共查询到20条相似文献,搜索用时 15 毫秒
1.
Crawford Lake, a meromictic lake located near Toronto, Canada, was cored to determine if algal pigments preserved in its sediments would make it possible to infer past changes in lake productivity over the last five hundred years. From 1500 to 1910 A.D. the sediments display extremely high levels of oscillaxanthin and myxoxanthophyll while chlorophyll derivatives and total carotenoids were relatively low. As the lake became increasingly more eutrophic in the latter part of the twentieth century, this relationship reversed itself. Competition for light between the deep dwelling cyanobacteria in the algal mat on the lake's bottom (8–14 m) and phytoplankton in the overlying surface layers of the water column (5–7 m) was attributed to the observed reduction in oscillaxanthin and myxoxanthophyll as Crawford Lake eutrophied. Because the major cyanobacteria in Crawford Lake are benthic mat forming Lyngbya and Oscillatoria, and not phytoplankton, competition for light with the overlying phytoplankton is critical in determining the total quantity of oscillaxanthin and myxoxanthophyll preserved in the lake's profundal sediments. These findings have major implications for the use of cyanobacterial pigments as indicators of lake trophic status in lakes where benthic algal mats are present. 相似文献
2.
Increasing degradation of the water quality, caused by overuse and salinization, leads to considerable changes of the phytoplankton
composition in Kenyan Rift Valley lakes. Exemplarily, the phytoplankton communities and biomasses of deteriorating freshwater
Lake Naivasha and salinizing Lake Oloidien were studied between 2001 and 2005, accompanied by physico-chemical measurements
(pH, total phosphorus and nitrogen, alkalinity, conductivity). Over the last three decades, the ecology of these two water
basins has been subjected to dramatic changes, caused by excessive use of water and catchment area by man. In L. Naivasha
a shift in the dominance of coccoid cyanobacteria towards dominance of Chlorophyceae (Botryococcus terribilis) was observed. Lake Oloidien exhibited a shift in the dominance of coccoid Chlorophyceae towards dominance of cyanobacteria
(Arthrospira fusiformis, Anabaenopsis elenkinii). Phytoplankton findings and chemical data demonstrate that L. Naivasha has developed towards a eutrophic freshwater lake
while L. Oloidien has progressed towards a hypereutrophic alkaline-saline lake.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.
Handling editor: J. Padisak 相似文献
3.
Andrew Clarke J. Cynan Ellis-Evans Mark W. Sanders Lesley J. Holmes 《Hydrobiologia》1989,172(1):183-191
The copepod Pseudoboeckella poppei (Daday) (Calanoida, Centropagidae) was sampled from Sombre and Heywood Lakes on Signy Island, Antarctica (60° S, 45° W) between January 1984 and March 1985. Sombre Lake is clear and oligotrophic with little phytoplankton and a bottom sediment low in organic content. By contrast Heywood Lake is turbid and mesotrophic; a substantial phytoplankton develops in summer and the bottom sediments are comparatively rich in organics. Both lakes freeze over for much of the year, forcing the copepods to adopt a benthic feeding strategy over winter. Adult Pseudoboeckella feed on phytoplankton when this is available, but also on detritus, diatoms and short algal filaments stirred up from the sediment. In Heywood Lake, male copepods show a smooth seasonal trend in lipid content with lipid being synthesised in early summer and utilised in late summer and winter. The summer increase in lipid content is associated with an increase in dry weight. Female lipid contents show evidence of two peaks of egg production. In Sombre Lake both male and female copepods increase in size during summer and show a wider range of lipid contents than in Heywood Lake; it is likely that this is due to the poorer winter feeding conditions which necessitate the synthesis of a much larger store of reserves during the summer. In contrast to marine calanoid copepods, lipid stores are exclusively triacylglycerol with no trace of wax ester. 相似文献
4.
The movement of sediment between the lake bottom and water column of shallow lakes can be sizeable due to the large potential
for resuspension in these systems. Resuspended sediments have been shown to alter phytoplankton community composition and
elevate water column production and nutrient concentrations. We measured the summer sedimentation rates of two lakes in 2003
and six lakes in 2004. All lakes were shallow and located in the Alaskan Arctic. In 2004, turbidity, light attenuation, total
sediment:chlorophyll a mass in the sediment traps, and thermal stratification were also measured in each of the lakes. The sediment:chlorophyll
a mass was much greater than if the sediment was derived from phytoplankton production in all of the lakes, indicating that
the source of the sedimenting material was resuspension and allochthonous inputs. Consistent with these findings, the temporal
variation in sedimentation rate was synchronous between most lakes, and sedimentation rate was positively related to wind
speed and rainfall suggesting that sedimentation rate was strongly influenced by landscape-scale factors (e.g., wind and rain
events). Two of the lakes are located on deposits of loess that accumulated during past glacial periods. These two lakes had
sedimentation rates that were significantly greater and more variable than any of the other lakes in the study, as well as
high turbidity and light attenuation. Our results indicate that sedimentation in these shallow arctic lakes is supported primarily
by allochthonous inputs and resuspension and that landscape-scale factors (e.g., weather and geology) impact on the transport
of materials between the lake bottom and water column.
Handling editor: J. Saros 相似文献
5.
G. Martins I. Henriques D. C. Ribeiro A. Correia P. L. E. Bodelier J. V. Cruz 《Geomicrobiology journal》2013,30(8):704-715
In the Azores, the advanced trophic state of the lakes requires a fast intervention to achieve the good ecological status prescribed by the Water Framework Directive. Despite the considerable effort made to describe the phytoplankton growing on the water column, the lack of information regarding the microbial processes in sediments is still high. Thus, for the successful implementation of internal management actions, the present work explored the relationships between geochemical profiles and dominant members of the bacterial community in sediments from eutrophic Azorean lakes. Lake Azul geochemical profiles were quite homogeneous for all parameters, while in lake Furnas the total iron profile presented a peak below the aerobic layer. For lake Verde, the concentrations of all studied parameters (20 ± 2% loss-on-ignition; 2.10 ± 0.08 mg g?1 total phosphorus; 1.31 ± 0.50 mg g?1 total nitrogen; 8.06 ± 0.13 mg g?1 total iron) in the uppermost sediment layer were approximately two times higher than the ones in sediments from other lakes, decreasing with sediment depth. The higher amounts of phosphorus and organic matter in lake Verde suggested a higher internal contribution of phosphorus to eutrophication. The dominant members of the sediment bacterial community, investigated by denaturing gradient gel electrophoresis, were mostly affiliated to Proteobacteria phylum (Alpha-, Delta-, and Gamma-subclasses), group Bacteroidetes/Chlorobi and phylum Chloroflexi. The Cyanobacteria phylum was solely detected in sediments from lake Verde and lake Furnas that presented the highest amounts of nitrogen and phosphorus both in the water column and sediments, while the other phyla were detected in sediments from the three studied lakes. In conclusion, management measurers to achieve the good ecological status until 2015 should be distinct for the different lakes taking into account the relative magnitude of the nutrient sources and the bacterial diversity in sediments. 相似文献
6.
Macroalgal blooms have occurred worldwide frequently in coastal areas in recent decades, which dramatically modify phosphorus (P) cycle in water column and the sediments. Rongcheng Swan Lake Wetland, a coastal wetland in China, is suffering from extensive macroalgal blooms. In order to verify the influence of macroalgal growth on sediment P release, the sediments and filamentous Chaetomorpha spp. were incubated in the laboratory to investigate the changes of water quality parameters, P levels in overlying water, and sediments during the growth period. In addition, algal biomass and tissue P concentration were determined. In general, Chaetomorpha biomasses were much higher in high P treatments than in low P treatments. Compared with algae+low P water treatment, the addition of sediments increased the algal growth rate and P accumulation amount. During the algal growth, water pH increased greatly, which showed significant correlation with algal biomass in treatments with high P (P < 0.05). P fractions in the sediments showed that Fe/Al–P and organic P concentrations declined during the algal growth, and great changes were observed in algae+low P water+sediment treatment for both. As a whole, the sediments can supply P for Chaetomorpha growth when water P level was low, and the probable mechanism was the release of Fe/Al–P at high pH condition induced by intensive Chaetomorpha blooms. 相似文献
7.
Effects of sediment resuspension on phytoplankton production: teasing apart the influences of light, nutrients and algal entrainment 总被引:13,自引:0,他引:13
1. Wind‐induced sediment resuspension can affect planktonic primary productivity by influencing light penetration and nutrient availability, and by contributing meroplankton (algae resuspended from the lake bed) to the water column. We established relationships between sediment resuspension, light and nutrient availability to phytoplankton in a shallow lake on four occasions. 2. The effects of additions of surficial sediments and nutrients on the productivity of phytoplankton communities were measured in 300 mL gas‐tight bottles attached to rotating plankton wheels and exposed to a light gradient, in 24 h incubations at in situ temperatures. 3. While sediment resuspension always increased primary productivity, resuspension released phytoplankton from nutrient limitation in only two of the four experiments because the amount of available nitrogen and phosphorus entrained from the sediments was small compared with typical baseline levels in the water column. In contrast, chlorophyll a entrainment was substantial compared with baseline water column concentrations and the contribution of meroplankton to primary production was important at times, especially when seasonal irradiance in the lake was high. 4. Comparison of the in situ light climate with the threshold of light‐limitation of the phytoplankton indicated that phytoplankton in the lake were only likely to be light‐limited at times of extreme turbidity (e.g. >200 nephelometric turbidity units), particularly when these occur in winter. Therefore, resuspension influenced phytoplankton production mainly via effects on available nutrients and by entraining algae. The importance of each of these varied in time. 5. The partitioning of primary productivity between the water column and sediments in shallow lakes greatly influences the outcome of resuspension events for water column primary productivity. 相似文献
8.
Jeroen Van Wichelen Steven Declerck Koenraad Muylaert Ivan Hoste Vanessa Geenens Jochen Vandekerkhove Erik Michels Niels De Pauw Maurice Hoffmann Luc De Meester Wim Vyverman 《Hydrobiologia》2007,584(1):291-303
Lake Kraenepoel (Belgium) is a shallow lake (22 ha), divided in two basins since 1957 by a shallow dike. The lake was used
for fish farming until World War II and was drawn down about every 5 years to harvest fish. Despite its dense historical carp
population, it had clear water and a rich Littorelletea vegetation. During the course of the 20th century, the lake became
eutrophic and the Littorelletea vegetation degraded. The northern basin, which was still drawn down about every decade after
1957, retained its clear water and had a dense submerged macrophyte vegetation. The southern basin, which was never drawn
down after 1957 and which received direct surface water inputs, had become a turbid shallow lake with phytoplankton blooms
in summer. In 2000, efforts were taken to restore the lake: the entire lake was drawn down, the fish community was biomanipulated,
nutrient-rich surface water inputs were diverted from the southern basin and sediments were removed (only in the northern
basin). Fish biomanipulation and sediment removal were successful in the northern basin, as nutrient levels declined and the
Littorelletea vegetation recovered. In the southern basin, sediment analyses indicated that drawdown resulted in sediments
with a lower water and organic matter content and water column turbidity decreased after the drawdown. But pH in the southern
basin declined to <4, probably because sulphides in the sediment were oxidized during drawdown and sediment desiccation. In
contrast, desiccated sediments were removed from the northern basin and pH did not decline below 6 after restoration. In spite
of the still high dissolved nutrient concentrations, phytoplankton biomass declined significantly in the southern basin, probably
due to acidification. However, no Littorelletea species colonised the lake bottom in the southern basin. Thus, lake drawdown
may be a useful management technique to promote clear water conditions in shallow lakes. However, acidification due to sulphide
oxidation may be an undesirable outcome and should be considered in drawdown and sediment desiccation manipulations. 相似文献
9.
Extreme water level decline effects sediment distribution and composition in Lake Alexandrina,South Australia 总被引:1,自引:0,他引:1
Water level decline affects the biophysical environment of shallow lakes. Unprecedented drought in Australia’s Murray–Darling Basin resulted in extreme water level drawdown in the large, shallow Lake Alexandrina at the end of the River Murray. Surface sediment was collected from 22 sites in the lake before and after water levels declined to assess the integrated limnological changes over the period of drawdown. Results indicate an increase in the proportion of organic particles in profundal sediments, as well as an increase of fine particles (<19.9 μm) in peripheral sediments. These changes to sediment composition corresponded to higher concentrations of suspended particles at low water levels. Increased autochthony and a shift in primary production from macrophytes to phytoplankton in Lake Alexandrina support these findings. Inorganic carbon and other nutrients were lost from sandy sediments most likely through carbonate dissolution driven by a localized decrease in pore water pH from increased mineralisation of organic matter. 相似文献
10.
The advective transport of algal cells into the interstices of the hyporheic zone of the River Elbe was spatially and temporally heterogenous. Even deep sediment layers were reached by large phytoplankton species. Therefore, it is suggested that (i) the advective interstitial transport patterns vary between different algal sizes and morphotypes and (ii) sediment characteristics, expressed by the permeability coefficient kf of porous media, affect retention and retardation of surface water algae during subsurface transport. The transport behaviour of different green algae (Chlorella sp., Scenedesmus acuminatus, Desmodesmus communis, and Pediastrum duplex) and algal sized microspheres was tested in flow‐through column experiments with hyporheic sediments. The algal cell transport was directly related to the permeability of the column sediments. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
11.
Methane in maritime Antarctic freshwater lakes 总被引:4,自引:0,他引:4
J. C. Ellis-Evans 《Polar Biology》1984,3(2):63-71
Summary Methane was found to occur in all freshwater lakes, irrespective of trophic status, sampled during this preliminary investigation at Signy Island, South Orkney Islands, Antarctica. Methane accumulated in the water column of these lakes during the winter period when ice cover prevented wind-induced mixing. Maritime Antarctic lakes are usually subject to wind-induced complete mixing during the summer open-water period but two major exceptions to the rule were found during this study. Methanogenesis occurred in both littoral and profundal regions of oligotrophic Sombre Lake. The presence of a substantial algal mat stabilized the Eh status of underlying sediments at the littoral site. Methane production was confined to the sediments in both littoral and profundal sediments during the study period (December–March) but in winter probably migrated to the sediment surface at the profundal site. All Signy Island lakes sampled were sulphate-poor and addition of sulphate markedly inhibited methanogenesis. Radio-isotope studies indicated that the H2/CO2 pathway was probably the predominant route for methanogenesis in these sediments through the acetate pathway appeared equally important at the sediment surface. In the absence of sulphate, sulphate reducers probably acted as net hydrogen donors to the methanogens. The process rate was permanently limited by the consistent low temperature (annual range 1–3°C). Rates increased with increasing temperature over the range 4–32°C, but no evidence was found to suggest cold sensitivity or psychrophily. The optimum temperature for methanogenesis was in excess of 30°C, temperatures never experienced at Signy Island. Rates of methanogenesis during the study period (Dec–Mar) ranged from 0.29 to 0.45 mg of carbon m-2 and on an annual basis methanogenesis was calculated equivalent to 13% of the organic carbon deposition rate. 相似文献
12.
We hypothesised that (i) a summer heat wave would increase the thermal stability of lakes and (ii) the size and trophic state
differences would modify the lakes’ responses to heating. Within 2 years, 2008 and 2009, we studied the thermal and optical
regimes of two adjacent stratified lakes in northern Italy, the oligo-mesotrophic Lake Monate (2.5 km2, max. depth 34 m) and the eutrophic Lake Varese (14.8 km2, 26 m). After the cold winter 2008–2009, a heat wave starting in May turned the whole year 2009 the second hottest after
2003. The particular sequence of meteorological events resulted in extreme vertical temperature gradients and unusually high
thermal stability of both lakes. All calculated thermal parameters showed the highest values in 2009 while also the values
for 2008 exceeded considerably those published for these lakes in the past. Due to the large wind exposed surface, wind mixing
was supposedly the dominating mechanism of heat transfer in the shallower eutrophic Lake Varese where, due to low water transparency,
large amount of solar energy trapped in the upper layers markedly increased the thermal stability. In the deeper and more
transparent Lake Monate, the deeper penetrating solar irradiance contributed to better energy dissipation within the water
column and smaller interannual differences in thermal stability. 相似文献
13.
Phytoplankton biomass and distribution in a shallow eutrophic lake (Lake George,Uganda) 总被引:8,自引:0,他引:8
G. G. Ganf 《Oecologia》1974,16(1):9-29
Summary Lake George, a shallow lake in western Uganda, supports a permanent and dense crop of phytoplankton, and may be regarded as eutrophic although the ambient concentrations of inorganic nitrogen and phosphorus are low. The figures for the annual nutrient loadings (Viner and Smith, 1973) would suggest, however, a eutrophic lake when analysed on the scheme of eutrophication proposed by Vollenweider (1968).The horizontal distribution of chlorophyll a shows a concentric pattern, with the maximum values occurring towards the center. This horizontal variation is thought to reflect water movements, and a general pattern of water flow is proposed.The majority of the species show no seasonal variation but populations of both Anabaena and Melosira show annual variations. These two species also have a horizontal distribution pattern which is the reverse of other species. This pattern is used to support the proposed movements of water.Phytoplankton generation times are discussed in relation to the diurnal cycle occurring in Lake George. 相似文献
14.
Diffusive exchange of linear alkylbenze suifonates (LAS) between overlying water and bottom sediment
Linear alkylbenzenesulfonate (LAS) was detected in a 0–30 cm deep sediment column collected in Lake Teganuma (one of the most polluted lakes in Japan). The range of the LAS concentration in sediments was between 0.1 and 500 µg g–1 (C11-C14 homologs per dry solid) and its vertical profile showed a seasonal variation. A mathematical model, which includes a diffusion term and a biodegradation term, was used to simulate the temporal variation of LAS in the sediment column and to calculate the diffusive flux rate of LAS across the sediment/water interface. An averaged diffusion coefficient of 2.4 × 10–5 cm2 s–1 for the sediment interstitial water was obtained from sediment core samples located in Lake Teganuma. The biodegradation rate constant (0.002 d–1) of LAS in the sediment obtained from the model analysis was considerably less than that reported for LAS in anaerobic waters. These results confirm that a model describing diffusive transport and biodegradation of LAS in the sediments can simulate the temporal variation of LAS in near surface sediments. The diffusive flux rate from overlying water to bottom sediment was calculated to be between –0.20 and 0.52 (C11-C14 LAS) mg m–2 h–1 and the annual net flux rate was 0.7 g m–2 y–1. 相似文献
15.
Oxygen concentration profiles have been measured, by means of with microelectrodes in sediments of Lake Baikal and Lake Malawi,
along transects allowing to give a survey of two major ancient Rift lakes: Lake Baikal (Eastern Siberia) and Lake Malawi (East
Africa), along depth transects in the constitutive basins of the lakes and/or of relevant depths with regard to oxygen (including
including the deepest point, 1680 m, in Lake Baikal). Sediment oxygen penetration depths (SOPs) display very different patterns,
depending on the lake in the two lakes. In Lake Baikal, SOPs are variable, show no significant relationship with bathymetric
depth and are surprisingly deep on Akademichesky ridge (> 50.0 mm), emphasizing the distinctive feature of this region in
the lake. While the Selenga river is an important source of eutrophication, the similarity of SOP-values in the Selenga shallow
with those of most other sites suggests either a dilution of organic material by allochthonous matter, or a strong south-to-north
transport of particles. In Lake Malawi, available oxygen is restricted to a maximum of three millimetres of the sediment,
and there is a negative relationship with bathymetric depth, as a result of a steady decline of oxygen concentration with
depth through the water column. Amongst the few parameters known to affect SOPs, the oxygen consumption by the sediment seems
the most significant in both lakes. SOP-values furthermore confirm differences in the trophic status of Baikal and Malawi,
respectively. The importance of oxygen as a factor likely to create ecological segregation for benthic organisms is discussed.
Lake Malawi offers possibilities of bathymetric segregation but no vertical segregation in the sediment. In contrast, no bathymetric
segregation related to oxygen is possible in Lake Baikal, but vertical segregation in the sediment is very likely.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
16.
Xinqing Zhao Liuyan Yang Can Chen Lin Xiao Lijuan Jiang Zhe Ma Haowei Zhu Zhenyang Yu Daqiang Yin 《Frontiers of Biology in China》2008,3(3):293-299
In this study, PCR-denaturing gradient gel electrophoresis (DGGE) was applied to analyze the microbial communities in lake
sediments from Lake Xuanwu, Lake Mochou in Nanjing and Lake Taihu in Wuxi. Sediment samples from seven locations in three
lakes were collected and their genomic DNAs were extracted. The DNA yields of the sediments of Lake Xuanwu and Lake Mochou
were high (10 μg/g), while that of sediments in Lake Taihu was relatively low. After DNA purification, the 16S rDNA genes
(V3 to V5 region) were amplified and the amplified DNA fragments were separated by parallel DGGE. The DGGE profiles showed
that there were five common bands in all the lake sediment samples indicating that there were similarities among the populations
of microorganisms in all the lake sediments. The DGGE profiles of Lake Xuanwu and Lake Mochou were similar and about 20 types
of microorganisms were identified in the sediment samples of both lakes. These results suggest that the sediment samples of
these two city lakes (Xuanwu, Mochou) have similar microbial communities. However, the DGGE profiles of sediment samples in
Lake Taihu were significantly different from these two lakes. Furthermore, the DGGE profiles of sediment samples in different
locations in Lake Taihu were also different, suggesting that the microbial communities in Lake Taihu are more diversified
than those in Lake Xuanwu and Lake Mochou. The differences in microbial diversity may be caused by the different environmental
conditions, such as redox potential, pH, and the concentrations of organic matters. Seven major bands of 16S rDNA genes fragments
from the DGGE profiles of sediment samples were further re-amplified and sequenced. The results of sequencing analysis indicate
that five sequences shared 99%–100% homology with known sequences (Bacillus and Brevibacillus, uncultured bacteria), while the other two sequences shared 93%–96% homology with known sequences (Acinetobacter, and Bacillus). The study shows that the PCR-DGGE technique combined with sequence analysis is a feasible and efficient method for the
determination of microbial communities in sediment samples.
__________
Translated from Acta Ecologica Sinica, 2006, 26(11): 3610–3616 [译自: 生态学报] 相似文献
17.
Dennis Trolle Guangwei Zhu David Hamilton Liancong Luo Chris McBride Lu Zhang 《Hydrobiologia》2009,627(1):31-44
Distinct horizontal water column concentration gradients of nutrients and chlorophyll a (Chl a) occur within large, shallow, eutrophic Lake Taihu, China. Concentrations are high in the north, where some of the major
polluted tributaries enter the lake, and relatively low in the south, where macrophytes generally are abundant. It is not
clear, however, whether these water column concentration gradients are similarly reflected in spatial heterogeneity of nutrient
concentrations within the bottom sediments. The main objective of this study was therefore to test if horizontal and vertical
variations in the phosphorus and nitrogen content in bottom sediments of Lake Taihu are significantly related to (1) horizontal
variations in overlying water column nutrient concentrations and (2) other sediment geochemical constituents. We measured
the concentration of total phosphorus (TP) and total nitrogen (TN) in surficial sediments (0–2 cm) and TP, TN and Chl a concentrations in water column samples, collected from 32 sites in 2005. In 2006 sediment, TP, TN, carbon, iron and manganese
concentrations were measured vertically at 2 cm intervals, extending to a depth of approximately 20 cm, at an additional eight
sites. Linear correlation analysis revealed that surficial sediment TP concentrations across the 32 stations were related
significantly, though weakly, to annual mean water column concentrations of TP, TN as well as Chl a. Correlations of surficial sediment TN with water column variables were, however, not significant (P > 0.05). Amongst the geochemical variables tested, the vertical variability of sediment TP concentrations was most strongly
related to sediment manganese and carbon concentrations. A multiple stepwise linear regression revealed that the combination
of sediment manganese and carbon concentrations explained 91% of the horizontal variability in sediment TP concentrations
and 65% of the vertical variability.
Handling editor: Luigi Naselli-Flores 相似文献
18.
Huan‐Sheng Cao Fan‐Xiang Kong Jian‐Kang Tan Xiao‐Feng Zhang Yi Tao Zhou Yang 《International Review of Hydrobiology》2005,90(4):347-357
Recruitment of total phytoplankton, chlorophytes and cyanobacteria from lake sediments to the water column was studied using photosynthetic pigments at one site (1.5 m) in Lake Taihu, a large shallow lake in China. Samples were taken weekly from the migration traps installed on the bottom from March to May 2004. Abundance of total phytoplankton, chlorophytes and cyanobacteria were represented by Chlorophyll (Chl) a, b, and phycocyanin (PC), respectively. Over the three months, total phytoplankton, chlorophytes, and cyanobacteria corresponding to 48.9%, 68.9% and 316.2% of their initial concentrations in surface sediments were recruited in Lake Taihu. However, compared with their increase in pelagic abundance over the same period, the recruitment accounted for a rather small inoculum. Accompanying the recruitment, total phytoplankton and chlorophytes declined and cyanobacteria increased in the upper 0–2 cm sediments; colonies of Microcystis aeruginosa in the water column enlarged from small size with several cells to large colonies with hundreds of cells. Thus, overwintering and subsequent growth renewal of pelagic phytoplankton merits further study and comparison with benthic survival and recruitment. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
19.
The diatom flora of three lakes in the ice-free Amery Oasis, East Antarctica, was studied. Two of the lakes are meltwater reservoirs, Terrasovoje Lake (31 m depth) and Radok Lake (362 m depth), while Beaver Lake (>435 m depth) is an epishelf lake. The lakes can be characterized as cold, ultra-oligotrophic and alkaline, displaying moderate (Radok and Terrasovoje lakes) to high (Beaver Lake) conductivities. There was no diatom phytoplankton present in any of the three lakes. While 34 benthic diatom taxa were identified from modern and Holocene sediments of Terrasovoje and Radok lakes, a 30-cm long sediment core recovered in Beaver Lake was barren. Five species (Luticola muticopsis, Muelleria peraustralis, Pinnularia cymatopleura, Psammothidium metakryophilum, P. stauroneioides) are endemic to the Antarctic region. All identified taxa are photographically documented and brief notes on their taxonomy, biogeography and ecology are provided. The most abundant diatom taxa are Amphora veneta, Craticula cf. molesta, Diadesmis
spp, M. peraustralis and Stauroneis anceps. This is the first report on the diatom flora in lakes of the Amery Oasis.This revised version was published online in May 2004 with corrections to Figure 1. 相似文献
20.
Coupling between benthic biomass of Microcystis and phosphorus release from the sediments of a highly eutrophic lake 总被引:2,自引:0,他引:2
Variations in microbial biomass and activity in the sediments of hypereutrophic Lake Vallentunasjön were followed during a period of 5 years. The data were compared to the calculated release of phosphorus from the sediments during the same period. A strong co-variation was found between biomass of Microcystis, heterotrophic bacterial activity in the sediments and internal phosphorus loading. These parameters exhibited mainly a declining trend during the investigation period. A pronounced stability of the sediment chemistry, including the fractional composition of the sediment phosphorus, during the studied period indicates that microbial activity affected the phosphorus release from the sediments. Calculations of the percentage of sediment bacteria that was associated to the mucilage of Microcystis colonies imply, together with the specific bacterial production, that Microcystis in the sediment stimulates bacterial production. In the highly phosphorus-saturated sediments of Lake Vallentunasjön this would ultimately lead to an increased release of phosphorus from the sediment. Lake Vallentunasjön does not follow the common pattern of recovery after reduction of external phosphorus loading. The large biomasses and long survival of Microcystis in the sediment are probably important reasons for the delayed recovery of the lake. 相似文献