Zhang Tanglin

Status and historical changes in the fish community in Erhai Lake

Erhai Lake is the second largest freshwater lake on the Yunnan Plateau, Southwest China. In recent decades, a number of exotic fish species have been introduced into the lake and the fish community has changed considerably. We evaluated the status of the fish community based on surveys with multimesh gillnet, trap net, and benthic fyke-net between May 2009 and April 2012. In addition, we evaluated the change in the community using historical data (1952–2010) describing the fish community and fishery harvest. The current fish community is dominated by small-sized fishes, including Pseudorasbora parva, Rhinogobius giurinus, Micropercops swinhonis, Hemiculter leucisculus, and Rhinogobius cliffordpopei. These accounted for 87.7% of the 22 546 total specimens collected. Omnivorous and carnivorous species dominated the community. A canonical correspondence analysis (CCA) plot revealed that the distribution of fishes in the lake is influenced by aquatic plants, water temperature, pH, and season. The abundance of indigenous species has declined sharply, and a majority of endemic species have been extirpated from the lake (a decrease from seven to two species). In contrast, the number of exotic species has increased since the 1960s to a total of 22 at present. The fishery harvest decreased initially following the 1960s, but has since increased due to the introduction of non-native fish and stocking of native fish. The fishery harvest was significantly correlated with total nitrogen, not total phosphorus, during the past 20 years. Based on our results, we discuss recommendations for the restoration and conservation of the fish resources in Erhai Lake.

Fish gut microecosystem: a model for detecting spatial pattern of microorganisms

The spatial distribution pattern of organisms is a basic issue in understanding the mechanisms of community assembly. Although the spatial distributions of animals and plants have been well studied, those of microorganisms are still being debated. In this study, we used a fish gut microecosystem to detect the spatial pattern of microbes, because it can provide a relatively unified and stable environment. Results suggest that the turnover of intestinal bacterial assemblages showed a weak but highly significant negative correlation between similarity and distances in the microbial community, in respect of both grass carp intestinal loci distances and the geographical distance between fish sampling sites. Our results also suggest that intestinal bacterial assemblages responded to differences within the external environment and within different parts of the fish themselves. These results show that some, or possibly all, microbes are restricted in their distribution and that environmental factors are also important influences on the structure of intestinal bacterial assemblages. The fish gut microecosystem is useful in promoting study of the spatial distribution patterns of microorganisms.

Response of rotifer community to environmental changes in five shallow lakes in the middle reach of Changjiang River, China

We evaluated the response of a rotifer community to environmental changes in five shallow lakes in the middle reach of the Changjiang (Yangtze) River in summer and autumn 2010. These five lakes differed in trophic status and rotifer community structure. Twenty-nine rotifer species were collected, of which Keratella cochlearis, Polyarthra dolichoptera, and Trichocerca elongate were dominant. The mean density, Shannon-Wiener diversity, and equitability among the five lakes differed significantly (P<0.05). The mean rotifer density was positively correlated with trophic state. The diversity was higher in lakes with high macrophyte coverage. The composition of rotifer species was closely associated with the trophic gradient. Five environmental variables, Secchi depth, conductivity, TN, NH4-N, and TP, significantly affected the composition of rotifer species. Keratella quadrata, Brachionus calyciflorus, and B. forficula were more common in eutrophic conditions. Our results suggest that eutrophication has a significant influence on the rotifer community structure and highlight the potential for using rotifer community structure as an indicator of trophic status in subtropical lakes.

The annual fluctuation of zooplankton community and its relation with environmental fac-tors in Lake Xiliang,Hubei Province

Four zooplanktonic investigations were carried out from November 2007 to October 2008 in Lake Xiliang.Totally,224 species of zooplankton including 112 species of protozoa,90 species of rotifer,15 species of cladocera,and 7 species of copepoda were found.The zooplankton species ranged from 75 to 111,with the lowest value(75) occurring in winter,and the highest one(111) in autumn.The density of zooplankton was the highest in winter(126731ind./L),and the lowest in spring(71356ind./L).The densities of zooplankton in summer and autumn were 109743ind./L and 107650ind./L,respectively,and the abundance of protozoa and rotifer were on predominance.The structure of zooplankton community was analyzed in relation to water quality parameters by canonical correspondence analysis(CCA).Temperature,pH,water depth,and the concentrations of TP,COD and DO were strongly correlated with the zooplankton community structure.The parameters that demonstrated a strong correlation with the zooplankton community structure differed among seasons,suggesting that the seasonal variations of zooplankton community structure were related closely to both the water temperature and water trophic status in Lake Xiliang.

Relationship between DNA fingerprinting structure of plankton community and physicochemical factors in Lake Niushan

Plankton are considered good indicators of water quality because they are highly sensitive to the environmental variation in their short life spans. However, traditional studies on plankton community constructure have depended on taxonomic identification which has historically been a difficult task. Recently, different fingerprinting techniques have been developed and applied successfully to analyze the community structure of bacterial and picoplankton. However, little is known to the whole plankton community. In this study, we analyze DNA polymorphism of plankton communities in five different sampling stations of Lake Niushan by RAPD and PCR-DGGE and explore the relationship between DNA fingerprinting structure of plankton communities and environmental physico-chemical factors. The results were: (i) 9 of 40 screened random primers used in the study amplified a total of 93 observable bands, 58 of which were polymorphic; the mean number of amplified bands at different sampling stations was 67, and station V had the maximum number (74) and station I had the minimum number (61); (ii) a total of 102 bands (56 of 16S rDNA bands and 46 of 18S rDNA bands) were detected by PCR-DGGE, station III, IV, and V had more bands, station I and II had few band; (iii) total phosphorus (TP), chlorophyll-a, chemical oxygen demanded (COD), hardness, and conductance rate at station II were the highest; dissolved oxygen (DO) and pH value were not obviously different among five stations. Based on physico-chemical factors, station I, III, IV, and V were grouped into a cluster, station II grouped into a single cluster. Based on RAPD markers and PCR-DGGE markers, five sampling stations can be grouped into two clusters: station I and II were grouped into a cluster, and station III, IV, and V were grouped into the other cluster. In conclusion, the DNA fingerprinting structure of plankton community was closely related to total phosphorus (TP). DNA based community level analysis is a fast, easy, accurate method to reflect the water quality, and such data accumulation will play an important role in constructing one easy and sensitive molecular system for water quality assessment.

Community structure of rotifers in relation to environmental factors in Lake Hongze

The spatial-temporal changes in rotifer species composition and community structure and their relationship with key environmental factors were investigated seasonally from May 2010( spring) to February 2011( winter) in a shallow freshwater lake,Lake Hongze,China.Totally 34 species of rotifer,belonging to 17 genera,were identified during the seasonal sampling.Keratella cochlearis,Asplanchna priodonta,Polyarthra dolichoptera,Brachionus calyciflorus and Keratella valga were the dominant species.Lake Hongze has three main areas that are Chengzihu,southwest and east area.The rotifer distribution in the three main areas was significantly different.There were 27,26 and 19 species in Chengzihu,southwest,east area,respectively.Meanwhile,the maximum density and biomass of rotifers was found in the southwest area of Lake Hongze while the minimum was found in the east area.In terms of seasonal variation,the density and biomass of rotifer was highest in spring,with higher values in autumn.The density and biomass in summer was lowest in the four seasons.Their relationship with environmental factors was analyzed using canonical correspondence analysis( CCA).From the result of CCA,environmental factors such as water temperature,dissolved oxygen and chlorophyll-a that representing seasonal variations of water quality were significantly correlated with the Axis 1 and affected the composition and the density of rotifer community.Moreover,environmental factors related to nutrient concentrations such as total phosphorus,total nitrogen and dissolved inorganic nitrogen were also important nutrient factors which influenced the community structure of rotifer of Lake Hongze.

Seasonal variation of plankton communities influenced by environmental factors in an artificial lake

We evaluated the seasonal variation in plankton community composition in an artificial lake. We conducted microscopic analysis and denaturing gradient gel electrophoresis (DGGE) of PCR-amplified partial 16S rRNA and 18S rRNA genes to characterize the plankton community. The clustering of unweighted pair group method with arithmetic mean (UPGMA) was then used to investigate the similarity of these plankton communities. DGGE fingerprinting revealed that samples collected at the different sites within a season shared high similarity and were generally grouped together. In contrast, we did not observe any seasonal variation based on microscopic analysis. Redundancy analysis (RDA) of the plankton operational taxonomic units (OTUs) in relation to environmental factors revealed that transparency was negatively correlated with the first axis (R=−0.931), and temperature and total phosphorus (TP) were positively correlated with the first axis (R=0.736 and R=0.660, respectively). In conclusion, plankton communities in the artificial lake exhibited significant seasonal variation. Transparency, phosphorus and temperature appear to be the major factors driving the differences in plankton composition.