[Spatial distribution of cladoceran assemblages in surface sediments of shallow lakes in Yunnan.] / æµ æ°´æ¹–æ³Šè¡¨å±‚æ²‰ç§¯ç‰©è®°å½•çš„æžè§’ç±»ç¾¤è½ç©ºé—´åˆ†å¸ƒç‰¹å¾.

Shallow lakes, sensitive to environmental changes due to low environmental carrying capacity, generally experience decreases in ecosystem function and even regime shifts after over-exploitation. Surface sediments of 18 shallow lakes in Yunnan were collected and analyzed to identify the spatial pattern and the influencing factors of cladoceran communities. The results showed that there was significant heterogeneity in the spatial distribution of cladocera in those lakes. For example, the cladoceran community was generally dominated by benthic taxa in alpine lakes, while there was a clear replacement of benthic cladocerans by planktonic ones with increasing nutrient levels across lakes from Southeast Yunnan. Altitude and total phosphorus were the main driving factors, which independently explained 22.0% and 7.7% of the change in cladocera communities, respectively. The altitude gradient and related changes in climate and catchment features were the main factors in structuring cladocerans for shallow lakes of Yunnan, while the anthropogenic impacts on cladoceran distribution was significant via the processes such as catchment development, pollutant input and macrophyte changes. Meanwhile, the interaction between elevation and total phosphorus explained 26.3% of the total variance in cladoceran community shift, indicating that the increase in human activity intensity in lakes at lower altitudes would have stronger impact on cladocerans through anthropogenic nutrient inputs.

[Spatial distributions and environmental control of diatom functional groups in sediments of Haixi Lake, Southwest China.] / åŸºäºŽç¡ è—»åŠŸèƒ½ç¾¤ç‰¹å¾æ­ç¤ºæµ·è¥¿æµ·è¿‘çŽ°ä»£ç”Ÿæ€çŽ¯å¢ƒå˜åŒ–.

Functional group classification based on the morphological, physiological and ecological characteristics of diatoms is advanced in describing the tolerance and sensibility of diatoms to environmental stressors. In this study, we examined the spatial distribution of diatom functional groups in surface sediments of Haixi Lake and explored the relationships between diatom distributions and environmental variables using multivariate analyses. Principal components analysis (PCA) and redundancy analysis (RDA) results showed that water depth and total nitrogen (TN) were the key drivers for the heterogeneous distribution of diatom functional groups. Water depth of ca. 8 m was the threshold depth in influencing diatom functional group structures linking with thermal stratification. These results provided a basis for fossil record interpretation of the short core. Diatom functional groups fluctuated over the last century, in keeping with mean annual temperature, sediment TN, and median grain size. Climate warming, accelerated nutrient enrichment and intensified hydrological changes led to the dominance of functional group D, MP and P. Additionally, climate warming and nutrient enrichment led to increased diatom functional group diversity, while increased water depth (led by damming and reservoir reinforcement) contributed to diversity loss around 1957 and 1990 AD, respectively.

[Spatio-temporal Variations of Diatom Community and Their Relationship with Water Environment in Fuxian Lake].

Fuxian Lake is an important deep lake in China with trophic status generally categorized as class I. However, there exists a trend of degradation in its ecological and environmental health under the increasing impacts derived from catchment development and recent global warming. Therefore, it is important to evaluate the community composition, distribution patterns, and driving factors of lake biota. In order to uncover the spatio-temporal variations in water quality and diatom communities, a monthly survey of diatom community composition and limnological characteristics was carried out in the surface waters of three sampling sites from the south, middle, and north of the lake basin in Fuxian in 2015. A total of 166 diatom species belonging to 31 genera were identified, which was dominated by planktonic diatoms with the extirpation of Cyclotella rhomboideo-elliptica, an endemic species for Yunnan. Diatom community structure showed significant seasonal succession across the three sites, which were dominated by Fragilaria crotonensis in January and February, by Aulacoseira granulata in March, by Cyclotella ocellata and F. crotonensis in April, and by C. ocellata for other months (i.e., relative abundance of ~80%). Over the spatial scale, the distribution of the dominant diatoms displayed a high degree of similarity. Principal component analysis further showed that there existed significant difference in the diatom community structure and lake environment over the temporal scale, but no significant deviance was found across the three sites. The results of redundancy analysis and variation partitioning revealed that the key driver included meteorological and physical factors (i.e., water temperature, wind velocity, and Secchi depth), which accounted for 27.6% of the total variance in diatom community changes. In combination with the thermocline analysis, the change in lake hydrodynamics may have influenced the thickness and duration of the thermal stratification of lake water, resulting in the reorganization of the diatom community. At the same time, the lake-water nutrients and ions also exerted an important influence on community structuring, which explained the 21.2% and 9.4% of the diatom variation, respectively. Therefore, regional warming and catchment development have significantly structured the biological community and ecosystem health of Fuxian Lake. In all, measures should be taken not only to control the watershed input of pollutants but also to actively mitigate the long-term impact of climate change for the protection and ecological remediation of Fuxian Lake.

[Identification of the long-term patterns of catchment development and diatom community changes in Xihu Lake, Dali, Yunnan, China]. / å¤§ç†è¥¿æ¹–æµåŸŸå¼€å‘åŽ†å²ä¸Žç¡ è—»ç¾¤è½å˜åŒ–çš„æ¨¡å¼è¯†åˆ«.

Limnological studies have long focused on the nine largest plateau lakes and ecological assessment of lake eutrophication in Yunnan. However, comprehensive surveys of small and me-dium-sized lakes and their response to multiple stressors are largely absent. Here, we combined multi-proxy sediment analyses and documentary data, aiming to identify the long-term pattern of diatom community changes under the influence of climate change and anthropogenic disturbances, and to quantify their driving strengths. The results showed that Xihu Lake was in a pre-impact state with little ecological variability before the 1950s. Thereafter, expansion of land use increased the nutrient input and altered the lake hydrology, resulting in a significant shift of dominant diatoms from Cocconeis placentula to Fragilaria spp. From 1997, accelerating nutrient enrichment and hydrological changes led to the replacement of benthic diatoms by planktonic ones, resulting in a consistent loss of macrophytes and a decrease of ecological stability. Therefore, the types and strength of catchment development should be fully evaluated for effective protection of small and medium-sized alpine lakes in the context of global warming.

[Comparative evaluation of models for infectious source control of schistosomiasis in lake and marshland regions].

OBJECTIVE: To compare the effect of different models for the control of infectious source of schistosomiasis, so as to explore the control models suitable for lake and marshland regions. METHODS: The models of "replacement of cattle with machine" and "grazing prohibition and establishing fixed pasture" were implemented in 2 towns of Gong'an and Jianli counties, Hubei Province, respectively, and the data of infection situation of human and livestock, Oncomelania hupensis snail situation and the contamination status of wild faeces were collected and analyzed from 2008 to 2010. RESULTS: In 2010, for the model of "replacement of cattle with machine", the infection rate of residents in the observation group decreased by 56.82% comparing to that in 2008, the difference had a statistical significance (chi2 = 78.197, P < 0.01), and the decrease extent in the observation group was larger than that in the control group; the infection rates of cattle and snails, and the density of infected snails of the former were all decreased to 0. No wild faeces were discovered in the observation group, while 58 pieces of wild faeces were discovered but no schistosome eggs were found in these faeces in the control group. In 2010, for the model of "grazing prohibition and establishing fixed pasture", the infection rate of residents in the observation group decreased by 39.00% without a statistic significance (chi2 = 1.594, P > 0.05), and the infection rate of cattle decreased by 43.98% without a statistically significant difference (chi2 = 0.751, P > 0.05) comparing to those in 2008. The density of living snails decreased by 89.83% in the observation group, while that in the control group increased by 6.80%. A total of 11 pieces of wild faeces were collected in the observation group, with a positive rate of 18.18%, and 7 pieces were collected in the control group, all of which were negative. During the 2 years, no acute and advanced schistosomiasis patients were newly discovered. CONCLUSIONS: "Replacement of cattle with machine" and "grazing prohibition and establishing fixed pasture" are the main measures for schistosomiasis control in lake and marshland regions, the former is suitable for inner embankment regions, while the latter is suitable for the outer-embankment areas.