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1.
It has been proposed that metal cyanide complexes would have acted as effective prebiotic catalysts. Insoluble metal cyanide
complexes could have concentrated biomonomers from the dilute prebiotic soup, facilitating certain prebiotic reactions. In
the light of the above hypothesis, interaction of four ribonucleotides, namely 5′-AMP, 5′-GMP, 5′-CMP, and 5′-UMP with copper(II)-
and cadmium(II) hexacyanocobaltate(III) has been studied. The interaction was found to be maximum at neutral pH. 5′-GMP showed
greater interaction with both the metal hexacyanocobaltate(III) while copper(II) hexacyanocobaltate(III) showed greater uptake
than cadmium(II) hexacyanocobaltate(III) for all the four ribonucleotides studied. Infrared spectral studies of ribonucleotides,
metal hexacyanocobaltate(III) and ribonucleotide – metal hexacyanocobaltate(III) adducts indicated that the nitrogen base
and phosphate moiety of ribonucleotides interact with outer divalent metal ion present in the lattice of metal hexacyanocobaltate(III). 相似文献
2.
Molecular aggregation of nucleotides and carbohydrates—their implication to prebiotic polymerization
Hydrogen bonding pattern of nucleotides and carbohydrates has been analysed using Cambridge database. An analysis on ribonucleotides
shows the 3′ …5′ hydrogen bond mediated aggregation to be the most common alignment. The 2′ …5′ alignment, which occurs under
special circumstances in nature, is found to be the second choice. An analysis on carbohydrates suggests that self assembly
of these molecules is not conducive to the formation of polysaccharides of the type which are found in present day living
organisms. Further, the role of water molecules in the polymerization of three important biomolecules, namely nucleotides,
carbohydrates and amino acids, has been analysed. Implication of these results to prebiotic polymerization is discussed
DCB contribution No. 804. 相似文献
3.
The sub-ice algal community in the Chukchi sea: large- and small-scale patterns of abundance based on images from a remotely operated vehicle 总被引:1,自引:0,他引:1
William G. Ambrose Jr Cecilie von Quillfeldt Lisa M. Clough Peter V. R. Tilney Terry Tucker 《Polar Biology》2005,28(10):784-795
We examined the sub-ice algal community in the Chukchi Sea during June 1998 using a remotely operated vehicle (ROV). Ice algae
were observed on the under-ice surface at all ten stations (from 70°29′N to 72°26′N; 162°00′W to 153°56′W) and varied in abundance
and distribution from small aggregations limited to depressions in the ice to nets, curtains and strands of Melosira. There was no relationship between percent cover of sub-ice algae and physical factors at the kilometer scale, but at the
scale of individual ice floes the percent cover of sub-ice algae was positively correlated with distance from the floe edge
and negatively correlated with snow depth. A significant positive relationship between the concentration of sediment pigments
and percent cover of sub-ice could indicate a coupling between ice algal and benthic systems. Pieces of ice algae that appeared
to be Melosira were observed on the seafloor to a depth of over 100 m and cells or spores of obligate ice algal taxa were collected from
sediments from 44-m to 1,000-m deep. The large biomass of sub-ice algae observed at many stations in the Chukchi Sea and the
presence of ice algae on the seafloor indicates that the distribution and abundance of sub-ice algae needs to be understood
if we are to evaluate the role of ice algae in the Arctic marine ecosystem. 相似文献
4.
Bacterial carbon demand, an important component of ecosystem dynamics in polar waters and sea ice, is a function of both bacterial
production (BP) and respiration (BR). BP has been found to be generally higher in sea ice than underlying waters, but rates
of BR and bacterial growth efficiency (BGE) are poorly characterized in sea ice. Using melted ice core incubations, community
respiration (CR), BP, and bacterial abundance (BA) were studied in sea ice and at the ice–water interface (IWI) in the Western
Canadian Arctic during the spring and summer 2008. CR was converted to BR empirically. BP increased over the season and was
on average 22 times higher in sea ice as compared with the IWI. Rates in ice samples were highly variable ranging from 0.2
to 18.3 μg C l−1 d−1. BR was also higher in ice and on average ~10 times higher than BP but was less variable ranging from 2.39 to 22.5 μg C l−1 d−1. Given the high variability in BP and the relatively more stable rates of BR, BP was the main driver of estimated BGE (r
2 = 0.97, P < 0.0001). We conclude that microbial respiration can consume a significant proportion of primary production in sea ice and
may play an important role in biogenic CO2 fluxes between the sea ice and atmosphere. 相似文献
5.
Da Xiong Han Hai Yan Wang Zhi Liang Ji An Fu Hu Yu Fen Zhao 《Journal of molecular evolution》2010,70(6):572-582
Phosphorylation has to have been one of the key events in prebiotic evolution on earth. In this article, the emergence of
phosphoryl amino acid 5′-nucleosides having a P–N bond is described as a model of the origin of amino acid homochirality and
Genetic Code. It is proposed that the intramolecular interaction between the nucleotide base and the amino acid side-chain
influences the stability of particular amino acid 5′-nucleotides, and the interaction also selects for the chirality of amino
acids. The differences between l- and d-conformation energies (ΔE
conf) are evaluated by DFT methods at the B3LYP/6-31G(d) level. Although, as expected, these ΔE
conf values are not large, they do give differences in energy that can distinguish the chirality of amino acids. Based on our
calculations, the chiral selection of the earliest amino acids for l-enantiomers seems to be determined by a clear stereochemical/physicochemical relationship. As later amino acids developed
from the earliest amino acids, we deduce that the chirality of these late amino acids was inherited from that of the early
amino acids. This idea reaches far back into evolution, and we hope that it will guide further experiments in this area. 相似文献
6.
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
7.
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
8.
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
9.
Kristin Laidre Mads Peter Heide-J?rgensen Harry Stern Pierre Richard 《Polar Biology》2012,35(1):149-154
Sea ice entrapments of narwhals (Monodon monoceros) occur when rapid changes in weather and wind conditions create a formation of fast ice in bays or passages used by whales.
Between 2008 and 2010, four entrapments of narwhals were reported in Canada and Greenland. In each case, large groups (40–600
individuals) succumbed in the sea ice at three separate summering localities, two of these where entrapments had never before
been reported. We examined long-term trends in autumn freeze-up timing (date when sea ice concentration rises above some threshold)
on the 6 largest narwhal summering areas using sea ice concentration from satellite passive microwave data (1979–2009). We
found strongly positive and significant trends (P < 0.001) in progressively later dates of autumn freeze-up in all summering areas. Autumn freeze-up occurs between 0.5 and
1 day later per year, or roughly 2–4 weeks later, over the 31-year time series. This indicates that sea ice conditions on
narwhal summering areas are changing rapidly. The question remains whether entrapment events on summering areas are random
or whether narwhals are adapting to changes in sea ice freeze-up by prolonging their summer residence time. 相似文献
10.
Roopesh M. Syamaladevi Kalehiwot N. Manahiloh Balasingam Muhunthan Shyam S. Sablani 《Food biophysics》2012,7(1):57-71
Temperature fluctuations during storage and distribution of frozen foods lead to ice recrystallization and microstructural
modifications that can affect food quality. Low temperature transitions may occur in frozen foods due to temperature fluctuations,
resulting in less viscous and partially melted food matrices. This study systematically investigated the influence of state/phase
transitions and temperature fluctuations on ice recrystallization during the frozen storage of salmon fillets. Using a modulated
differential scanning calorimeter, we identified the characteristics glass transition temperature (T
g
′) of −27 °C and the onset temperature for ice crystal melting (T
m
′) of −17 °C in salmon. The temperature of salmon fillets in sealed plastic trays was lowered to −35 °C in a freezer to achieve
the glassy state. The temperature (T) of frozen salmon fillets in sealed plastic trays was modulated to achieve a rubbery state (T > T
m
′), a partially freeze-concentrated state (T
g
′ < T < T
m
′) and a glassy state (T < T
g
′). We performed temperature modulation experiments by exposing packaged salmon to room temperature twice a day for 2 to 26 min
during 4 weeks of storage. We also analyzed ice crystal morphology using environmental scanning electron microscopy and X-ray
computed tomography techniques to observe the pore distribution after sublimation of ice crystals. Melt–refreeze and isomass
rounding mechanisms of ice recrystallization were noticed in the frozen salmon subjected to temperature modulations. Results
show that ice crystal growth occurred even in the glassy state of frozen salmon during storage, with or without temperature
fluctuations. Ice crystal size in frozen salmon was greater in the rubbery state (T > T
m
′) due to the increased mobility of unfrozen water compared to the glassy state. The morphological/geometric parameters of
ice crystals in frozen salmon stored for 1 month differed significantly from those in 0-day storage. These findings are important
to the frozen food industry because they can help optimize storage and distribution conditions and minimize quality loss of
frozen salmon due to recrystallization. 相似文献
11.
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
12.
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
13.
Microorganisms in a high altitude Glacier Ice in Tibet 总被引:3,自引:0,他引:3
Eighty-one strains of viable microorganisms were recovered from 23 samples collected from Ice Core 3 of Malan Glacier (China,
91° 45.3′ E, 35° 48.4′ N) drilled at high altitude (5620 m). All the strains were prokaryotes—75 of bacteria (including spore-forming
ones) and 6 of actinomycetes. The characteristic genera differ from those of Arctic and Antarctic ice, in which many fungi
and algae are widely distributed; this shows an difference of environmental conditions between Tibet and polar regions. The
variation in number and species ofBacillus in different ice core layers implied changes of environmental conditions in the past. 相似文献
14.
The porous medium of sea ice, a surface-rich environment characterized by low temperature and high salinity, has been proposed
as a favorable site for horizontal gene transfer, but few measurements are available to assess the possibility of this mode
of evolution in ice. Here, we report the first measurements of dissolved DNA in sea ice, measured by fluorescent dye staining
of centrifugal-filter-concentrated samples of melted ice. Newly formed landfast and pack ice on the Canadian Arctic Shelf
(ca. 71°N, 125°W) contained higher concentrations (scaled to volume of brine) of the major components of dissolved DNA—extracellular
DNA and viruses—than the underlying seawater. Dissolved DNA was dominated by extracellular DNA in surface seawater (up to
95%), with viruses making up relatively larger fractions at depths below 100 m (up to 27%) and in thick sea ice (66–78 cm;
up to 100%). Extracellular DNA was heterogeneously distributed, with concentrations up to 135 μg DNA L−1 brine detected in landfast sea ice, higher than previously reported from any marine environment. Additionally, extracellular
DNA was significantly highly enriched at the base of ice of medium thickness (33–37 cm), suggestive of in situ production.
Relative to underlying seawater, higher concentrations of extracellular DNA, viruses, and bacteria, and the availability of
numerous surfaces for attachment within the ice matrix suggest that sea ice may be a hotspot for HGT in the marine environment. 相似文献
15.
The impact of sea ice on the initiation of the spring bloom on the Newfoundland and Labrador Shelves
Wu Yongsheng; Peterson Ingrid K.; Tang Charles C. L.; Platt Trevor; Sathyendranath Shubha; Fuentes-Yaco Cesar 《Journal of plankton research》2007,29(6):509-514
The relationship between sea ice and the phytoplankton springbloom over the Newfoundland and Labrador shelves is examinedusing remotely-sensed chlorophyll data and sea-ice data forthe period 19982004. A regression analysis between thetwo data sets shows that the retreat of sea ice precedes thespring bloom, and the inter-annual variation of the spring bloomis closely correlated with the start time of ice retreat. Thespring bloom off Canada's east coast usually starts on the easternGrand Banks. Here, the water properties are strongly influencedby sea ice on the Newfoundland shelves in early spring whenaccelerated ice melting causes the ice edge to retreat northand the melt water is advected south by the Labrador Current.After the ice retreat, the water on the eastern Grand Banksis rapidly stratified and the mixed layer shallows as a resultof surface freshening. The shallow mixed layer promotes phytoplanktongrowth. The regression analysis also reveals that an early springbloom or ice retreat tends to prolong the duration of the springbloom. 相似文献
16.
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
17.
Ben Raymond K. Meiners C. W. Fowler B. Pasquer G. D. Williams S. Nicol 《Polar Biology》2009,32(3):443-452
We present a computational model of the large-scale cumulative light exposure of sea ice in the Southern Ocean off East Antarctica
(30°E–150°E). The model uses remotely sensed or modelled sea ice concentration, snow depth over sea ice, and solar irradiance
data, and tracks sea ice motion over the season of interest in order to calculate the cumulative exposure of the ice field
to photosynthetically active radiation (PAR). Light is the limiting factor to sea ice algal growth over winter and early spring,
and so the results have implications for the estimation of algal biomass in East Antarctica. The model results indicate that
highly light-exposed ice is restricted to within a few degrees of the coast in the eastern part of the study region, but extends
much further north in the 30°E–100°E sector. The relative influences of sea ice motion, solar flux, and snow depth variations
on interannual variations in model predictions were evaluated. The model estimates of cumulative PAR were found to correlate
with satellite estimates of subsequent open-water chlorophyll-a concentration, consistent with the notion that sea ice algae can provide inocula for phytoplankton blooms. 相似文献
18.
Summer plankton beneath the McMurdo Ice Shelf at white Island,McMurdo Sound,Antarctica 总被引:3,自引:3,他引:0
The zooplankton of the under-shelf-ice ecosystem at White Island (78°10′ S, 167°30′ E), McMurdo Sound, Antarctica was investigated during December 1976 and January 1977. The water column was sampled through
a hole in the McMurdo Ice Shelf over a water depth of 67 m. Seawater temperatures under the ice shelf ranged from −1.91 to
1.96°C. Dissolved oxygen levels ranged from 5.0–6.05 ml l-1 in early December to 4.65–4.8 ml l-1 in late January. Current speeds of up to 0.13 m s-1 were recorded at a depth of 50 m and a predominantly northward flow was detected. Light levels under the shelf ice were low
with less than 1% of the incident light being transmitted to a depth of 3 m. No chlorophyll a was detected within the water column throughout the investigation. Mean zooplankton biomass values in the water column ranged
from 12 to 447 mg wet weight m-3 and were similar to values recorded elsewhere from Antarctic inshore waters, but were very much higher than those recorded
from under seasonal sea ice in McMurdo Sound. Thirty-two zooplankton species were recorded including 1 ostracod, 21 copepods
(10 calanoids, 3 cyclopoids and 8 harpacticoids), 4 amphipods, 2 euphausiids, a chaetognath and 3 pteropods. Larvae of polychaetes
and fish were found on some occasions. The species composition in general was similar to that recorded from McMurdo Sound
and other Antarctic inshore localities. Among the Copepoda, however, there were a number of species, especially among the
Harpacticoidea, that have not been found previously in McMurdo Sound and the Ross Sea, but that are known to be associated
with ice in other localities in Antarctica. Two recently described species are known only from White Island. They were present
in the water column but were most abundant in the surface water of the tide crack where they were the most abundant zooplankters.
The tide crack, which probably is an extension of the under-ice habitat, is apparently a significant nursery area for amphipods
and copepod species.
Received: 23 November 1994/Accepted 7 May 1995 相似文献
19.
Henry R. Scharf Mevin B. Hooten Ryan R. Wilson George M. Durner Todd C. Atwood 《Biometrics》2019,75(3):810-820
The analysis of animal tracking data provides important scientific understanding and discovery in ecology. Observations of animal trajectories using telemetry devices provide researchers with information about the way animals interact with their environment and each other. For many species, specific geographical features in the landscape can have a strong effect on behavior. Such features may correspond to a single point (eg, dens or kill sites), or to higher dimensional subspaces (eg, rivers or lakes). Features may be relatively static in time (eg, coastlines or home‐range centers), or may be dynamic (eg, sea ice extent or areas of high‐quality forage for herbivores). We introduce a novel model for animal movement that incorporates active selection for dynamic features in a landscape. Our approach is motivated by the study of polar bear (Ursus maritimus) movement. During the sea ice melt season, polar bears spend much of their time on sea ice above shallow, biologically productive water where they hunt seals. The changing distribution and characteristics of sea ice throughout the year mean that the location of valuable habitat is constantly shifting. We develop a model for the movement of polar bears that accounts for the effect of this important landscape feature. We introduce a two‐stage procedure for approximate Bayesian inference that allows us to analyze over 300 000 observed locations of 186 polar bears from 2012 to 2016. We use our model to estimate a spatial boundary of interest to wildlife managers that separates two subpopulations of polar bears from the Beaufort and Chukchi seas. 相似文献
20.
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