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1.
Molecular cloning and expression analysis of a cytosolic Hsp70 gene from Antarctic ice algae Chlamydomonas sp. ICE-L 总被引:1,自引:0,他引:1
Shenghao Liu Pengying Zhang Bailin Cong Chenlin Liu Xuezheng Lin Jihong Shen Xiaohang Huang 《Extremophiles : life under extreme conditions》2010,14(3):329-337
A cDNA encoding heat shock protein 70 of Antarctic ice algae Chlamydomonas sp. ICE-L (designated as CiHsp70) was identified by RT-PCR and rapid amplification of cDNA ends approaches. The full-length
cDNA of CiHsp70 was 2,232 bp, consisting of a 5′-terminal untranslated region (UTR) of 76 bp, a 3′-terminal UTR of 203 bp
with a poly (A) tail, and an open reading frame of 1,953 bp. The CiHsp70 cDNA encoded a polypeptide of 651 amino acids with
an ATPase domain of 388 amino acids, the substrate peptide binding domain of 246 amino acids and a C-terminus domain of 17
amino acids. The inducible CiHsp70 cDNA was highly homologous to other plant cytosolic Hsp70 genes and clustered together
with green algae and higher plant rather than brown algae, diatom and Cryptophyta. Antarctic ice algae were treated with different
stress conditions and messenger RNA (mRNA) expression levels of CiHsp70 were quantified by quantitative RT-PCR. The results
showed that both cold and heat shock treatments could stimulate CiHsp70 mRNA expression. Meanwhile, CiHsp70 mRNA expression
level increased 2.9-fold in response to UV-B radiation for 6 h, while the expression levels of CiHsp70 were remarkably increased
after removing the UV-B radiation and immediately providing additional 6 h visible light. Furthermore, treating with 62 or
93‰ NaCl for 2 h, CiHsp70 mRNA expression level increased 3.0- and 2.1-fold, respectively. Together, our observations revealed
that CiHsp70 as a molecular chaperone might play an important role in Antarctic ice algae Chlamydomonas sp. ICE-L acclimatizing to polar environment. 相似文献
2.
We report the effect of UV-B radiation (0.8 ± 0.1 mW cm−2) and UV-B radiation supplemented with low-intensity PAR (∼80 μmol photons m−2 s−1) on the photosynthesis, photosynthetic pigments, phosphoglycolipids, oxidative damage, enzymatic antioxidants, and UV-absorbing
compounds in Phormidium tenue, a marine cyanobacterium. UV-B radiation resulted in a decline in photosynthesis and photosynthetic pigments leading to lower
biomass. P. tenue synthesized UV-absorbing compounds like mycosporine-like amino acids (MAAs) and scytonemin in response to UV-B radiation.
Quantity of MAAs and scytonemin was higher when UV-B was supplemented with low-level PAR. UV-B treatment also resulted in
quantitative changes in phosphoglycolipids of the membrane. The UV-B treatment resulted in a slight increase in the level
of peroxidation of cell membrane and very little increase in the activity of superoxide dismutase (SOD). Results indicate
that UV-B affected photosynthesis and that the main protective system was the synthesis of MAAs and scytonemin-like compounds
rather than antioxidant enzymes such as SOD. 相似文献
3.
The response of Antarctic, tropical and temperate microalgae of similar taxonomic grouping to ultraviolet radiation (UVR)
stress was compared based on their growth and fatty acid profiles. Microalgae of similar taxa from the Antarctic (Chlamydomonas UMACC 229, Chlorella UMACC 237 and Navicula UMACC 231), tropical (Chlamydomonas augustae UMACC 246, Chlorella vulgaris UMACC 001 and Amphiprora UMACC 259) and temperate (Chlamydomonas augustae UMACC 247, Chlorella vulgaris UMACC 248 and Navicula incerta UMACC 249) regions were exposed to different UVR conditions. The cultures were exposed to the following conditions: PAR (42 μmol
photons m−2 s−1), PAR + UVA (854 μW cm−2) and PAR + UVA + UVB (117 μW cm−2). The cultures were subjected to UVA doses of 46.1, 92.2 and 184.4 J cm−2 and UVB doses of 6.3, 12.6 and 25.2 J cm−2 by varying the duration of their exposure (1.5, 3 and 6 h) to UVR during the light period (12:12 h light-dark cycle). UVA
did not affect the growth of the microalgae, even at the highest dose. In contrast, growth was adversely affected by UVB,
especially at the highest dose. The dose that caused 50% inhibition (ID50) in growth was used to assess the sensitivity of the microalgae to UVB. Sensitivity of the microalgae to UVB was species-dependent
and also dependent on their biogeographic origin. Of the nine microalgae, the Antarctic Chlorella was most tolerant to UVB stress (ID50 = 21.0 J cm−2). Except for this Chlorella, the percentage of polyunsaturated fatty acids of the microalgae decreased in response to high doses of UVB. Fatty acid profile
is a useful biomarker for UVB stress for some microalgae.
Presented at the 6th Meeting of the Asian Pacific Society of Applied Phycology, Manila, Philippines. 相似文献
4.
5.
Y. Kitaya L. Xiao A. Masuda T. Ozawa M. Tsuda K. Omasa 《Journal of applied phycology》2008,20(5):737-742
Symbiotic dinoflagellates of the species Amphidinium are expected to be pharmaceutically useful microalgae because they produce antitumor macrolides. A microalgae production
system with a large number of cells at a high density has been developed for the efficient production of macrolide compounds.
In the present study, the effects of culture conditions on the cellular growth rate of dinoflagellates were investigated to
determine the optimum culture conditions for obtaining high yields of microalgae. Amphidinium species was cultured under conditions with six temperature levels (21–35°C), six levels of photosynthetic photon flux density
(15–70 μmol photons m−2 s−1), three levels of CO2 concentration (0.02–0.1%), and three levels of O2 concentration (0.2–21%). The number of cells cultured in a certain volume of solution was monitored microscopically and the
cellular growth rate was expressed as the specific growth rate. The maximum specific growth rate was 0.022 h−1 at a temperature of 26°C and O2 concentration of 5%, and the specific growth rate was saturated at a CO2 concentration of 0.05%, a photosynthetic photon flux density of 35 μmol photons m−2 s−1 and a photoperiod of 12 h day−1 upon increasing each environmental parameter. The results demonstrate that Amphidinium species can multiply efficiently under conditions of relatively low light intensity and low O2 concentration. 相似文献
6.
Yu Ding Jin-Lai Miao Quan-Fu Wang Zhou Zheng Guang-You Li Ji-Chang Jian Zao-He Wu 《Polar Biology》2007,31(1):23-30
A psychrophilic glutathione reductase from Antarctic ice microalgae Chlamydomonas sp. Strain ICE-L was purified by ammonium sulfate fractionation and three steps of chromatography. The yield was up to 25.1%
of total glutathione reductase in the crude enzyme extract. The glutathione reductase activity was characterized by the spectrophotometric
method under different conditions. Purified glutathione reductase was separated by SDS-PAGE, which furnished a homogeneous
band. The native molecular mass of the enzyme was 115 kDa. Apparent Km values for NADPH and NADH (both at 0.5 mmol L−1 oxidized glutathione) were 22.3 and 83.8 μmol L−1, respectively. It was optimally active at pH 7.5, and it was stable from pH 5 to 9. Its optimum temperature was 25°C, with
activity at 0°C 23.5% of the maximum. Its optimum ion strength and optimum Mg2+ were 50–90 and 7.5 mmol L−1, respectively. Ca2+, Mg2+, and cysteine substantially increased the activity of the enzyme but chelating agents, heavy metals (Cd2+, Pb2+, Cu2+, Zn2+, etc.), NADPH, and ADP had significant inhibitory effects. This glutathione reductase can be used to study the adaptation
and mechanism of catalysis of psychrophilic enzymes, and it has a high potential as an environmental biochemical indicator
under extreme conditions. 相似文献
7.
Stephen A. Diamond Peter C. Trenham Michael J. Adams Blake R. Hossack Roland A. Knapp Stacey L. Stark David Bradford P. Stephen Corn Ken Czarnowski Paul D. Brooks Dan Fagre Bob Breen Naomi E. Detenbeck Kathy Tonnessen 《Ecosystems》2005,8(5):462-477
Ultraviolet-B radiation (UV-B, 280–320-nm wavelengths) doses were estimated for 1024 wetlands in six national parks: Acadia
(Acadia), Glacier (Glacier), Great Smoky Mountains (Smoky), Olympic (Olympic), Rocky Mountain (Rocky), and Sequoia/Kings Canyon
(Sequoia). Estimates were made using ground-based UV-B data (Brewer spectrophotometers), solar radiation models, GIS tools,
field characterization of vegetative features, and quantification of DOC concentration and spectral absorbance. UV-B dose
estimates were made for the summer solstice, at a depth of 1 cm in each wetland. The mean dose across all wetlands and parks
was 19.3 W-h m−2 (range of 3.4–32.1 W-h m−2). The mean dose was lowest in Acadia (13.7 W-h m−2) and highest in Rocky (24.4 W-h m−2). Doses were significantly different among all parks. These wetland doses correspond to UV-B flux of 125.0 μW cm−2 (range 21.4–194.7 μW cm−2) based on a day length, averaged among all parks, of 15.5 h. Dissolved organic carbon (DOC), a key determinant of water-column
UV-B flux, ranged from 0.6 (analytical detection limit) to 36.7 mg C L−1 over all wetlands and parks, and reduced potential maximal UV-B doses at 1-cm depth by 1%–87 %. DOC concentration, as well
as its effect on dose, was lowest in Sequoia and highest in Acadia (DOC was equivalent in Acadia, Glacier, and Rocky). Landscape
reduction of potential maximal UV-B doses ranged from zero to 77% and was lowest in Sequoia. These regional differences in
UV-B wetland dose illustrate the importance of considering all aspects of exposure in evaluating the potential impact of UV-B
on aquatic organisms. 相似文献
8.
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
9.
The tolerances of 20 Beauveria bassiana isolates derived from host insects worldwide to UV-B irradiation were assessed quantitatively in multi-dose bioassays. Conidial
suspensions of the isolates smeared on glass slides were exposed to the gradient UV-B doses of 0.1–1.6 J cm−2 (D), which generated from 0.75 to 10.17 min irradiation of weighted 312-nm wavelength at 2.0–2.61 mW cm−2. Irradiated conidia were then incubated for 24 h at 25°C under saturated humidity. The ratio of germination at each dose
over that in the blank control was defined as survival index (I
s). For all isolates, the I
s − D observations fit well with the survival model I
s = 1/[1 + exp(a + bD)] (0.94 ≤ r
2 ≤ 0.99) generated widely spanned lethal doses of 0.154–0.928, 0.240–1.139, and 0.383–1.493 J cm−2 for their losses of 50%, 75%, and 95% viabilities, respectively. These were far below the solar UV-B dose of 2.439 J cm−2 measured in a sunny day during the summer. The large variation of UV-B tolerance among the isolates indicates a necessity
to select UV-tolerant candidates for formulations applied to insect control during summer. The highly efficient bioassay method
was developed to measure accurately the UV-B tolerances of fungal biocontrol agents as lethal doses. 相似文献
10.
G. E. Zdorovennova 《Aquatic Ecology》2009,43(3):629-639
The thermal structures in the vicinity of the ice–water and water–sediment boundaries of a shallow lake, L. Vendyurskoe (Northwestern
Russia) during four winter seasons are described. The heat flux at the water-ice boundary was 0.1–0.2 W m−2 during winter. The maximal heat flux at the water–sediment boundary was 4.5 W m−2 at the beginning and 0.5 W m−2 at the end of winter. The daily average value of the solar radiation penetrating into the water was 0.5 W m−2 during main part of winter and 2–50 W m−2 during April. During winter, temperature showed an oscillation in the vicinity of the sediment-water interface. Most periods
corresponding to the main oscillation frequencies in the near-bottom water layer (0–0.4 m) and upper layer sediment (0–0.35 m),
identified by FFT analysis, fall within the scale of synoptic variations (3–10 days), and in a number of cases were equal
to 1 day. The theoretical periods of the first baroclinic seiche mode of Lake Vendyurskoe are 4.5–8.5 days that compares well
with identified temperature oscillation periods. The comparison between the rate of heat content change in a water column
and the difference of vertical heat fluxes from sediment to water and from water to ice show that the horizontal heat transport
takes place in the lake during winter as a result of heat advection along the bottom. 相似文献
11.
12.
While global climate change in polar regions is expected to cause significant warming, the annual cycle of light and dark
will remain unchanged. Cultures of three species of Antarctic sea ice diatoms, Fragilariopsis cylindrus (Grunow) Krieger, Thalassiosira antarctica Comber and Entomoneis kjellmanii (P.T. Cleve) Poulin and Cardinal, were incubated in the dark and exposed to differing temperatures. Maximum dark survival times varied between 30 and 60 days.
Photosynthetic parameters, photosynthetic efficiency (α), maximum quantum yield (Fv/Fm), maximum relative electron transport
rate (rETRmax) and non-photochemical quenching (NPQ), showed that dark exposure had a significant impact on photoacclimation.
In contrast, elevated temperatures had a relatively minor impact on photosynthetic functioning during the dark exposure period
but had a considerable impact on dark survival with minimal dark survival times reduced to only 7 days when exposed to 10°C.
Recovery of maximum quantum yield of fluorescence (Fv/Fm) was not significantly impacted by temperature, species or dark exposure
length. Recovery rates of Fv/Fm ranged from −5.06E−7 ± 2.71E−7 s−1 to 1.36E−5 ± 1.53E−5 s−1 for monthly experiments and from −9.63E−7 ± 7.71E−7 s−1 to 2.65E−5 ± 2.97E−5 s−1 for weekly experiments. NPQ recovery was greater and more consistent than Fv/Fm recovery, ranging between 5.74E−7 ± 8.11E−7 s−1 to 7.50E−3 ± 7.1E−4 s−1. The concentration of chl-a and monosaccharides remained relatively constant in both experiments. These results suggest that there will probably be little
effect on Antarctic microalgae with increasing water temperatures during the Antarctic winter. 相似文献
13.
Preliminary investigation of Okhotsk Sea ice algae; taxonomic composition and photosynthetic activity 总被引:1,自引:1,他引:0
Okhotsk Sea pack ice from Shiretoko in northern Hokkaido, sampled in March 2007, contained microalgal communities dominated
by the centric diatoms Thalassiosira
nordenskioeldi and T. punctigera. Domination by this genus is very unusual in sea ice. Communities from nearby fast ice at Saroma-ko lagoon were dominated by Detonula conferavea and Odontella aurita. Average microalgal biomass of the Okhotsk Sea pack ice (surface and bottom) was 1.59 ± 1.09 μg chla l−1 and for fast ice (bottom only) at nearby Saroma-ko lagoon, 16.5 ± 3.2 μg l−1 (=31.1 ± 5.0 mg chla m−2). Maximum quantum yield of the Shiretoko pack ice algal communities was 0.618 ± 0.056 with species-specific data ranging
between 0.211 and 0.653. These community values are amongst the highest recorded for sea ice algae. Rapid light curves (RLC) on individual cells indicated maximum relative electron transfer rates (relETR) between 20.8 and
60.6, photosynthetic efficiency values (α) between 0.31 and 0.93 and onset of saturation values (E
k) between 33 and 91 μmol photons m−2 s−1. These data imply that the pack ice algal community at Shiretoko was healthy and actively photosynthesising. Maximum quantum
yield of the Saroma-ko fast ice community was 0.401 ± 0.086, with values for different species between 0.361 and 0.560. RLC
data from individual Saroma-ko fast ice algal cells indicated relETR between 55.3 and 60.6, α values between 0.609 and 0.816
and E
k values between 74 and 91 μmol photons m−2 s−1 which are consistent with measurements in previous years. 相似文献
14.
Abrevaya XC Sacco N Mauas PJ Cortón E 《Extremophiles : life under extreme conditions》2011,15(6):633-642
In this work, two archaea microorganisms (Haloferax volcanii and Natrialba magadii) used as biocatalyst at a microbial fuel cell (MFC) anode were evaluated. Both archaea are able to grow at high salt concentrations.
By increasing the media conductivity, the internal resistance was diminished, improving the MFC’s performance. Without any
added redox mediator, maximum power (P
max) and current at P
max were 11.87/4.57/0.12 μW cm−2 and 49.67/22.03/0.59 μA cm−2 for H. volcanii, N. magadii and E. coli, respectively. When neutral red was used as the redox mediator, P
max was 50.98 and 5.39 μW cm−2 for H. volcanii and N. magadii, respectively. In this paper, an archaea MFC is described and compared with other MFC systems; the high salt concentration
assayed here, comparable with that used in Pt-catalyzed alkaline hydrogen fuel cells, will open new options when MFC scaling
up is the objective necessary for practical applications. 相似文献
15.
Nelso P. Navarro Andrés Mansilla Estela M. Plastino 《Journal of applied phycology》2010,22(4):385-394
The effects of UVB radiation on the different developmental stages of the carrageenan-producing red alga Iridaea cordata were evaluated considering: (1) carpospore and discoid germling mortality; (2) growth rates and morphology of young tetrasporophytes;
and (3) growth rates and pigment content of field-collected plant fragments. Unialgal cultures were submitted to 0.17, 0.5,
or 0.83 W m−2 of UVB radiation for 3 h per day. The general culture conditions were as follows: 12 h light/12 h dark cycles; irradiance
of 55 μmol photon.per square meter per second; temperature of 9 ± 1°C; and seawater enriched with Provasoli solution. All UVB irradiation treatments
were harmful to carpospores (
0.17 \textW \textm - 2 = 40.9 ±6.9% 0.17\;{\text{W}}\,{{\text{m}}^{ - 2}} = 40.9 \pm 6.9\% ,
0.5 \textW \textm - 2 = 59.8 ±13.4% 0.5\;{\text{W}}\,{{\text{m}}^{ - 2}} = 59.8 \pm 13.4\% ,
0.83 \textW \textm - 2 = 49 ±17.4% 0.83\;{\text{W}}\,{{\text{m}}^{ - 2}} = 49 \pm 17.4\% mortality in 3 days). Even though the mortality of all discoid germlings exposed to UVB radiation was unchanged when compared
to the control, those germlings exposed to 0.5 and 0.83 W m−2 treatments became paler and had smaller diameters than those cultivated under control treatment. Decreases in growth rates
were observed in young tetrasporophytes, mainly in 0.5 and 0.83 W m−2 treatments. Similar effects were only observed in fragments of adult plants cultivated at 0.83 W m−2. Additionally, UVB radiation caused morphological changes in fragments of adult plants in the first week, while the young
individuals only displayed this pattern during the third week. The verified morphological alterations in I. cordata could be interpreted as a defense against UVB by reducing the area exposed to radiation. However, a high level of radiation
appears to produce irreparable damage, especially under long-term exposure. Our results suggest that the sensitivity to ultraviolet
radiation decreases with increased algal age and that the various developmental stages have different responses when exposed
to the same doses of UVB radiation. 相似文献
16.
The algal, protozoan and metazoan communities within different drift-ice types (newly formed, pancake and rafted ice) and
in under-ice water were studied in the Gulf of Bothnia in March 2006. In ice, diatoms together with unidentified flagellates
dominated the algal biomass (226 ± 154 μg ww l−1) and rotifers the metazoan and protozoan biomass (32 ± 25 μg ww l−1). The under-ice water communities were dominated by flagellates and ciliates, which resulted in lower biomasses (97 ± 25
and 21 ± 14 μg ww l−1, respectively). The under-ice water and newly formed ice separated from all other samples to their own cluster in hierarchical
cluster analysis. The most important discriminating factors, according to discriminant analysis, were chlorophyll-a, phosphate and silicate. The under-ice water/newly formed ice cluster was characterized by high nutrient and low chlorophyll-a values, while the opposite held true for the ice cluster. Increasing trends in chlorophyll-a concentration and biomass were observed with increasing ice thickness. Within the thick ice columns (>40 cm), the highest
chlorophyll-a concentrations (6.6–22.2 μg l−1) were in the bottom layers indicating photoacclimation of the sympagic community. The ice algal biomass showed additional
peaks in the centric diatom-dominated surface layers coinciding with the highest photosynthetic efficiencies [0.019–0.032 μg C (μg Chl-a
−1 h−1) (μE m−2 s−1)−1] and maximum photosynthetic capacities [0.43-1.29 μg C (μg Chl-a
−1 h−1)]. Rafting and snow-ice formation, determined from thin sections and stable oxygen isotopic composition, strongly influenced
the physical, chemical and biological properties of the ice. Snow-ice formation provided the surface layers with nutrients
and possibly habitable space, which seemed to have favored centric diatoms in our study. 相似文献
17.
The photosynthetic performance of Microcystis aeruginosa FACHB 854 during the process of UV-B exposure and its subsequent recovery under photosynthetic active radiation (PAR) was
investigated in the present study. Eight hours UV-B radiation (3.15 W m−2) stimulated the increase of photosynthetic pigments content at the early stage of UV-B exposure followed by a significant
decline. It suggested that UV-B damage was not an immediate process, and there existed a dynamic balance between damage and
adaptation in the exposed cells. Short-term UV-B exposure severely inhibited the photosynthetic capability, but it could restore
quickly after being transferred to PAR. Further investigations revealed that the PS II of M. aeruginosa FACHB 854 was more sensitive to UV-B exposure than PS I, and the oxygen-evolving complex of PS II was an important damage
target of UV-B. The inhibition of photosynthetic performance caused by UV-B could be recovered to 90.9% of pretreated samples
after 20 h exposure at low PAR, but it could not be recovered in the dark as well as under low PAR in the presence of Chloromycetin.
It can be concluded that PAR and de novo protein synthesis were essential for the recovery of UV-B-damaged photosynthetic
apparatus. 相似文献
18.
Exposure to high temperatures affects the photosynthetic processes in marine benthic microalgae by limiting the transport
of electrons, thus reducing the ability of the cell to use light. This causes damage to the Photosystem II (PSII) and may
lead to photoinhibition. However, the PSII of benthic microalgal communities from Brown Bay, eastern Antarctica, were relatively
unaffected by significant changes in temperature. Benthic microalgae exposed to temperatures up to 8°C and an irradiance of
450 μmol photons m−2 s−1 did not experience any photosynthetic damage or irreversible photoinhibition. The effective quantum yield (∆F/F
m′) at 8°C (0.433 ± 0.042) was higher by comparison to cell incubated at −0.1°C (0.373 ± 0.015) with similar irradiances. Temperatures
down to −5°C at a similar irradiance showed a decrease in photosynthesis with decreasing temperature, but no severe photoinhibition
as the cells were able to dissipate excess energy via non-photochemical quenching and recover from damage. These responses
are consistent with those recorded in past studies on Antarctic benthic microalgae and suggest that short-term temperature
change (from −5 to 8°C) will not do irreversible damage to the PSII and will not affect the photosynthesis of the benthic
microalgae. 相似文献
19.
Denitrification activity and oxygen dynamics in Arctic sea ice 总被引:1,自引:0,他引:1
Søren Rysgaard Ronnie N. Glud Mikael K. Sejr Martin E. Blicher Henrik J. Stahl 《Polar Biology》2008,31(5):527-537
Denitrification and oxygen dynamics were investigated in the sea ice of Franklin Bay (70°N), Canada. These investigations
were complemented with measurements of denitrification rates in sea ice from different parts of the Arctic (69°N–85°N). Potential
for bacterial denitrification activity (5–194 μmol N m−2 day−1) and anammox activity (3–5 μmol N m−2 day−1) in melt water from both first-year and multi-year sea ice was found. These values correspond to 27 and 7%, respectively,
of the benthic denitrification and anammox activities in Arctic sediments. Although we report only potential denitrification
and anammox rates, we present several indications that active denitrification in sea ice may occur in Franklin Bay (and elsewhere):
(1) despite sea ice-algal primary production in the lower sea ice layers, heterotrophic activity resulted in net oxygen consumption
in the sea ice of 1–3 μmol l−1 sea ice per day at in situ light conditions, suggesting that O2 depletion may occur prior to the spring bloom. (2) The ample organic carbon (DOC) and NO3
− present in sea ice may support an active denitrification population. (3) Measurements of O2 conditions in melted sea ice cores showed very low bulk concentrations, and in some cases anoxic conditions prevailed. (4)
Laboratory studies using planar optodes for measuring the high-resolution two-dimensional O2 distributions in sea ice confirmed the very dynamic and heterogeneous O2 distribution in sea ice, displaying a mosaic of microsites of high and low O2 concentrations. Brine enclosures and channels were strongly O2 depleted in actively melting sea ice, and anoxic conditions in parts of the brine system would favour anaerobic processes. 相似文献
20.
Pietro Carlozzi Cristina Pintucci Raffaella Piccardi Arianna Buccioni Sara Minieri Maurizio Lambardi 《Biotechnology letters》2010,32(4):477-481
Rhodopseudomonas palustris was grown under continuous irradiances of 36, 56, 75, 151, 320, 500, and 803 W m−2, for a co-production of both bio-H2 and biodiesel (lipids) using fed-batch conditions. The highest overall bio-H2 produced [4.2 l(H2) lculture
−1] was achieved at 320 W m−2, while the highest dry biomass (3.18 g l−1) was attained at 500 W m−2. Dry biomass contained between 22 and 39% lipid. The total energy conversion efficiency was at its highest (6.9%) at 36 W m−2. 相似文献