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1.
Benthic algal mats and phytoplankton of Lake Gondwana (Northern Victoria Land, Antarctica) were investigated. Biomass, chlorophyll content and floristic analyses were carried out on algal mats. The mats are composed of two layers different in colour, floristic composition and chlorophyll content. The algal flora of the mats amount to 34 taxa (19 Cyanophyta, 7 Bacillariophyta, 8 Chlorophyta). The phytoplankton community is species-poor (only 5 taxa). Crytophyta account for about 98% of total algal density. 相似文献
2.
Nitrogen dynamics in two antarctic streams 总被引:1,自引:1,他引:0
The many glacier meltwater streams of southern Victoria Land flow through catchments where life forms are almost entirely microbial. Allochthonous inputs of nitrogen from two study streams near McMurdo Sound were derived mostly from the melting glaciers (ca. 100–200 mg N m–3) with some originating from N2-fixation by heterocystous cyanobacteria (max. 939 mg N m–2 year–1). Thirty to fifty per cent of the glacier derived N was dissolved organic N and a major proportion of this was identified as urea N which was utilised by the rich algal and cyanobacterial mats in the streams. A nutrient budget for Fryxell Stream was estimated, quantifying uptake of urea-N and dissolved inorganic N and the release of dissolved organic (non urea) and particulate N by the stream communities. An index of in-stream nitrogen processing, the Net Uptake Length Constant in these streams was compared with that from temperate climates and was found to be similar. Despite the influence of low temperatures on microbial activity (mean daily water temperature = 5 °C) nutrient removal rates from these antarctic streams are high because of the large standing stock of microbial biomass there. 相似文献
3.
Fernández-Valiente E Camacho A Rochera C Rico E Vincent WF Quesada A 《FEMS microbiology ecology》2007,59(2):377-385
The community structure and physiological characteristics of three microbial mat communities in Byers Peninsula (Livingston Island, South Shetland Islands, Antarctica) were compared. One of the mats was located at the edge of a stream and was dominated by diatoms (with a thin basal layer of oscillatorian cyanobacteria), whereas the other two mats, located over moist soil and the bottom of a pond, respectively, were dominated by cyanobacteria throughout their vertical profiles. The predominant xanthophyll was fucoxanthin in the stream mat and myxoxanthophyll in the cyanobacteria-dominated mats. The sheath pigment scytonemin was absent in the stream mat but present in the soil and pond mats. The stream mat showed significantly lower delta13C and higher delta15N values than the other two mats. Consistent with the delta15N values, N2 fixation was negligible in the stream mat. The soil mat was the physiologically most active community. It showed rates of photosynthesis three times higher than in the other mats, and had the highest rates of ammonium uptake, nitrate uptake and N2 fixation. These observations underscore the taxonomic and physiological diversity of microbial mat communities in the maritime Antarctic region. 相似文献
4.
Biodiversity in extreme aquatic environments: Lakes, ponds and streams of the Ross Sea sector, Antarctica 总被引:3,自引:0,他引:3
The Ross Sea Sector (RSS) of Antarcticallies between the lines of longitude 150°E and 150°W and contains diverse landscapes with a variety of lakes, ponds and streams. Neither insects nor crustacean species have been recorded in these ecosystems but most contain planktonic and/or benthic communities that are composed exclusively of microscopic organisms. Microbial brodiversity is low with a small number of species (e.g. filamentous cyanobacteria of the family Oscillatoriaceae) occurring under a broad range of environmental conditions throughout the region. There is no evidence to date of microbial endemism in the RSS; however, there is a need to apply molecular and cellular techniques to compare biodiversity and genetic characteristics with assemblages elsewhere in Antarctica and with comparable communities in the north polar zone. A series of hypotheses are advanced to help guide further work. These derive from the conclusion that environmental extremes plus biogeographical isolation control the biodiversity of RSS communities, and that biological interactions (competition, grazing, predation, parasitism) are weak and play a minor role by comparison with temperate latitude ecosystems. 相似文献
5.
Paul L. Koch Brenda L. Hall Mark de Bruyn A. Rus Hoelzel Carlo Baroni M. Cristina Salvatore 《Marine Mammal Science》2019,35(3):934-956
We report on an accumulation of mummified southern elephant seals (Mirounga leonina) from Inexpressible Island on the Victoria Land Coast (VLC), western Ross Sea, Antarctica. This accumulation is unusual, as elephant seals typically breed and molt on sub‐Antarctic islands further north and do not currently occupy the VLC. Prior ancient DNA analyses revealed that these seals were part of a large, Antarctic breeding population that crashed ~1,000 yr ago. Radiocarbon dates for Inexpressible Island mummies range from 380 to 3,270 yr before present, too old to have been created by Scott's Northern Party in 1912 and varying too widely in age to represent a catastrophic death assemblage. Skeletal measurements reveal that most Inexpressible Island mummies are adult or subadult males. The presence of male elephant seals on Inexpressible Island until several hundred years ago suggests that, at a minimum, it served as a haul‐out site for the large Antarctic population and may have hosted a breeding colony. The conditions that allowed this Antarctic population to use the Ross Sea, the factors spurring its decline, and the implications for the adaptability and sensitivity of the species to environmental change all merit further study. 相似文献
6.
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.
This study aimed to: (1) assess differences between two quantitative sampling methods of soil microarthropods (visual census
vs. stone washing) in ice-free areas located along a latitudinal gradient (from 72°37′S to 74°42′S) in northern Victoria Land
(Antarctica); (2) furnish preliminary results on the abundance and diversity of mites and springtails in the studied areas.
Visual census yielded reliable density estimates for adult collembolans and larger prostigmatic mites but did not detect small
species. The study updates the distribution of several mites, including the southernmost record of an Oribatida species at
global scale. Species composition was correlated with latitude but the uneven abundance distribution and local high beta-diversity
probably reflect habitat fragmentation and population isolation. Under this circumstance nested sampling design should be
usefully employed. Priorities and suitable methods for studying terrestrial microarthropod communities in continental Antarctica
are discussed. 相似文献
9.
10.
William J. Green Thomas J. Gardner Timothy G. Ferdelman Michael P. Angle Lawrence C. Varner Philip Nixon 《Hydrobiologia》1989,172(1):129-148
Major ion, nutrient, transition metal, and cadmium concentrations are presented for nine meltwater streams flowing into Lake Fryxell, a permanently stratified lake with an anoxic hypolimnion in Taylor Valley, Antarctica. For the major ions, stream compositions are considered in terms of dissolution of marine-derived salts and chemical weathering of local rocks. Although Lake Fryxell has undergone significant evaporative concentration, only calcite, of the simple salts, is predicted to precipitate. Geochemical budgets indicate, however, that large quantities of K, Mg, and SO4 have also been removed from the lake. Reverse weathering may be an important sink for K and Mg, although magnesium removal with calcium carbonate phases is also likely. Assuming constancy of composition over recent geologic time, all of the salts in the Fryxell water column could have been delivered under present flows in about three thousand years (chloride age).Comparison of nutrient concentrations in these meltwater streams with other flowing waters in the world reveals that the Fryxell streams are strikingly deficient in NO3-N but not PO4-P. The apparent nitrogen deficiency in Lake Fryxell itself can be attributed to the low annual stream loadings of this nutrient.Stream concentrations and loadings are also presented for Mn, Fe, Co, Ni, Cu, and Cd. Dissolved metal concentrations correlate roughly with average crustal abundances, suggesting that chemical weathering is the major source for these elements. Vertical metal profiles within Lake Fryxell itself appear to be governed by the formation of insoluble sulfide phases, or, in the case of Mn, by MnHPO4. However, dissolved nickel levels in sulfide-bearing waters are much higher than can be explained in terms of metal-sulfide equilibria, and we suspect that significant organic complexing of this metal is occurring in the deeper waters. 相似文献
11.
Helge Abildhauge Thomsen 《欧洲藻类学杂志》2013,48(4):335-342
Wigwamma scenozonion sp. nov. (Prymnesiophyceae) is described on the basis of electron microscopy of shadowcast whole mounts prepared from water samples collected in the vicinity of Godhavn (West Greenland) in July and August 1977. This nanoplanktonic coccolithophorid possesses two smooth flagella and a shorter coiling haptonema. Coccoliths of one type cover the whole cell. Each coccolith is composed of a ring of rod-like crystallites joined end to end and arranged parallel to the edge of the oval coccolith base-plates. A single enlarged crystallite is found on most coccoliths. W. scenozonion is distinguished from the two previously described Wigwamma species by the lack of coccolith superstructures and by having one, rather than two rings of crystallites along the base-plate edge. In addition to the West Greenland specimens a single W. scenozonion cell has been encountered in a water sample from Denmark. 相似文献
12.
13.
The aim of our work was to assess photosynthetic plasticity of two hairgrass species with different ecological origins (a temperate zone species, Deschampsia caespitosa (L.) Beauv. and an Antarctic species, D. antarctica) and to consider how the anticipated climate change may affect vitality of these plants. Measurements of chlorophyll fluorescence showed that the photosystem Ⅱ (PSII) quantum efficiency of D. caespitosa decreased during 4 d of incubation at 4℃ but it remained stable in D. antarctica. The fluorescence half-rise times were almost always lower in D. caespitosa than in D. antarctica,irrespective of the incubation temperature. These results indicate that the photosynthetic apparatus of D. caespitosa has poorer performance in these conditions. D. caespitosa reached the maximum photosynthesis rate at a higher temperature than D. antarctica although the values obtained at 8℃ were similar in both species. The photosynthetic water-use efficiency (photosynthesis-to-transpiration ratio, P/E) emerges as an important factor demonstrating presence of mechanisms which facilitate functioning of a plant in non-optimal conditions. Comparison of the P/E values, which were higher in D. antarctica than in D. caespitosa at low and medium temperatures, confirms a high degree of adjustability of the photosynthetic apparatus in D. antarctica and unveils the lack of such a feature in D. caespitosa. 相似文献
14.
The following study was the first to describe composition and structure of the peracarid fauna systematically along a latitudinal
transect off Victoria Land (Ross Sea, Antarctica). During the 19th Antarctic expedition of the Italian research vessel “Italica”
in February 2004, macrobenthic samples were collected by means of a Rauschert dredge with a mesh size of 500 μm at depths
between 85 and 515 m. The composition of peracarid crustaceans, especially Cumacea was investigated. Peracarida contributed
63% to the total abundance of the fauna. The peracarid samples were dominated by amphipods (66%), whereas cumaceans were represented
with 7%. Previously, only 13 cumacean species were known, now the number of species recorded from the Ross Sea increased to
34. Thus, the cumacean fauna of the Ross Sea, which was regarded as the poorest in terms of species richness, has to be considered
as equivalent to that of other high Antarctic areas. Most important cumacean families concerning abundance and species richness
were Leuconidae, Nannastacidae, and Diastylidae. Cumacean diversity was lowest at the northernmost area (Cape Adare). At the
area off Coulman Island, which is characterized by muddy sediment, diversity was highest. Diversity and species number were
higher at the deeper stations and abundance increased with latitude. A review of the bathymetric distribution of the Cumacea
from the Ross Sea reveals that most species distribute across the Antarctic continental shelf and slope. So far, only few
deep-sea records justify the assumption of a shallow-water–deep-sea relationship in some species of Ross Sea Cumacea, which
is discussed from an evolutionary point of view. 相似文献
15.
《Marine Biology Research》2007,3(6):438-445
Specimens belonging to the pycnogonid family Ammotheidae collected during the Victoria Land Transect 2004 cruise (Ross Sea, Antarctica) were studied. Five species are recognized in this collection, three species of Ammothea, one of Achelia and one of Austroraptus. Some information about the variability of the propodal armature of Ammothea glacialis is discussed. The rare species Ammothea meridionalis is reported for the fifth time, enlarging its known bathymetric range. A new species in the genus Ammothea is described, Ammothea victoriae. The new taxon is compared with its closest congeners, especially with A. armentis, A. gordonae and A. carolinensis. Both morphotypes of Achelia spicata are reported, some additional morphological differences having been detected between them. Austroraptus calcaratus is reported for the third time, and with our specimens 14 individuals are now known. Present and previous data show a restricted geographical and bathymetric distribution. 相似文献
16.
The underwater light field in the Bellingshausen andAdmundsen Seas was characterised using data collectedduring the R/V Polarstern cruise ANT XI/3, from12.1.94 to 27.3.94. The euphotic zone varied from 24to 100 m depth. Spectral diffuse vertical attenuationcoefficients (K
d
())were determined for 12narrow wavebands as well as for photosyntheticallyavailable radiation (PAR, 400–700 nm): K
d
(490)ranged from 0.03 to 0.26 m1; K
d
(550) from0.04 to 0.17 m1; K
d
(683) from 0.04 to0.17 m1; and K
d
(PAR) varied from 0.02 to0.25 m1. K
d
() for wavelengths centred at412 nm, 443 nm, 465 nm, 490 nm, 510 nm, 520 nm and550 nm were significantly correlated with chlorophyllconcentration (ranging from 0.1 to 6 mg m3). Thevertical attenuation coefficients for 340 nm and380 nm ranged from 0.10 to 0.69 m1 and from 0.05to 0.34 m1, respectively, and were also highlycorrelated with chlorophyll concentrations. These K
d
values indicate that the 1% penetration depthmay reach maxima of 46 m and 92 m for 340 nm and380 nm, respectively. The spectral radiancereflectances (Rr()) for 443 nm, 510 nm and 550 nmwere less than 0.01 sr1. Rr() for 665 nm and683 nm increased with depth up to 0.2 sr1 because ofchlorophyll fluorescence. Using a model that predicts downwardirradiances by taking into account the attenuation bywater and absorption by chlorophyll, we show thatchlorophyll fluorescence has a significant influenceon the red downward irradiance (E
d
(633, 665, 683))in deeper layers. The ability of the phytoplanktonpopulation to influence the light environment byautofluorescence and absorption processes depends onthe light conditions and on the photoacclimation ofthe cells, represented by the in vivo crosssection absorption coefficient of chlorophyll (a*). Theobtained mean chlorophyll-specific light attenuationcoefficients of phytoplankton in situ (k
d
) are higherthan the in vivo absorption coefficient of chlorophyll,more than to be excepted from the scattering. a*(), m2 mg chl1, decreased due topackaging effect with increasing chlorophyllconcentrations. 相似文献
17.
Changes in epilithic cyanobacterial communities were determined in a river characterized by variations in nutrient content.
The cyanobacterial community composition of the upstream sites was different from that of the downstream communities, where
anthropogenic influences lead to an increase in nutrients (principally soluble reactive phosphate, SRP). There was a general
trend in downstream sites towards a decrease in species richness, abundance, and diversity of cyanobacteria. The reduced cyanobacterial
species richness in downstream locations was due largely to a marked decrease in the number of heterocystous species, although
the number of non-heterocystous species also decreased. Epilithic phycobiliprotein content was positively correlated with
the number of cyanobacterial cells, implying that this pigment provides information about the abundance of the cyanobacteria
community in the epilithon. The lowest concentrations of phycobiliprotein in the epilithon were observed where concentrations
of phosphate were highest. Similarly, the number of heterocystous and non-heterocystous species tended to decrease as the
SRP increased, and as the DIN:SRP ratio decreased. However, no relation was found with dissolved inorganic nitrogen (DIN).
The differences among cyanobacterial communities could be interpreted as being a consequence of variations in nutrient composition.
Finally, the usefulness of cyanobacteria as an alternative tool for assessing changes in water quality is discussed.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
18.
Abstract: Limopsis is one of the most speciose and widespread bivalve genera in the Southern Ocean at the present day. However, the fossil record of the genus is poorly known from the southern high latitudes. Here, we review the fossil record in this region to help understand the evolutionary origins of the genus. Limopsis infericola sp. nov. and additional specimens of a previously described species are added to the fossil record of Antarctica. The globally distributed limopsid clade had its earliest occurrences in the Early Cretaceous of Europe and New Zealand, then radiated during the Late Cretaceous (Maastrichtian, 70.6–65.5 Ma). Fossil evidence shows that the genus underwent a second, Cenozoic, radiation related to the isolation of Antarctica and the onset of cooling in the southern hemisphere. The genus has persisted in Antarctica for the last 50 myr, adapting to extreme changes in the environmental conditions, including surviving the last glacial maximum in marine refugia. 相似文献
19.
When NH4 + or NO3 ? was supplied to NO3 ? ‐stressed cells of the microalga Dunaliella tertiolecta Butcher, immediate transient changes in chl a fluorescence were observed over several minutes that were not seen in N‐replete cells. These changes were predominantly due to nonphotochemical fluorescence quenching. Fluorescence changes were accompanied by changes in photosynthetic oxygen evolution, indicating interactions between photosynthesis and N assimilation. The magnitude of the fluorescence change showed a Michaelis‐Menten relationship with half‐saturation concentration of 0.5 μM for NO3 ? and 10 μM for NH4 + . Changes in fluorescence responses were characterized in D. tertiolecta both over 5 days of N starvation and in cells cultured at a range of NO3 ? ‐limited growth rates. Variation in responses was more marked in starved than in limited cells. During N starvation, the timing and onset of the fluorescence responses were different for NO3 ? versus NH4 + and were correlated with changes in maximum N uptake rate during N starvation. In severely N‐starved cells, the major fluorescence response to NO3 ? disappeared, whereas the response to NH4 + persisted. N‐starved cells previously grown with NH4 + alone showed fluorescence responses with NH4 + but not NO3 ? additions. The distinct responses to NO3 ? and NH4 + may be due to the differences between regulation of the uptake mechanisms for the two N sources during N starvation. This method offers potential for assessing the importance of NO3 ? or NH4 + as an N source to phytoplankton populations and as a diagnostic tool for N limitation. 相似文献
20.
Laminaria saccharina Lamour. sporophytes were grown in enriched and synthetic media through a range of nitrate concentrations, There was an approximately linear relationship between growth and nutrient concentration up to 10 μ substrate concentration. The half-saturation constant (K2) was ca. 1.4 μ NO3-. The internal levels of NO3- increased at substrate concentrations above 10 μM b>3- and reached levels several thousand times higher than the surrounding medium. Thus there is evidence for luxury consumption of NOsb>3-. The chlorophyll content and photosynthetic capacities of plants also increased with increasing external NO3- The ecological implications of this work are considered. 相似文献