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1.
Integrated abundance and biomass of sympagic meiofauna in Arctic and Antarctic pack ice 总被引:3,自引:0,他引:3
R. Gradinger 《Polar Biology》1999,22(3):169-177
The abundance and biomass of sympagic meiofauna were studied during three cruises to the Antarctic and one summer expedition
to the central Arctic Ocean. Ice samples were collected by ice coring and algal pigment concentrations and meiofauna abundances
were determined for entire cores. Median meiofauna abundances for the expeditions ranged from 4.4 to 139.5 × 103 organisms m−2 in Antarctic sea ice and accounted for 40.6 × 103 organisms m−2 in Arctic multi-year sea ice. While most taxa (ciliates, foraminifers, turbellarians, crustaceans) were common in both Arctic
and Antarctic sea ice, nematodes and rotifers occurred only in the Arctic. Based on the calculated biomass, the potential
meiofauna ingestion rates were determined by applying an allometric model. For both hemispheres, daily and yearly potential
ingestion rates were below the production values of the ice algal communities, pointing towards non-limited feeding conditions
for ice meiofauna year-round.
Accepted: 29 March 1999 相似文献
2.
Influence of sea ice on the composition of the spring phytoplankton bloom in the northern Baltic Sea 总被引:5,自引:2,他引:3
During the late winter and spring of 1994, the influence of sea ice on phytoplankton succession in the water was studied
at a coastal station in the northern Baltic Sea. Ice cores were taken together with water samples from the underlying water
and analysed for algal composition, chlorophyll a and nutrients. Sediment traps were placed under the ice and near the bottom, and the sedimented material was analysed for
algal composition. The highest concentration of ice algae (4.1 mmol C m−2) was found shortly before ice break-up in the middle of April, coincidental with the onset of an under-ice phytoplankton
bloom. The ice algae were dominated by the diatoms Chaetoceros wighamii Brightwell, Melosira arctica (Ehrenberg) Dickie and Nitzschia frigida Grunow. Under the ice the diatom Achnanthes taeniata Grunow and the dinoflagellate Peridiniella catenata (Levander) Balech were dominant. Calculations of sinking rates and residence times of the dominant ice algal species in the
photic water column indicated that only one ice algal species (Chaetoceros wighamii) had a seeding effect on the water column: this diatom dominated the spring phytoplankton bloom in the water together with
Achnanthes taeniata and Peridiniella catenata.
Received: 9 May 1997 / Accepted: 15 February 1998 相似文献
3.
Abundance, biomass and small-scale distribution of cryopelagic amphipods in the Franz Josef Land area (Arctic) 总被引:3,自引:3,他引:0
M. Poltermann 《Polar Biology》1998,20(2):134-138
Arctic sea ice is inhabited by several amphipod species. Abundance, biomass and small-scale distribution of these cryopelagic
(=ice associated) amphipods were investigated near Franz Josef Land in summer 1994. The mean abundance of all species was
420 ind./m2; the mean biomass was 10.61 g ww/m2. Gammarus wilkitzkii was the dominant species, whereas Apherusa glacialis, Onisimus nanseni and O. glacialis were only scarcely found. Amphipods were concentrated at the edges of ice floes and were less frequent in areas further away
under the ice. The relationship between the distribution and ecological/physiological requirements of cryopelagic amphipods,
as well as the small-scale morphology of Arctic sea ice, are discussed.
Received: 14 January 1998 / Accepted 14 April 1998 相似文献
4.
Spatial changes of small nanoplankton (2–10 μm) were investigated in relation to sea-ice conditions, hydrography and receding
ice processes in the Ross Sea (Antarctica) during spring 1994. Abundance and biomass of heterotrophic and autotrophic nanoplankton,
as well as bacterioplankton, were determined along a south-north transect from the open waters polynya towards the pack ice.
Autotrophic and heterotrophic nanoplankton biomass ranged from 758 to 4570 mgC m−2 and from 3 to 387 mgC m−2, respectively. Heterotrophic nanoplankton accounted, on average, for about 9% of the total (i.e. autotrophic plus heterotrophic)
nanoplankton biomass. The size structure of both auto- and heterotrophic nanoplankton in the Ross Sea continental shelf receding
ice edge was different from that of nanoplankton associated with the shelf break and open Antarctic ice-edge area. Generally,
the highest heterotrophic biomass was found in the pack-ice zone on the continental shelf, while the highest heterotrophic
contribution to the total nanoplankton biomass (up to 25%) was encountered at the shelf break where phytoplankton was largely
dominated by 2- to 3-μm-size cells.
Accepted: 2 May 1999 相似文献
5.
L. Guglielmo G. C. Carrada G. Catalano A. Dell'Anno M. Fabiano L. Lazzara O. Mangoni A. Pusceddu V. Saggiomo 《Polar Biology》2000,23(2):137-146
Studies on the chemical and biological properties of annual pack ice at a coastal station in Terra Nova Bay (74°41.72′S,
164°11.63′E) were carried out during austral spring at 3-day intervals from 5 November to 1 December 1997. Temporal changes
of nutrient concentrations, algal biomasses, taxonomic composition, photosynthetic pigment spectra and P–E relationships were
studied. Quantity, composition and degradation rates of organic matter in the intact sea ice were also investigated. In addition,
microcosm experiments were carried out to evaluate photosynthetic and photo-acclimation processes of the sympagic flora in
relation to different light regimes. High concentrations of ammonia were measured in four ice-cores (weighted mean values
of the cores ranged from 4.3 ± 1.9 μM to 7.2 ± 3.4 μM), whereas nitrate and phosphate displayed high concentrations (up to
35.9 μM and 7.6 μM, respectively) only in the bottom layer (135–145 cm depth). Particulate carbohydrate and protein concentrations
in the intact sea ice ranged from 0.5 to 2.3 mg l−1 and 0.2 to 2.0 mg l−1, respectively, displaying a notable accumulation of organic matter in the bottom colored layer, where bacterial enzymatic
activities also reached the highest values. Aminopeptidase activity was extremely high (up to 19.7 μM l−1 h−1 ± 0.05 in the bottom layer), suggesting a rapid turnover rate of nitrogen–enriched organic compounds (e.g. proteins). By
contrast, bacterial secondary production was low, suggesting that only a very small fraction of mobilized organic matter was
converted into bacterial biomass (<0.01‰). The sympagic autotrophic biomass (in terms of chlorophaeopigments) of the bottom
layer was high, increasing during the sampling period from 680 to 2480 μg l−1. Analyses of pigments performed by HPLC, as well as microscope observations, indicated that diatoms dominated bottom communities.
The most important species were Amphiprora sp. and Nitschia cfr. stellata. Bottom sympagic communities showed an average P
B
max
of 0.12 mgC mg Chl−1 and low photoadaptation index (E
k=18 μE m−2 s−1, E
m=65 μE m−2 s−1). Results of the microcosm experiment also indicated that communities were photo-oxidized when irradiance exceeded 100 μE m−2 s−1. This result suggests that micro- autotrophs inhabiting sea ice might have a minor role in the pelagic algal blooms.
Accepted: 4 August 1999 相似文献
6.
During January 1989, phytoplankton biomass and species composition were studied in a north / south transect at the Weddell / Scotia
Confluence (47°W), between 57° and 61°30′S. Results showed a diatom bloom in the Scotia Sea (chlorophyll a 1.9 μg l−1, particulate organic carbon 239 μg l−1), dominated by Fragilariopsis cylindrus, Dactyliosolen antarcticus and Chaetoceros dichaeta. Low chlorophyll a / phaeopigments ratios (about 1.4) and silicate concentrations (15 μmol l−1) suggested that this was an advanced bloom phase, probably linked to high grazing pressure. Minimum chlorophyll a values of 0.1–0.2 μg l−1 and particulate organic carbon 46 μg l−1 were found at the Weddell / Scotia Front and in a subsurface layer of the Weddell Sea Water. In the southern part of the
transect (61°30′S), in the Weddell Sea, a second surface maximum was found (chlorophyll a 0.9 μg l−1, particulate organic carbon 120 μg l−1), but with a different species composition, with Cryptomonas sp. dominant. Our results show a succession within the diatom community in the Weddell / Scotia Confluence Waters when comparing
the three EPOS legs. In the Weddell Sea from spring to summer, nanoflagellates, with only a minor contribution from diatoms,
persist over a long period with little change in the community structure. We suggest that the frontal system, together with
the receding ice edge and the grazing pressure of either krill or protozooplankton, are mainly responsible for the phytoplankton
distribution patterns found.
Received: 3 July 1996 / Accepted: 3 November 1996 相似文献
7.
Semeneh Mengesha Frank Dehairs Michel Fiala Marc Elskens Leo Goeyens 《Polar Biology》1998,20(4):259-272
This study investigates the dynamics of phytoplankton communities and nitrogen uptake in the Indian sector of the Southern
Ocean during spring and summer. The study area is oligotrophic (Chl a stocks <50 mg m−2); nevertheless, a large spatial variation of phytoplankton biomass and community structure was observed. During both seasons
the phytoplankton community in the seasonal ice zone showed higher biomasses and was mainly composed of large diatom cells.
However, in the permanently open ocean zone the community had low biomass and was chiefly composed of nano- and picoflagellates.
In the polar front zone, although biomass was higher, the community structure was similar to the open ocean zone. The results
suggest that the variation in phytoplankton community structure on a larger scale resonates with gradients in water column
stability and nutrient distribution. However, significant changes in biomass and nutrient stocks but little change in community
structure were observed. Absolute nitrogen uptake rates were generally low, but their seasonal variations were highly significant.
During spring the communities displayed high specific nitrate uptake (mean rate = 0.0048 h−1), and diatoms (in the seasonal ice zone) as well as nano- and picoflagellates (in the permanently open ocean zone and polar
front zone) were mainly based on new production (mean ƒ-ratio = 0.69). The transition to summer was accompanied by a significant
reduction in nitrate uptake rate (0.0048 h−1 → 0.0011 h−1) and a shift from predominantly new to regenerated production (ƒ-ratio 0.69 → 0.39). Ammonium played a major role in the
seasonal dynamics of phytoplankton nutrition. The results emphasize that, despite a large contrast in community structure,
the seasonal dynamics of the nitrogen uptake regime and phytoplankton community structure in all three subsystems were similar.
Additionally, this study supports our previous conclusion that the seasonal shift in nitrogen uptake regime can occur with,
as well as without, marked changes in community structure.
Received: 2 December 1997 / Accepted: 20 April 1998 相似文献
8.
Jürgen Weissenberger 《Polar Biology》1998,19(3):151-159
A mesocosm experiment (enclosure volume 220 l) was designed such that sea ice inhabited by Arctic Sea ice organisms was formed
and maintained under natural conditions at 66°N in Rovaniemi, Finland. The experiment was run from natural freezing in December
1994 to melting in April 1995. The ice was inhabited by diatoms, chlorophyceae, heterotrophic flagellates, ciliates, nematodes
and turbellarians. Biomass in the ice, expressed as Chlorophyll a concentration, was 20–110 μg l−1; total cell densities varied from 5 × 106 to 35 × 106 cells l−1. Amongst phototrophic organisms, a succession from a flagellate-dominated community (Chlamydomonas sp.) to a multi-species diatom-dominated community was observed. Typical Arctic species such as Nitzschia frigida and Melosira arctica were present in the ice. Bacterial concentration varied between 2 × 108 and 7 × 108 cells l−1. At least two trophic levels were present in the ice.
Received: 3 April 1997 / Accepted: 9 September 1997 相似文献
9.
Nitrogen uptake in the infiltration community, an ice algal community in Antarctic pack-ice 总被引:1,自引:0,他引:1
S. Kristiansen T. Farbrot H. Kuosa S. M. Myklestad C. H. von Quillfeldt 《Polar Biology》1998,19(5):307-315
An infiltration community was the dominating ice algal community in pack-ice off Queen Maud Land, Southern Ocean, in January
1993. The community was dominated by autotrophic processes, and the most common species were the prymnesiophyte Phaeocystis antarctica and the diatoms Chaetoceros neglectus and Fragilariopsis cylindrus. The concentration of chlorophyll a was 1.3–47.9 μg l−1, and the inner part of the community was nitrate depleted. Uptake rates of nitrate, nitrite, ammonium, urea and amino acids
were measured using 15N. Nitrate was the major nitrogen source for ice algal growth (67 ± 6% nitrate uptake). It is suggested that % nitrate uptake
in the infiltration community decreases during the growth season, from 92% during spring (literature data) to 67% during summer.
Scalar irradiance in the infiltration community was high and variable. It reached ca. 2000 μmol m−2 s−1 at some locations, and nitrate uptake rate was potentially photoinhibited at irradiances >500 μmol m−2 s−1. Nitrate uptake rate in an average infiltration community (0.6 m of snow cover) was lowered by 13% over a 2-week period due
to photoinhibition.
Received: 16 December 1996 / Accepted: 5 January 1998 相似文献
10.
A. McMinn 《Polar Biology》1996,16(4):301-307
Algae released from fast-ice in Ellis Fjord, eastern Antarctica, made little contribution to subsequent phytoplankton growth.
Dominant taxa in the interior ice community included Nitzschia cylindrus (Grun) Hasle, Navicula glaciei V.H. and a dinoflagellate cyst. Diatom mortality within the ice was high. The algal contribution to the phytoplankton from
the fast ice was estimated by calculating the difference between algal biomass in ice cores taken on 14 November with those
taken on 18 December 1992. The biomass of sedimenting phytoplankton was estimated using sediment traps; weekly cell counts
of water were used to monitor net phytoplankton growth. The low contribution from the fast-ice of Ellis Fjord to the phytoplankton
is similar to results from other Antarctic fast-ice communities but is not necessarily reflective of processes occurring within
either Antarctic or Arctic pack ice communities. An algal mat growing on the base of the fast-ice had a carbon standing crop
of between 0.231 gC m-2 and 0.022 gC m-2. Much of this was delivered to the water column as the ice melted while the remainder was exported.
Received: 15 March 1995/Accepted: 4 September 1995 相似文献
11.
Evidence for active microbial nitrogen transformations in sea ice (Gulf of Bothnia, Baltic Sea) in midwinter 总被引:5,自引:3,他引:2
Hermanni Kaartokallio 《Polar Biology》2001,24(1):21-28
Nutrient concentrations, chlorophyll-a, bacterial biomass and relative activity of denitrifying organisms were investigated from ice-core, brine and underlying
water samples in February 1998 in the Gulf of Bothnia, Baltic Sea. Examined sea ice was typical for the Baltic Sea; ice bulk
salinity varied from 0.1 to 1.6 psu, and in underlying water salinity was from 4.2 to 4.7 psu. In 2- to 3-months-old sea ice
(thickness 0.4–0.6 m), sea-ice communities were at the winter stage; chl-a concentrations were generally below 1 mg m−3 and heterotrophic organisms composed 7–20% of organism assemblage. In 1-month-old ice (thickness 0.2–0.25 m), an ice spring
bloom was already developing and chl-a concentrations were up to 5.6 mg m−3. In relation to low salinity, high concentrations of NH+
4, NO−
2, PO3+
4 and SiOH4 were found in the ice column. The results suggest that the upper part of ice accumulates atmospheric nutrient load during
the ice season, and nutrients in the upper 10–20 cm of ice are mainly of atmospheric origin. The most important biological
processes controlling the sea-ice nutrient status are nutrient regeneration, nutrient uptake and nitrogen transformations.
Nutrient regeneration is specially active in the middle parts of the 50- to 60-cm-thick ice and subsequent accumulation of
nutrients probably enhances the ice spring bloom. Nitrite accumulation and denitrifying activity were located in the same
ice layers with nutrient regeneration, which together with the observed significant correlation between the concentrations
of nitrogenous nutrients points to active nitrogen transformations occurring in the interior layers of sea ice in the Baltic
Sea.
Accepted: 12 June 2000 相似文献
12.
Timothy D. Siferd Harold E. Welch Martin A. Bergmann Martin F. Curtis 《Polar Biology》1997,18(1):16-22
The seasonal distribution of sympagic amphipods was investigated in the Chesterfield Inlet area of northwestern Hudson Bay
(63°30′N). Amphipod abundance was measured by photographic samples and species composition was determined by sweep net samples.
Twelve species of amphipods were collected, the most common being Ischyrocerus anguipes, Pontogeneia inermis, Apherusa megalops and Weyprechtia pinguis. The major environmental variable affecting amphipod distribution was water depth. Amphipod abundance was highest near 20
m and near zero past 50 m. The maximum recorded abundance was 1367 m−2. A minor factor affecting the distribution of amphipods was snow depth, through its modifying effect on light and thereby
the growth of ice algae. Amphipods began to inhabit the sea ice shortly after its formation. From the beginning of March,
the number of amphipods on the ice increased steadily to about the 3rd week of April, after which numbers declined. This pattern
coincided with the seasonal ice algae abundance. Amphipods reduced ice algal biomass over 20-m depth by 63%. No evidence of
diurnal changes in abundance was observed.
Received: 15 May 1996 / Accepted: 4 November 1996 相似文献
13.
The efficiency of physical concentration mechanisms for enrichment of algae and bacteria in newly formed sea-ice was investigated
under defined conditions in the laboratory. Sea-ice formation was simulated in a 3,000 l tank under different patterns of
water movement. When ice formed in an artificially generated current pattern, algal cells were substantially enriched within
the ice matrix. Enrichment factors for chlorophyll a calculated from the ratio between the concentrations in ice and underlying water reached values of up to 53. Repeated mixing
of ice crystals into the water column, as well as flow of water through the new ice layer, contributed to the enrichment of
algae in the ice. Wave action during ice formation revealed lower phytoplankton enrichment factors of up to 9. Mixing of floating
ice crystals with underlying water and pumping of water into the ice matrix by periodical expansion and compression of the
slush ice layer were responsible for the wave-induced enrichment of algal cells. Physical enrichment of bacteria within the
ice was negligible. Bacterial biomass within new ice was enhanced only when the concentration of algae was high. At low algal
biomass, bacteria experienced substantial losses in the ice, most likely due to brine drainage, which were not observed for
the microalgae. Bacterial cells are therefore not scavenged by ice crystals and the observed enrichment and sustainment of
bacterial biomass within newly formed ice depend on their attachment to cells or aggregates of algae. Division rates of bacteria
changed only slightly during ice formation.
Received: 21 October 1997 / Accepted: 9 April 1998 相似文献
14.
In order to provide a better understanding of the dynamics of phytoplankton in the coastal regions of high latitudes, a study
was carried out to estimate the dynamics of carbon biomass of autotrophic and heterotrophic algal groups over the austral
spring-summer 1997/1998 period. At a fixed station located in the central basin (Paso Ancho) of the Straits of Magellan (53°S),
surface water samples were collected at least once a week from September 1997 (early spring) to March 1998 (late summer).
Quantitative analysis of biomass of phytoplankton was estimated from geometric volumes, using non-linear equations, and converted
to biomass. The pattern of chlorophyll a showed a strong temporal variability, with maximum values (mean 2.8 mg m−3) at the austral spring phytoplankton increase or bloom (October/November) and minimum values during early spring (September:
<0.5 mg m−3) and summer (January/March: 0.5–1.0 mg m−3). During the spring bloom, diatoms made up to 90% of the total phytoplankton carbon (0.01–189 μg l−1), followed by a maximum of thecate dinoflagellates (0.08–34 μg l−1), and sporadic high biomass of phytoflagellates during summer. Heterotrophic algal groups such as Gymnodinium and Gyrodinium spp. dominated (70%, in the 5- to 25-μm size range) shortly before the main diatom bloom, and small peaks were observed within
spring and early summer periods (0–0.4 μg l−1). Phytoflagellates dominated earlier (spring) with higher carbon biomass (8 μg l−1) and post-bloom periods (summer) when carbon biomass ranged between 1 and 4 μg l−1.
Accepted: 6 September 2000 相似文献
15.
The biomass and productivity of sea ice algae was assessed in the northwestern Barents Sea in May 2004. Sea ice algal pigment
content was patchy with a mean of 18.5 ± 8.9 mg Chla m−2. The algal community was dominated by the diatom Nitzschia frigida. Primary production measured by 14C incubations was between 0.37 and 2.8 mg C m−2 h−1, which compared well with oxygen-based methods using the diffusive boundary layer approach (0.071–1.1 mg C m−2 h−1). Given the differences in the irradiances under which these two sets of measurements were made, there was a strong level
of consistency between the two sets of results. Measurements of primary production were consistent with previous Arctic measurements
but high spatial heterogeneity made a regional estimate of production inappropriate. 相似文献
16.
J. M. Fernández Sevilla E. Molina Grima F. García Camacho F. G. Acién Fernández J. A. Sánchez Pérez 《Applied microbiology and biotechnology》1998,50(2):199-205
Eicosapentaenoic acid (EPA) productivity from continuous cultures of the marine microalga Isochrysis galbana was studied, taking into account the irradiance on the reactor surface, that is, the photolimitation/photoinhibition regime
to which the cells are exposed. Experiments were conducted under a wide variety of operating conditions. The dilution rate
ranged from 0.005 h−1 to 0.040 h−1 at five external irradiances (820, 1620, 2050, 2450 and 3270 μmol photons m−2 s−1) covering photolimited to photoinhibited growth. Under these conditions, the specific growth rate (μ) was found to be the
main factor influencing EPA content (ranging from 2.35% to 5.23% dryweight) and productivity (up to 0.88 mg l−1 h−1). The fatty acid content was not significantly affected by the external irradiance, but was influenced by the state of growth
of the microalga, depending on whether the light regime was photolimiting or photoinhibiting. It might be suggested that light
should no longer be considered an isolated factor affecting EPA synthesis, but an indirect influence through the photolimitation/photoinhibition
regime and growth rate. At a given dilution rate, EPA content and biomass concentration are lower under photoinhibiting external
irradiances than those corresponding to photolimiting conditions, and consequently EPA productivity decays. Since the effect
of photoinhibition is less marked at high biomass concentration, a strategy to optimize EPA productivity from microalgal cultures
could consist of reducing the dilution rate when the external irradiance increases above the phoinhibition threshold.
Received: 16 January 1998 / Revised revision: 27 March 1998 / Accepted: 27 March 1998 相似文献
17.
Phytoplankton biomass and primary production in the marginal ice zone of the northwestern Weddell Sea during austral summer 总被引:2,自引:0,他引:2
Myung Gil Park Sung Ryull Yang Sung-Ho Kang Kyung Ho Chung Jae Hyung Shim 《Polar Biology》1999,21(4):251-261
During the austral summer of 1995, distributions of phytoplankton biomass (as chlorophyll a), primary production, and nutrient concentrations along two north-south transects in the marginal ice zone of the northwestern
Weddell Sea were examined as part of the 8th Korean Antarctic Research Program. An extensive phytoplankton bloom, ranging
from 1.6 to 11.2 mg m−3 in surface chlorophyll a concentration, was encountered along the eastern transect and extended ca. 180 km north of the ice edge. The spatial extent
of the bloom was closely related to the density field induced by the input of meltwater from the retreating sea ice. However,
the extent (ca. 200 km) of the phytoplankton bloom along the western transect exceeded the meltwater-influenced zone (ca.
18 km). The extensive bloom along the western transect was more closely related to local hydrography than to the proximity
of the ice edge and the resulting meltwater-induced stability of the upper water column. In addition, the marginal ice zone
on the western transect was characterized by a deep, high phytoplankton biomass (up to 8 mg Chl a m−3) extending to 100-m depth, and the decreased nutrient concentration, which was probably caused by passive sinking from the
upper euphotic zone and in situ growth. Despite the low bloom intensity relative to the marginal ice zone in both of the transects,
mean primary productivity (2.6 g C m−2 day−1) in shelf waters corresponding to the northern side of the western transect was as high as in the marginal ice zone (2.1 g C m−2 day−1), and was 4.8 times greater than that in open waters, suggesting that shelf waters are as highly productive as the marginal
ice zone. A comparison between the historical productivity data and our data also shows that the most productive regions in
the Southern Ocean are shelf waters and the marginal ice zone, with emerging evidence of frontal regions as another major
productive site.
Accepted: 27 September 1998 相似文献
18.
Janne-Markus Rintala Jonna Piiparinen Jens Ehn Riitta Autio Harri Kuosa 《Hydrobiologia》2006,554(1):11-24
The response of Baltic Sea ice communities to changing light climate was studied in three subsequent 3 week in situ experiments on the SW coast of Finland. The investigation covered three different winter periods, short day with low solar
angles leading to limited light in the ice, late winter with deep snow cover and early spring with melting snow and increasing
light availability. The experimental setup consisted of transparent (no snow) and completely darkened (heavy snow cover) plexiglass
tubes in which the ice cores were incubated in situ from 1 to 2 weeks. Changes in the concentrations of inorganic nutrients (NO3−-–N, PO43−-–P, SiO4−-–Si) and chlorophyll-a concentration in the phytoplankton community composition were recorded as responses to different light manipulations. Changes
in inner ice light intensity in untreated ice as well as the temperature both in air and ice were recorded over the entire
study period. Increased irradiance in late winter/early spring and during meltdown affected the chlorophyll-a amount in the sea ice. During these periods the phytoplankton community in the top layers decreased possibly as a consequence
of photo-acclimation. Closer to the bottom of the ice, however, the increased inner ice light intensity induced algal growth.
Complete exclusion of light stopped the algal growth in the whole ice column. Darkening the ice cores also slowed down the
ice melting opposite to accelerated melting caused by increased light. The significant differences found in nutrient concentrations
between the light and dark treatments were mostly explicable by changes in algal biomass. No obvious changes were observed
in the phytoplankton community composition due to light manipulation, diatoms and heterotrophic flagellates dominating throughout
the study period. 相似文献
19.
Algal communities and export of organic matter from sea ice were studied in the offshore marginal ice zone (MIZ) of the northern
Barents Sea and Nansen Basin of the Arctic Ocean north of Svalbard by means of ice cores and short-term deployed sediment
traps. The observations cover a total of ten stations within the drifting pack ice, visited over a period of 3 years during
the period of ice melt in May and July. Maximum flux of particulate organic carbon and chlorophyll a from the ice at 1 m depth (1,537 mg C m−2 per day and 20 mg Chl a m−2 per day) exceeded the flux at 30 m by a factor of 2 during spring, a pattern that was reversed later in the season. Although
diatoms dominated the ice-associated algal biomass, flagellates at times revealed similarly high biomass and typically dominated
the exported algal carbon. Importance of flagellates to the vertical flux increased as melting progressed, whereas diatoms
made the highest contribution during the early melting stage. High export of ice-derived organic matter and phytoplankton
took place simultaneously in the offshore MIZ, likely as a consequence of ice drift dynamics and the mosaic structure of ice-covered
and open water characteristic of this region. 相似文献
20.
M. Wenk T. Baumgartner J. Dobovšek T. Fuchs J. Kucsera J. Zopfi G. Stucki 《Applied microbiology and biotechnology》1998,49(5):624-630
The evaluation of pesticide-mineralising microorganisms to clean-up contaminated soils was studied with the widely applied
and easily detectable compound atrazine, which is rapidly mineralised by several microorganisms including the Pseudomonas sp. strain Yaya 6. The rate of atrazine removal was proportional to the water content of the soil and the amount of bacteria
added to the soil. In soil slurry, 6 mg atrazine kg soil−1 was eliminated within 1 day after application of 0.3 g dry weight inoculant biomass kg soil−1 and within 5 days when 0.003 g kg soil−1 was used. In partially saturated soil (60% of the maximal water-holding capacity) 15 mg atrazine kg soil−1 was eliminated within 2 days by 1 g biomass kg soil−1 and within 25 days when 0.01 g biomass kg soil−1 was used. In unsaturated soil, about 60% [U-ring-14C]atrazine was converted to 14CO2 within 14 days. Atrazine was very efficiently removed by the inoculant biomass, not only in soil that was freshly contaminated
but also in soil aged with atrazine for up to 260 days. The bacteria exposed to atrazine in unsaturated sterile soil were
still active after a starvation period of 240 days: 15 mg newly added atrazine kg soil−1 was eliminated within 5 days.
Received: 31 October 1997 / Received revision: 16 January 1998 / Accepted: 18 January 1998 相似文献