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1.
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
2.
Robert E. Foley James R. Spotila John P. Giesy Carolyn H. Wall 《Environmental Biology of Fishes》1978,3(4):361-367
Synopsis Arsenic persists in Chautauqua Lake, New York waters 13 years after cessation of herbicide (sodium arsenite) application and continues to cycle within the lake. Arsenic concentrations in lake water ranged from 22.4–114.81 g l–1, = 49.0 ag l–1. Well water samples generally contained less than 10 g l–1 arsenic. Arsenic concentrations in lake water exceeded U.S. Public Health Service recommended maximum concentrations (10 g l–1) and many samples exceeded the maximum permissible limit (50 g l–1). Fish accumulated arsenic from water but did not magnify it. Fish to water arsenic ratios ranged from 0.4–41.6. Black crappie (Pomoxis nigromaculatus) contained the highest arsenic concentrations (0.14–2.04 g g–1 ), X = 0.7 g g–1) while perch (Perca flavescens), muskellunge (Esox masquinongy) and largemouth bass (Micropterus salmoides) contained the lowest concentrations (0.02–0.13 g g–1). Arsenic concentrations in fish do not appear to pose a health hazard for human consumers. 相似文献
3.
Cell suspension cultures of Commiphora wightii, grown in modified MS medium containing 2,4-dichlorophenoxyacetic acid (0.5 mg l−1) and kinetin (0.25 mg l−1), produced ∼5 μg guggulsterone g−1 dry wt. In a 2 l stirred tank bioreactor, the biomass was 5.5 g l−1 and total guggulsterone was 36 μg l−1. 相似文献
4.
Landfast ice algal communities were studied in the strongly riverine-influenced northernmost part of the Baltic Sea, the Bothnian
Bay, during the winter-spring transition of 2004. The under-ice river plume, detected by its low salinity and elevated nutrient
concentrations, was observed only at the station closest to the river mouth. The bottommost ice layer at this station was
formed from the plume water (brine volume 0.71%). This was reflected by the low flagellate-dominated (93%) algal biomass in
the bottom layer, which was one-fifth of the diatom-dominated (74%) surface-layer biomass of 88 μg C l−1. Our results indicate that habitable space plays a controlling role for ice algae in the Bothnian Bay fast ice. Similarly
to the water column in the Bothnian Bay, average dissolved inorganic N:P-ratios in the ice were high, varying between 12 and
265. The integrated chlorophyll a (0.1–2.2 mg m−2) and algal biomass in the ice (1–31 mg C m−2) correlated significantly (Spearman ρ = 0.79), with the highest values being measured close to the river mouth in March and during the melt season in April. Flagellates
<20 μm generally dominated in both the ice and water columns in February–March. In April the main ice-algal biomass was composed
of Melosira arctica and unidentified pennate diatoms, while in the water column Achnanthes taeniata, Scrippsiella hangoei and flagellates dominated. The photosynthetic efficiency (0.003–0.013 (μg C [μg chl a
−1] h−1)(μE m−2s−1)−1) and maximum capacity (0.18–1.11 μg C [μg chl a
−1] h−1) could not always be linked to the algal composition, but in the case of a clear diatom dominance, pennate species showed
to be more dark-adapted than centric diatoms. 相似文献
5.
The freshwater microalga Chlorella vulgaris was grown heterotrophically in fed-batch 50–600-L fermenters at 36°C, on aerated and mixed nutrient solution with urea as
a nitrogen and glucose as a carbon and energy source. Cell density increased from the initial value 6.25 to 117.18 g DW L−1 in 32 h in the fermenter 50 L at a mean growth rate 3.52 g DW L−1 h−1. The DW increase in the fermenter 200 L was from 7.25 to 94.82 g DW L−1 in 26.5 h at a mean growth rate 3.37 g DW L−1 h−1. Mean specific growth rate μ was about 0.1 h−1 in the both fermenters, if nutrients and oxygen were adequately supplied. The DW increase in the fermenter 600 L was from
0.8 to 81.6 g DW L−1 in 66.5 h at a mean growth rate 1.22 g DW L−1 h−1 and μ = 0.07 h−1. A limitation of the cell growth rate in 600 L fermenter caused by a low dissolved oxygen concentration above cell densities
higher than 10 g DW L−1) occurred. Specific growth rate decreased approximately linearly with increasing glucose concentration (25–80 g glucose L−1) at the beginning of cultivation and decreased with the time of cultivation. The cell yield was 0.55–0.69 g DW (g glucose)−1. The content of proteins, β-carotene, and chlorophylls in the cells steadily increased and starch content decreased, by keeping
aerated and mixed culture another 12 h in fermenter after the cell growth was stopped due to glucose deficiency. 相似文献
6.
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
7.
An ecotype of brake fern (Pteris vittata) was assessed for arsenic tolerance and accumulation in its biomass under in vivo and in vitro condition; using soil, and
agar-gelled Murashige and Skoog (MS) medium supplemented with different concentrations of arsenic. The plants were raised
in soil amended with 100–1000 mg arsenic kg−1 soil, and MS medium was supplemented with 10–300 mg arsenic 1−1 medium using Na2HAsO4 · 7H2O. The spores and haploid gametophytic-prothalli were raised in vitro on MS medium supplemented with arsenic. The field plants
showed normal growth and biomass formation in arsenic amended soil, and accumulated 1908–4700 mg arsenic kg−1 dry aerial biomass after 10 weeks of growth. Arsenic toxicity was observed above >200 mg arsenic kg−1 soil. The concentrations of arsenic accumulated in the plant biomass were statistically significant (p < 0.05). Normal plants were developed from spores and gametophyte prothalli on the MS media supplemented with 50–200 mg arsenic
1−1 medium. The in vitro raised plants were tolerant to 300 mg arsenic kg−1 of soil and accumulated up to 3232 mg arsenic kg−1 dry aerial biomass that showed better growth performance, biomass generation and arsenic accumulation in comparison to the
field plants.
The text was submitted by the authors in English. 相似文献
8.
Jang K. Kim George P. Kraemer Christopher D. Neefus Ik Kyo Chung Charles Yarish 《Journal of applied phycology》2007,19(5):431-440
Porphyra is one of the world’s most valued maricultured seaweeds and has been cultivated for several hundred years in Asia. The objective
of this study was to produce critical information as a guide for the selection of an appropriate Porphyra species from coastal New England for the development of a land-based aquaculture system. Four Northwest Atlantic Porphyra species: P. leucosticta,
P. amplissima, P. linearis and P. umbilicalis, were cultivated for 1 and 2 weeks at saturated light intensities (100–150 μmol photons m−2s−1) and six combinations of ammonium (25 and 250 μmoles L−1) and temperature (10, 15 and 20°C). Specific growth rate (SGR) increased with decreasing temperature in P. leucosticta, P. linearis and P. umbilicalis and increased with increasing temperature in P. amplissima. The SGR of all species was greater at the higher ammonium concentration. Porphyra linearis had the highest SGR, increasing in biomass by approximately 16% day−1. Phycoerythrin (PE) content was higher at 10°C and 250 μmoles L−1 in all species except P. amplissima. The PE content, measured as fresh weight (FW), of P. linearis (29 mg g−1 FW−1) and P. umbilicalis (26 mg g−1 FW−1) was significantly higher than the other two species. Tissue nitrogen content of all species measured in dry weight was on
average 1.45% higher at 250 μmoles L−1 than at 25 μmoles L−1 ammonium concentration. Porphyra umbilicalis had the highest tissue nitrogen contents (6.76%) at 10°C and 250 μmoles L−1 ammonium. Based on these results, P. linearis and P. umbilicalis should be considered as potential candidates for bioremediation with finfish and shellfish mariculture. 相似文献
9.
Shannon KE Saleh-Lakha S Burton DL Zebarth BJ Goyer C Trevors JT 《Antonie van Leeuwenhoek》2011,100(2):183-195
The effect of glucose addition (0 and 500 μg C g−1 soil) and nitrate (NO3) addition (0, 10, 50 and 500 μg NO3–N g−1 soil) on nitric oxide reductase (cnorB) gene abundance and mRNA levels, and cumulative denitrification were quantified over 48 h in anoxic soils inoculated with
Pseudomonas mandelii. Addition of glucose-C significantly increased cnorB
p
(P. mandelii and related species) mRNA levels and abundance compared with soil with no glucose added, averaged over time and NO3 addition treatments. Without glucose addition, cnorB
p
mRNA levels were higher when 500 μg NO3–N g−1 soil was added compared with other NO3 additions. In treatments with glucose added, addition of 50 μg NO3–N g−1 soil resulted in higher cnorB
p
mRNA levels than soil without NO3 but was not different from the 10 and 500 μg NO3–N g−1 treatments. cnorB
p
abundance in soils without glucose addition was significantly higher in soils with 500 μg NO3–N g−1 soil compared to lower N-treated soils. Conversely, addition of 500 μg NO3–N g−1 soil resulted in lower cnorB
p
abundance compared with soil without N-addition. Over 48 h, cumulative denitrification in soils with 500 μg glucose-C g−1 soil, and 50 or 500 μg NO3–N g−1 was higher than all other treatments. There was a positive correlation between cnorB
p
abundance and cumulative denitrification, but only in soils without glucose addition. Glucose-treated soils generally had
higher cnorB
p
abundance and mRNA levels than soils without glucose added, however response of cnorB
p
abundance and mRNA levels to NO3 supply depended on carbon availability. 相似文献
10.
Biosynthesis of six saponins (ginsenosides) in suspension culture of P. quinquefolium Z5 was investigated. Ginsenoside content in biomass reached the highest level, nearly 30 mg g−1 d.w., between 25 and 30 days of the culture. Saponins were synthesized simultaneously with cell growth but their synthesis
rate was not proportional to the growth rate. During the phase of rapid biomass multiplication, after which biomass reached
90% of its maximum yield, only half examined ginsenosides was produced. The second half of the final saponins yield was produced
during the slow growth phase, in which only 10% of biomass was grown. During the intensive growth phase the productivity of
six saponins examined per biomass (dry weight) unit was 3.4 μg mg−1 d.w. day−1, however, this parameter calculated for slow growth phase reached nearly 30 μg mg−1 d.w. day−1. There were differences in increase of the contents of six saponins determined in biomass, and it was the highest for saponins
Re (20(S)-protopanaxatriol-6-[O-α-l-rhamnopyranosyl(1 → 2)-β-d-glucopyranoside]-20-O-β-d-glucopyranoside) and Rg1 (20(S)-protopanaxatriol-6,20-di-O-β-d-glucoside). 相似文献
11.
Aluminum in lake water and in the organs of the fish Tribolodon hakonensis was investigated in Lake Usoriko (pH 3.6), Lake Inawashiroko (pH 5.0), and the Tenryu River (pH 7.7). The concentration of
total soluble aluminum in the water was 0.51 mg l−1 in Usoriko, 0.05 mg l−1 in Inawashiroko, and less than 0.01 mg l−1 in the Tenryu. The chemical forms of soluble aluminum in the acid water were characterized as Al3+, AlL2+, and AlL≦1+. More than 90% of soluble aluminum in the water of Usoriko was Al3+, whereas AlL2+ was dominant in the water of Inawashiroko. The aluminum concentration in the organs of T. hakonensis in Usoriko was 42 μg g−1 wet weight in gills, 4.2 μg g−1 in muscle, 6.9 μg g−1 in bone, 12.7 μg g−1 in liver, 6.0 μg g−1 in kidney, and 6.0 μg g−1 in intestine, indicating accumulation of aluminum in the gills. The aluminum concentration in the organs of T. hakonensis living in Inawashiroko was approximately the same, in spite of the difference in water chemistry of the two acid lakes, especially
for pH and aluminum. This suggests that aluminum accumulation might be controlled in the fish living in the acid lakes. In
contrast, the aluminum concentration in the gills of T. hakonensis from the Tenryu was 2 μg g−1.
Received: May 20, 1999 / Accepted: December 10, 1999 相似文献
12.
Kaarel Adamberg Petri-Jaan Lahtvee Kaspar Valgepea Kristo Abner Raivo Vilu 《Antonie van Leeuwenhoek》2009,95(3):219-226
Quasi steady state growth of Lactococcus
lactis IL 1403 was studied in glucose-limited A-stat cultivation experiments with acceleration rates (a) from 0.003 to 0.06 h−2 after initial stabilization of the cultures in chemostat at D = 0.2–0.3 h−1. It was shown that the high limit of quasi steady state growth rate depended on the acceleration rate used—at an acceleration
rate 0.003 h−2 the quasi steady state growth was observed until μ
crit = 0.59 h−1, which is also the μ
max value for the culture. Lower values of μ
crit were observed at higher acceleration rates. The steady state growth of bacteria stabilized at dilution rate 0.2 h−1 was immediately disrupted after initiating acceleration at the highest acceleration rate studied—0.06 h−2. Observation was made that differences [Δ(μ − D)] of the specific growth rates from pre-programmed dilution rates were the lowest using an acceleration rate of 0.003 h−2 (< 4% of preset changing growth rate). The adaptability of cells to follow preprogrammed growth rate was found to decrease
with increasing dilution rate—it was shown that lower acceleration rates should be applied at higher growth rates to maintain
the culture in the quasi steady state. The critical specific growth rate and the biomass yields based on glucose consumption
were higher if the medium contained S
0 = 5 g L−1 glucose instead of S
0 = 10 g L−1. It was assumed that this was due to the inhibitory effect of lactate accumulating at higher concentrations in the latter
cultures. Parallel A-stat experiments at the same acceleration and dilution rates showed good reproducibility—Δ(μ − D) was less than 5%, standard deviations of biomass yields per ATP produced (Y
ATP), and biomass yields per glucose consumed (Y
XS) were less than 15%. 相似文献
13.
The isolation, identification and quantification of exometabolites from culture media of the cyanobacterium Nostoc insulare are described. Besides the known exometabolite 4,4′-dihydroxybiphenyl (I), two more compounds, the β-carboline 9H-pyrido(3,4-b)indole
(norharmane, II) and N,N′-(4,5-dimethyl-1,2-phenylene)bis-acetamide (III), were discovered. Concentrations of all three compounds
in media and biomass of five 250 L cultures of N. insulare were determined. Culture medium values for I ranged between 200 and 1,250 μg L−1 (1.1–6.7 μmol L−1), for III between 115 and 390 μg L−1 (0.5–1.8 μmol L−1), whereas concentrations of II were conspicuously lower (2–16 μg L−1 or 0.014–0.094 μmol L−1). Amounts of III per volume of culture medium were about tenfold higher than in the biomass contained in an equal culture
volume. This difference is an indication for an active excretion of III. Amounts of I and II in biomass and media were of
no significant difference. In the neutral red uptake assay, I and II were found to be toxic against eukaryotic cells as follows:
I was of considerable cytotoxicity in concentrations from 1,000 to 10 mg L−1 and of lower cytotoxicity (causing a 27 % decrease of cell viability) in a concentration of 1,000 μg L−1, whereas II was merely of considerable cytotoxicity in concentrations from 1,000 to 100 mg L−1. Because of the cytotoxicity of I and because of the many known pharmacological effects of II there is a possibility that
a certain amount of risk to humans and livestock comes from cultures or even from biomass- free culture media of N. insulare. The natural function of the examined exometabolites is discussed. 相似文献
14.
C. S. Jeong H. N. Murthy E. J. Hahn H. L. Lee K. Y. Paek 《Acta Physiologiae Plantarum》2009,31(1):219-222
The effect of the root-inoculum size and axuin concentration on growth of adventitious roots and accumulation of ginsenosides
were studied during suspension cultures of ginseng (Panax ginseng C.A. Meyer). Of the various concentrations of indole-3-butyric acid (IBA) and γ-naphthaleneacetic acid (NAA) used as supplementary
growth regulators along with Murashige and Skoog medium, 25 μM IBA was found suitable for lateral root induction and growth,
as well as accumulation of ginsenosides. Inoculum size of 5 g L−1 was found suitable for optimal biomass (10.5 g L−1 dry biomass) and ginsenosides (5.4 mg g−1 DW) accumulation. Of the various length of root inocula tested (chopped to 1–3, 4–6, 7–10 mm and un-chopped), root inocula
of 7–10 mm was found suitable for biomass and ginsenoside accumulation. 相似文献
15.
Cell cultures of Commiphora wightii (Arnott.) Bhandari were grown in shake flasks and a bioreactor and an increase in guggulsterone accumulation up to 18 μg
l−1 was recorded in cells grown in the production medium containing a combination of sucrose:glucose (4% total), precursors (phenylalanine,
pyruvic acid, xylose, and sodium acetate), morphactin, and 2iP. A yield of 10 g l−1 biomass and ∼200 μg l−1 guggulsterone was recorded in a 3-l flask and in a 2-l stirred tank bioreactor compared with 6.6 g biomass and 67 μg l−1 guggulsterone in 250-ml flasks. Increased vessel size was correlated with increased biomass and guggulsterone accumulation.
2iP alone was not effective for biomass and guggulsterone accumulation in cell cultures of C. wightii. 相似文献
16.
Critical levels of selenium in raya (Brassica juncea Czern L.), maize (Zea mays L.), wheat (Triticum aestivum L.) and rice (Oryza sativa L.) were worked out by growing these crops in an alkaline silty loam soil treated with different levels of selenite-Se ranging
from 1 to 25 μg g−1 soil. Significant decrease in dry matter yield was observed above a level of 5 μg Se g−1 soil in raya and maize; 4 μg Se g−1 soil in wheat and 10 μg Se g−1 soil in rice shoots. The critical level of Se in plants above which significant decrease in yield would occur was found to
be 104.8 μg g−1 in raya, 76.9 μg g−1 in maize, 41.5 μg g−1 in rice and 18.9 μg g−1 in wheat shoots. Significant coefficients of correlation were observed between Se content above the critical level and dry
matter yield of raya as well as rice (r = −0.99, P ≤ 0.01), wheat (r = −0.97, P ≤ 0.01) and maize ((r = −0.96, P ≤ 0.01). A synergistic relationship was observed between S and Se content of raya (r = 0.96, P ≤ 0.01), wheat (r = 0.89, P ≤ 0.01), rice (r = 0.85, P ≤ 0.01) and maize (r = 0.84, P ≤ 0.01). Raya, maize and rice absorbed Se in levels toxic for animal consumption (i.e. > 5 mg Se kg−1) when the soil was treated with more than 1.5 μg Se g−1. In case of wheat, application of Se more than 3 μg g−1 soil resulted in production of toxic plants. 相似文献
17.
A transect of ten profiles was laid out in 20 m intervals on a tidal sand flat approximately 100 m from the east shore of
Sylt until the next tideway was reached. Sediment samples were taken from 0–2 cm depth (oxic layer) and 2–4 cm depth (anoxic
layer). The average content of organic carbon (C) was 2.41 mg g−1 in the oxic layer and 1.86 mg g−1 in the anoxic layer. The organic C content correlated positively with non-biomass C, 0.5M K2SO4 extractable C, total nitrogen (N), cation exchange capacity (CEC), and the textural classes <200 μm, and negatively correlated
with the coarse sand fraction. The average total C:N ratio was 7.0 in the oxic layer and 6.7 in the anoxic layer, indicating
that the C input comes entirely from the microflora. CHCl3-labile C was measured by the fumigation-extraction method and was converted to microbial biomass C (values in brackets).
The average content of CHCl3-labile C was 407 μg g−1 (903 μg g−1) in the oxic layer and 214 μg g−1 (476 μg g−1) in the anoxic layer. CHCl3-labile C did not correlate with CEC and the textural classes <200 μm, indicating that conditions other than the physical
environment determine this fraction (C input, grazing). 相似文献
18.
Comparative study of periphyton community structure in long and short-hydroperiod Everglades marshes 总被引:1,自引:0,他引:1
The Florida Everglades is a mosaic of short and long-hydroperiod marshes that differ in the depth, duration, and timing of
inundation. Algae are important primary producers in widespread Everglades’ periphyton mats, but relationships of algal production
and community structure to hydrologic variability are poorly understood. We quantified differences in algal biomass and community
structure between periphyton mats in 5 short and 6 long-hydroperiod marshes in Everglades National Park (ENP) in October 2000.
We related differences to water depth and total phosphorus (TP) concentration in the water, periphyton and soils. Long and
short-hydroperiod marshes differed in water depth (73 cm vs. 13 cm), periphyton TP concentrations (172μg g−1 vs. 107 μg g−1, respectively) and soil TP (284 μg g−1 vs. 145 μg g−1). Periphyton was abundant in both marshes, with short-hydroperiod sites having greater biomass than long-hydroperiod sites
(2936 vs. 575 grams ash-free dry mass m−2). A total of 156 algal taxa were identified and separated into diatom (68 species from 21 genera) and “soft algae” (88 non-diatom
species from 47 genera) categories for further analyses. Although diatom total abundance was greater in long-hydroperiod mats,
diatom species richness was significantly greater in short- hydroperiod periphyton mats (62 vs. 47 diatom taxa). Soft algal
species richness was greater in long-hydroperiod sites (81 vs. 67 soft algae taxa). Relative abundances of individual taxa
were significantly different among the two site types, with soft algal distributions being driven by water depth, and diatom
distributions by water depth and TP concentration in the water and periphyton. Periphyton communities differ between short
and long-hydroperiod marshes, but because they share many taxa, alterations in hydroperiod could rapidly promote the alternate
community.
Electronic supplementary material Electronic supplementary material is available for this article at
and accessible for authorised users. 相似文献
19.
Part of the Larsen A Ice Shelf (64°15′S to 74°15′S) collapsed during January 1995. A first oceanographic and biological data
set from the newly free waters was obtained during December 1996. Typical shelf waters with temperatures near and below the
freezing point were found. A nutrient-rich water mass (max: PO4
3− 1.80 μmol L−1 and NO3
− 27.64 μmol L−1) was found between 70 and 200 m depth. Chlorophyll-a (Chl-a) values (max 14.24 μg L−1) were high; surface oxygen saturation ranged between 86 and 148%. Diatoms of the genera Nitzschia and Navicula and the prymnesiophyte Phaeocystis sp. were the most abundant taxa found. Mean daily primary production (Pc) estimated from nutrient consumption was 14.80 ± 0.17 mgC m−3 day−1. Pc was significantly correlated with total diatom abundance and Chl-a. Calculated ΔpCO2 (difference of the CO2 partial pressure between surface seawater and the atmosphere) was –30.5 μatm, which could have contributed to a net CO2 flux from the atmosphere to the sea and suggests the area has been a CO2 sink during the studied period. High phytoplankton biomass and production values were found in this freshly open area, suggesting
its importance for biological CO2 pumping. 相似文献
20.
The objective of this study was to improve the biological water–gas shift reaction for producing hydrogen (H2) by conversion of carbon monoxide (CO) using an anaerobic thermophilic pure strain, Carboxydothermus hydrogenoformans. Specific hydrogen production rates and yields were investigated at initial biomass densities varying from 5 to 20 mg volatile
suspended solid (VSS) L−1. Results showed that the gas–liquid mass transfer limits the CO conversion rate at high biomass concentrations. At 100-rpm
agitation and at CO partial pressure of 1 atm, the optimal substrate/biomass ratio must exceed 5 mol CO g−1 biomass VSS in order to avoid gas–liquid substrate transfer limitation. An average H2 yield of 94 ± 3% and a specific hydrogen production rate of ca. 3 mol g−1 VSS day−1 were obtained at initial biomass densities between 5 and 8 mg VSS−1. In addition, CO bioconversion kinetics was assessed at CO partial pressure from 0.16 to 2 atm, corresponding to a dissolved
CO concentration at 70°C from 0.09 to 1.1 mM. Specific bioactivity was maximal at 3.5 mol CO g−1 VSS day−1 for a dissolved CO concentration of 0.55 mM in the culture. This optimal concentration is higher than with most other hydrogenogenic
carboxydotrophic species. 相似文献