotechnology》2008,24(11):2653-2658
Effects of inoculation of wheat (Triticum aestivum L.) with the rhizobacterium Pseudomonas chlororaphis subsp. aurantiaca strain SR1 (termed SR1) were studied at an experimental field site in Río Cuarto, Argentina. Treatments involved SR1 inoculation
with or without nitrogen/phosphorus fertilization. Inoculation produced a significant increase in plant height and root length
in early growth stages. Inoculation plus fertilization with 40 kg ha−1 urea/30 kg ha−1 diamonic phosphate (“50% dose”) gave a yield increase of 636 kg ha−1 relative to control, and an increase of 472 kg ha−1 relative to fertilization with 80 kg ha−1 urea/60 kg ha−1 phosphate without inoculation. SR1 inoculation without fertilization, compared to control, produced increases of 6% in weight
of 1,000 grains, 13% in number of spikes per plant, and 30% in number of grains per spike. Inoculation plus 50% dose fertilization
also improved these parameters. Results of the study indicate that inoculation of wheat with SR1 improves various growth and
yield parameters, and allows reduced dosage of nitrogen/phosphorus fertilizers in the field. 相似文献
17.
Herlânder Azevedo Alberto Dias Rui Manuel Tavares 《Plant Cell, Tissue and Organ Culture》2008,93(1):115-121
We report the establishment of a Pinus pinaster (Ait.) cell suspension culture in a modified MS medium supplemented with 2 mg ml−1 2,4-D and 1 mg ml−1 BA. Calli were obtained from seedling root segments and established a friable isodiametric cell suspension, suitable for in vitro studies
of maritime pine at the cellular level. Growth (dry weight), cell viability, pH, and nutrient consumption: carbon source (sucrose,
fructose and glucose), nitrogen source (ammonia and nitrate) and phosphate were monitored over 24 h. Suspension cells exhibited
a 15-day exponential growth stage, during which a biphasic consumption profile was observed for all nutrients. Phosphate was
the first limiting nutrient and preferable consumption was observed for glucose over fructose and nitrate over ammonium. 相似文献
18.
Extracellular Matrix in Early Stages of Direct Somatic Embryogenesis in Leaves of Drosera spathulata
The growth and water relations of Paulownia fortunei in photoautotrophic cultures (nutrient medium lacking sucrose and growth regulator) with CO2 enrichment (PWAH) or without CO2 enrichment (PWAL) were compared with those in photomixotrophic shoot (PWC; 30 g dm−3 sucrose and 0.3 mg dm−3 N6-benzyladenine) and root cultures (PWR; 0.3 mg dm−3 indole-3-butyric acid). The photoautotrophic and photomixotrophic cultures were incubated under photosynthetic photon flux
125 and 60 μmol m−2 s−1, respectively. 100 % sprouting and significantly higher number of shoots (1.6) were obtained with PWAH as compared to PWAL
and PWC. PWAH and PWAL stimulated spontaneous rooting from the cut end of axillary shoots. In PWAH, 84 % of shoots rooted
with an average of 5.9 roots per shoot and 4.0 cm of root length in 21 d. Rooting of photomixotrophic shoot cultures were
stimulated by an auxin treatment. In this case, 98.3 % of shoots were rooted with an average of 4.6 roots per shoot and 1.9
cm length. A microscopic observation on leaf abaxial surface prints from photomixotrophic shoot and root cultures showed widely
open (6 – 8 μm) spherical stomata (12 – 14 μm) and from photoautotrophic cultures elliptical stomata (10 – 12 μm) with narrow
openings (3 – 4 μm). Leaves from photomixo-trophic cultures had higher stomatal index as compared to photoautotrophic cultures.
The rate of moisture loss from detached leaves was not varying significantly in different cultures.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
19.
Biofilms formed by the green alga Trentepohlia aurea could be a useful tool in the removal of nitrate and phosphate from water. When a prepared biofilter was dampened with medium
and incubated under low light intensity (10 μmol photons m−2 s−1) between 5 and 50 μmol photons m−2 s−1, the efficiency of removal of inorganic compounds from water was higher without the decomposition of chlorophylls in the
cells. Algal cells immobilized on a glass fiber filter could be kept for 12 weeks under dark conditions at 4°C in the refrigerator.
We tried to construct a laboratory-scale photobioreactor for the removal of inorganic nitrogen and phosphate from water by
the biofilm. In this study, the synthetic wastewater was prepared by diluting 18-fold Bold’s basal medium with deionized water.
The photobioreactor could efficiently remove nitrate and phosphate from the synthetic wastewater under continuous illumination.
The removal ability of nitrate and phosphate per sheet of the biofilter in the photobioreactor exhibited about an 8- and 16-fold
increase, respectively, in 3 days, compared with the bath experimental results. This study showed that the cycling of wastewater
in the reactor by the pump led to a significant improvement in the efficiency of the inorganic ion uptake from water. 相似文献
20.
The Status and Characteristics of Eutrophication in the Yangtze River (Changjiang) Estuary and the Adjacent East China Sea, China 总被引:19,自引:0,他引:19
Eutrophication has become increasingly serious and noxious algal blooms have been of more frequent occurrence in the Yangtze
River Estuary and in the adjacent East China Sea. In 2003 and 2004, four cruises were undertaken in three zones in the estuary
and in the adjacent sea to investigate nitrate (NO3–N), ammonium (NH4–N), nitrite (NO2–N), soluble reactive phosphorus (SRP), dissolved reactive silica (DRSi), dissolved oxygen (DO), phytoplankton chlorophyll
a (Chl a) and suspended particulate matter (SPM). The highest concentrations of DIN (NO3–N+NH4–N+NO2–N), SRP and DRSi were 131.6, 1.2 and 155.6 μM, respectively. The maximum Chl a concentration was 19.5 mg m−3 in spring. An analysis of historical and recent data revealed that in the last 40 years, nitrate and SRP concentrations increased
from 11 to 97 μM and from 0.4 to 0.95 μM, respectively. From 1963 to 2004, N:P ratios also increased from 30–40 up to 150. In parallel with the N and P enrichment,
a significant increase of Chl a was detected, Chl a maximum being 20 mg m−3, nearly four times higher than in the 1980s. In 2004, the mean DO concentration in bottom waters was 4.35 mg l−1, much lower than in the 1980s. In comparison with other estuaries, the Yangtze River Estuary was characterized by high DIN
and DRSi concentrations, with low SRP concentrations. Despite the higher nutrient concentrations, Chl a concentrations were lower in the inner estuary (Zones 1 and 2) than in the adjacent sea (Zone 3). Based on nutrient availability,
SPM and hydrodynamics, we assumed that in Zones 1 and 2 phytoplankton growth was suppressed by high turbidity, large tidal
amplitude and short residence time. Furthermore, in Zone 3 water stratification was also an important factor that resulted
in a greater phytoplankton biomass and lower DO concentrations. Due to hydrodynamics and turbidity, the open sea was unexpectedly
more sensitive to nutrient enrichment and related eutrophication processes. 相似文献