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1.
Relatively little is known about the distribution of fish in deep water (>200 m) in the Beaufort Sea. Data collected by an
Acoustic Doppler Current Profiler operated in the Chukchi and Beaufort seas in summer were examined for evidence of fish biomass
detections between 18 and 400 m. The presence of fish in waters between 1 and 30 m was explored opportunistically with a non-scientific
echo sounder. Evaluation of findings was enhanced by measurements of water column properties (temperature, salinity, fluorescence
and transmissivity). Relatively small shoals of fish were detected on the Chukchi shelf and eastern Chukchi shelf break, and
also on the Alaskan and Canadian Beaufort shelves in the upper 20 m (T = 2–5°C). Much larger shoals (putative polar cod) were detected within Atlantic Water along the Beaufort continental slope
(250–350 m) and near the bottom of Barrow and Mackenzie canyons, where temperatures were above 0°C. A warm-water plume of
Alaska Coastal Current water with high concentrations of phytoplankton, zooplankton, and fish was found extending along the
shelf 300 km eastward of Barrow Canyon. In contrast to the warm surface and Atlantic Water layers, very few fish were found
in colder, intermediate depth Pacific-origin water between them. The large biomass of fish in the Atlantic Water along the
continental slope of the Chukchi and Beaufort seas represents previously undescribed polar cod habitat. It has important implications
with regard to considerations of resource development in this area as well as understanding impacts of climate change. 相似文献
2.
Reference conditions for phytoplankton at Danish Water Framework Directive intercalibration sites 总被引:2,自引:2,他引:0
Peter Henriksen 《Hydrobiologia》2009,629(1):255-262
Phytoplankton is one of the biological quality elements included in the EU Water Framework Directive (WFD). Classification
of water quality according to the WFD is based on the deviation of the present conditions from reference conditions. Given
the lack of data from pristine conditions, this study used approximately 100-year-old measurements of Secchi depths from Danish
waters in combination with relationships between Secchi depth and chlorophyll a (as a proxy for phytoplankton biomass) obtained from recent monitoring to calculate ‘historical’ or reference chlorophyll
a (Chl-a) concentrations. Historical Secchi depth data were available for 9 out of the 11 Danish WFD intercalibration sites. At eight
of the sites, reference summer (May–September) Chl-a concentrations were in the range 0.7–1.2 μg l−1. At one site, west of Bornholm in the western Baltic Sea, historical Secchi depth measurements date back to only the late
1950s corresponding to a calculated Chl-a concentration of 1.3 μg l−1. This value cannot be considered representative of reference conditions.
Guest editors: J. H. Andersen & D. J. Conley
Eutrophication in Coastal Ecosystems: Selected papers from the Second International Symposium on Research and Management of
Eutrophication in Coastal Ecosystems, 20–23 June 2006, Nyborg, Denmark 相似文献
3.
The algal, protozoan and metazoan communities within different drift-ice types (newly formed, pancake and rafted ice) and
in under-ice water were studied in the Gulf of Bothnia in March 2006. In ice, diatoms together with unidentified flagellates
dominated the algal biomass (226 ± 154 μg ww l−1) and rotifers the metazoan and protozoan biomass (32 ± 25 μg ww l−1). The under-ice water communities were dominated by flagellates and ciliates, which resulted in lower biomasses (97 ± 25
and 21 ± 14 μg ww l−1, respectively). The under-ice water and newly formed ice separated from all other samples to their own cluster in hierarchical
cluster analysis. The most important discriminating factors, according to discriminant analysis, were chlorophyll-a, phosphate and silicate. The under-ice water/newly formed ice cluster was characterized by high nutrient and low chlorophyll-a values, while the opposite held true for the ice cluster. Increasing trends in chlorophyll-a concentration and biomass were observed with increasing ice thickness. Within the thick ice columns (>40 cm), the highest
chlorophyll-a concentrations (6.6–22.2 μg l−1) were in the bottom layers indicating photoacclimation of the sympagic community. The ice algal biomass showed additional
peaks in the centric diatom-dominated surface layers coinciding with the highest photosynthetic efficiencies [0.019–0.032 μg C (μg Chl-a
−1 h−1) (μE m−2 s−1)−1] and maximum photosynthetic capacities [0.43-1.29 μg C (μg Chl-a
−1 h−1)]. Rafting and snow-ice formation, determined from thin sections and stable oxygen isotopic composition, strongly influenced
the physical, chemical and biological properties of the ice. Snow-ice formation provided the surface layers with nutrients
and possibly habitable space, which seemed to have favored centric diatoms in our study. 相似文献
4.
Little is known about species composition, distribution, and abundance of pelagic fish in the U.S. portion of the Beaufort
Sea continental shelf and slope. To inventory the community and describe pelagic fish distributions relative to water characteristics,
a systematic survey was conducted in August 2008. Acoustics (38 kHz), midwater trawling, and CTD casts were used to sample
water depths from 20 to 500 m. Age-1+ polar cod (Boreogadus saida) was the dominant fish species, with peak densities of 155,000 # ha−1 at bottom depths of 100–350 m. Age-0 fish (polar cod, sculpin (Cottidae family), and eelblenny (Lumpenus sp.)), dominated the pelagic biomass at bottom depths between 20 and 75 m, with peak densities of 160,000 # ha−1, but were also found in surface waters at bottom depths >75 m. Age-1+ polar cod were associated with cold, saline waters
likely of Chukchi Sea origin and mirrored published foraging distributions for beluga whales (Delphinapterus leucas). Conversely, age-0 fish were found in warm, fresher water, likely of ice melt and/or riverine origin, throughout the study
area. This study provides a necessary baseline for the development of Arctic assessment surveys and management plans for polar
cod. 相似文献
5.
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
6.
Landfast ice algal communities were studied in the strongly riverine-influenced northernmost part of the Baltic Sea, the Bothnian
Bay, during the winter-spring transition of 2004. The under-ice river plume, detected by its low salinity and elevated nutrient
concentrations, was observed only at the station closest to the river mouth. The bottommost ice layer at this station was
formed from the plume water (brine volume 0.71%). This was reflected by the low flagellate-dominated (93%) algal biomass in
the bottom layer, which was one-fifth of the diatom-dominated (74%) surface-layer biomass of 88 μg C l−1. Our results indicate that habitable space plays a controlling role for ice algae in the Bothnian Bay fast ice. Similarly
to the water column in the Bothnian Bay, average dissolved inorganic N:P-ratios in the ice were high, varying between 12 and
265. The integrated chlorophyll a (0.1–2.2 mg m−2) and algal biomass in the ice (1–31 mg C m−2) correlated significantly (Spearman ρ = 0.79), with the highest values being measured close to the river mouth in March and during the melt season in April. Flagellates
<20 μm generally dominated in both the ice and water columns in February–March. In April the main ice-algal biomass was composed
of Melosira arctica and unidentified pennate diatoms, while in the water column Achnanthes taeniata, Scrippsiella hangoei and flagellates dominated. The photosynthetic efficiency (0.003–0.013 (μg C [μg chl a
−1] h−1)(μE m−2s−1)−1) and maximum capacity (0.18–1.11 μg C [μg chl a
−1] h−1) could not always be linked to the algal composition, but in the case of a clear diatom dominance, pennate species showed
to be more dark-adapted than centric diatoms. 相似文献
7.
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
8.
Molly A. Palmer Kevin R. Arrigo C. J. Mundy Jens K. Ehn Michel Gosselin David G. Barber Johannie Martin Eva Alou Suzanne Roy Jean-��ric Tremblay 《Polar Biology》2011,34(12):1915-1928
During summer 2008, as part of the Circumpolar Flaw Lead system study, we measured phytoplankton photosynthetic parameters
to understand regional patterns in primary productivity, including the degree and timescale of photoacclimation and how variability
in environmental conditions influences this response. Photosynthesis–irradiance measurements were taken at 15 sites primarily
from the depth of the subsurface chlorophyll a (Chl a) maximum (SCM) within the Beaufort Sea flaw lead polynya. The physiological response of phytoplankton to a range of light
levels was used to assess maximum rates of carbon (C) fixation (P
m*), photosynthetic efficiency (α
*), photoacclimation (E
k), and photoinhibition (β
*). SCM samples taken along a transect from under ice into open water exhibited a >3-fold increase in α
* and P
m*, showing these parameters can vary substantially over relatively small spatial scales, primarily in response to changes in
the ambient light field. Algae were able to maintain relatively high rates of C fixation despite low light at the SCM, particularly
in the large (>5 μm) size fraction at open water sites. This may substantially impact biogenic C drawdown if species composition
shifts in response to future climate change. Our results suggest that phytoplankton in this region are well acclimated to
existing environmental conditions, including sea ice cover, low light, and nutrient pulses. Furthermore, this photoacclimatory
response can be rapid and keep pace with a developing SCM, as phytoplankton maintain photosynthetic rates and efficiencies
in a narrow “shade-acclimated” range. 相似文献
9.
Hilde Eggermont James M. Russell Georg Schettler Kay Van Damme Ilse Bessems Dirk Verschuren 《Hydrobiologia》2007,592(1):151-173
This study describes the physical and chemical properties of 17 Afroalpine lakes (>2 m deep) and 11 pools (<2 m deep) in the
Rwenzori mountains, Uganda-DR Congo, with the aim to establish the baseline conditions against which to evaluate future environmental
and biological changes in these unique tropical ecosystems, and to provide the foundation for lake-based paleoenvironmental
studies. Most Rwenzori lakes are located above 3,500 m elevation, and dilute (5–52 μS/cm specific conductance at 25°C) open
systems with surface in- and outflow. Multivariate ordination and pairwise correlations between environmental variables mainly
differentiate between (1) lakes located near or above 4,000 m (3,890–4,487 m), with at least some direct input of glacial
meltwater and surrounded by rocky catchments or alpine vegetation; and (2) lakes located mostly below 4,000 m (2,990–4,054
m), remote from glaciers and surrounded by Ericaceous vegetation and/or bogs. The former group are mildly acidic to neutral
clear-water lakes (surface pH: 5.80–7.82; Secchi depth: 120–280 cm) with often above-average dissolved ion concentrations
(18–52 μS/cm). These lakes are (ultra-) oligotrophic to mesotrophic (TP: 3.1–12.4 μg/l; Chl-a: 0.3–10.9 μg/l) and phosphorus-limited (mass TN/TP: 22.9–81.4). The latter group are mildly to strongly acidic (pH: 4.30–6.69)
waters stained by dissolved organic carbon (DOC: 6.8–13.6 mg/l) and more modest transparency (Secchi-disk depth: 60–132 cm).
Ratios of particulate carbon, particulate nitrogen and chlorophyll a in these lakes indicate that organic matter in suspension is primarily derived from the lakes’ catchments rather than aquatic
primary productivity. Since key features in the Rwenzori lakes’ abiotic environment are strongly tied to temperature and catchment
hydrology, these Afroalpine lake ecosystems can be expected to respond sensitively to climate change and glacier melting.
Electronic supplementary material The online version of this article (doi: ) contains supplementary material, which is available to authorized users. 相似文献
10.
Toshi Nagata 《Ecological Research》1986,1(2):207-221
The seasonal changes in the size-fractionated chlorophylla concentrations (<3 μm, 3 to 25 μm, and >25 μm) were investigated at a pelagic site of the north basin of Lake Biwa during
June to December 1985. Autofluorescing plankton cells in the <3-μm fractions were also examined using the fluorescein isothiocyanate
staining epifluorescence microscopic technique. The <3-μm phytoplankton (usually dominated by chroococcoid cyanobacteria except
for a few cases dominated by small eukaryotes) showed a clearly different pattern of seasonal change compared with the larger
fractions. That is, from August to early September, chlorophylla of the larger fractions declined considerably, while the <3-μm chlorophylla did not decrease significantly. Moreover, cyanobacterial cell density in the <3-μm fraction showed a maximum value (2–3.5×105 cells·ml−1) during this period. The relative contribution of the <3-μm chlorophylla to the total chlorophylla increased from <5% to 45% during the course of this change. No clear vertical trend in the distribution and composition of
the <3-μm phytoplankton was found, except that relatively large cyanobacteria (>4 μm3) appeared at a depth of 15m but not at 0,5 and 10 m from late July to August. These large cells were also found in November
and December. The drastic seasonal change of phytoplankton size structure occurring in this basin was discussed in relation
to grazing, nutrient depletion and sinking.
Contribution from Otsu Hydrobiological Station, Kyoto Univeristy (No. 308, foreign language series). 相似文献
11.
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
12.
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
13.
During spring, extensive blooms of microalgae grow on the underside of arctic sea ice. The brownish, algal layer penetrates ca. 2 cm into the bottom surface of the ice and the algae are potentially exposed to very high salinities. Four diatom species, Melosira juergensii Ag., Porosira glacialis (Grun.) Jørg., Navicula transitans var. derasa (Grun.) Cleve, and Coscinodiscus lacustris Grun., isolated from, sea ice samples taken from the Beaufort and Chukchi seas near Barrow, Alaska, were grown at 11 salinities ranging from 5 to 70‰ at 5 C under constant illumination. All of the species grew at 5‰ except N. transitans whose lower growth limit was 15‰. Growth was high over a broad range of salinities, but none of the species grew at salinities above 60‰. These diatom species appear to be well suited to tolerate the salinities in the brine pockets near the bottom of annual arctic sea ice where they are found. High brine-cell salinity, however, may limit the upward, penetration of ice algae into the bottom of sea ice. 相似文献
14.
Net growth of ice algae in response to changes in overlying snow cover was studied after manipulating snow thickness on land-fast,
Arctic sea ice. Parallel laboratory experiments measured the effect of changing irradiance on growth rate of the ice diatom,
Nitzschia frigida. After complete removal of thick snow (≥9 cm), in situ ice algae biomass declined (over 7–12 days), while removal of thin
snow layers (4–5 cm), or partial snow removal, increased net algal growth. Ice bottom ablation sometimes followed snow removal,
but did not always result in net loss of algae. Similarly, in laboratory experiments, small increases in irradiance increased
algal growth rate, while greater light shifts suppressed growth for 3–6 days. However, N. frigida could acclimate to relatively high irradiance (110 μmol photons m2 s−1). The results suggest that algal loss following removal of a thick snow layer was due to the combination of photoinhibition
and bottom ablation. The smaller relative increase in irradiance after removal of thin or partial snow layers allowed algae
to maintain high specific-growth rates that compensated for loss from physical mechanisms. Thus, the response of ice algae
to snow loss depends both on the amount of change in snow depth and algal photophysiology. The complex response of ice algae
growth and export loss to frequently changing snow fields may contribute to horizontal and temporal patchiness of ecologically
and biogeochemically important variables in sea ice and should be considered in predictions of how climate change will affect
Arctic marine ecosystems. 相似文献
15.
During the International Polar Year (IPY), acoustic recorders were deployed on oceanographic moorings in Fram Strait and on
the Chukchi Plateau, representing the first coordinated year-round sampling of underwater acoustic habitats at two sites in
the High Arctic. Examination of species-specific marine mammal calls recorded from autumn 2008–2009 revealed distinctly different
acoustic habitats at each site. Overall, the Fram Strait site was acoustically complex compared with the Chukchi Plateau site.
In Fram Strait, calls from bowhead whales (Balaena mysticetus) and a variety of toothed whales (odontocetes) were recorded year-round, as were airgun pulses from seismic surveys. In addition,
calls from blue whales (Balaenoptera musculus) and fin whales (B. physalus) were recorded from June to October and August to March, respectively. Conversely, at the Chukchi Plateau site, beluga (Delphinapterus leucas) and bowhead whale calls were recorded primarily from May to August, with airgun signals detected only in September–October.
Ribbon seal (Phoca fasciata) calls were detected in October–November, with no marine mammals calls at all recorded from December to February. Of note,
ice-adapted bearded seals (Erignathus barbatus) were recorded at both sites, primarily in spring and summer, corresponding with the mating season for that species. Differences
in acoustic habitats between the two sites were related to contrasts in sea ice cover, temperature, patterns of ocean circulation
and contributions from anthropogenic noise sources. These data provide a provisional baseline for the comparison of underwater
acoustic habitats between Pacific and Atlantic sectors of the High Arctic. 相似文献
16.
Heike Link Philippe Archambault Tobias Tamelander Paul E. Renaud Dieter Piepenburg 《Polar Biology》2011,34(12):2025-2038
Seasonal dynamics in the activity of Arctic shelf benthos have been the subject of few local studies, and the pronounced among-site
variability characterizing their results makes it difficult to upscale and generalize their conclusions. In a regional study
encompassing five sites at 100–595 m water depth in the southeastern Beaufort Sea, we found that total pigment concentrations
in surficial sediments, used as proxies of general food supply to the benthos, rose significantly after the transition from
ice-covered conditions in spring (March–June 2008) to open-water conditions in summer (June–August 2008), whereas sediment
Chl a concentrations, typical markers of fresh food input, did not. Macrobenthic biomass (including agglutinated foraminifera >500 μm)
varied significantly among sites (1.2–6.4 g C m−2 in spring, 1.1–12.6 g C m−2 in summer), whereas a general spring-to-summer increase was not detected. Benthic carbon remineralisation also ranged significantly
among sites (11.9–33.2 mg C m−2 day−1 in spring, 11.6–44.4 mg C m−2 day−1 in summer) and did in addition exhibit a general significant increase from spring-to-summer. Multiple regression analysis
suggests that in both spring and summer, sediment Chl a concentration is the prime determinant of benthic carbon remineralisation, but other factors have a significant secondary
influence, such as foraminiferan biomass (negative in both seasons), water depth (in spring) and infaunal biomass (in summer).
Our findings indicate the importance of the combined and dynamic effects of food supply and benthic community patterns on
the carbon remineralisation of the polar shelf benthos in seasonally ice-covered seas. 相似文献
17.
To clarify the ecological significance of the association of sulfate-reducing bacteria (SRB) with sediment particle size,
SRB utilizing lactate (l-SRB), propionate (p-SRB) and acetate (a-SRB) were examined with different sizes of sediment particles in a hypertrophic freshwater lake using the anaerobic plate
count method. The numbers ofl-SRB anda-SRB were 104–105 colony forming units (CFU) per ml in the 0–3 cm layer and 102–103 CFU ml−1 in the 10–13 cm layer while the numbers ofp-SRB were one or two orders lower than those ofl-SRB anda-SRB. A sediment suspension was fractionated into four fractions (<1, 1–10, 10–94 and >94 μm). The highest proportions ofl-SRB anda-SRB were found in the 10–94 μm fraction: 66–97% forl-SRB and 53–98% fora-SRB. The highest proportion ofp-SRB was found in the >94 μm fraction (70–74%). These results indicate that most SRB were associated with sediment particles.
One isolate from an acetate-utilizing enrichment culture was similar toDesulfotomaculum acetoxidans, a spore-forming sulfate-reducing bacterium. When lactate and sulfate were added to sediment samples,l-SRB anda-SRB in the <10 μm-fraction grew more rapidly than those in whole sediment for the first 2 days. This result suggests that
nutrients uptake by free-living and small particle-associated (<10 μm) SRB is higher than that by SRB associated with larger
particles. 相似文献
18.
Movements and behavior of satellite-tagged spotted seals (Phoca largha) in the Bering and Chukchi Seas 总被引:1,自引:0,他引:1
Lloyd F. Lowry Kathryn J. Frost Randall Davis Douglas P. DeMaster Robert S. Suydam 《Polar Biology》1998,19(4):221-230
Satellite-linked tags were attached to 12 spotted seals (Phoca largha) captured at a coastal lagoon in the eastern Chukchi Sea during August 1991–1993. Movements of seals were tracked for 32–298
days using the Argos system. Of 9,651 total location records obtained, 7,268 were usable. Individual seals were located on
41–96% of the days that tags were operational. During August–November, tagged seals alternated haul-outs at coastal sites
lasting 1–304 h with trips to sea of 14–901 h. Coastal haul-outs occurred at 14 sites in western Alaska and eastern Russia.
On several trips to sea, seals covered distances of more than 1,000 km. Movement southward from the Chukchi Sea generally
began in October, with most of the seals passing through the Bering Strait during November. Seals first hauled out on sea
ice in October (Chukchi Sea) or November (Bering Sea), and generally moved southward during October–December as sea-ice coverage
increased. Seven seals, whose transmitters were still operating, spent December to June in the Bering Sea region between Kuskokwim
Bay and Anadyr Gulf, which corresponded to the location of the ice front. The seals made active east-west movements within
the ice front. Spotted seals are unlike other ice-breeding seals in that they regularly use coastal haul-outs during summer
and autumn. Compared to the closely related Pacific harbor seal (Phoca vitulina richardsi), spotted seals make much longer trips to sea and spend longer continuous periods at their haul-outs during summer and autumn.
Received: 9 April 1997 / Accepted: 30 September 1997 相似文献
19.
Attenuation of the vertical flux of copepod fecal pellets under Arctic sea ice: evidence for an active detrital food web in winter 总被引:1,自引:0,他引:1
Makoto Sampei Alexandre Forest Hiroshi Sasaki Hiroshi Hattori Ryosuke Makabe Mitsuo Fukuchi Louis Fortier 《Polar Biology》2009,32(2):225-232
A variable fraction of fecal pellets produced in the epipelagic layer is intercepted and retained before reaching the bottom.
We assessed fecal pellet retention in the ice-covered Beaufort Sea in early February by comparing the shape and size-frequency
distribution of pellets collected by a sediment trap moored at 210 m to that produced in vitro. Appendicularian ellipsoidal
and copepod cylindrical pellets made up 75 and 24% of the flux (165 μg C m−2 day−1). In contrast, production (135 μg C m−2 day−1) was dominated by cylindrical pellets (93%). The vertical flux of cylindrical pellets at 210 m was attenuated by 70%. Pellets
>120 μm in width, represented 42% of the production, but were not detected in the trap. Retention most likely resulted from
coprorhexic feeding by copepods such as Metridia longa. Our observations suggest that the detritivore food web prevailing under the ice of the Arctic Ocean in winter is dominated
by appendicularians feeding on pellets fragmented by copepods. 相似文献
20.
Toshiya Katano Shin-ichi Nakano Hiroyuki Ueno Osamu Mitamura Kaori Anbutsu Masayuki Kihira Yasuhiro Satoh Takeshi Satoh Valentin V. Drucker Yuji Tanaka Yuki Akagashi Masahito Sugiyama 《Limnology》2008,9(3):243-250
The abundance and composition of phytoplankton were investigated at six stations along a transect from the Barguzin River
inflow to the central basin of Lake Baikal in August 2002 to clarify the effect of the river inflow on the phytoplankton community
in the lake. The water temperature in the epilimnion was high near the shore at Station 1 (17.3°C), probably due to the higher
temperature of the river water, and gradually decreased offshore at Station 6 (14.5°C). Thermal stratification developed at
Stations 2–6, and a thermocline was observed at a 17–22-m depth at Stations 2–4 and an 8–12-m depth at Stations 5 and 6. The
concentrations of nitrogen and phosphorus nutrients in the epilimnion at all stations were <1.0 μmol N l−1 and <0.16 μmol P l−1, respectively. Relatively high concentrations of nutrients (0.56–7.38 μmol N l−1 and 0.03–0.28 μmol P l−1) were detected in the deeper parts of the euphotic zone. Silicate was not exhausted at all stations (>20 μmol Si l−1). The chlorophyll a (chl. a) concentration was high (>10 μg l−1) near the shore at Station 1 and low (<3 μg l−1) at five other stations. The <2 μm fraction of chl. a in Stations 2–6 ranged between 0.80 and 1.85 μg l−1, and its contribution to total chl. a was high (>60%). In this fraction, picocyanobacteria were abundant at all stations and ranged between 5 × 104 and 5 × 105 cells ml−1. In contrast, chl. a in the >2 μm fraction varied significantly (0.14–11.17 μg l−1), and the highest value was observed at Station 1. In this fraction, the dominant phytoplankton was Aulacoseira and centric diatoms at Station 1 and Cryptomonas, Ankistrodesmus, Asterionella, and Nitzschia at Stations 2–6. The present study demonstrated the dominance of picophytoplankton in the pelagic zone, while higher abundance
of phytoplankton dominated by diatoms was observed in the shallower littoral zone. These larger phytoplankters in the littoral
zone probably depend on nutrients from the Barguzin River. 相似文献