Shallow Lake Taihu Research Articles

Effects of benthic macrofauna bioturbation on the bacterial community composition in lake sediments.

Benthic macrofauna are considered to be an important part of the lacustrine ecosystem, and bioturbation may greatly affect the biogeochemical processes and microbial activities in sediments. In the present study, the bacterial community composition in sediments inhabited by 3 different types of benthic macrofauna (Corbicula fluminea, Chironomidae larvae, and tubificid worms) in the shallow and eutrophic Lake Taihu was studied to investigate the different effects of bioturbation on the composition of these communities. Microcosms were constructed, and culture-independent methods, including terminal restriction fragment length polymorphism (T-RFLP) and clone library analysis, were performed to evaluate the bacterial communities. Analysis of similarities (ANOSIM) and multidimensional scaling (MDS) analysis of T-RFLP patterns demonstrated that differences in the bacterial community composition between the control and the macrofauna-inhabited sediments were not as great as expected, although the chemical properties of the sediments changed remarkably. Nevertheless, the dominant bacterial group in each type of macrofauna-inhabited sediment was different. Acidobacteria, Betaproteobacteria, and Deltaproteobacteria were the dominant bacterial groups in sediments inhabited by C. fluminea, tubificid worms, and Chironomidae larvae, respectively. The data obtained in this study are helpful for understanding the effects of bioturbation in a shallow, eutrophic lake.

Submerged macrophyte communities and the controlling factors in large, shallow Lake Taihu (China): Sediment distribution and water depth

Lake Taihu, the third largest lake in China, is subjected to severe eutrophication and cyanobacterial blooms as a result of development and urbanization. In order to restore the degraded lake ecosystem, it is important to identify which environmental factors control the submerged macrophytes which declined during eutrophication. To characterize community structure of submerged macrophytes and to assess the plant–environmental relationships in Lake Taihu, a monthly investigation was conducted from May to October in 2010. A total of six species were recorded, dominated by Potamogeton malaianus and Vallisneria natans. Multivariate analysis showed that water depth, depth of soft sediments and nutrient variables (orthophosphate of water, organic matter of sediment, total nitrogen and total phosphorus of sediment) were the major factors determining growth and community composition of submerged macrophytes in the lake. A strong predictive association of soft-sediment depth and plant biomass indicated preference of submerged macrophytes for firm bottoms along the eastern shore and approximately 0.2m could be regarded as an optimum depth for the growth of plants. The biomass of plants responded proportionately to water depth, and approximately 1.8m could be regarded as the optimum depth for the growth of submerged macrophyte in Lake Taihu. Our results indicated that improvement of habitat and the selection of appropriate submerged macrophytes species are very important for ecological restoration in large eutrophic lakes. This study could provide useful information for managers and policy makers to evaluate and modify restoration practices in large, shallow lakes.

Temporal and spatial variations in radiation and energy balance across a large freshwater lake in China

The surface radiation and energy exchange processes are important drivers of lake evaporation and the associated hydrological cycle. In this paper, we investigated the temporal and spatial variations in evaporation and the associated radiation and energy fluxes across Lake Taihu, China with an eddy covariance mesonet consisting of three lake sites and one land site. The results indicate that on the diurnal scale, water heat storage showed a similar behavior to net radiation with comparable magnitudes and fueled the substantial nighttime evaporation (48% of annual evaporation). Unlike boreal deep lakes, the monthly mean sensible and latent heat flux was tightly coupled with seasonal variations in net radiation at this large (size 2400km2), subtropical (30.9–31.6°N) shallow (mean depth 1.9m) Lake Taihu. On the monthly to annual scales, the radiation and energy fluxes showed little spatial variations across the lake, indicating a lack of sensitivity to wind speed, water depth, water quality and the presence of submerged macrophytes. The annual mean Bowen ratio (0.12–0.13) of the lake was lower than those found in the literature for subtropical and northern lakes and also much lower than that observed at the adjacent land site (0.58). The experimental data were used to evaluate the performance of 19 lake evaporation models of varying complexities.

太湖浮游纤毛虫群落结构及其与环境因子的关系

Ciliates,as a keystone microorganism in water bodies,link bacteria and phytoplankton and higher trophic levels.Accurate quantitative assessment of ciliates would lead to better predictions of material and energy flux through planktonic food web in lake systems. Ciliates were quarterly collected in 2009 at 32 sampling sites in shallow eutrophic Lake Taihu,fixed by Bouin's solution,and stained by quantitative protargol stain( QPS). In this study,the distribution patterns of ciliate community compositions and functional groups were studied. The relationship between the ciliate community compositions and environmental variables including abiotic and biotic parameters was analyzed by canonical correspondence analysis( CCA). In the 128 samples,a total of 117 species belonging to 3 classes,15 orders and 78 genera were found.Among the functional groups,39 species are fallen into the bacterivorous group,represented by orders Scuticociliatida,Hymenostomatida,Peritrichida and Colpodida. Algivorous group had 25 species,mostly belonging to oligotrichids. The mixotrophic,omnivorous and predacious groups had 15,11 and 10 species,respectively. The rest 17 species belong to the group mainly feeding on heterotrophic flagellates or are in the unclear position. The dominant species were Askenasiaacrostomia,Balanion planctonicum, Codonella cratera, Cyclidium glaucoma, Halteria bifurcata, H. grandinella,Rimostrombidium brachykinetum,R. humile,Tintinnopsis cylindrata,Urotricha farcta,Vorticella aquadulcis complex and V. campanula. Ciliate abundance ranged from 1 500 to 139 150 cells /L( mean 27 170 cells /L) and biomass from 16. 7 to8736. 0 μg /L( mean 600. 6 μg /L). Oligotrichids occupied 45. 9% of total ciliate abundance,followed by prostomatids( 34. 1%),scuticociliatids( 11.8%),peritrichids( 3.6%) and haptorids( 2.6%). The ciliate community compositions had a high heterogeneity and seasonal succession. Ciliate abundance was significantly higher in summer( August) than in other seasons. Their biomass was significantly higher in spring and autumn than in winter and summer. Generally,ciliate abundance had an increase tendency from the south part to north part of Lake Taihu,and from the pelagic area to the littoral. The small-sized species belonging to oligotrichids, scuticociliatids and prostomatids dominated the ciliate communities in the north part of Lake Taihu while the meso- and large-bodied oligotrichids species dominated in the south part. Among the functional groups,the mixotrophic taxa accounted for a substantial proportion of the ciliate assemblages in May and August. The bacterivorous and algivorous taxa dominated in the north and south parts of Lake Taihu,respectively.Unlike the above three groups,the omnivorous,predacious and the others groups only constituted a far smaller percentage of the total ciliate abundance. Results from CCA analysis showed that spatial variations of the ciliate community compositions were determined by difference factors among four seasons. The nitrogen,total dissolved carbon and chlorophyll a content mainly determined the ciliate communities in winter. Copepod, pH, nitrate and ammonium controlled the ciliate communities in spring. The ciliate communities in summer were shaped by copepod,turbidity and dissolved nitrogen,Copepod and total dissolved carbon structured the ciliate communities in autumn. These results illustrated that both the trophic level and predation jointly shaped the ciliate community compositions in Lake Taihu.

High-frequency optical measurements in shallow Lake Taihu, China: determining the relationships between hydrodynamic processes and inherent optical properties

In order to determine the effect of wind-induced waves (influenced by wind velocity and direction) on the dynamics of optical properties in shallow lakes, we determined the short-term variability of the inherent optical properties (IOPs) in Meiliang Bay, Lake Taihu, China, by examining high-frequency data collected between 8 and 21 September 2010 from meteorology and optical sensors. The absorption and beam attenuation coefficients under strong winds were significantly higher than those under weak and moderate winds (t test, P < 0.001). Significant correlations were found between absorption, scattering, beam attenuation, and wind speed, showing that the hydrodynamic process was an important factor that influenced the instantaneous IOPs of the water. However, the different wind directions have a different effect degree on the IOPs. Western wind is the most important driven wind direction of this site. In addition, significant correlations were found between b p(440), c p+g(440), b p(677), c p+g(677), b p(440), and turbidity under each wind direction (P < 0.001). Exponential and hyperbolic exponent models of the absorption and beam attenuation coefficients were fitted, and linear models between a p+g(677), c p+g(677), and turbidity were developed. Thus, in shallow lakes such as Lake Taihu, using real-time high-frequency monitoring of the turbidity to deduce the water IOPs could be an efficient and practical approach. Our study will be helpful in monitoring the IOPs and in improving the accuracy of bio-optical models to estimate water quality parameters in Lake Taihu.

Controlling of cyanobacteria bloom during bottleneck stages of algal cycling in shallow Lake Taihu (China)

To suppress the occurrence of phytoplankton blooms dominated by cyanobacteria, control measures were implemented during the bottleneck stages of algal succession, overwintering and pre-recruitment, using a combination of chemical and biological algicides. First, water and sediment samples were incubated in the laboratory to determine the threshold temperature for cyanobacteria recruitment. Second, the functional characteristics of candidate algicides were screened. Third, an in situ pilot experiment was conducted to test the feasibility of this method. Our results indicated that (1) the recruitment of cyanophytes was initiated at 15°C, (2) H2O2 and rice straw were the optimum algicides and their optimal concentrations were 10 mg/L and 1 g/L, respectively, and (3) following the combined application of H2O2 and rice straw during overwintering and pre-recruitment, the biomass of cyanobacteria decreased by 27.1% during recruitment and by 53.2% during the first algal bloom. These results suggested that the combined application of H2O2 and rice straw, during the bottleneck stages of algal cycling, suppressed the recruitment of cyanobacteria and decreased the magnitude of algal blooms, thus offering a promising choice for prevention of cyanobacterial blooms.

Vertical diversity of sediment bacterial communities in two different trophic states of the eutrophic Lake Taihu, China

Vertical diversity of sediment bacterial communities in 2 different trophic states (macrophyte-dominated and algae-dominated) of the large shallow eutrophic Lake Taihu, China, were investigated using denaturing gradient gel electrophoresis (DGGE) and 16S rRNA sequence analysis. Clustering analysis of DGGE profiles showed that different clusters were recognized in different depths of sediment cores in the 2 lake trophic states. Analyses of the bacterial diversity, as estimated by the Shannon index (H'), showed that different sediment layers of the macrophyte-dominated state had higher diversity than the algae-dominated state. In addition, bacterial diversity of the sediment in the macrophyte-dominated state changed abruptly throughout the layers, but bacterial diversity of the algae-dominated state decreased gradually with sediment depth. Phylogenetic analysis showed that Proteobacteria was the most abundant phylum in the middle sediment of the 2 lake trophic states. In the macrophyte-dominated state, clone sequences related to Betaproteobacteria (50.0%) were the most abundant, followed by Epsilonproteobacteria (21.1%), Acidobacteria (7.9%), Deltaproteobacteria (7.9%), Chloroflexi (7.9%), and Bacteroidetes (5.3%); whereas in the algae-dominated state, sequences affiliated with Betaproteobacteria (84.4%) were predominant, followed by Deltaproteobacteria (12.5%) and Acidobacteria (3.1%). Canonical correspondence analysis showed that organic matter and pH play key roles in driving the vertical changes of bacterial community composition.

Dynamics of cyanobacterial bloom formation during short-term hydrodynamic fluctuation in a large shallow, eutrophic, and wind-exposed Lake Taihu, China

Short-term hydrodynamic fluctuations caused by extreme weather events are expected to increase worldwide because of global climate change, and such fluctuations can strongly influence cyanobacterial blooms. In this study, the cyanobacterial bloom disappearance and reappearance in Lake Taihu, China, in response to short-term hydrodynamic fluctuations, was investigated by field sampling, long-term ecological records, high-frequency sensors and MODIS satellite images. The horizontal drift caused by the dominant easterly wind during the phytoplankton growth season was mainly responsible for cyanobacterial biomass accumulation in the western and northern regions of the lake and subsequent bloom formation over relatively long time scales. The cyanobacterial bloom changed slowly under calm or gentle wind conditions. In contrast, the short-term bloom events within a day were mainly caused by entrainment and disentrainment of cyanobacterial colonies by wind-induced hydrodynamics. Observation of a westerly event in Lake Taihu revealed that when the 30 min mean wind speed (flow speed) exceeded the threshold value of 6 m/s (5.7 cm/s), cyanobacteria in colonies were entrained by the wind-induced hydrodynamics. Subsequently, the vertical migration of cyanobacterial colonies was controlled by hydrodynamics, resulting in thorough mixing of algal biomass throughout the water depth and the eventual disappearance of surface blooms. Moreover, the intense mixing can also increase the chance for forming larger and more cyanobacterial colonies, namely, aggregation. Subsequently, when the hydrodynamics became weak, the cyanobacterial colonies continuously float upward without effective buoyancy regulation, and cause cyanobacterial bloom explosive expansion after the westerly. Furthermore, the results of this study indicate that the strong wind happening frequently during April and October can be an important cause of the formation and expansion of cyanobacterial blooms in Lake Taihu.

Wind and submerged aquatic vegetation influence bio‐optical properties in large shallow Lake Taihu, China

AbstractWe studied the bio‐optical properties and sediment dynamics of typical phytoplankton‐dominated (PD) and macrophyte‐dominated (MD) regions in shallow Lake Taihu in China, from long‐term site‐specific studies and short‐term high‐frequency observations. The long‐term studies showed that five parameters were significantly lower in the MD region than in the PD region: photosynthetically active radiation (PAR) diffuse attenuation coefficient (Kd(PAR)), concentrations of total suspended matter (CTSM), tripton (CTripton), and phytoplankton pigment (CChla+Pa), and CDOM absorption coefficient (aCDOM(350)). In winter in the MD region, with only scarce submerged aquatic vegetation (SAV) coverage, the Kd(PAR), CTSM, and CTripton were significantly higher than in the PD region with no SAV; in contrast, CChla+Pa and aCDOM(350) were significantly lower in the MD region than in the PD region. In the other three seasons with high SAV coverage, Kd(PAR), CTSM, CTripton, CChla+Pa, and aCDOM(350) were all significantly lower in the MD region than in the PD region. The appearance and growth of SAV decreased CTSM, CTripton, and Kd(PAR). The short‐term high‐frequency study showed that phytoplankton and tripton absorption coefficients were significantly lower in the MD region than in the PD region. In the PD region, there were highly significant exponential relationships between wind speed, wave height, and wave shear stress, and CTripton and Kd(PAR), showing that wind‐driven sediment resuspension could significantly affect both the tripton concentration and PAR attenuation. However, in the MD region, there were only weakly significant correlations, or no significant correlations, between wind speed, wave height, and wave shear stress, and CTripton, and Kd(PAR). The combination of the long‐term site‐specific and short‐term high‐frequency observations is an excellent tool for study of the bio‐optical properties in lake environments.

Low Resilience of the Particle-Attached Bacterial Community in Response to Frequent Wind-Wave Disturbance in Freshwater Mesocosms

The most common natural disturbances in shallow lakes are wind-induced waves, which cause catastrophic changes in the aquatic fauna of lakes. Recovery from these changes is always prolonged. The objective of this study was to understand the resilience and recovery of the particle-attached bacterial community composition (PABCC) after frequent wind-wave disturbance in a large shallow eutrophic lake. To accomplish this, we designed a mesocosm experiment including an undisturbed control, and a physically disturbed treatment that stimulated the superposition of two different intensities of wind-induced waves in the large shallow eutrophic Lake Taihu, China. The PABCC was determined by denaturing gradient gel electrophoresis, following by cloning and sequencing of the selected samples. We observed that the most marked change of the PABCC occurred in the disturbed treatment, in which the concentrations of suspended solids (SS) and the water turbidity varied strongly. However, we observed low recovery of the PABCC within 4 days post-disturbance when the investigated environmental factors had also recovered. Our results indicated that the resistance of the PABCC is low, and resilience is also low following frequent disturbance by wind-waves in a large shallow eutrophic lake.

Temporal and spatial dynamics of Cryptophytes biomass in the north of Lake Taihu

The variation of the abundance of Cryptophytes was analyzed using monthly monitoring data during 2005-2009in large shallow eutrophic Lake Taihu in China.The environmental factors and variations in cyanobacterial biomass were analyzed to explain the spatial and temporal distribution of Cryptophytes at three stations in Lake Taihu(Zhushan Bay,Meiliang Bay and Gonghu Bay).The results showed that: The mean biomass of the Cryptophytes in Zhushan Bay(1.89mg/L) was much higher than that of Meiliang Bay(0.87mg/L) and Gonghu Bay(0.43mg/L);The average biomass of Cryptophytes in 2008-2009(2.12mg/L) was much higher than that in 2005-2007(0.28mg/L);Principally,Cryptophytes were most prevalent in Zhushan Bay which was marked by higher nutrient levels,higher organic matter and suspended solid concentrations.The succession of Cryptophytes was mainly affected by the grazing of zooplankton in Gonghu Bay.Furthermore,Cryptophytes and Cyanobacteria abundances were found to be inversely correlated,temporally,in Lake Taihu.Cyanobacteria seem able to reduce the biomass of Cryptophytes.

Effects of typhoon Morakot on a large shallow lake ecosystem, Lake Taihu, China

ABSTRACTA case study of typhoon‐induced sediment resuspension and its effects on some indicators of water quality (dissolved oxygen, pH and turbidity) and nutrient release in the large shallow eutrophic Lake Taihu, the third largest freshwater lake in China, was documented, and its effect on the algal biomass was investigated. Typhoon Morakot that swept from the west of Lake Taihu in August 2009 led to a number of changes in the lake ecosystem: (1) intensive winds produced large seiches, strong waves and large wave‐induced shear stress; (2) typhoon Morakot led to increased suspended solids and nutrients in the water column. Post‐typhoon concentrations of suspended solid, total phosphorus, total nitrogen, soluble reactive phosphorus (SRP). NO3‐N and NH4‐N were 4, 2, 1·5, 2·5, 3·5 and 1·5 times those observed in the pre‐typhoon water column, respectively; and (3) during typhoon Morakot, there was no obvious stratification between the surface and bottom of the water column in chlorophyll a (Chl a), the post‐typhoon Chl a concentration throughout the water column increased with a maximum daily mean of 87·8 µg l−1, and the algal bloom recurred. Typhoon‐induced sediment resuspension could lead to both nutrient and light limitations for algal growth, whereas after the typhoon had passed, water column conditions (water temperature, solar radiation, light penetration and nutrient availability) favoured the growth and production of algae. Copyright © 2011 John Wiley &amp; Sons, Ltd.

Modelling the spectral absorption of tripton using exponential and hyperbolic models

The optical properties of tripton, and the correlation between the absorption coefficient and tripton concentration, were investigated based on a large dataset of 727 samples, collected from different regions of shallow Lake Taihu, in China, from July 2004 to April 2007. Four models describing tripton absorption spectra in the visible domain (400–700 nm) were examined to find the optimal model. The conventional single exponential model performed the poorest. Statistically, the most ‘useful’ model was the hyperbolic model; judged by the root mean square error (RMSE) and the magnitude of the F statistic from an analysis of variance, this was found to give a closer fit for the measured absorption (70.1% reduction in RMSE and 449.7% increase in F value) than did the simple exponential model method. The mean S d value derived for the hyperbolic model was 5.98 ± 0.30 nm–1, with a very small coefficient of variation of 5.0%. Significant linear correlations were found between a d(440) and total suspended matter, inorganic suspended matter and tripton concentrations, but with the minimal RMSE of a d(440) estimation (0.815 m–1) for tripton. The results demonstrate that it is possible to develop regional models for the estimation of tripton absorption coefficient from the concentration.

Stratification and its driving factors of water physicochemical variables in large,shallow Lake Taihu

A nine-day observation on the process of vertical stratification of physicochemical variables was taken from 24th July to 1st August,2010 in Lake Taihu,a large shallow lake of China.Frequent stratification processes occurred during the 9 days.But the stratifying state was unstable,and normally last less than 1 day.The main factors causing stratification were water temperature and its diel variation,cyanobacterial bloom scum and wind-induced wave disturbance.The vertical difference of water temperaturemay reached 3.94℃,which was mainly influenced by diel variation of air temperature and solar radiation.And the stratification of water temperature was the basic factor causing the stratification of dissolved oxygen,electric conductivity,and pH.Cyanobacterial bloom scum could cause the strongest stratification,which could cause vertical difference of 8.67mg/L of dissolved oxygen,48μC/cm of electric conductivity,1.49 of pH,9.1μg/L of chlorophyll-a and 26.5NTU of turbidity.Besides turbidity,stratification of physicochemical variables became weaker with the increase of wind speed.No stratification happened during strong wind period in which of wind speed over 6m/s,while it often happened during weak condition in which of wind speed less than 2m/s.The study indicated that,stratification processes could frequently short-term occurred in large shallow lakes,and might have potential influences on the processes of biological activities and exchange on air-water interface and water-sediment interface.

Ecological restoration in eutrophic Lake Wuli: A large enclosure experiment

A large-scale enclosure experiment for lake restoration was carried out in Lake Wuli, a northern bay of shallow and eutrophic Lake Taihu in China. The large enclosure with an area of 10 ha was set up in the littoral zone and was bordered by waterproof fabric which did not cover the sediments. Multiple approaches were used and included fish removal, piscivorous fish stocking, shoreline reconstruction, aquatic macrophyte planting, benthic macro-animal stocking, and silver carp cultivation in pens for reduction of cyanobacteria. The results showed that the coverage of aquatic macrophytes increased from 0% to 45.7%. Mean concentrations of TN and TP inside the enclosure from May 2004 to May 2008 were 22.2% and 26.0% of those outside, respectively. Secchi depth was 0.40 m outside the enclosures and 0.75 m inside. However, responses of phytoplankton to the restoration project lagged behind improvement of water quality and reestablishment of aquatic plants. The phytoplankton biomass gradually decreased after the third year of the restoration. Stocking piscivorous fish and planting submerged macrophytes could not increase zooplankton biomass and enhance graze pressure on phytoplankton, most likely due to high omnivorous fish density and lower nutrition inside the enclosure. Higher grazing pressure of zooplankton on phytoplankton was observed in May and October every year. Zooplankton to phytoplankton biomass ratios were significantly negatively correlated with phytoplankton biomass outside ( r = −0.440, p < 0.01) and inside the enclosure ( r = −0.336, p < 0.05) from February 2004 to March 2007. Therefore, phytoplankton biomass inside and outside the enclosure was lower in May and October. Higher grazing pressure of zooplankton on phytoplankton in spring may result in occurrence of the clear-water phase that facilitated growth of submerged macrophytes in the littoral in Lake Wuli, and a clear-water state and improved water quality would likely be sustained throughout the year after reestablishment of submerged macrophytes.

Effects of Light and Wind Speed on the Vertical Distribution of Microcystis aeruginosa Colonies of Different Sizes during a Summer Bloom

AbstractDifferent dynamics, of the vertical distribution of Microcystis aeruginosa colonies of different sizes, were examined in a large shallow lake (Taihu Lake) during a summer bloom. During the observation the Microcystis colonies, larger than 120 μm, were mainly concentrated in the upper layer both under calm and windy conditions. Colonies from 36 μm to 120 μm showed a clear relationship to wind conditions whereas colonies less than 36 μm showed a nearly uniform vertical distribution at the different depths. There was no clear relationship between the vertical distribution of colonies larger than 36 μm and light intensity. However, at solar noon, colonies less than 36 μm were mainly distributed in the middle layers of the water column. The results indicate that small colonies are easily affected by the wind‐induced mixing, and they show an ability for active movement in response to light intensity under calm conditions. In contrast, large colonies tend to show little diurnal repositioning to light intensity and thereby are mainly concentrated in the surface layer. (© 2009 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Characterization of Bacterial Communities Associated with Organic Aggregates in a Large, Shallow, Eutrophic Freshwater Lake (Lake Taihu, China)

Although organic-aggregate-associated bacteria play a pivotal role in microbial food webs and in the cycling of major elements, their community composition and diversity have not been extensively studied, especially in shallow freshwater systems. This study is among the first to explore intra-lake horizontal heterogeneity of organic-aggregate-associated bacterial community composition (OABC) in the large, shallow, and eutrophic Lake Taihu. During November 2006, samples were collected at four locations representing different trophic states and food web structures. Regional variability of OABC and diversity were studied by amplified ribosomal DNA restriction analysis and comparative analysis of four large 16S ribosomal RNA clone libraries. Our results demonstrate that OABC were numerically dominated by members of the beta-proteobacteria (19.2-38.6%), Bacteroidetes (3.6-20.0%), and alpha-proteobacteria (11.5-19.2%) groups. The dominance of the Bacteroidetes group was related to algae-based aggregates. Horizontal heterogeneity of OABC exists within habitats, suggesting that the trophic state of the water and the physicochemical properties of organic aggregates (OA) play a key role. Diverse bacterial communities found on OA were substantially different from free-living ones. Comparative statistical analyses of the habitats of OA-associated bacteria highlight the potential ecological importance of the exchange between OABC and the surrounding planktonic community. Lastly, we found at least 45% of sequences closely related to ones previously found in soils, sludge, sediments, and other habitats. This demonstrates that microorganisms from terrestrial and sediment habitats are an important component of OA.

Variability of Phosphorus Concentration in Large, Shallow and Eutrophic Lake Taihu, China

To understand the variation of total phosphorus and the factors influencing total phosphorus in large, shallow, eutrophic lakes, two years of monthly investigation and one month of daily investigation was carried out in Lake Taihu, China. High temporal variations of total phosphorus in surface water were observed, ranging from 42 microg/L to 250 microg/L during the two years of monitoring at the center of the lake, and 134 microg/L to 737 microg/L during the one month of monitoring in Meiliang Bay during the algal bloom season. High variation in phytoplankton biomass during the bloom season significantly affected total-phosphorus concentration in lake water. The accumulated total phosphorus in algae may be caused by the release from sediment during the blooms. Intensive sediment resuspension caused by wind-induced waves also had significant effects on total phosphorus. Therefore, care should be taken when using total phosphorus or ratios of total nitrogen to total phosphorus for trophic state evaluation in large, shallow and eutrophic lakes.

Hypoxia and its environmental influences in large, shallow, and eutrophic Lake Taihu, China

(2008). Hypoxia and its environmental influences in large, shallow, and eutrophic Lake Taihu, China. SIL Proceedings, 1922-2010: Vol. 30, No. 3, pp. 361-365.

Eutrophic status and causing factors for a large, shallow and subtropical Lake Taihu, China

As the third largest freshwater lakes of China and seriously suffered by Microcystis algal bloom in recent 20 years, Lake Taihu's eutrophic status had been analyzed based on the monthly monitoring data in recent S years. The analysis indicated that eutrophication of Lake Taihu became more and more serious since 2000. Comparing to the mean values in recent S years, the water quality variables like total nitrogen, total phosphorus, and transparency, water quality of Lake Taihu were worse than that between 1991 and 2001. The summer mean of TN between 2002 and 2006 was significantly higher than that of between 1992 and 2001 (p = 0.005). And the transparency mean of summer of 2002-2006 in center of Lake Taihu was only 0.34 m, which was significantly lower than that of 1992-2001 with a mean 0.63 m (p = 0.003). Moreover, Microcystis blooming areas in summer increased from about one fourth of the lake before 2000 to over half of the lake in 2006. Blooming season from June to October before 2000 also extend from May to December in 2006. Microcystis blooms occur more and more regularly in the lake. And dominant areas of submerged macrophytes decreased quickly. The deteriorate trend of eutrophication in Lake Taihu may partly due to the abnormal dry and hot climate in recent 2 years. However, destroy of submerged macrophytes also possibly contributed to the fast widespread of bloom.