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1.
We employed culture-dependent and -independent techniques to study microbial diversity in Lake Chaka, a unique hypersaline lake (32.5% salinity) in northwest China. It is situated at 3,214 m above sea level in a dry climate. The average water depth is 2 to 3 cm. Halophilic isolates were obtained from the lake water, and halotolerant isolates were obtained from the shallow sediment. The isolates exhibited resistance to UV and gamma radiation. Microbial abundance in the sediments ranged from 10(8) cells/g at the water-sediment interface to 10(7) cells/g at a sediment depth of 42 cm. A major change in the bacterial community composition was observed across the interface. In the lake water, clone sequences affiliated with the Bacteroidetes were the most abundant, whereas in the sediments, sequences related to low G+C gram-positive bacteria were predominant. A similar change was also present in the archaeal community. While all archaeal clone sequences in the lake water belonged to the Halobacteriales, the majority of the sequences in the sediments were related to those previously obtained from methanogenic soils and sediments. The observed changes in the microbial community structure across the water-sediment interface were correlated with a decrease in salinity from the lake water (32.5%) to the sediments (approximately 4%). Across the interface, the redox state also changed from oxic to anoxic and may also have contributed to the observed shift in the microbial community. 相似文献
2.
A field study was conducted (May 1981 to June 1982) to develop a data-base on seasonal changes of water and sediment chemistry of Lake Monroe (4 000 ha surface and ca. 2 m deep) located in central Florida, USA. This shallow eutrophic lake is a part of the St. Johns River. Quantitative samples of lake water and sediments were collected on a monthly basis from 16 stations and analyzed for various physico-chemical parameters. Relatively high levels of dissolved solids (mean electrical conductivity (EC) = 1832 µS cm 1) prevailed in the lake water, and seasonal changes in EC were probably associated with hydrologic flushing from external sources, such as incoming water from upstream as well as precipitation. Average monthly levels of total N and P during the study period were 1.82 and 0.21 mg l –1, respectively. Nutrient concentrations in the water did not show any strong seasonal trends. Organic matter content of lake sediments ranged from 1 to 182 g C kg –1 of dry sediment, reflecting considerable spatial variability. All nutrient elements in the sediments showed highly significant (P < 0.01) correlations with sediment organic C, though little or no significant relationship appeared at any sampling period between water and sediment chemistry of the lake. Temporal trends in water and sediment chemical parameters may have been concealed by periodic hydrologic flushing of the St. Johns River into Lake Monroe.Florida Agricultural Experiment Stations Journal Series No. 7836. 相似文献
3.
- Planktonic and benthic bacterial communities hold central roles in the functioning of freshwater ecosystems and mediate key ecosystem services such as primary production and nutrient remineralisation. Although it is clear that such communities vary in composition both within and between lakes, the environmental factors and processes shaping the diversity and composition of freshwater bacteria are still not fully understood.
- In order to assess seasonal and spatial variability in lake bacterial communities and identify environmental factors underpinning biogeographical patterns, we performed a large-scale sampling campaign with paired water and sediment sample collection at 18 locations during four seasons in Lake Balihe, a subtropical shallow fish-farming lake in mid-eastern China.
- Pelagic and benthic bacterial communities were distinctly different in terms of diversity, taxonomic composition and community structure, with Actinobacteria, Bacteroidetes, Cyanobacteria and Alphaproteobacteria dominating lake water, and Acidobacteria, Bacteroidetes, Chloroflexi, Gammaproteobacteria and Deltaproteobacteria dominating sediment. Nevertheless, these two communities had stronger spatial concordance and overlap in taxa during spring and autumn seasons. Together, the main drivers of both the spatial and temporal variations in Lake Balihe bacterial communities were identified as water temperature, turbidity, nitrogen and phosphorus availability, and thermal stratification controlled by wind-mixing and activity of the dense farmed fish populations. Notably, populations affiliated with Firmicutes, known to be abundant in fish gut microbiome, were especially abundant in the summer season and locations where high fish biomass was found, suggesting a potential link between fish gut microbiome and the pelagic bacterial communities.
- Our findings demonstrated seasonal homogenisation of pelagic and benthic bacterial communities linked to marked shifts in a set of seasonally-driven environmental variables including water temperature and nutrient availability.
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4.
Sediment and water column phosphorus fractions were recorded monthly for one year (April 2004–April 2005) in a shallow lake
recovering from nutrient pollution (Loch Leven, Scotland). Equilibrium phosphate concentration (EPC0) and gross sediment phosphorus
(P) release rates were estimated from laboratory experiments. Pore water and organic P pools were lowest during warm water
periods whereas bottom water P was lowest during cold water periods. Reductant-soluble, organic, metal oxide-adsorbed, residual
and sediment total phosphorus pools all varied significantly with overlying water depth. Short-term, high magnitude, redox
initiated P release events occurred in late summer and winter as a result of anoxic sediment conditions. Lower magnitude long-term
release conditions were maintained for most of the year, most likely as a result of organic P cycling and maintenance of high
concentration gradients between the pore and bottom water P pools. Estimates of summer P uptake/release rates, across an intact
sediment-water interface, suggested that maximum gross internal release was ~12 mg SRP m −2 lake surface area d −1 with EPC0 values ranging between 180 and 270 μg P L −1. This study highlights the biological mediation of internal loading in shallow eutrophic lakes, and in particular, the role
of sediment algae in decreasing, and sediment bacteria in enhancing, sediment P release. 相似文献
5.
Sediment bacterial community and their relation with environmental factors were investigated in the five different trophic status lake regions sediment, Meiliang Bay, Wuli Lake, Gonghu Bay, Western Lake Taihu and Xukou Bay in a large, shallow, eutrophic freshwater lake (Lake Taihu, China). Water and surface sediment samples were collected at 35 sampling sites in January 2014 (winter) and July 2015 (summer). The physicochemical characterization showed that there were obvious changes in the trophic status and eutrophic index of five lake regions, which was mainly due to the difference of organic matter source. Based on the analysis of aquatic environmental characteristics, the organic nitrogen or nitrate nitrogen was the main storing form in the overlying water of five lake regions. In addition, nitrate nitrogen in pore water was lower than in overlying water, while ammonia nitrogen in pore water was higher than in overlying water. According to the DGGE profiles, temporal and spatial variations of bacterial community were apparent. Bacterial diversity was higher in summer than in winter and increased with the decrease in the lake region trophic status. The dendrogram of the bacterial community similarities revealed that samples were almost all grouped into two defined clusters (summer and winter), which indicated that season rather than region was the dominant factor. Canonical correspondence analysis demonstrated that ammonia nitrogen and nitrate–nitrite nitrogen in the sediment and pore water, organic matter and temperature significantly influenced the sediment bacterial community in the five lake regions. 相似文献
6.
The vertical distribution of the variables relevant to P forms in sediments were studied in a shallow Chinese freshwater lake (Lake Donghu) in 1997, 1998, 1999 and 2000, to assess the contribution of enzyme to P availability in sediment cores. Sediment P was fractionationd into iron-bound P, calcium-bound P, acid soluble organic P (ASOP) and hot NaOH extractable residual organic P. The former two species made the largest contribution to the sediment P pool. All P species exhibited significantly higher concentrations in different depths at Station I, compared with those found at Station II, except for ASOP. Coupled with these lower ASOP concentrations, the V
max data of alkaline phosphatase, measured on the same samples, were significantly higher at station I. Taken together, ASOP were probably important in supplying the enzymatic substrate (Phosphatase Hydrolyzable Phosphorus, PHP) into interstitial water. Dissolved orthophosphate and PHP concentrations were highly heterogeneous , but peaked in subsurface, paralleled by higher V
max and lower K
m values of alkaline phosphatase, throughout the sediment core. Sediment in the eutrophic lake is not only enriched in available P (iron-bound P), or stores residual P, but also tends to release PHP, thereby inducing the production of alkaline phosphatase and releasing o-P into water column by enzymatic hydrolysis. The latter process may also occur in relatively deep sediment layers. 相似文献
7.
The temporal and spatial distribution of total nitrogen and total phosphate in the sediments of a shallow eutrophic Chinese lake (Lake Chao), and their relationships with the physical and chemical features of sediments, and their effects on the lake water quality and trophic state, are presented in this paper. The following results were obtained: (1) higher concentration of Tot-N and Tot-P in the sediments occurred in the summer and the autumn seasons; (2) higher annual average Tot-N and Tot-P concentrations were observed in the sediments near the various river mouths and in the western part of the lake; (3) Tot-N and Tot-P concentration in the lake sediments generally increased with increase in lake sediment Eh, pH, and Al 2O 3, and declined with decrease in lake sediment size diameters and SiO 2; and, (4) correlations were observed in both the temporal and spatial distributions between the trophic state, Tot-N and Tot-P concentration in the lake water, and the Tot-N and Tot-P concentration found in the lake sediments. 相似文献
8.
Biomanipulation via fish regulation combined with submerged plant introduction is an effective measure to restore eutrophic shallow lakes. Improved water quality and clarity promote growth of benthic algae, which with submerged plants may limit sediment phosphorus (P) release, thereby reinforce lake recovery. Our study sought to evaluate the effect of such a biomanipulation on water quality, benthic algal development and sediment P release in a shallow, tropical lake by (1) comparing porewater and lake water quality, light intensity and benthic algal development in restored and unrestored sections; (2) conducting a 32P radiotracer experiment to track P release from sediment cores sampled from both sections. The biomanipulation led to lower total P, total dissolved P, and soluble reactive P concentrations in lake water, lower phytoplankton biomass, and increased light intensity at sediment surface, stimulating benthic algal development. Moreover, sediment 32P release was lower in the restored than unrestored section. Concurrently, dissolved oxygen levels in upper layers of the sediment cores were higher in the restored section. Our study indicates that the biomanipulation improved water quality and enhanced growth of benthic algae, thereby reducing sediment P release, which may be one of the main mechanisms to create successful restoration. 相似文献
9.
We measured water quality monthly for 22 years in water entering, within, and exiting a 65 km2 shallow polymictic and eutrophic freshwater lake in the northern Gulf of Mexico. Fertilizer use in the watershed is the dominate source of phosphorous (P) going into the lake and controls the lake’s P concentrations, but nitrogen (N) fertilizer use was not related to total nitrogen concentration in the lake. Half of the particulate P entering the lake is trapped within it and there is a net accumulation of N that appears to be from the stimulation of nitrogen fixation. The lake’s concentration of Chlorophyll a (µg Chl a l?1) and increase in N in the lake was directly related to the concentration of P in water entering the lake. Variations in the Chl a concentration within a freshwater lake downstream are also directly related to the annual use of P fertilizer, but not to N fertilizer use. Reducing agriculture-sourced P runoff will lower (but not eliminate) both the frequency of algal blooms within Lac des Allemands and the amount of N delivered to the estuary. 相似文献
10.
The compositions of archaeal and bacterial populations at different depths (60 m [mixolimnion-chemocline interface], 70 m [chemocline-subchemocline interface], 90 m, and 92 m [the water-sediment interface]) in the anoxic zone of the water column in Lake Pavin, a freshwater permanently stratified mountain lake in France, were determined. Phylogenetic trees were constructed from sequences to assess archaeal and bacterial diversity at the four sites. 相似文献
11.
Bacteria are thought to be closely involved in the biogeochemical cycling of the nutrient elements in freshwater ecosystems.
In contrast, little is known about the relationship between the bacterial community structure and the environmental factors.
In order to investigate the spatial variety of bacteriplankton community structure in Lake Xuanwu (Nanjing, China) and the
effects of water quality on the microbial community composition, denaturing gradient gel electrophoresis (DGGE) and multivariate
statistical analysis were carried out. Eight major factors of water quality such as total organic carbon, ammonium, nitrate,
nitrite, total nitrogen, total phosphorus, dissolved oxygen and pH were measured in eight different samples. The significant
differences of water characteristics among different sites were revealed by principal component analysis. Results of multidimensional
scaling analysis demonstrated that lake water quality played a crucial role in bacterioplankton community composition. Canonical
correspondence analysis was carried out to infer the relationship between environmental variables and bacterial community
structure. An influence of total nitrogen, ammonium and pH on the bacterial community was observed. The sequencing analysis
results of excised DGGE bands revealed that Bacteroidetes and Proteobacteria were the dominant bacterial groups in Lake Xuanwu. 相似文献
12.
In shallow lakes, increasing phosphorus (P) loading has often been accompanied by a shift from a clear-water, macrophyte-dominated state to a turbid state featuring phytoplankton dominance. The effect of a regime shift on P burial and P fractions in lake sediments, however, is poorly understood. We used sediment cores from a eutrophic hard-water lake (Lake Gollinsee, Germany) that had undergone a regime shift (in approximately 1917) to investigate the effect on the accumulation rate of P and on changes in P forms. The cores were dated using Hg contents and radioisotopes (210Pb, 137Cs, and 241Am). A combination of total organic carbon to total nitrogen ratios (TOC:TN), δ13TOC values, X-ray fluorescence calcium (Ca) counts, and sediment colour clearly distinguished sediment layers that were deposited during periods of macrophyte or phytoplankton dominance. The accumulation rate of total P (TP) in the sediments was 1.8 times higher after the regime shift and was associated with changes in the distribution of P fractions. The proportions of loosely-(NH4Cl-extracted TP) and Ca-(HCl-extracted TP) bound P decreased significantly, whilst the proportions of biogenic P (NaOH-extracted NRP) and aluminium-bound P (NaOH-extracted SRP) increased significantly. A higher dry mass deposition rate, reduced burial of stable Ca-P complexes, and increased contents and proportions of the mobile iron-bound (BD-extracted TP) and biogenic P fractions in the near-surface sediment layers are assumed to have enhanced the internal cycling of P and hence to have helped to maintain a state of phytoplankton dominance. 相似文献
13.
This study examined phosphorus (P) dynamics by surveying the solid-phase and pore-water of the surficial sediment in a mesotrophic and eutrophic shallow lake in Maine, USA. Both lakes were dimictic, developed hypolimnetic anoxia, and released sedimentary P. We examined the controls on sedimentary P release by considering two possible mechanisms; mineralization and release of sedimentary organic P, and dissolution of Fe hydroxide following the onset of anoxia. The temporal investigation of solid-phase included sequential chemical extraction and 31P NMR analysis, and the pore-water included use of equilibrium samplers. In both lakes, the relative contribution of organic P to total sedimentary P release was minor compared to Fe hydroxide-associated P. The eutrophic lake, however, had more evidence of microbial uptake of sedimentary P and a higher degree of rapid P transformation in the water column. Sediment polyphosphates were dynamic and possibly contributed to hypolimnetic P accumulation. The pore-water Fe and P profiles exhibited similar temporal patterns as the solid-phase results. Together, they showed an upward migration of the redoxcline in the sediment, from winter to summer, resulting in the accumulation of Fe-bound P at the sediment?Cwater interface in the winter followed by its release into the summer. 相似文献
14.
We employed culture-dependent and -independent techniques to study microbial diversity in Lake Chaka, a unique hypersaline lake (32.5% salinity) in northwest China. It is situated at 3,214 m above sea level in a dry climate. The average water depth is 2 to 3 cm. Halophilic isolates were obtained from the lake water, and halotolerant isolates were obtained from the shallow sediment. The isolates exhibited resistance to UV and gamma radiation. Microbial abundance in the sediments ranged from 10 8 cells/g at the water-sediment interface to 10 7 cells/g at a sediment depth of 42 cm. A major change in the bacterial community composition was observed across the interface. In the lake water, clone sequences affiliated with the Bacteroidetes were the most abundant, whereas in the sediments, sequences related to low G+C gram-positive bacteria were predominant. A similar change was also present in the archaeal community. While all archaeal clone sequences in the lake water belonged to the Halobacteriales, the majority of the sequences in the sediments were related to those previously obtained from methanogenic soils and sediments. The observed changes in the microbial community structure across the water-sediment interface were correlated with a decrease in salinity from the lake water (32.5%) to the sediments (approximately 4%). Across the interface, the redox state also changed from oxic to anoxic and may also have contributed to the observed shift in the microbial community. 相似文献
15.
The partitioning of heavy metals in sediment from Poyang Lake, the largest freshwater lake in China, was studied. The majority of the heavy metals, copper, lead and zinc, were found to be bound to the organic matter and iron oxide phases. The distribution of the metals among the different geochemical phases in sediments was controlled by the abundance of the geochemical phases. An equilibrium adsorption model developed by Oakley et al. (1981) and Davies-Colley et al. (1984) was applied to predict the partitioning of copper among different geochemical phases in the sediments of Poyang Lake. The conditional equilibrium constants (slopes of the linear portions of the adsorption isotherms) were determined using an artificial water-sediment system at various pH's. This model was used to describe the heavy metal partitioning in sediment samples from Poyang Lake and the predicted results were consistent with those measured in the laboratory. 相似文献
16.
SUMMARY. 1. Phosphorus and nitrogen concentration in the surface sediment was analysed before, during and after fertilization of a small, stratified, subarctic lake. During stratification most (70%) of the added nutrients were deposited in the epilimnion sediment. 2. After 2 years of fertilization there was a significant increase of both nutrients at all water depths, although values were 30–50% higher per square metre in the shallow areas. 3. Nutrient budget calculations based on the sediment analyses showed that 75% of the added phosphorus and 45% of the nitrogen were accumulated in the sediment after fertilization. 相似文献
17.
Nitrogen dynamics and microbial food web structure were characterized in subtropical, eutrophic, large (2,338 km 2), shallow (1.9 m mean depth), and polymictic Lake Taihu (China) in Sept–Oct 2002 during a cyanobacterial bloom. Population
growth and industrialization are factors in trophic status deterioration in Lake Taihu. Sites for investigation were selected
along a transect from the Liangxihe River discharge into Meiliang Bay to the main lake. Water column nitrogen and microbial
food web measurements were combined with sediment–water interface incubations to characterize and identify important processes
related to system nitrogen dynamics. Results indicate a gradient from strong phosphorus limitation at the river discharge
to nitrogen limitation or co-limitation in the main lake. Denitrification in Meiliang Bay may drive main lake nitrogen limitation
by removing excess nitrogen before physical transport to the main lake. Five times higher nutrient mineralization rates in
the water column versus sediments indicate that sediment nutrient transformations were not as important as water column processes
for fueling primary production. However, sediments provide a site for denitrification, which, along with nitrogen fixation
and other processes, can determine available nutrient ratios. Dissimilatory nitrate reduction to ammonium (DNRA) was important,
relative to denitrification, only at the river discharge site, and nitrogen fixation was observed only in the main lake. Reflecting
nitrogen cycling patterns, microbial food web structure shifted from autotrophic (phytoplankton dominated) at the river discharge
to heterotrophic (bacteria dominated) in and near the main lake. 相似文献
18.
While water and sediment microbial communities exhibit pronounced spatio-temporal patterns in freshwater lakes, the underlying drivers are yet poorly understood. Here, we evaluated the importance of spatial and temporal variation in abiotic environmental factors for bacterial and microeukaryotic community assembly and distance–decay relationships in water and sediment niches in Hongze Lake. By sampling across the whole lake during both Autumn and Spring sampling time points, we show that only bacterial sediment communities were governed by deterministic community assembly processes due to abiotic environmental drivers. Nevertheless, consistent distance–decay relationships were found with both bacterial and microeukaryotic communities, which were relatively stable with both sampling time points. Our results suggest that spatio-temporal variation in environmental factors was important in explaining mainly bacterial community assembly in the sediment, possibly due lesser disturbance. However, clear distance–decay patterns emerged also when the community assembly was stochastic. Together, these results suggest that abiotic environmental factors do not clearly drive the spatial structuring of lake microbial communities, highlighting the need to understand the role of other potential drivers, such as spatial heterogeneity and biotic species interactions. 相似文献
19.
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
20.
The increased nitrogen loading from anthropogenic sources has affected aquatic ecosystems and has cascaded through food webs worldwide. Therefore, the evaluation of ecological impacts of anthropogenic nitrogen has become increasingly important. In this paper, we investigated the effect of nutrient enrichment in the planktonic and benthic food webs of a hypereutrophic urban lake using stable nitrogen isotope analysis. The stable isotope mixing model revealed that zooplanktons rely mainly on planktonic nitrogen, and that Chironomus and Oligochaete rely mainly on benthic nitrogen. The stable nitrogen isotope signatures of seston and the sediment organic matter can be a sensitive indicator, because they are correlated with the nitrogen content of water and sediment. Furthermore, the relationships between the stable nitrogen isotope values of primary production and primary consumers indicate that polluted nitrogen has transferred through the planktonic and benthic food webs, respectively. For primary consumers, the stable nitrogen isotope values of zooplanktons were correlated to nitrogen concentrations of water, and the stable nitrogen values of Chironomus and Oligochaete were correlated to the nitrogen content of sediment, respectively. This finding indicates that these primary consumers can be used as promising bioindicators of the anthropogenic nitrogen input in planktonic and benthic food webs, respectively. Our results suggest that stable nitrogen isotope of primary consumers can act as bioindicators to detect the dispersal patterns of anthropogenic contamination and understand the incorporation into and movement of waste nitrogen in pelagic and benthic food chains. 相似文献
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