共查询到20条相似文献，搜索用时 533 毫秒
1.
Mutsuo Ichinomiya Yasushi Gomi Miwa Nakamachi Masaki Honda Mitsuo Fukuchi Akira Taniguchi 《Polar Science》2008,2(1):33-40
To investigate the fate of ice algae released from sea ice, we investigated the abundance, species composition, and sinking flux of diatoms in the water column under fast ice near Syowa Station, Antarctica during the summer of 2005/2006. The diatom assemblage in the water column consisted of chain-forming planktonic species, in contrast to the under-ice assemblage dominated by pennate species reported from this site in the past; this dissimilarity suggests the presence of an unconsolidated platelet ice layer under the congelation ice, within which planktonic species can bloom. Among the dominant diatoms, Porosira pseudodenticulata and Pseudo-nitzschia cf. turgiduloides were dominant in the water column, and their water column stocks were higher than their mass sedimentation. These species apparently maintain their populations in the surface layer, as their production remains in the water column. In contrast, Fragilariopsis kerguelensis and Thalassiosira australis were scarce in the water column but rich in the flux, indicating active sinking and export of their production to the benthic ecosystem. This distinction in buoyancy control and sinking characteristics of the dominant diatoms on release from the fast ice influences the diatom species composition and carbon flow under the ice. 相似文献
2.
3.
对1999年春季采集于北极拉普捷夫海东南部的冰藻和冰下浮游植物群落的种类组成进行了分析,并对丰度和生物量进行了统计和对比。藻种以硅藻占绝对优势,其中又以羽纹硅藻为主。优势种集中,主要包括海洋拟脆杆藻(Fragilariopsisoceanica)、圆柱拟脆杆藻(F.cylindrus)、寒冷菱形藻(Nitzschiafrigida)、普罗马勒菱形藻(N. promare)、带纹曲壳藻(Ach nanthestaeniata)、新寒冷菱形藻(Nitzschianeofrigida)、大洋舟形藻(Naviculapelagica)、范氏舟形藻(N. vanhoeffenii)、北极直链藻(Melosiraarctica)、北方舟形藻(N. septentrionalis)、新月细柱藻(Clindrothecaclosterium)和绿藻门的塔形藻(Pyramimonassp. )。微藻主要集中在冰底10cm,丰度为14. 6-1562. 2×104 cells·L-1,平均为639. 0×104 cells·L-1;生物量为7. 89-2093. 5μgC·L-1,平均为886. 9μgC·L-1,总体上比次冰底高1个数量级,比冰下表层水柱高2个数量级。冰底20cm冰柱的累计丰度和生物量平均分别为冰下20m水柱累计量的7. 7和12. 2倍,显示冰藻在春季海冰融化前在近岸生态系统中的重要作用。尽管各站位冰底和冰下表层水柱藻类群落的相似性普遍不高,但整个调查海域冰底和冰下水柱优势种极为相似,春季期间冰藻对冰下浮游植物群落的影响明显。由于 相似文献
4.
5.
自１９９２年４月１２日至１２月３０日对中山站以西内拉峡湾海冰和冰下水柱中藻类优势种组成和丰度进行了测定。４月份和１１月中旬至１２月中旬冰柱和水柱（０～５０ｍ）藻类丰度高达１０８～１０９ｃｅｌｓ／ｍ２。冰藻的普遍或季节性优势种主要包括Ａｍｐｈｉｐｒｏｒａｋｊｅｌｍａｎｉ、Ｂｅｒｋｅｌｅｙａｒｕｔｉｌａｎｓ、Ｎａｖｉｃｕｌａｇｌａｃｉｅｉ、Ｎｉｔｚｓｃｈｉａｂａｒｋｌｅｙｉ、Ｎ．ｃｙｌｉｎｄｒｕｓ、Ｎ．ｌｅｃｏｉｎｔｅｉ和Ｎｉｔｚｓｃｈｉａｓｐ．。由于藻类结合入冰后自身的演替，春－夏季海冰剖面中所记录的优势种组成并不能准确反映冰底优势种的季节演替过程。从冰底和水表藻种组成的对比表明，两者仅在春末冰底冰藻水华期间具有较强的相似性。秋、春季冰底冰藻水华的形成以现场生长为主，夏初冰藻释放入水后对冰下浮游植物的播种作用不明显。 相似文献
6.
The seasonality of physical, chemical, and biological water variables is a major characteristic of temperate, dimictic lakes.
Yet, few investigations have considered the potential information that is encoded in seasonal dynamics with respect to the
paleolimnological record. We used a one-year sequence of diatoms obtained from sediment traps and water samples, as well as
the sedimentary diatom record covering the past ca. 1000 years in Bates Pond, Connecticut (USA), to investigate which variables
influence the seasonal distribution of diatoms and how this can be used for the interpretation of the fossil record. The seasonal
patterns in diatom assemblages were related to stratification and, to a lesser extent, to nitrate, silica, and phosphorus.
During mixing periods in spring and autumn, both planktonic and benthic species were collected in the traps, while few lightly
silicified, spindle-shaped planktonic diatoms dominated during thermal stratification in summer. Changes in fossil diatom
assemblages reflected human activity in the watershed after European settlement and subsequent recovery in the 20th century.
A long-term trend in diatom assemblage change initiated before European settlement was probably related to increased length
of mixing periods during the Little Ice Age, indicated by the increase of taxa that presently grow during mixing periods and
by application of a preliminary seasonal temperature model. We argue that the analysis of seasonal diatom dynamics in temperate
lakes may provide important information for the refinement of paleolimnological interpretations. However, investigations of
several lakes and years would be desirable in order to establish a more robust seasonal data set for the enhancement of paleolimnological
interpretations. 相似文献
7.
Microbial composition-including microalgae, bacteria and protozoans- and potential metabolic activity of its autotrophic compartment were measured in December 1988 in several micro-environments that characterise the North-West Sector of the marginal area of the Weddell Sea; infiltration and band assemblages of ice floes and adjacent waters were investigated. At the time of ice melting, a shift from a diatom dominated population (ice) to a flagellate dominated population (water column) was observed. Nevertheless, this shift was not due to an "inability" of the ice-diatoms to grow in the water colum. Macro-grazing and/or sedimentation are suggested as possible causes of the disappearance of diatoms during ice melting. The remaining small autotrophic forms released by the ice would constitute a significant seeding stock for the growth of ice-edge blooms. 相似文献
8.
A sedimentary blue-green algal record has been investigated through measurement of myxoxanthophyll and oscillaxanthin in two cores taken from deep and shallow sites in Lake Wabamun, Alberta, Canada (Longitudes 114° 26 and 114° 44 W; Latitudes 50° 30 and 50° 35 N). Blue-green algae have been a component of the algal flora of this lake throughout the Holocene period. Myxoxanthophyll and oscillaxanthin maxima occur in early Holocene sediments (ca. 9000 years BP), whereas oscillaxanthin concentrations are high between 7000 and 3800 years BP. High oscillaxanthin levels suggest that a phytoplankton assemblage, which included Oscillatoria spp., existed during this latter period and the lake was more eutrophic than at present. Decreases in the number of planktonic diatoms in the core from the deep site (Seba core) appear to be related to increased eutrophy, increased salinity, and sediment redistribution as well as possible competition with Oscillatoria. That the lake has been less productive during the last 2500 years in supported by the diatom record, the diatom: chrysophyte statospore (stomatocyst) ratio and concentrations of the blue-green algal pigments. In the core from the shallow site (Moonlight Bay) concentrations of blue-green algal pigments are initially high, which along with the diatom assemblage, indicates a younger basal age of the sediments. It is possible that benthic blue-green algae contributed significantly to sedimentary pigment concentrations in the Moonlight Bay core. Major fluctuations in the Osc: Myx ratio, particularly in the Seba core, casts some doubt upon the usefulness of this ratio, and suggests that it is not degradation-independent. 相似文献
9.
Inferences of past climate from the fossil record in lakes rely on the accurate quantification of a relationship of fossilizing organisms to their environment. Whereas the relationship of diatoms to water chemistry parameters has been modeled in many systems, few studies adequately address the relationship of diatoms to physical properties, such as water depth or hydrology, that may be more directly tied to climate. We examined the composition of modern diatoms in surface sediments of 75 isolated ponds (mostly Carolina bays) of the Atlantic Coastal Plain to: (1) assess the influence of physical and chemical variables on the distribution of diatoms among ponds of the region, and (2) develop a model that predicts hydroperiod (a measure of pond permanence) from diatom assemblages. We constructed two hydroperiod calibration models: the first infers hydroperiod from the weighted-average optima and tolerances of taxa along the hydroperiod gradient, the second bases inferences on the hydroperiod estimates of compositionally similar samples. Both approaches incorporate a-priori and post-hoc tests of assumptions often inherent in the construction of transfer functions. Diatom assemblage composition had strong, approximately linear relationships to hydroperiod, water depth, and calcium concentration in non-metric multidimensional ordination space; effects of other variables, including pH, were non-linear or ambiguous. Overall, the assemblages reflected the dilute, acidic chemical characteristics of bays. The assemblages contained differing abundances of euterrestrial, benthic and planktonic taxa, depending on a pond's susceptibility to drying. A weighted-averaging regression model based on taxon-specific hydroperiod optima generated adequate, unbiased hydroperiod inferences from diatom species composition (r2 = 0.81). This model may be used to infer past drought episodes from fossil diatom assemblages at appropriate sites on the Atlantic Coastal Plain. 相似文献
10.
Cale A. C. Gushulak Kathleen R. Laird Joseph R. Bennett Brian F. Cumming 《Journal of Paleolimnology》2017,58(2):231-241
There has been much debate over the relative importance of environmental selection and spatial variation on community organization in microorganisms. To assess the importance of environmental or spatial variables in diatom species assemblages in Gall Lake, northwest Ontario, 41 surface-sediment samples were collected in a two-dimensional gridded pattern along and across depth contours. A depth-constrained cluster analysis separated the diatom flora into three communities: a shallow-water benthic zone (B1); a deeper-water benthic zone (B2); and a planktonic zone (P). Redundancy analysis (RDA) confirmed that water depth was a major predictor of variation in the flora. Further RDAs and variation partitioning using orthogonal polynomials and Moran’s eigenvector maps showed that spatial location had minimal effect on the diatom assemblages. Principal components analysis grouped the diatom flora not only by assemblage, but also by water depth, regardless of two-dimensional spatial separation, suggesting the importance of the environmental gradients associated with lake depth. These findings indicate that environment is a more important explanatory variable than spatial variables for diatoms within lakes, suggesting dispersal plays a limited role in intra-lake diatom distributions. 相似文献
11.
The recent sediment record of Lake Belau (Schleswig–Holstein, Germany), deposited in the period 1945–2002, was compared with instrumental meteorological and limnological data. The sediments deposited during this period are annually laminated. A varve chronology was established and supported by 137Cs measurements. Micro-facies and diatom assemblage composition analyses were confirmed in thin sections and compared statistically with limnological and meteorological data. Comparison of phytoplankton data with diatom assemblage data from the sediment for the time interval from 1988 to 1999 proved that the sediments reflect limnological processes in the lake and record seasonal changes in the primary producer communities. Among the climatological data, the number of contiguous ice days (days with maximal temperatures ≤0 °C) and the state of the winter NAO are strong predictors for micro-facies development and diatom assemblage composition. Furthermore, solar and local (nutrient input) influences are visible in the diatom assemblage compositions. Our study illustrates the high potential for using analyses of micro-facies and diatom assemblages to reconstruct past weather conditions in varved sediments of Lake Belau. 相似文献
12.
Diatom assemblages and water depth in Lake 239 (Experimental Lakes Area,Ontario): implications for paleoclimatic studies 总被引：3，自引：0，他引：3
Diatom assemblages in surface sediments were sampled along three transects in Lake 239, from the Experimental Lakes Area (NW Ontario), and analyzed in order to explore the relationship between modern species distributions and water depth. Approximately 170 diatom species were identified in surficial sediments at lake depths from 2 to 30 m. The species composition varied with sample depth but remained highly similar across all three transects. The main patterns of variation in the diatom assemblages across transects, derived from a detrended correspondence analysis (DCA), showed that assemblages were highly correlated (r = 0.97 to 0.98). At depths > 8 m the pattern of predominantly benthic composition changed to a planktonic assemblage dominated by Cyclotella stelligera. This depth currently corresponds to the depth of 1% light penetration as assessed from extinction coefficient measurements. Diatom species diversity increases with the switch to the near-shore benthic taxa in all three transects. Additionally, there is a large decrease in the ratio of chrysophyte scales to diatoms at depths < 8 m. Light transmission data from wet and dry periods over the last 35 years suggests that during dry periods the extent of the littoral zone should change by over 2 m. We suggest that cores along a transect from 8 to 14 m should provide a highly sensitive location for detailed paleoclimatic study. 相似文献
13.
Diatom assemblages of surface sediments in 46 billabongs from four river floodplains in the southeast Murray-Darling Basin,
Australia were sampled to investigate drivers of species distribution. The principal purpose of the study was to derive information
to aid interpretation of diatom-based palaeoecological studies of these systems and of floodplain lakes more generally. Patterns
in billabong diatom assemblages in relation to river reach, hydrology and farming intensity on surrounding land were examined,
as were correlations with water quality variables. Seasonal variation in billabong water quality was high relative to spatial
variation, and spatial patterns in billabong water quality were weak. In contrast, strong patterns were evident in diatom
assemblages. Three main patterns were observed: (1) a distinction between billabongs dominated by planktonic diatoms from
those dominated by benthic and attached forms; (2) differences in diatom assemblages in billabongs on different river reaches;
and (3) differences in assemblages in billabongs with different hydrology. Of all water quality variables tested, total phosphorus
(TP), total nitrogen (TN) and pH exerted the strongest independent influence on diatom distribution; however, only TP remained
an important variable when species variation due to river reach, hydrology, and aquatic plant cover was taken into account.
The weak influence of water quality on diatom distribution is interpreted as reflecting the dichotomy between plankton and
non-plankton-dominated billabongs, the influence of hydrology and biogeography, the lack of strong spatial water quality gradients
and the high degree of temporal variability in water quality. The findings show that diatom records from billabong sediments
can provide evidence of long-term changes in the abundance of aquatic macrophytes and hydrology. They also suggest that merging
calibration data sets across regions for the purpose of improving diatom transfer functions for water quality reconstruction
is of limited value for floodplain lakes, and that performance is more likely to be gained by boosting site numbers within
regions. 相似文献
14.
Variability in diatom and chrysophyte assemblages and inferred pH: paleolimnological studies of Big Moose Lake,New York,USA 总被引：1，自引：0，他引：1
Donald F. Charles Sushil S. Dixit Brian F. Cumming John P. Smol 《Journal of Paleolimnology》1991,5(3):267-284
We measured variability in the composition of diatom and chrysophyte assemblages, and the pH inferred from these assemblages, in sediment samples from Big Moose Lake, in the Adirondack Mountains of New York. Replicate samples were analyzed from (1) a single sediment core interval, (2) 12 different intervals from each of 3 separate cores, and (3) 10 widely spaced surface sediment samples (0–1 cm). The variability associated with sample preparation (subsampling, processing, and counting) was relatively small compared to between-core and within-lake variability. The relative abundances of the dominant diatom taxa varied to a greater extent than those of the chrysophyte scale assemblages. Standard deviations of pH inferences for multiple counts from the same sediment interval from diatom, chrysophyte, and diatom plus chrysophyte inference equations were 0.04 (n=8), 0.06 (n=32), and 0.06 (n=8) of a pH unit, respectively. Stratigraphic analysis of diatoms and chrysophytes from three widely spaced pelagic sediment cores provided a similar record of lake acidification trends, although with slight differences in temporal rates of change. Average standard deviations of pH inferences from diatom, chrysophyte and diatom plus chrysophyte inference equations for eight sediment intervals representing similar time periods but in different cores were 0.10, 0.20, and 0.09 pH unit, respectively. Our data support the assumption that a single sediment core can provide an accurate representation of historical change in a lake. The major sources of diatom variability in the surface sediments (i.e., top 1.0 cm) were (1) differences in diatom assemblage contributions from benthic and littoral sources, and (2) the rapid change in assemblage composition with sediment depth, which is characteristic of recently acidified lakes. Because scaled chrysophytes are exclusively planktonic, their spatial distribution in lake sediments is less variable than the diatom assemblages. Standard deviations of pH inferences for 10 widely spaced surface sediment samples from diatom, chrysophyte and diatom plus chrysophyte inference equations were 0.21, 0.09, and 0.16 of a pH unit, respectively. 相似文献
15.
Abundance,biomass and composition of spring ice algal and phytoplankton communities of the Laptev Sea(Arctic) 
下载免费PDF全文
下载免费PDF全文 <正> Abundance,biomass and composition of the ice algal and phytoplank-ton communities were investigated in the southeastern Laptev Sea in spring 1999.Diatoms dominated the algal communities and pennate diatoms dominated the dia-tom population.12 dominant algal species occurred within sea ice and underlyingwater column,including Fragilariopsis oceanica,F.cylindrus,Nitzschiafrigida,N.promare,Achnanthes taeniata,Nitzschia neofrigida,Naviculapelagica,N.vanhoef fenii,N.septentrionalis,Melosira arctica,Clindrothecaclosterium and Pyrarnimonas sp.The algal abundance of bottom 10 cm sea icevaried between 14.6 and 1562.2×10~4 ceils l~(-1)with an average of 639.0×10~4cells l~(-1),and the algal biomass ranged from 7.89 to 2093.5μg C l~(-1)with an av-erage of 886.9μg C l~(-1),which were generally one order of magnitude higherthan those of sub-bottom ice and two orders of magnitude higher than those ofunderlying surface water.The integrated algal abundance and biomass of lower-most 20 cm ice column were averagely 7.7 and 12.2 times as those of upper 20 mwater column,respectively,suggesting that the ice algae might play an importantrole in maintaining the coastal marine ecosystem before the thawing of sea ice.Icealgae influenced the phytoplankton community of the underlying water column.However,the“seeding”of ice algae for phytoplankton bloom was negligible be-cause of the iow phytoplankton biomass within the underlying water column. 相似文献
16.
Twenty high Arctic lakes and ponds were sampled for water chemistry and modern diatom assemblages in two distinct physiographic
sectors of Sirmilik National Park, Nunavut, Canada. Sites on southwestern Bylot Island were warmer, more alkaline, less dilute,
and had higher concentrations of nutrients, DOC and Chl-a (mesotrophic to oligo-mesotrophic), whereas sites on Qorbignaluk Headland on northern Baffin Island were deeper, very dilute,
mostly oligotrophic and had lower pH. Diatom assemblages differed markedly between these two regions as a consequence of limnological
differences between them. Paleolimnological records, spanning > 200 years and dated by 210Pb activity, were produced from each region to compare biological responses to recent warming inferred from glaciological
studies on Bylot Island and regional syntheses for the Arctic. Diatom assemblages began to change around AD 1900 at both sites.
At Qorbignaluk Headland, marked shifts in diatom community composition occurred during the twentieth century, with large increases
in the abundance of planktonic diatoms. At Bylot Island, diatom community changes began around the same time, and involved
modest decreases in planktonic diatoms and increases in inferred specific conductance, likely because of a decrease in the
areal extent of the small lake as a response to warming. The study confirms that responses of freshwater ecosystems to climate
warming vary depending on local physiographic factors. 相似文献
17.
Two short sediment cores from the Archipelago Sea in the northern Baltic Sea were examined for their siliceous microfossils
in order to study recent eutrophication in the area. The diatom record was divided into diatom assemblage zones. Locally weighted
weighted averaging regression and calibration was applied for the quantitative reconstruction of past TN concentrations. The
cores were dated using radiometric (210Pb, 226Ra and 137Cs) methods. The diatom assemblages in the topmost zones in both cores indicate eutrophication during the last decade. TN
reconstructions partially fail to trace the actual measured TN concentrations. Especially from the late 1980s to the mid 1990s,
the dominating diatom species are more influenced by other factors, such as the length of the ice season, than by nutrient
concentrations. It seems that in the Archipelago Sea, diatom assemblages are principally governed by climatic fluctuations
with a moderate influence of eutrophication in recent years. The peak in sedimentation in the early 1990s coincides with the
short ice seasons indicating that sedimentation may increase with decreasing ice-cover extent due to warming climate. 相似文献
18.
A coupled ice-ocean ecosystem model for 1-D and 3-D applications in the Bering and Chukchi Seas 下载免费PDF全文
下载免费PDF全文 Clara Deal 《极地研究》2008,19(2):218-229
Primary production in the Bering and Chukchi Seas is strongly influenced by the annual cycle of sea ice.Here pelagic and sea ice algal ecosystems coexist and interact with each other.Ecosystem modeling of sea ice associated phytoplankton blooms has been understudied compared to open water ecosystem model applications. This study introduces a general coupled ice-ocean ecosystem model with equations and parameters for 1-D and 3-D applications that is based on 1-D coupled ice-ocean ecosystem model development in the landfast ice in the Chukchi Sea and marginal ice zone of Bering Sea.The biological model includes both pelagic and sea ice algal habitats with 10 compartments:three phytoplankton(pelagic diatom,flagellates and ice algae:D,F,and Ai),three zooplankton(copepods,large zooplankton,and micro-zooplankton :ZS,ZL,ZP),three nutrients(nitrate+nitrite,ammonium,silicon: NO_3,NH_4,Si) and detritus(Det).The coupling of the biological models with physical ocean models is straightforward with just the addition of the advection and diffusion terms to the ecosystem model.The coupling with a multi-category sea ice model requires the same calculation of the sea ice ecosystem model in each ice thickness category and the redistribution between categories caused by both dynamic and thermodynamic forcing as in the physical model.Phytoplankton and ice algal self-shading effect is the sole feedback from the ecosystem model to the physical model. 相似文献
19.
采用表面荧光显微分析方法对2014年夏季中国第6次北极科学考察期间采集于加拿大海盆7个海冰站位的融池、冰芯和冰下海水样品进行了细菌和原生生物群落分析。结果表明,上述3类生境中的第一优势类群均为细菌(不包括ICE07站位出现水华融池的统计),分别占总生物量的42.8%、37.8%和50.7%;第二优势类群均为鞭毛虫,分别占总生物量的40.2%、34.3%和37.5%。包含细菌、鞭毛虫和纤毛虫在内的异养生物在总生物量中占有优势,显示微食物环在其中起着重要作用。在北冰洋夏季快速融冰的背景下,3类生境总体上缺少快速生长的条件,总生物量偏低。其中ICE07站位出现融池水华和冰表自养鞭毛藻高值,推测合适的藻种和营养盐的额外补充共同促成了该站位冰表(融池)藻华的形成。 相似文献
20.
Ulrike Hoff Oleg Dirksen Veronika Dirksen Ulrike Herzschuh Hans-Wolfgang Hubberten Hanno Meyer Christel van den Bogaard Bernhard Diekmann 《Journal of Paleolimnology》2012,47(4):549-560
Fossil diatom assemblages in a sediment core from a small lake in Central Kamchatka (Russia) were used to reconstruct palaeoenvironmental
conditions of the late Holocene. The waterbody may be a kettle lake that formed on a moraine of the Two-Yurts Lake Valley,
located on the eastern slope of the Central Kamchatka Mountain Chain. At present, it is a seepage lake with no surficial outflow.
Fossil diatom assemblages show an almost constant ratio between planktonic and periphytic forms throughout the record. Downcore
variations in the relative abundances of diatom species enabled division of the core into four diatom assemblage zones, mainly
related to changes in abundances of Aulacoseira subarctica, Stephanodiscus minutulus, and Discostella pseudostelligera and several benthic species. Associated variations in the composition and content of organic matter are consistent with the
diatom stratigraphy. The oldest recovered sediments date to about 3220 BC. They lie below a sedimentation hiatus and likely
include reworked deposits from nearby Two-Yurts Lake. The initial lake stage between 870 and 400 BC was characterized by acidic
shallow-water conditions. Between 400 BC and AD 1400, lacustrine conditions were established, with highest contributions from
planktonic diatoms. The interval between AD 1400 and 1900 might reflect summer cooling during the Little Ice Age, indicated
by diatoms that prefer strong turbulence, nutrient recycling and cooler summer conditions. The timing of palaeolimnological
changes generally fits the pattern of neoglacial cooling during the late Holocene on Kamchatka and in the neighbouring Sea
of Okhotsk, mainly driven by the prevailing modes of regional atmospheric circulation. 相似文献