Use of PFU protozoan community structural and functional characteristics in assessment of water quality in a large, highly polluted freshwater lake in China

Protozoan communities serve as a strong indicator of water quality in the Nile River

The relationship between the protozoan communities and environmental variables was studied in the Nile River to evaluate their potential as water quality indicators. Protozoans were sampled monthly at six sampling sites in the Nile's Damietta Branch across a spatial gradient of environmental conditions during a 1-year cycle (February 2016-January 2017). The Protozoa community was comprised of 54 species belonging to six main heterotrophic Protozoa phyla. The abundance (average, 1089 ± 576.18 individuals L-1) and biomass (average, 86.60 ± 106.13 μg L-1) were comparable between sites. Ciliates comprised the majority of protozoan species richness (30 species), abundance (79.72%), and biomass (82.90%). Cluster analysis resulted in the distribution of protozoan species into three groups, with the most dominant species being the omnivorous ciliate Paradileptus elephantinus. Aluminium, fluoride, and turbidity negatively affected abundance and biomass, while dissolved oxygen and potassium positively impacted biomass. Of the dominant species recorded over the study area, the amoebozoa Centropyxis aculeata was associated with runoff variables, while the bacterivorous ciliates Colpidium colpoda, Glaucoma scintillans, and Vorticella convallaria were related to the abundance of heterotrophic bacteria, phytoplankton biomass, and total organic carbon. Total dissolved salts, PO4, NH3, NO2, dissolved oxygen, and total organic carbon were the strongest causative factors for protozoa distribution. The α-Mesosaprobic environment at site VI confirmed a high load of agricultural runoffs compared to other sites. This study demonstrates that protozoans can be a potential bioindicator of water quality status in this subtropical freshwater river system.

Microbial Community Colonization Process Unveiled through eDNA-PFU Technology in Mesocosm Ecosystems

Microbial communities are essential components of aquatic ecosystems and are widely employed for the detection, protection, and restoration of water ecosystems. The polyurethane foam unit (PFU) method, an effective and widely used environmental monitoring technique, has been improved with the eDNA-PFU method, offering efficiency, rapidity, and standardization advantages. This research aimed to explore the colonization process of microbial communities within PFUs using eDNA-PFU technology. To achieve this, we conducted ten-day monitoring and sequencing of microbial communities within PFUs in a stable and controlled artificial aquatic ecosystem, comparing them with water environmental samples (eDNA samples). Results showed 1065 genera in eDNA-PFU and 1059 in eDNA, with eDNA-PFU detecting 99.95% of eDNA-identified species. Additionally, the diversity indices of bacteria and eukaryotes in both methods showed similar trends over time in the colonization process; however, relative abundance differed. We further analyzed the colonization dynamics of microbes in eDNA-PFU and identified four clusters with varying colonization speeds. Notably, we found differences in colonization rates between bacteria and eukaryotes. Furthermore, the Molecular Ecological Networks (MEN) showed that the network in eDNA-PFU was more modular, forming a unique microbial community differentiated from the aquatic environment. In conclusion, this study, using eDNA-PFU, comprehensively explored microbial colonization and interrelationships in a controlled mesocosm system, providing foundational data and reference standards for its application in aquatic ecosystem monitoring and beyond.

Responses of Zooplankton Community Pattern to Environmental Factors along the Salinity Gradient in a Seagoing River in Tianjin, China

As the primary consumers in aquatic organisms, zooplankton play an important role in aquatic ecosystems. It is valuable for management and researchers to have an insight into the responses of zooplankton community patterns to environmental factors. In this study, RDA and variation partitioning analysis were adopted to determine the important environmental factors affecting zooplankton abundance and biomass, as well as the relative importance of different environmental factors. The findings reveal that TN (total nitrogen), WD (water depth), pH, and SAL (salinity) were all important abiotic factors shaping the zooplankton community pattern in the study area. TN affected protozoa by influencing Stentor amethystinus, while the effects of WD on copepods may have been mainly induced by the responses of Calanus sinicus and Paracyclopina nana. By inhibiting Stentor amethystinus and Vorticella lutea, pH significantly affected protozoa. In addition, Rotifera and copepods were affected by SAL mainly through the responses of Brachionus calyciflorus, Calanus sinicus, and Ectocyclops phaleratus. Importantly, fundamental alternations in the variation trends of zooplankton abundance and biomass along the salinity gradient were found when the salinity was approximately 4-5. By combining these results with the findings on phytoplankton responses to salinity in previous studies, it can be concluded that salinity may influence the river ecosystem by influencing zooplankton abundance and biomass rather than phytoplankton.

Distribution of Zooplankton Functional Groups in the Chaohu Lake Basin, China

To analyze the structural characteristics of zooplankton functional groups (ZFGs) and their correlation with environmental physicochemical factors in the Chaohu Lake Basin, water samples were collected from October 2019 to July 2020, and the zooplankton species and ZFGs were investigated. A total of 250 species, including 88 protozoa, 115 rotifers, 28 cladocerans, and 19 copepod species, were detected and divided into 16 ZFGs. The ZFGs exhibited obvious spatiotemporal heterogeneity. ZFGs in the Chaohu Lake were notably different from those in rivers and were different between the rivers. In the ecosystem, network analysis showed that protozoan algae/protozoan bacteria (PA/PB), rotifer particle filter (RF), and rotifer small predator (RSG) were important in the spring, summer, and autumn that and small zooplankton filter (SCF) was important in spring, autumn, and winter, while the importance of other ZFGs changed with seasons. Redundancy analysis showed that the environmental factors with a strong correlation between the ZFG compositions differed in each season. Different ZFGs exhibited different correlations with environmental factors. This study showed that ZFGs were closely related to environmental factors and that functional traits can reflect responses to changes in the water environment.

Socioeconomic Risks and Their Impacts on Ecological River Health in South Korea: An Application of the Analytic Hierarchy Process

It is imperative to develop a methodology to identify river impairment sources, particularly the relative impact of socioeconomic sources, to enhance the efficiency of various river restoration schemes and policies and to have an internal diagnosis system in place. This study, therefore, aims to identify and analyze the relative importance of the socioeconomic factors affecting river ecosystem impairment in South Korea. To achieve this goal, we applied the Analytical Hierarchy Process (AHP) to evaluate expert judgement of the relative importance of different socioeconomic factors influencing river ecosystem impairment. Based on a list of socioeconomic factors influencing stream health, an AHP questionnaire was prepared and administered to experts in aquatic ecology. Our analysis reveals that secondary industries form the most significant source of stream ecosystem impairment. Moreover, the most critical socioeconomic factors affecting stream impairment are direct inflow pollution, policy implementation, and industrial wastewater. The results also suggest that the AHP is a rapid and robust approach to assessing the relative importance of different socioeconomic factors that affect river ecosystem health. The results can be used to assist decision makers in focusing on actions to improve river ecosystem health.

Environmental Parameters and Substrate Type Drive Microeukaryotic Community Structure During Short-Term Experimental Colonization in Subtropical Eutrophic Freshwaters

Microeukaryotes are key components of aquatic ecosystems and play crucial roles in aquatic food webs. However, influencing factors and potential assembly mechanisms for microeukaryotic community on biofilms are rarely studied. Here, those of microeukaryotic biofilms in subtropical eutrophic freshwaters were investigated for the first time based on 2,585 operational taxonomic units (OTUs) from 41 samples, across different environmental conditions and substrate types. Following conclusions were drawn: (1) Environmental parameters were more important than substrate types in structuring microeukaryotic community of biofilms in subtropical eutrophic freshwaters. (2) In the fluctuating river, there was a higher diversity of OTUs and less predictability of community composition than in the stable lake. Sessile species were more likely to be enriched on smooth surfaces of glass slides, while both free-swimming and attached organisms occurred within holes inside PFUs (polyurethane foam units). (3) Both species sorting and neutral process were mechanisms for assembly of microeukaryotic biofilms, but their importance varied depending on different habitats and substrates. (4) The effect of species sorting was slightly higher than the neutral process in river biofilms due to stronger environmental filtering. Species sorting was a stronger force structuring communities on glass slides than PFUs with more niche availability. Our study sheds light on assembly mechanisms for microeukaryotic community on different habitat and substrate types, showing that the resulting communities are determined by both sets of variables, in this case primarily habitat type. The balance of neutral process and species sorting differed between habitats, but the high alpha diversity of microeukaryotes in both led to similar sets of lifecycle traits being selected for in each case.

Colonization dynamics of protozoan communities in marine bioassessment surveys using two modified sampling systems

Colonization dynamics of protozoan communities were investigated at a depth of 1 m in the coastal waters of the Yellow Sea, northern China from May to June 2019, using modified glass slide (mGS) and modified polyurethane foam unit (mPFU) systems. The colonization process and growth curves of protozoa were well fitted to the MacArthur-Wilson and logistic models in both systems, respectively. However, they showed significant differences in both colonization dynamics and biodiversity/functional parameters between the mGS and mPFU systems. The H' (species diversity), the G (colonization rate), and A_max (maximum abundance) were higher, while the value of T_90% (the time for reaching 90% equilibrium species number) was lower in the mGS system than those in the mPFU system. Multivariate analyses demonstrated that protozoa showed different models of colonization dynamics in both systems. The results suggest that the mGS system might be more effective than the mPFU system in marine bioassessment surveys.

Water pollution characteristics and analysis of Chaohu Lake basin by using different assessment methods

In the context of the water environmental protection and local economic sustainable growth, it is of great importance to conduct a comprehensive water quality assessment in Chaohu Lake basin. In this study, dissolved oxygen (DO), permanganate index (COD_Mn), 5-day biochemical oxygen demand (BOD₅), ammonia nitrogen (NH₃-N), total nitrogen (TN), and total phosphorus (TP) were investigated monthly at 24 sampling sites in Chaohu Lake basin during 2015 to 2017. Five methods were used to evaluate water quality and identify dominant pollutants. Results showed that the dominant pollutants in Chaohu Lake were TN (4.17~11.61 mg L^-1) and TP (0.27~0.75 mg L^-1). The upstream of Chaohu Lake was influenced by Nanfei River, Shiwuli River, and Paihe River, and water quality of the upstream (eutrophic) was worse than that of the downstream (mesotrophic) part of Chaohu Lake. Comprehensive Water Quality Identification Index Method (CWQII) can better assess the water quality compared with the other methods by providing qualitative and quantitative analysis. The index values assessed by CWQII method for Nanfei River, Shiwuli River, and Paihe River were 5.819, 5.986, and 5.141, respectively, and water quality were all assessed as grade V. Overall, water quality of Chaohu Lake has been slightly improved during 2015~2017, but water quality of western inflowing rivers was still heavily polluted. These findings provide valuable information and guidance for water pollution control and water resource management in Chaohu Lake basin. Several feasible measures are proposed.

Impacts of land use and population density on seasonal surface water quality using a modified geographically weighted regression

As an important regulator of pollutants in overland flow and interflow, land use has become an essential research component for determining the relationships between surface water quality and pollution sources. This study investigated the use of ordinary least squares (OLS) and geographically weighted regression (GWR) models to identify the impact of land use and population density on surface water quality in the Wen-Rui Tang River watershed of eastern China. A manual variable excluding-selecting method was explored to resolve multicollinearity issues. Standard regression coefficient analysis coupled with cluster analysis was introduced to determine which variable had the greatest influence on water quality. Results showed that: (1) Impact of land use on water quality varied with spatial and seasonal scales. Both positive and negative effects for certain land-use indicators were found in different subcatchments. (2) Urban land was the dominant factor influencing N, P and chemical oxygen demand (COD) in highly urbanized regions, but the relationship was weak as the pollutants were mainly from point sources. Agricultural land was the primary factor influencing N and P in suburban and rural areas; the relationship was strong as the pollutants were mainly from agricultural surface runoff. Subcatchments located in suburban areas were identified with urban land as the primary influencing factor during the wet season while agricultural land was identified as a more prevalent influencing factor during the dry season. (3) Adjusted R² values in OLS models using the manual variable excluding-selecting method averaged 14.3% higher than using stepwise multiple linear regressions. However, the corresponding GWR models had adjusted R² ~59.2% higher than the optimal OLS models, confirming that GWR models demonstrated better prediction accuracy. Based on our findings, water resource protection policies should consider site-specific land-use conditions within each watershed to optimize mitigation strategies for contrasting land-use characteristics and seasonal variations.

Insights into bioassessment of marine pollution using body-size distinctness of planktonic ciliates based on a modified trait hierarchy

Based on a modified trait hierarchy of body-size units, the feasibility for bioassessment of water pollution using body-size distinctness of planktonic ciliates was studied in a semi-enclosed bay, northern China. An annual dataset was collected at five sampling stations within a gradient of heavy metal contaminants. Results showed that: (1) in terms of probability density, the body-size spectra of the ciliates represented significant differences among the five stations; (2) bootstrap average analysis demonstrated a spatial variation in body-size rank patterns in response to pollution stress due to heavy metals; and (3) the average body-size distinctness (Δz(+)) and variation in body-size distinctness (Λz(+)), based on the modified trait hierarchy, revealed a clear departure pattern from the expected body-size spectra in areas with pollutants. These results suggest that the body-size diversity measures based on the modified trait hierarchy of the ciliates may be used as a potential indicator of marine pollution.

Using ciliates to monitor different aquatic environments in Daya Bay, South China Sea

Spatial patterns of planktonic ciliate communities were studied to monitor marine water quality during winter, spring, summer, and autumn of 2014 in Daya Bay, South China Sea. A total of 41 species, with eight dominant species, were identified. Multivariate and univariate analyses demonstrated that spatial taxonomic pattern of planktonic ciliate communities was significantly correlated with environmental condition; ciliate abundance, species diversity, and species richness were significantly correlated with NO3– and salinity or temperature. Additionally, two dominant species (Tintinnopsis minuta Wailes, 1925 and Tintinnopsis beroidea Stein, 1867) were significantly positively correlated with nutrients, particularly with nitrogen nutrients. Three dominant species (Strombidium conicum (Lohmann, 1908) Wulff, 1919; Spirotontonia turbinata (Song & Bradbury, 1998) Agatha, 2004; Laboea strobila Lohmann, 1908) showed more sensitivity to salinity, whereas Mesodinium rubrum (Lohmann, 1908) was significantly correlated with temperature. Our findings suggest that planktonic ciliate communities can be considered a favorable bioindicator of marine water quality.

Effects of flow speed and circulation interval on water quality and zooplankton in a pond-ditch circulation system

A pond-ditch circulation system (PDCS) shows great promises for ecological restoration of rural contaminated water in southern China. In this study, the optimal flow speed, circulation interval, and their combination for the system were investigated for higher pollutant removal efficiency and lower costs in three separate experiments: I, II, and III, respectively. In each experiment, there are three PDCSs (S1, S2, and S3) with different water circulation speeds or circulation intervals, respectively. The results demonstrated that in experiment I, total nitrogen (TN) removal rates, species numbers, and diversity indexes of zooplankton in S1 with a flow speed of 3.6 L/h were significantly higher than those in S2 (7.2 L/h) and S3 (10.2 L/h), respectively. Similarly, in experiment II, S3 circulating every other 4 h had significantly higher TN reduction rates, species numbers, and diversity indexes than S1 and S2 circulating every other 1 and 2 h, respectively. In experiment III, water qualities in S1 (circulation of 3.6 L/h + interval of 4 h) were better than those in S2 (7.2 L/h + 4 h) and S3 (10.2 L/h + 6 h), respectively. Together, circulation at every other 4 h (3.6 L/h) is probably the optimal operating condition for the PDCS in remediating rural contaminated water.

Do early colonization patterns of periphytic ciliate fauna reveal environmental quality status in coastal waters?

The feasibility for developing a protocol to assess marine water quality based on early colonization features of periphytic ciliate fauna was studied in coastal waters of the Yellow Sea, northern China. The ciliate communities with 3-28-day ages were collected monthly at four stations with a spatial gradient of environmental stress from August 2011 to July 2012. The spatial patterns of both early (3-7 days) and mature (>10 days) communities of the ciliates represented significant differences among the four stations, and were significantly correlated with environmental variables, especially nutrients and chemical oxygen demand (COD). Seven and eight dominant species were significantly correlated with nutrients or COD within the early and mature communities, respectively. The species richness indices were strongly correlated with nutrients, especially in mature communities. These findings suggest that it is possible to assess the status of water quality using early colonization features of periphytic ciliate fauna in coastal waters.

Use of biofilm-dwelling ciliate communities to determine environmental quality status of coastal waters

It has increasingly been recognized that the ecological features of protozoan communities have many advantages as a favorable bioindicator to evaluate environmental stress and anthropogenic impact in many aquatic ecosystems. The ability of biofilm-dwelling ciliate communities for assessing environmental quality status was studied, using glass slides as an artificial substratum, during a 1-year cycle (August 2011-July 2012) in coastal waters of the Yellow Sea, northern China. The samples were collected monthly at a depth of 1m from four sampling stations with a spatial gradient of environmental stress. Environmental variables, e.g., salinity, dissolved oxygen (DO), chemical oxygen demand (COD), nitrate nitrogen (NO3-N), ammonium nitrogen (NH4-N) and soluble reactive phosphates (SRP), were measured synchronously for comparison with biotic parameters. Results showed that: (1) the community structures of the ciliates represented significant differences among the four sampling stations; (2) spatial patterns of the ciliate communities were significantly correlated with environmental variables, especially COD and the nutrients; (3) five dominant species (Hartmannula angustipilosa, Metaurostylopsis sp.1, Discocephalus ehrenbergi, Stephanopogon minuta and Pseudovorticella paracratera) were significantly correlated with nutrients or COD; and (4) the species richness measure was significantly correlated with the nutrient NO3-N. It is suggested that biofilm-dwelling ciliate communities might be used as a potentially robust bioindicator for discriminating environmental quality status in coastal waters.

Influence of enumeration time periods on analyzing colonization features and taxonomic relatedness of periphytic ciliate communities using an artificial substratum for marine bioassessment

Colonization features and taxonomic relatedness measures of ciliate communities have been used as useful indicators for marine bioassessment. The influence of enumeration time periods on analyzing colonization features measures of periphytic ciliate communities was studied in coastal waters of the Yellow Sea, northern China, during the period of May-June 2010. Ciliated protozoan samples were collected at depths of 1 m using an artificial substratum and were analyzed with different enumeration schemes. The ciliate species were identified using living observation and silver impregnation. Data analyses were conducted using a range of multivariate statistical routines. Enumeration time periods represented a strong influence on analyzing both colonization and taxonomic relatedness features of periphytic ciliate communities, although no significant changes occurred in colonization patterns between two enumeration schemes (within 24 and 24-48 h after sampling). The delayed enumeration (within 24-48 h) may result in the species richness, individual abundance, colonization rate decreasing to standard errors of >10 % in samples with almost all colonization ages, and in the similarities of the communities being reduced to 11-38 %. However, the species biodiversity (e.g., species diversity and evenness, except species richness) and taxonomic relatedness (taxonomic diversity, taxonomic distinctness and average taxonomic distinctness, except variation in taxonomic distinctness) measures of periphytic ciliate communities were weakly sensitive to disturbance from the delayed enumeration, achieving standard errors of <10 and <5 % during the colonization periods, respectively. These results suggest that the enumeration should be completed as soon as possible within 24 h after sampling to analyze colonization and taxonomic relatedness features of periphytic ciliate communities, and that the species diversity and taxonomic distinctness measures can be used on a robust bioindicator with weak dependence on enumeration time limits for monitoring programs and ecological investigations in marine ecosystems.

Can body-size patterns of ciliated zooplankton be used for assessing marine water quality? A case study on bioassessment in Jiaozhou Bay, northern Yellow Sea

INTRODUCTION

In order to reveal the potential relationships between body-size patterns of microzooplankton and environmental status, the spatial patterns in body-size spectra of ciliated zooplanktons were studied based on an annual dataset in a bay of the Yellow Sea, northern China.

MATERIALS AND METHODS

A total of 120 samples were collected at a depth of 1 m from each of five sampling sites with a spatial gradient of environmental stress from June 2007 to May 2008. A range of physico-chemical variables were measured synchronously for comparison with biotic parameters.

RESULTS

The spatial body-size patterns of ciliated zooplankton represented significant differences among the five sites, and were significantly correlated with the changes of physico-chemical parameters, especially salinity, dissolved oxygen and nutrients. Two paired indices, the average body-size distinctness (AvBSD) and the variation in body-size distinctness (VarBSD), were proposed based on the trait resemblances among ciliate species in body-size pattern. The paired measures showed a clear decreasing trend of departure from the expected body-size spectra in response to water quality status.

CONCLUSION

These results suggest that the body-size pattern of ciliated zooplankton might be used as a potential indicator of marine water quality.

Spatial distribution and multiple sources of heavy metals in the water of Chaohu Lake, Anhui, China

In this study, a survey for the spatial distribution of heavy metals in Chaohu Lake of China was conducted. Sixty-two surface water samples were collected from entire lake including three of its main river entrances. This is the first systematic report concerning the content, distribution, and origin of heavy metals (Cu, Cr, Cd, Hg, Zn, and Ni) in the Chaohu Lake water. The results showed that heavy metals (Cu, Cr, Zn, and Ni) concentrations in the estuary of Nanfei River were relatively higher than those in the other areas, while content of Hg is higher in the southeast lake than northwest lake. Moreover, Cd has locally concentration in the surface water from the entire Chaohu Lake. The heavy metal average concentrations, except Hg, were lower than the cutoff values for the first-grade water quality (China Environment Quality Standard) which was set as the highest standard to protect the social nature reserves. The Hg content is between the grades three and four water quality, and other heavy metals contents are higher than background values. The aquatic environment of Chaohu Lake has apparently been contaminated. Both the cluster analysis (CA) and correlation analysis provide information about the origin of heavy metals in the Lake. Our findings indicated that agricultural activities and adjacent plants chimneys may contribute the most to Cd and Hg contamination of Chaohu Lake, respectively.

An approach to analyzing spatial patterns of protozoan communities for assessing water quality in the Hangzhou section of Jing-Hang Grand Canal in China

INTRODUCTION

In order to evaluate water quality of a canal system, the spatial pattern of protozoan communities in response to physicochemical variables was studied in the Hangzhou section of the Grand Canal, northern China during a 1-year cycle (February 2008-January 2009).

MATERIALS AND METHODS

Protozoan samples were monthly collected at six sampling stations with a spatial gradient of environmental status. Physicochemical parameters, e.g., water temperature, dissolved oxygen, chemical oxygen demand (COD), biological oxygen demand, total nitrogen (TN), and total phosphorus (TP), were measured synchronously for comparison with biotic parameters.

RESULTS

The protozoan community structures represented significant differences among the six sampling stations. The spatial patterns of protozoan communities were significantly correlated with the changes of chemical variables, especially COD, either alone or in combination with TP and/or TN. Of 88 protozoan taxa recorded over the study period, ten species (e.g., Carchesium polypinum, Colpidium campylum, Prorodon teres, Vorticella putrina, Zoothamnium arbuscula, Euglena spp., and Phacus spp.) were significantly related to COD, either alone or in combination with TP and/or TN.

CONCLUSION

These findings suggest that protozoa can be used as a robust bioindicator of water quality in freshwater river systems.

An approach to determining the sampling effort for analyzing biofilm-dwelling ciliate colonization using an artificial substratum in coastal waters

A new approach to determining sampling effort for analyzing biofilm-dwelling ciliate colonization was studied in the coastal waters of the Yellow Sea, northern China, from May to June 2010. The optimal sample size for evaluating biofilm-dwelling ciliate colonization increased with shortening exposure time, and can be determined according to the probability of recovering those species with a specified cumulative contribution to communities. More slide-replicates were required at a depth of 3 m than at 1 m to recover equivalent proportions of the ciliate communities. For routine colonization dynamics analyses, 10 slide-replicates (175 cm(2)) were sufficient to achieve a 95% probability of recovering those species with a cumulative contribution of >90% to the ciliate communities at a depth of 1 m. These results suggest that 10 slide-replicates immersed at a depth of 1 m may be an optimal sampling strategy for analyzing the colonization dynamics of biofilm-dwelling ciliate communities in marine habitats.

An approach to analyzing spatial patterns of planktonic ciliate communities for monitoring water quality in Jiaozhou Bay, northern China

Spatial patterns of planktonic ciliate communities for assessment of marine environmental status were studied from June 2007 to May 2008 in Jiaozhou Bay, Qingdao, northern China. Ciliate communities were sampled biweekly at five sampling sites with a spatial gradient of environmental stress. Multivariate/univariate analyses demonstrated that: (1) the planktonic ciliate community structures represented significant differences among the five sites; (2) spatial patterns of the ciliate communities were significantly correlated with environmental variables, especially the nutrients nitrate nitrogen (NO₃-N) and soluble reactive phosphates (SRP); (3) five dominant species (e.g., Rimostrombidium veniliae, Strombidium capitatum, Mesodinium pupula and Strombidinopsis acutum) were significantly correlated with nitrogen and/or SRP; and (4) both species richness and species diversity indices were correlated with NO₃-N and salinity. These results suggest that planktonic ciliated protozoa might be used as a robust bioindicator of marine water quality.

Some potential hazardous trace elements contamination and their ecological risk in sediments of western Chaohu Lake, China

The Chaohu is one of the largest five freshwater lakes in China. It provides freshwater for agriculture, life, and part of industry. The quality of water becomes worst and worst due to the toxic matter. In this study, we collected the samples from the sedimentary mud in the lake. The distribution of some potential hazardous trace elements (Cu, Ni, Cr, As, Pb, Cd, and Hg) in the sediments of western Chaohu Lake, has been determined and studied, and the enrichment factors, the index of geoaccumulation, and potential ecological risk were analyzed and calculated. The results show that: the levels of selected potential hazardous trace element vary from different sampling sites and significant anthropogenic impact of Pb and Cd occur in sediments. The contamination rank of Pb and Cd are moderate, and Pb has a light potential ecological risk, but Cd is heavy. The total potential ecological risk of the selected hazardous trace elements in this study in Chaohu Lake is moderate. Cluster and correlation analysis indicate that the selected potential hazardous trace element pollutant has different source and co-contamination also occur in sediments.

Studies on the restoration succession of PFU microbial communities in a pilot-scale microcosm

In order to imitate the restoration succession process of natural water ecosystem, a laboratory microcosm system of constant-flow-restoration was designed and established. A eutrophycation lake, Lake Donghu, was selected as the subject investigated. Six sampling stations were set on the lake, among which the water of station IV was natural clean water, and others were polluted with different degrees. Polyurethane foam unit microbial communities, which had colonized in the stations for a month, were collected from these stations and placed in their respective microcosms, using clean water of station IV to gradually replace the water of these microcosms. In this process, the healthy community in clean water continuously replaced the damaged communities in polluted water, the restoration succession of the damaged communities was characterized by weekly determination of several functional and structural community parameters, including species number (S), diversity index (DI), community pollution value (CPV), heterotrophy index (HI), and similarity coefficient. Cluster analysis based on similarity coefficient was used to compare the succession discrepancies of these microbial communities from different stations. The ecological succession of microbial communities during restoration was investigated by the variable patterns of these parameters, and based on which, the restoration standards of these polluted stations were suggested in an ecological sense. That was, while being restored, the water of station 0 (supereutrophycation) should be substituted with natural clean water by 95%; station I (eutrophycation), more than 90%; station II (eutrophycation), more than 85%; station III (eutrophycation), about 85%; station V (mesoeutrophycation), less than 50%. The effects of the structural and functional parameters in monitoring and assessing ecological restoration are analyzed and compared.

Effects of seasonal succession and water pollution on the protozoan community structure in an eutrophic lake

The purpose of the research is to study the seasonal succession of protozoa community and the effect of water quality on the protozoa community to characterize biochemical processes occurring at a eutrophic Lake Donghu, a large shallow lake in Wuhan City, China. Samples of protozoa communities were obtained monthly at three stations by PFU (polyurethane foam unit) method over a year. Synchronously, water samples also were taken from the stations for the water chemical quality analysis. Six major variables were examined in a principal component analysis (PCA), which indicate the fast changes of water quality in this station I and less within-year variation and a comparatively stable water quality in stations II and III. The community data were analyzed using multivariate techniques, and we show that clusters are rather mixed and poorly separated, suggesting that the community structure is changing gradually, giving a slight merging of clusters form the summer to the autumn and the autumn to the winter. Canonical correspondence analysis (CCA) was used to infer the relationship between water quality variables and phytoplankton community structure, which changed substantially over the survey period. From the analysis of cluster and CCA, coupled by community pollution value (CPV), it is concluded that the key factors driving the change in protozoa community composition in Lake Donghu was water qualities rather than seasons.

Monitoring of organochlorine pesticides using PFU systems in Yunnan lakes and rivers, China

Polyurethane foam unit (PFU) systems were collected from 11 lakes and three rivers in the Yunnan Plateau, China and, the PFU extrusion liquids were analyzed for organochlorine pesticides (OCPs) by gas chromatography with electron capture detection (GC-ECD). The concentrations of pp'-DDE, HCB and HCHs were undetectable to 1.86 microgl-1 (mean 0.27 microgl-1), undetectable to 0.72 microgl-1 (mean 0.11 microgl-1), and 0.24-21.95 microgl-1 (mean 7.39 microgl-1) respectively in lakes; and those in rivers were undetectable to 0.23 microgl-1 (mean 0.08 microgl-1), 0.68-2.93 microgl-1 (mean 1.70 microgl-1), and 2.71-37.56 microgl-1 (mean 17.01 microgl-1) respectively. Notably, some residue levels of OCPs exceeded the US National Recommended Water Quality Criteria, implying Yunnan has levels of OCPs potentially harmful to human health. Further, the contamination by OCPs showed an obvious spatial distribution pattern. Amongst the lakes, Dianchi, Xingyun, Lugu and Yangzonghai had the highest OCP levels dominated by beta-HCH, whereas among rivers, Nujiang and Lancang Rivers had the highest contents of OCPs dominated by alpha-HCH. This demonstrates that HCHs are the predominant contaminants and some point sources of HCHs may still exist in Yunnan. The pollution levels in Yunnan were compared with other studies, suggesting the PFU method is suitable for long-term on-line monitoring of trace OCPs in aquatic ecosystems. Therefore, continuous studies monitoring OCPs in lakes and rivers are needed to further understand the future trend of contamination.