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1.
Viruses play a significant role in nutrient cycling within the world’s oceans and are important agents of horizontal gene
transfer, but little is know about their entrainment into sea ice or their temporal dynamics once entrained. Nilas, grease
ice, pancake ice, first-year sea ice floes up to 78 cm in thickness, and under-ice seawater were sampled widely across Amundsen
Gulf (ca. 71° N, 125° W71^\circ \hbox{N}, 125^\circ \hbox{W}) for concentrations of viruses and bacteria. Here, we report exceptionally high virus-to-bacteria ratios in seawater (45–340)
and sea ice (93–2,820) during the autumn freeze-up. Virus concentrations ranged from 4.8 to 27 × 106 ml−1 in seawater and, scaled to brine volume, 5.5 to 170 × 107 ml−1 in sea ice. Large enrichment indices indicated processes of active entrainment from source seawater, or viral production
within the ice, which was observed in 2 of 3 bottle incubations of sea ice brine at a temperature (-7°C-7^\circ\hbox{C}) and salinity (
110 \permille110 \permille) approximating that in situ. Median predicted virus-to-bacteria contact rates (relative to underlying seawater) were greatest
in the top of thick sea ice (66–78 cm: 130×) and lowest in the bottom of medium-thickness ice (33–37 cm: 23×). The great abundance
of viruses and more frequent interactions between bacteria and viruses predicted in sea ice relative to underlying seawater
suggest that sea ice may be a hot spot for virally mediated horizontal gene transfer in the polar marine environment. 相似文献
2.
Klaus Martin Meiners S. Papadimitriou D. N. Thomas L. Norman G. S. Dieckmann 《Polar Biology》2009,32(7):1055-1065
Physical, biogeochemical and photosynthetic parameters were measured in sea ice brine and ice core bottom samples in the north-western
Weddell Sea during early spring 2006. Sea ice brines collected from sackholes were characterised by cold temperatures (range
−7.4 to −3.8°C), high salinities (range 61.4–118.0), and partly elevated dissolved oxygen concentrations (range 159–413 μmol kg−1) when compared to surface seawater. Nitrate (range 0.5–76.3 μmol kg−1), dissolved inorganic phosphate (range 0.2–7.0 μmol kg−1) and silicic acid (range 74–285 μmol kg−1) concentrations in sea ice brines were depleted when compared to surface seawater. In contrast, NH4
+ (range 0.3–23.0 μmol kg−1) and dissolved organic carbon (range 140–707 μmol kg−1) were enriched in the sea ice brines. Ice core bottom samples exhibited moderate temperatures and brine salinities, but high
algal biomass (4.9–435.5 μg Chl a l−1 brine) and silicic acid depletion. Pulse amplitude modulated fluorometry was used for the determination of the photosynthetic
parameters F
v/F
m, α, rETRmax and E
k. The maximum quantum yield of photosystem II, F
v/F
m, ranged from 0.101 to 0.500 (average 0.284 ± 0.132) and 0.235 to 0.595 (average 0.368 ± 0.127) in the sea ice internal and
bottom communities, respectively. The fluorometric measurements indicated medium ice algal photosynthetic activity both in
the internal and bottom communities of the sea ice. An observed lack of correlation between biogeochemical and photosynthetic
parameters was most likely due to temporally and spatially decoupled physical and biological processes in the sea ice brine
channel system, and was also influenced by the temporal and spatial resolution of applied sampling techniques. 相似文献
3.
Viral abundance, burst sizes, lytic production and temperate phage were investigated in land-fast ice at two sites in Prydz
Bay Antarctica (68°S, 77°E) between April and November 2008. Both ice cores and brine were collected. There was no seasonal
pattern in viral or bacterial numbers. Across the two sites virus abundances ranged between 0.5 × 105 and 5.1 × 105 viruses ml−1 in melted ice cores and 0.6 × 105–3.5 × 105 viruses ml−1 in brine, and bacterial abundances between 2.7 × 104 and 17.3 × 104 cells ml−1 in melted ice cores and 3.9 × 104–32.5 × 104 cells ml−1 in brine. Virus to bacterium ratios (VBR) showed a clear seasonal pattern in ice cores with lowest values in winter (range
1.2–20.8), while VBRs in brine were lower (0.2–4.9). Lytic viral production range from undetectable to 2.0 × 104 viruses ml−1 h−1 in ice cores with maximum rates in September and November. In brine maximum, lytic viral production occurred in November
(1.18 × 104 viruses ml−1 h−1). Low burst sizes were typical (3.94–4.03 viruses per bacterium in ice cores and 3.16–4.0 viruses per bacterium in brine)
with unusually high levels of visibly infected cells—range 40–50%. This long-term investigation revealed that viral activity
was apparent within the sea ice throughout its annual cycle. The findings are discussed within the context of limited data
available on viruses in sea ice. 相似文献
4.
We describe a model based on diffusion theory and the temperature-dependent mechanism of brine concentration in sea ice to argue that, if viruses partition with bacteria into sea-ice brine inclusions, contact rates between the two can be higher in winter sea ice than in seawater, increasing the probability of infection and possible virus production. To examine this hypothesis, we determined viral and bacterial concentrations in select winter sea-ice horizons using epifluorescence microscopy. Viral concentrations ranged from 1.6 to 82 x 10(6) ml(-1) of brine volume of the ice, with highest values in brines from coldest (-24 to -31 degrees C) ice horizons. Calculated virus-bacteria contact rates in underlying -1 degrees C seawater were similar to those in brines of -11 degrees C ice but up to 600 times lower than those in ice brines at or below -24 degrees C. We then incubated native bacterial and viral assemblages from winter sea ice for 8 days in brine at a temperature (-12 degrees C) and salinity ( approximately 160 psu) near expected in situ values, monitoring their concentrations microscopically. While different cores yielded different results, consistent with known spatial heterogeneity in sea ice, these experiments provided unambiguous evidence for viral persistence and production, as well as for bacterial growth, in -12 degrees C brine. 相似文献
5.
Antonio Pusceddu Antonio Dell’Anno Luigi Vezzulli Mauro Fabiano Vincenzo Saggiomo Stefano Cozzi Giulio Catalano Letterio Guglielmo 《Polar Biology》2009,32(3):337-346
We investigated organic carbon quantity and biochemical composition, prokaryotic abundance, biomass and carbon production
in the annual and platelet sea ice of Terra Nova Bay (Antarctica), as well as the downward fluxes of organic matter released
by melting ice during early spring. Huge amounts of biopolymeric C accumulated in the bottom layer of the ice column concomitantly
with the early spring increase in sympagic algal biomass. Such organic material, mostly accounted for by autotrophic biomass,
was characterised by a high food quality and was rapidly exported to the sea bottom during sea ice melting. Prokaryote abundance
(up to 1.3 × 109 cells L−1) and extracellular enzymatic activities (up to 24.3 μM h−1 for amino-peptidase activity) were extremely high, indicating high rates of organic C degradation in the bottom sea ice.
Despite this, prokaryote C production values were very low (range 5–30 ng C L−1 h−1), suggesting that most of the degraded organic C was not channelled into prokaryote biomass. In the platelet ice, we found
similar organic C concentrations, prokaryote abundance and biomass values and even higher extracellular enzymatic activities,
but values of prokaryote C production (range 800–4,200 ng C L−1 h−1) were up to three orders of magnitude higher than in the intact bottom sea ice. Additional field and laboratory experiments
revealed that the dissolved organic material derived from algae accumulating in the bottom sea ice significantly reduced prokaryote
C production, suggesting the presence of a potential allopathic control of sympagic algae on prokaryote growth.
This article belongs to a special topic: Five articles on Sea-ice communities in Terra Nova Bay (Ross Sea), coordinated by
L. Guglielmo and V. Saggiomo, appear in this issue of Polar Biology. The studies were conducted in the frame of the National
Program of Research in Antarctica (PNRA) of Italy. 相似文献
6.
Thomas A. Brown Simon T. Belt Beno?t Philippe Christopher J. Mundy Guillaume Mass�� Michel Poulin Michel Gosselin 《Polar Biology》2011,34(12):1857-1868
Variations in the concentrations of the sea ice diatom biomarker, IP25 (Ice Proxy with 25 carbon atoms), were measured in the bottom 10 cm of sea ice collected from the eastern Beaufort Sea and
Amundsen Gulf from January to June 2008, as part of the International Polar Year–Circumpolar Flaw Lead system study. Temporal
and vertical changes in IP25 concentrations were compared against other biomarkers and indicators of ice algal production. IP25 was not detected in sea ice samples collected from mid-winter to early spring, likely as a result of light-limiting conditions
for algal growth and accumulation. From early March to mid-June, IP25 concentrations correlated well with those of fatty acids (r = 0.79; P < 0.001), less so with total sterols (r = 0.63; P < 0.001) and qualitatively with chlorophyll a concentrations and diatom cell abundances from adjacent sea ice cores. Approximately 90% of the total sea ice IP25 accumulation occurred from mid-March to late-May, coincident with the ice algal bloom period. The majority (ca. 87–93%) of
IP25 was biosynthesised within the lower 5 cm of the sea ice where brine volume fractions were >5% which is consistent with the
hypothesis that brine channel connectivity limits the internal colonisation of sea ice by diatoms. Maximum IP25 concentrations occurred at 1–3 cm from the ice–water interface providing further evidence for a selective sea ice diatom
origin for this biomarker. In contrast, vertical concentration profiles for fatty acids and sterols indicated mixed sources
for these biomarkers. 相似文献
7.
Bodil A. Bluhm Haakon Hop Mikko Vihtakari Rolf Gradinger Katrin Iken Igor A. Melnikov Janne E. Søreide 《Ecology and evolution》2018,8(4):2350-2364
Arctic sea ice provides microhabitats for biota that inhabit the liquid‐filled network of brine channels and the ice–water interface. We used meta‐analysis of 23 published and unpublished datasets comprising 721 ice cores to synthesize the variability in composition and abundance of sea ice meiofauna at spatial scales ranging from within a single ice core to pan‐Arctic and seasonal scales. Two‐thirds of meiofauna individuals occurred in the bottom 10 cm of the ice. Locally, replicate cores taken within meters of each other were broadly similar in meiofauna composition and abundance, while those a few km apart varied more; 75% of variation was explained by station. At the regional scale (Bering Sea first‐year ice), meiofauna abundance varied over two orders of magnitude. At the pan‐Arctic scale, the same phyla were found across the region, with taxa that have resting stages or tolerance to extreme conditions (e.g., nematodes and rotifers) dominating abundances. Meroplankton, however, was restricted to nearshore locations and landfast sea ice. Light availability, ice thickness, and distance from land were significant predictor variables for community composition on different scales. On a seasonal scale, abundances varied broadly for all taxa and in relation to the annual ice algal bloom cycle in both landfast and pack ice. Documentation of ice biota composition, abundance, and natural variability is critical for evaluating responses to decline in Arctic sea ice. Consistent methodology and protocols must be established for comparability of meiofauna monitoring across the Arctic. We recommend to (1) increase taxonomic resolution of sea ice meiofauna, (2) focus sampling on times of peak abundance when seasonal sampling is impossible, (3) include the bottom 30 cm of ice cores rather than only bottom 10 cm, (4) preserve specimens for molecular analysis to improve taxonomic resolution, and (5) formulate a trait‐based framework that relates to ecosystem functioning. 相似文献
8.
The distributions of bacterial populations in sea ice and underlying seawater were investigated on the continental shelf of
the “Terre Adélie” area. A reference station was sampled weekly from January 1991 to January 1992. In winter, the survey included
a minimum of six sampling layers: surface and bottom ice, brine, seawater from the interface, and at 0.5 and 2 m depth. In
seawater, the total bacterial abundance ranged from 0.5 × 105 cells ml−1 in July to 6.0 × 105 cells ml−1 after ice break. Values reaching 2.5 × 106 cells ml−1 were recorded in the overlying ice cover. Mean cell volumes were twice as high in brine as in seawater. The saprophytic bacterial
abundance ranged from 5.0 × 104 CFU (colony-forming units) ml−1 in some winter interface samples to less than 1.0 × 103 CFU ml−1 in most of the summer seawater samples. In sea ice a clear decreasing gradient for most of the studied bacterial parameters
from the surface layers towards the bottom layer was found. The ice cover had a discernible impact on underlying seawater,
but its influence was restricted to a limited interface layer. 相似文献
9.
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
10.
Photosynthetic parameters of phytoplankton and sea ice algae from landfast sea ice of the Chukchi Sea off Point Barrow, Alaska,
were assessed in spring 2005 and winter through spring 2006 using Pulse Amplitude Modulated (PAM) fluorometry including estimates
of maximum quantum efficiency (F
v/F
m), maximum relative electron transport rate (rETRmax), photosynthetic efficiency (α), and the photoadaptive index (E
k). The use of centrifuged brine samples allowed to document vertical gradients in ice algal acclimation with 5 cm vertical
resolution for the first time. Bottom ice algae (0–5 cm from ice–water interface) expressed low F
v/F
m (0.331–0.426) and low α (0.098–0.130 (μmol photons m−2s−1)−1) in December. F
v/F
m and α increased in March and May (0.468–0.588 and 0.141–0.438 (μmol photons m−2s−1)−1, respectively) indicating increased photosynthetic activity. In addition, increases in rETRmax (3.3–16.4 a.u.) and E
k (20–88 μmol photons m−2 s−1) from December to May illustrates a higher potential for primary productivity as communities become better acclimated to
under-ice light conditions. In conclusion, photosynthetic performance by ice algae (as assessed by PAM fluorometry) was tightly
linked to sea ice salinity, temperature, and inorganic nutrient concentrations (mainly nitrogen). 相似文献
11.
Haakon Hop Christopher J. Mundy Michel Gosselin Andrea L. Rossnagel David G. Barber 《Polar Biology》2011,34(12):1947-1958
Early summer in the Arctic with extensive ice melt and break-up represents a dramatic change for sympagic–pelagic fauna below
seasonal sea ice. As part of the International Polar Year-Circumpolar Flaw Lead system study (IPY-CFL), this investigation
quantified zooplankton in the meltwater layer below landfast ice and remaining ice fauna below melting ice during June (2008)
in Franklin Bay and Darnley Bay, Amundsen Gulf, Canada. The ice was in a state of advanced melt, with fully developed melt
ponds. Intense melting resulted in a 0.3- to 0.5-m-thick meltwater layer below the ice, with a strong halocline to the Arctic
water below. Zooplankton under the ice, in and below the meltwater layer, was sampled by SCUBA divers. Dense concentrations
(max. 1,400 ind. m−3) of Calanus glacialis were associated with the meltwater layer, with dominant copepodid stages CIV and CV and high abundance of nauplii. Less abundant
species included Pseudocalanus spp., Oithona similis and C. hyperboreus. The copepods were likely feeding on phytoplankton (0.5–2.3 mg Chl-a m−3) in the meltwater layer. Ice amphipods were present at low abundance (<10 ind. m−2) and wet biomass (<0.2 g m−2). Onisimus glacialis and Apherusa glacialis made up 64 and 51% of the total ice faunal abundance in Darnley Bay and Franklin Bay, respectively. During early summer,
the autochthonous ice fauna becomes gradually replaced by allochthonous zooplankton, with an abundance boom near the meltwater
layer. The ice amphipod bust occurs during late stages of melting and break-up, when their sympagic habitat is diminished
then lost. 相似文献
12.
Effects of Incubation Temperature on Growth and Production of Exopolysaccharides by an Antarctic Sea Ice Bacterium Grown in Batch Culture 总被引:3,自引:0,他引:3 下载免费PDF全文
The sea ice microbial community plays a key role in the productivity of the Southern Ocean. Exopolysaccharide (EPS) is a major component of the exopolymer secreted by many marine bacteria to enhance survival and is abundant in sea ice brine channels, but little is known about its function there. This study investigated the effects of temperature on EPS production in batch culture by CAM025, a marine bacterium isolated from sea ice sampled from the Southern Ocean. Previous studies have shown that CAM025 is a member of the genus Pseudoalteromonas and therefore belongs to a group found to be abundant in sea ice by culture-dependent and -independent techniques. Batch cultures were grown at −2°C, 10°C, and 20°C, and cell number, optical density, pH, glucose concentration, and viscosity were monitored. The yield of EPS at −2°C and 10°C was 30 times higher than at 20°C, which is the optimum growth temperature for many psychrotolerant strains. EPS may have a cryoprotective role in brine channels of sea ice, where extremes of high salinity and low temperature impose pressures on microbial growth and survival. The EPS produced at −2°C and 10°C had a higher uronic acid content than that produced at 20°C. The availability of iron as a trace metal is of critical importance in the Southern Ocean, where it is known to limit primary production. EPS from strain CAM025 is polyanionic and may bind dissolved cations such at trace metals, and therefore the presence of bacterial EPS in the Antarctic marine environment may have important ecological implications. 相似文献
13.
Shazia N. Aslam Graham J. C. Underwood Hermanni Kaartokallio Louiza Norman Riitta Autio Michael Fischer Harri Kuosa Gerhard S. Dieckmann David N. Thomas 《Polar Biology》2012,35(5):661-676
Extracellular polymeric substances (EPS) are known to help microorganisms to survive under extreme conditions in sea ice.
High concentrations of EPS are reported in sea ice from both poles; however, production and dynamics of EPS during sea ice
formation have been little studied to date. This investigation followed the production and partitioning of existing and newly
formed dissolved organic matter (DOM) including dissolved carbohydrates (dCHO), dissolved uronic acids (dUA) and dissolved
EPS (dEPS), along with bacterial abundances during early stages of ice formation. Sea ice was formed from North Sea water
with (A) ambient DOM (NSW) and (B) with additional algal-derived DOM (ADOM) in a 6d experiment in replicated mesocosms. In
ADOM seawater, total bacterial numbers (TBN) increased throughout the experiment, whereas bacterial growth occurred for 5d
only in the NSW seawater. TBN progressively decreased within developing sea ice but with a 2-fold greater decline in NSW compared
to ADOM ice. There were significant increases in the concentrations of dCHO in ice. Percentage contribution of dEPS was highest
(63%) in the colder, uppermost parts in ADOM ice suggesting the development of a cold-adapted community, producing dEPS possibly
for cryo-protection and/or protection from high salinity brines. We conclude that in the early stages of ice formation, allochthonous
organic matter was incorporated from parent seawater into sea ice and that once ice formation had established, there were
significant changes in the concentrations and composition of dissolved organic carbon pool, resulting mainly from the production
of autochthonous DOM by the bacteria. 相似文献
14.
Nathalie Fenner Robert Williams Hannah Toberman Steve Hughes Brian Reynolds Chris Freeman 《Hydrobiologia》2011,665(1):51-66
The hypothesis that specific components of seawater, such as particulate, dissolved and colloidal organic and inorganic material,
render virions non-infective has long been postulated, but never rigorously tested. To address this hypothesis, the plaque
assay method was used to derive infective decay rates, k, of two bacteriophages—P1 (marine host: PWH3a) and T4 (enteric host: E. coli B). We compared k values of bacteriophage suspended in serial filtrations of seawater, with and without autoclaving and UV oxidation. Both
phages exhibited reduced decay rates in particle-free water (<0.2 μm) compared to <10 μm filtrate. The largest decrease in
virion decay rates was achieved by autoclaving the 0.2 μm filtrate. UV oxidation of <0.2 μm filtrate, however, yielded higher
decay rates than observed in autoclaved treatments. The lowest k values were seen in ultra-filtered seawater (<10 kDa). Exposure to a wide range of concentrations of Pronase E (a proteolytic
enzyme), inorganic clay (kaolinite or montmorillonite), and organic particles (phytoplankton debris) did not promote phage
inactivation. P1 infective titers were also not consistently reduced by exposures to axenic cultures of a resistant host mutant
(PWH3a-R) and a non-host marine bacterium (MB-5). Finally, phage were exposed to a range of temperatures to derive activation
energies required for phage inactivation. Application of the Arrhenius model to inactivation of T4 and P1 yielded activation
energies (E
a) of 49 and 40 kJ mol−1, respectively. This is the first comprehensive analysis in which specific seawater components were assayed for their ability
to inactivate bacteriophage. Inactivation of these phage does not appear to depend on capsomere denaturation, proteolytic
extracellular enzymes, sorption to non-host bacteria, clay particles or particulate organic debris, but is accelerated by
naturally occurring particles, which include living organisms, and heat-labile colloids and macromolecules >10 kDa. 相似文献
15.
Summary The amphipod Gammarus wilkitzkii does not survive being frozen totally into solid sea ice. When the animals are cooled in air or freezing seawater, they will freeze and die at a temperature of about-4° C. However, during sea ice growth, the amphipods may tolerate to stay in the vicinity of the ice by conforming to the ambient brine in a salinity range of 34 ppt to about 60 ppt. A passive relationship between the concentrations of the haemolymph and seawater Na+ and Cl-, lowers the melting point of the body fluids of the animals, thus preventing internal ice formation at low temperatures. 相似文献
16.
Effects of incubation temperature on growth and production of exopolysaccharides by an antarctic sea ice bacterium grown in batch culture 总被引:1,自引:0,他引:1
The sea ice microbial community plays a key role in the productivity of the Southern Ocean. Exopolysaccharide (EPS) is a major component of the exopolymer secreted by many marine bacteria to enhance survival and is abundant in sea ice brine channels, but little is known about its function there. This study investigated the effects of temperature on EPS production in batch culture by CAM025, a marine bacterium isolated from sea ice sampled from the Southern Ocean. Previous studies have shown that CAM025 is a member of the genus Pseudoalteromonas and therefore belongs to a group found to be abundant in sea ice by culture-dependent and -independent techniques. Batch cultures were grown at -2 degrees C, 10 degrees C, and 20 degrees C, and cell number, optical density, pH, glucose concentration, and viscosity were monitored. The yield of EPS at -2 degrees C and 10 degrees C was 30 times higher than at 20 degrees C, which is the optimum growth temperature for many psychrotolerant strains. EPS may have a cryoprotective role in brine channels of sea ice, where extremes of high salinity and low temperature impose pressures on microbial growth and survival. The EPS produced at -2 degrees C and 10 degrees C had a higher uronic acid content than that produced at 20 degrees C. The availability of iron as a trace metal is of critical importance in the Southern Ocean, where it is known to limit primary production. EPS from strain CAM025 is polyanionic and may bind dissolved cations such at trace metals, and therefore the presence of bacterial EPS in the Antarctic marine environment may have important ecological implications. 相似文献
17.
Microscale photographs were taken of the ice bottom to examine linkages of algal chlorophyll a (chl a) biomass distribution with bottom ice features in thick Arctic first-year sea ice during a spring field program which took
place from May 5 to 21, 2003. The photographic technique developed in this paper has resulted in the first in situ observations
of microscale variability in bottom ice algae distribution in Arctic first-year sea ice in relation to ice morphology. Observations
of brine channel diameter (1.65–2.68 mm) and number density (5.33–10.35 per 100 cm2) showed that the number of these channels at the bottom of thick first-year sea ice may be greater than previously measured
on extracted ice samples. A variogram analysis showed that over areas of low chl a biomass (≤20.7 mg chl a m−2), patchiness in bottom ice chl a biomass was at the scale of brine layer spacing and small brine channels (∼1–3 mm). Over areas of high chl a biomass (≥34.6 mg chl a m−2), patchiness in biomass was related to the spacing of larger brine channels on the ice bottom (∼10–26 mm). Brine layers and
channels are thought to provide microscale maxima of light, nutrient replenishment and space availability which would explain
the small scale patchiness over areas of low algal biomass. However, ice melt and erosion near brine channels may play a more
important role in areas with high algal biomass and low snow cover. 相似文献
18.
D. Lannuzel V. Schoemann I. Dumont M. Content J. de Jong J.-L. Tison B. Delille S. Becquevort 《Polar Biology》2013,36(10):1483-1497
Although algal growth in the iron-deficient Southern Ocean surface waters is generally low, there is considerable evidence that winter sea ice contains high amounts of iron and organic matter leading to ice-edge blooms during austral spring. We used field observations and ship-based microcosm experiments to study the effect of the seeding by sea ice microorganisms, and the fertilization by organic matter and iron on the planktonic community at the onset of spring/summer in the Weddell Sea. Pack ice was a major source of autotrophs resulting in a ninefold to 27-fold increase in the sea ice-fertilized seawater microcosm compared to the ice-free seawater microcosm. However, heterotrophs were released in lower numbers (only a 2- to 6-fold increase). Pack ice was also an important source of dissolved organic matter for the planktonic community. Small algae (<10 μm) and bacteria released from melting sea ice were able to thrive in seawater. Field observations show that the supply of iron from melting sea ice had occurred well before our arrival onsite, and the supply of iron to the microcosms was therefore low. We finally ran a “sequential melting” experiment to monitor the release of ice constituents in seawater. Brine drainage occurred first and was associated with the release of dissolved elements (salts, dissolved organic carbon and dissolved iron). Particulate organic carbon and particulate iron were released with low-salinity waters at a later stage. 相似文献
19.
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
20.
W. S. Reeburgh 《Polar Biology》1984,3(1):29-33
Summary Laboratory and field studies have demonstrated that fluid motion occurs at two locations in growing sea ice: in a network of brine channels and within the skeletal layer at the ice-water interface. Brine channel fluxes estimated using brine channel areal density from natural sea ice and channel velocities from laboratory studies are compared with recent measurements reported in the literature. Fluxes into the porous skeletal layer of sea ice may be estimated using rates of nutrient uptake by ice algae and adjacent seawater nutrient concentrations. Both approaches indicate fluxes of the order of 10-6 cc cm-2 s-1 (l m-2 h-1), which are about equal to fluxes reported in bioirrigated sediments. Fluxes of this magnitude indicate a very short residence time for the liquid phase in the skeletal layer, suggesting that this fluid motion may be important in maintaining the ice algae community. 相似文献