Community structure and species diversity dynamics of a subtropical evergreen broad-leaved forest in China:2005 to 2020

Here,we characterize the temporal and spatial dynamics of forest community structure and species diversity in a subtropical evergreen broad-leaved forest in China.We found that community structure in this forest changed over a 15-year period.Specifically,renewal and death of common species was large,with the renewal of individuals mainly concentrated within a few populations,especially those of Aidia canthioides and Cryptocarya concinna.The numbers of individual deaths for common species were concentrated in the small and mid-diameter level.The spatial distribution of community species diversity fluctuated in each monitoring period,showing a more dispersed diversity after the 15-year study period,and the coefficient of variation on quadrats increased.In 2010,the death and renewal of the community and the spatial variation of species diversity were different compared to other survey years.Extreme weather may have affected species regeneration and community stability in our subtropical monsoon evergreen broad-leaved forests.Our findings suggest that strengthening the monitoring and management of the forest community will help better understand the long-and short-term causes of dynamic fluctuations of community structure and species diversity,and reveal the factors that drive changes in community structure.

Effects of nitrogen and phosphorus additions on soil microbial community structure and ecological processes in the farmland of Chinese Loess Plateau

Microorganisms regulate the responses of terrestrial ecosystems to anthropogenic nutrient inputs.The escalation of anthropogenic activities has resulted in a rise in the primary terrestrial constraining elements,namely nitrogen(N)and phosphorus(P).Nevertheless,the specific mechanisms governing the influence of soil microbial community structure and ecological processes in ecologically vulnerable and delicate semi-arid loess agroecosystems remain inadequately understood.Therefore,we explored the effects of different N and P additions on soil microbial community structure and its associated ecological processes in the farmland of Chinese Loess Plateau based on a 36-a long-term experiment.Nine fertilization treatments with complete interactions of high,medium,and low N and P gradients were set up.Soil physical and chemical properties,along with the microbial community structure were measured in this study.Additionally,relevant ecological processes such as microbial biomass,respiration,N mineralization,and enzyme activity were quantified.To elucidate the relationships between these variables,we examined correlation-mediated processes using statistical techniques,including redundancy analysis(RDA)and structural equation modeling(SEM).The results showed that the addition of N alone had a detrimental effect on soil microbial biomass,mineralized N accumulation,andβ-1,4-glucosidase activity.Conversely,the addition of P exhibited an opposing effect,leading to positive influences on these soil parameters.The interactive addition of N and P significantly changed the microbial community structure,increasing microbial activity(microbial biomass and soil respiration),but decreasing the accumulation of mineralized N.Among them,N24P12 treatment showed the greatest increase in the soil nutrient content and respiration.N12P12 treatment increased the overall enzyme activity and total phospholipid fatty acid(PLFA)content by 70.93%.N and P nutrient contents of the soil dominate the microbial community structure and the corresponding changes in hydrolytic enzymes.Soil microbial biomass,respiration,and overall enzyme activity are driven by mineralized N.Our study provides a theoretical basis for exploring energy conversion processes of soil microbial community and environmental sustainability under long-term N and P additions in semi-arid loess areas.

Effects of Bamboo Charcoal-based Biochar on Soil Enzyme Activity and Microbial Community Structure

[Objectives]This study was conducted to reveal the effects of bamboo charcoal-based biochar(or bamboo charcoal for short)on soil enzyme activity and microbial community structure.[Methods]The field experiment was carried out at the Modern Agriculture Demonstration Base of Gaoping Village,Gaoping Town,Suichang County,Zhejiang Province.Bamboo charcoal was applied at four different levels:T_(0)(no bamboo charcoal),T_(1)(1125 kg/hm^(2)bamboo charcoal),T_(2)(2250 kg/hm^(2)bamboo charcoal)and T_(3)(3375 kg/hm^(2)bamboo charcoal).Soil physicochemical properties and enzyme activities in different treatments were measured.[Results]The soil fungal,bacterial and actinomycete populations increased significantly in the soils surrounding capsicum roots.The bacterial population,fungal population and fungus/bacterium ratio peaked in Treatment T_(2),up to 7.32×10^(6)cfu/g,2.65×10^(4)cfu/g and 0.36×10^(-2),respectively.The effect of bamboo charcoal in promotingβ-glucoside,catalase,acid phosphatase and sucrase activities was T_(2)>T_(3)>T_(1)>T_(0).With bamboo charcoal increasing,the bacterium population,fungus population,fungus/bacterium ratio,β-glucoside,catalase,acid phosphatase and sucrase activities all increased at first and then decreased.T_(2)treatment showed the best effects in improving soil physicochemical properties and microbial community structure.[Conclusions]Bamboo charcoal significantly improves soil enzyme activity and increases soil microbial population,and thus has important positive effects on the soil ecosystem.

Community Structure of Fish in Nanji Islands National Nature Reserve and Its Relationship with Environmental Variation

Community structure of fish in relation to environmental variation was investigated in Nanji Islands National Nature Reserve (NINNR). In order to test this relationship, we delineated 25 survey stations with bottom trawling and measured environmental variables. Samples were taken from November 2013 (autumn), February 2014 (winter), May 2014 (spring) and September 2014 (summer). We found a very strong correlation in space and time between temperature and salinity;abundance and biomass in winter;depth and DO in summer then a strong correlation was found respectively between temperature and biomass;salinity and biomass in winter too and finally a moderate correlation between depth and biomass in spring, (P-value < 0.01) with positive correlation (that the other variable or factor has a tendency to increase). We also found out a negative correlation (P-value < 0.05), respectively between salinity and DO;DO and chlorophyll in summer;temperature and salinity;salinity and DO in spring period (mean that the other variable or factor has a tendency to decrease). A negative correlation observed between temperature, salinity and chlorophyll in winter, spring and autumn period were due by a temperature and salinity window open for species blooms through the movement of the TWC and Jiangzhe coastal current close to shore. By comparing diversity of fish species with environmental factors, the community structure of fish varied significantly as physicochemical parameters changed between different stations for each season. As results and according to the species referencing of environmental factors;species diversity, abundance and evenness vary among different stations, corresponding to significant differences of environmental factors (e.g. physicochemical parameters and chlorophyll-a concentration in different sites). Species richness of microfauna was negatively correlated with salinity levels. Furthermore, they were related to the fish community according to the results. This may be due to the fish community’s adaptability in these different variations of environmental factors, but only tolerant members remaining.

Effect of nutrient level on phytoplankton community structure in different water bodies

Increasing levels of pollution within water bodies can cause eutrophication and an associated rapid growth in and reproduction of phytoplankton. Although most frequently occurring in bodies of water such as lakes and dams, in recent years an increasing number of river systems in China have suffered serious algal blooms. The community structure of phytoplankton may differ, however, dependent on the hydrodynamic conditions and nutrient levels within the water body. The field investigation results obtained from a stagnant river in Suzhou City and Taihu Lake, China, showed that in water with higher concentrations of nitrogen and phosphorus, Chlorophyta became the predominant species and in water with lower concentrations of nitrogen and phosphorus, Cyanobacteria became the predominant species. Growth experiments with competitive species, Microcystis aeruginosa Kutz and Scenedesmus quadricauda （Turp.）, were conducted at three different nutrient levels. The biomass of algae in pure and mixed cultures was measured under conditions of different N/P ratios at oligotrophic, eutrophic and hypertrophic nutrient levels. The results indicated that the most suitable state for the growth and reproduction of M. aeruginosa and S. quadricauda were eutrophic conditions in both pure and mixed cultures. Under competition, however, the lower medium nutrient levels favoured M. aeruginosa, while the higher medium nutrient levels better suited S. quadricauda. Under similar hydrodynamic conditions, the community structure of phytoplankton in the water body was determined by the dominant species in competition for nutrients.

Effects of sediment dredging on water quality and zooplankton community structure in a shallow of eutrophic lake

Effects of suction dredging on water quality and zooplankton community structure in a shallow of eutrophic lake, were evaluated. The results showed that a decreasing trend for levels of phosphorus, organic matter, total suspended solids, Chlorophyll a and Secchi transparency in the water column was found, while levels of water depth, electrical conductivity, total dissolved solids and NO3^--N concentration increased markedly post-dredging. The effects of dredging on dissolved oxygen, pH value and temperature were almost negligible. The zooplankton community structure responded rapidly to the environmental changes caused mainly by dredging. As a result, the abundance of rotifers decreased, while the density of zooplanktonic crustaceans increased markedly. The representative taxa were Brachionus angularis, B. budapestinensis, B. diversicornis, Synchaeta spp. and Neodiaptomus schmackeri. A distinct relationship between zooplankton taxa composition and their environment, unraveled by a redundancy analysis, indicating that the measured environment contributed to the variations in the zooplankton community structure to some extent. The first four synthetic environmental variables explained 51.7% of the taxonomic structure. Therefore, with the reduction of internal nutrient load and a shift in dominance by less eutrophic species, it inferred that dredging might be one of effective measures for environmental improvements of such lakes.

Comparative study of microbial community structure in different filter media of constructed wetland

Comparisons of microbial community structure, in eight filter media of zeolites, anthracite, shale, vermiculite, ceramic filter media, gravel, steel slag and bio-ceramic, were undertaken by analyzing the phospholipid fatty acid （PLFA） composition. A total of 20 fatty acids in the range of C18to C20 were determined but only 13 PLFAs were detected in steel slag. They consist of saturated fatty acids, branched fatty acids, monounsaturated fatty acids, and polyunsaturated fatty acids. The variation of fatty acids was revealed in the relative proportions of these fatty acids in different media. The aerobic prokaryotes were the predominant group in all media. The PLFA composition showed significant differences among the eight different media by Tukey＇s honestly test. It was found that steel slag was significantly different in the microbial community as compared to other filter media, probably due to its alkaline effluent. Steel slag alone is probably not a good choice of substratum in constructed wetlands. The principle components analysis （PCA） showed that zeolites, bio-ceramic, shale and vermiculite had a similar microbial community structure while steel slag and ceramic filter media were distinct from other media.

Community structure of macrobenthos in coastal water off Rushan, southern Shandong Peninsula, and the relationships with environmental factors

To understand the present actuality of the marine ecosystem in the southern coastal water region of the Shandong Peninsula and the impact of the global change and the human activities to the marine ecosystem of the region, the macrobenthic community structure was researched based on data from 26 sampling stations carried out on four seasonal cruises from December 2006 to November 2007. The data was analyzed using PRIMER 6.0 and SPSS 15.0 software packages. The results showed that 236 macrobenthic species in total were collected from the research region by the field works. Most of the species belong to Polychaeta （76 species）, Mollusca （75） and Crustacea （60）. Of which, 33 species were common species by the four cruises. The dominant species were different among the four seasons, however, the polychaete species Nephtys oligobranchia and Sternaspis scutata were always dominant in the four seasons. The abundances and biomasses of the macrobenthos from the research region were variable in the four seasons. The results of CLUSTER and MDS analysis showed that the similarities of macrobenthic structures among the stations were low, most of the similarities were at about 40% of similarity values, only that of two stations were up to 60%. In accordance with the similarity values of the macrobenthic structures, the 26 stations were clustered as six groups at arbitrary similarity level of 30%. The ABC curve indicated that the marcofauna communities in the research region had not been disturbed distinctly. The results of BIOENV and BVSTEP （Spearman） analysis implied that the concentrations of organic matter in bottom water and heavy metal copper in sediment, water depth and temperature of bottom were the most significant environmental factors to affect the macrobentic community.

Macrobenthic community structure in the Changjiang Estuary and its adjacent waters in summer

On the basis of data collected in the summer of 2006 from 27 sampling stations in the Changjiang Estuary and its adjacent waters, the ecological characteristics of macrobenthos and the relationship between the macrobenthos and the environmental factors were studied using hierarchical cluster and non-metric multidimensional scaling （MDS）. The biomass, abundance, Shannon -Wiener＇s and Margalef＇ s indices of the macrobenthos were presented. The results showed that a total of 253 macrobenthic species were found in the research region, and most of them belong to mollusks and polychaetes. The dominant species were Cossurella dimorpha, Eocylichna cylindrella, Episiphon kiaochowwanense, Nassarius semiplicatus, Ocstergrenia variabilis and Sternaspis scutata. The average abundance of the macrobenthos was （313. 15 ±233.4） ind./m^2, and the average biomass was （ 15. 2 ± 11.2 ）g/m^2. The distribution patterns of the abundance and biomass of the macrobenthos were similar. The abundance and biomass in the area close to the estuary were lower than those from the area more distant to the estuary; the central part of the research region had higher abundance and biomass than other parts of the research region. In accordance with the results, four macrobenthic communities with distinct spatial differences were identified. The low abundance and biomass in the area close to the estuary should be caused by the high sedimentation rate. The statistical analysis indicated that the depth is the most important factor affecting the distribution of macrobenthos.

Dynamic changes in microbial activity and community structure during biodegradation of petroleum compounds:A laboratory experiment

With 110-d incubation experiment in laboratory, the responses of microbial quantity, soil enzymatic activity, and bacterial community structure to different amounts of diesel fuel amendments were studied to reveal whether certain biological and biochemical characteristics could serve as reliable indicators of petroleum hydrocarbon contamination in meadow-brown soil, and use these indicators to evaluate the actual ecological impacts of 50-year petroleum-refining wastewater irrigation on soil function in Shenfu irrigation area. Results showed that amendments of ~ 1000 mg/kg diesel fuel stimulated the growth of aerobic heterotrophic bacteria, and increased the activity of soil dehydrogenase, hydrogenperoxidase, polyphenol oxidase and substrate-induced respiration. Soil bacterial diversity decreased slightly during the first 15 d of incubation and recovered to the control level on day 30. The significant decrease of the colony forming units of soil actinomyces and filamentous fungi can be taken as the sensitive biological indicators of petroleum contamination when soil was amended with 〉15000 mg/kg diesel fuel. The sharp decrease in urease activity was recommended as the most sensitive biochemical indicator of heavy diesel fuel contamination. The shifts in community structure to a community documented by Sphingomonadaceae within a-subgroup of Proteobacteria could be served as a sensitive and precise indicator of diesel fuel contamination. Based on the results described in this paper, the soil function in Shenfu irrigation area was disturbed to some extent.

Microbial community structure in an integrated A/O reactor treating diluted livestock wastewater during start-up period

In order to investigate the correlation between reactor performance and the microorganisms,an integrated A/O reactor was operated for 72 days to treat diluted livestock wastewater.Chemical oxygen demand （COD） removal efficiency increased from 79% to 94%,with total nitrogen （TN） removal efficiency from 37% to 50% （HRT 7.4 hr） when the influent COD and TN were ca.1500 mg/L and 95 mg/L,respectively,and the outlet COD concentration was less than 100 mg/L at the end.Microbial community was monitored during start-up period by denaturing gradient gel electrophoresis （DGGE） based on 16S rRNA gene.DGGE profiles showed that microbial community had changed significantly during the start-up and these shifts were in accordance with the reactor performance.UPGMA clustering analysis showed that 14 anaerobic samples fell into five main groups and so did the aerobic ones,but the grouping patterns were different.Phylogenetic analysis indicated that microbial populations in the anaerobic compartment belonged to Firmicutes,Proteobacteria,Chloroflexi and Bacteroidetes,while Proteobacteria,Bacteroidetes,Firmicutes,Verrucomicrobiae and Nitrospira were present in the aerobic compartment.In the anaerobic compartment,more fermentative and acetogenic bacteria were detected during the start-up while denitrifying bacteria faded away.Two functional populations such as Nitrospira defluvii and Dechloromonas denitrificans were observed when nitrogen removal was high,indicating that simultaneous nitrification and denitrification occurred in the aerobic compartment.

Effect of Different Vegetation Types on the Rhizosphere Soil Microbial Community Structure in the Loess Plateau of China

The Loess Plateau in China is one of the most eroded areas in the world. Accordingly, vegetation restoration has been implemented in this area over the past two decades to remedy the soil degradation problem. Understanding the microbial community structure is essential for the sustainability of ecosystems and for the reclamation of degraded arable land. This study aimed to determine the effect of different vegetation types on microbial processes and community structure in rhizosphere soils in the Loess Plateau. The six vegetation types were as follows：two natural grassland （Artemisia capillaries and Heteropappus altaicus）, two artificial grassland （Astragalus adsurgens and Panicum virgatum）, and two artificial shrubland （Caragana korshinskii and Hippophae rhamnoides） species. The microbial community structure and functional diversity were examined by analyzing the phospholipid fatty acids （PLFAs） and community-level physiological profiles. The results showed that rhizosphere soil sampled from the H. altaicus and A. capillaries plots had the highest values of microbial biomass C, average well color development of carbon resources, Gram-negative （G-） bacterial PLFA, bacterial PLFA, total PLFA, Shannon richness, and Shannon evenness, as well as the lowest metabolic quotient. Soil sampled from the H. rhamnoides plots had the highest metabolic quotient and Gram-positive （G＋） bacterial PLFA, and soil sampled from the A. adsurgens and A. capillaries plots had the highest fungal PLFA and fungal：bacterial PLFA ratio. Correlation analysis indicated a signiifcant positive relationship among the microbial biomass C, G- bacterial PLFA, bacterial PLFA, and total PLFA. In conclusion, plant species under arid climatic conditions signiifcantly affected the microbial community structure in rhizosphere soil. Among the studied plants, natural grassland species generated the most favorable microbial conditions.

Community structure and controlled factor of attached green algae on the Porphyra yezoensis aquaculture rafts in the Subei Shoal, China

This study analyzes the community structure, the quantity changes of the algae and the effect of important environmental factors and estimates the total biomass of the attached green algae in the survey areas. The study uses data from surveys of the attached green algae on the Porphyra yezoensis aquaculture rafts and data regarding the environmental factors from October 2010 to April 2011 in the Subei Shoal. The attached green algae on the rafts included Ulva prolifera, Capsosiphon groenlandicus, U. linza, U. intestinalis, U. clathrata, and U. cornpressa. The biomass changes of the attached green algae exhibited an inverted parabola： the biomass was the highest （14 898 t） in April, and was the second highest （2 034 t） in November; it was lowest in February （only 729 t） and increased sharply from March to April. The species diversity differed significantly among the seasons. In September and October, when the P. yezoensis aquaculture rafts were initially set up, the attached green algae had a high biodiversity, while from December to the next February, a variety of green algae species coexisted on the rafts, although the biomass was low, and from March to April, as the biomass increased sharply, the species diversity dropped to the minimum. During this time, C. groenlandicus was apparently dominant with the maximum biomass proportion up to 80%, while the U. prolifera proportion increased exponentially to 20% to 40%. The water temperature had a direct regulating effect on the biomass and the species succession of the attached green algae. The estimation of the community dynamics and the biomass of the green algae provided the evidence needed to track the origin of the large-scale green tide in the southern Yellow Sea.

A comprehensive analysis of the response of the fungal community structure to long-term continuous cropping in three typical upland crops

Certain agricultural management practices are known to affect the soil microbial community structure;however,knowledge of the response of the fungal community structure to the long-term continuous cropping and rotation of soybean,maize and wheat in the same agroecosystem is limited.We assessed the fungal abundance,composition and diversity among soybean rotation,maize rotation and wheat rotation systems and among long-term continuous cropping systems of soybean,maize and wheat as the effect of crop types on fungal community structure.We compared these fungal parameters of same crop between long-term crop rotation and continuous cropping systems as the effect of cropping systems on fungal community structure.The fungal abundance and composition were measured by quantitative real-time PCR and Illumina MiSeq sequencing.The results revealed that long-term continuous soybean cropping increased the soil fungal abundance compared with soybean rotation,and the fungal abundance was decreased in long-term continuous maize cropping compared with maize rotation.The long-term continuous soybean cropping also exhibited increased soil fungal diversity.The variation in the fungal community structure among the three crops was greater than that between long-term continuous cropping and rotation cropping.Mortierella,Guehomyces and Alternaria were the most important contributors to the dissimilarity of the fungal communities between the continuous cropping and rotation cropping of soybean,maize and wheat.There were 11 potential pathogen and 11 potential biocontrol fungi identified,and the relative abundance of most of the potential pathogenic fungi increased during the long-term continuous cropping of all three crops.The relative abundance of most biocontrol fungi increased in long-term continuous soybean cropping but decreased in long-term continuous maize and wheat cropping.Our results indicate that the response of the soil fungal community structure to long-term continuous cropping varies based upon crop types.

Effects of Soil Texture on the Growth of Young Apple Trees and Soil Microbial Community Structure Under Replanted Conditions

A two-year field experiment was carried out in order to study the occurrence degree and mechanism of apple replant disease(ARD)in the apple orchards with different soil textures.So we can adopt appropriate controlmeasures according to the severity of ARD.Healthy two-year-old seedlings with consistent growth were selected,of which the root stock was T337 and the scion was Yanfu 3.There were significant differences in biomass between methyl bromide fumigation and replanted treatments,and the difference was the largest in clay loam,followed by sandy loam,and loam,which verified ARD in clay loam was most serious,followed by sandy loam and loam.Based on high-throughput sequencing of fungi in soil samples,fungal richness and diversity were the highest in clay loam,followed by sandy loam,and loam.The relative abundance of Fusarium in SX,SL,FX,FL,WX and WL was 7.33%,19.32%,2.70%,4.24%,10.71%and 23.87%,respectively.Based on Real-time quantitative analysis,there were significant differences in the number of Fusarium oxysporum and Fusarium solani between methyl bromide fumigation and replanted treatments,i.e.,clay loam>sandy loam>loam.Fusarium was the main pathogen causing ARD.This shows that ARD is the most serious under replanted clay loam condition.High-throughput sequencing technology was used to prove the difference in Fusarium was one of the important reasons for ARD under different soil textures.This technology provides a new idea for the prevention and control of ARD.

Community structure and spatial distribution of macrobenthos in the shelf area of the Bering Sea

Field investigations of marine macrobenthos were conducted at ten sites in the Bering Sea in July 2010. Altogether 90 species of macrobenthos belonging to 59 families and 78 genera were identified. Among them, 41 polychaetes, 16 mollusks, 23 crustaceans, three echinoderms, two cnidarians, one nemertean, one priapulid, two sipunculids, and one echiuran were identified. The average density and biomass of total macrobenthos were 984 ind./m2 and 1207.1 g/ma of wet weight, respectively. The predominant species in the study area were Scoloplos armiger, Eudorella pacifica, Ophiura sarsii, Heteromastus filiformis, Ennucula tenuis, and Harpiniopsis vadiculus by abundance, while the predominant species in this area was Echinarachnius parma by biomass. Hierarchical cluster analysis （Bray-Curtis similarity measure） revealed that two impor- tant benthic assemblages in the study area were CommunityA and Community B. CommunityA was stable and Community B was unstable, as shown by the Abundance/Biomass Comparisons （ABC） approach. The macrobenthic community structure in the shelf of the Bering Sea was characterized by its high abundance and biomass, high productivity but great heterogeneity.

Standing stock and community structure of photosynthetic picoplankton in the northern South China Sea

The investigation on community structure of standing stock of photosynthetic picoplankton: Synechococcus (Syn), Prochlorococcus (Pro) and Picoeukaryotes (Euk) and their environmental regulation mechanisms in the northern South China Sea was carried out in the summer of 1999. The results showed that the average abundances of Syn, Pro and Euk in the study sea areas were (5.0±7.6)×104 cell/cm3 (51%), (4.6±4.2)×104 cell /cm3 (47%) and (1.8±1.1)×103 cell/cm3 (2%) respectively, and those of their carbon biomass were (12.5±18.9) ?滋g/dm3 (74%), (2.7±2.5) ?滋g/dm3 (16 %) and (1.7±1.0) ?滋g /dm3 (10%). The most of high values of Syn appeared in the estuaries, coastal zone and continental shelf in the sea area to the east of Leizhou Peninsula and Hainan Island where nutrients were rich, and those appeared in the Beibu Gulf were the second, while those appeared in continental slope and open sea were tens times lower than the above those. Its distribution in water column was mainly above the thermocline and its abundance below it sharply decreased. Two different populations of Pro were found, the surface population and deep one. The distribution pattern of the former was similar to that of Syn; while with marked difference from that of the former, the abundance and biomass of the latter markedly increased towards outer sea, continental slope and open sea where nutrients were poor; the high values in the water column mainly appeared at the bottom of euphotic zone and above the nitrocline, where it often vigorously grow. The distribution difference of Euk in the various sea areas is not as obvious as those of Syn and Pro, but it was high in coastal and shelf waters and low in continental slope and open sea. The high values in the water column were mostly appeared at the bottom of euphotic zone. This difference of distribution pattern for the three type of photosynthetic picoplankton depends on environmental effects and their ecophysiological differences.

Changes in zooplankton community structure in Sanmen Bay,China

Seasonal variations in zooplankton abundance, biomass, species diversity and community structure were investigated in the Sanmen Bay, China. Samples were collected from 15 stations, on the seasonal basis, in April （spring）, July （summer） and October 2005 （autumn） and January 2006 （winter）, respectively. The results show that zooplankton species number, abundance and biomass varied widely and had distinct spatial heterogeneity in the Sanmen Bay. A total of 72 species of zooplankton belonging to 56 genera and 17 groups of pelagic larvae were identified. The zooplankton species richness was strongly related to salinity. Based on hierarchical cluster analysis, zooplankton in this study area were classified into three groups： coastal, neritic and pelagic groups, which corresponded to the upper, middle and lower portion of the Sanmen Bay, respectively. The coastal low-saline species were dominant in the study area. The zooplankton abundance and biomass reached a peak in summer, moderate in spring and autumn, and the lowest in winter. Zooplankton abundance decreased from the upper to lower portion of the bay in April, when the highest biomass occurred in the middle portion of the bay. There were the same spatial distribution patterns for the biomass and abundance in July, with the maximum in the middle of the bay. However, zooplankton abundance was the highest in the middle of tile bay in October, when maximum biomass occurred near the lower of the bay. Zooplankton abundance and biomass were evenly distributed in the Sanmen Bay in January. Spatial and temporal variations in zooplankton and their relationship with environmental factors were also analyzed. The BIOENV results indicate that the combination of chlorophyll a （Chl-a）, salinity, dissolved inorganic nitrogen （DIN）, dissolved oxygen （DO） and silicate （SiO3） was responsible for the variations in zooplankton community structure in the Sanmen Bay. The environmental changes played an important role in changes in the zooplankton community structure in the Sanmen Bay.

Relationships Between Community Structure and Environmental Factors in Xixiakou Artificial Reef Area

The construction of artificial reefs has unparallelly developed for a few decades in China.Artificial reefs can be used to manage and conserve commercially exploited fish and crustacea.However,their suitability as ecological niche is poorly characterized.Therefore,in this study,we detected the seasonal variation of community biodiversity and the corresponding driving environmental factors.We also explored the relationships between dominant species and environmental factors to identify appropriate ecological niche areas.Different statistical analysis methods were used to assess species distribution within an artificial reef area in Xixiakou during nine sampling events in four seasons between 2017 and 2018.Non-metric multidimensional scaling(NMDS)and cluster analysis results indicated that the components of community can be divided into two clusters.Complexity of community,which is exhibited by species number,biodiversity,and catch per unit effort(CPUE),was significantly higher in summer than in other seasons.Generalized additive model(GAMs)results revealed the significant effects of temperature and chlorophyll a on the community structure.Sebastes schlegelii,Hexagrammos otakii,Conger myriaster and Charybdis japonica were the dominant species in four seasons.GAMs results indicated that temperature,dissolved oxygen(DO),pH and chlorophyll a affect the CPUE of dominant species significantly.The distinct suitable ecological niche for each dominant species was found in this study.For example,Charybdis japonica preferred to live in the area with 20.7–22.1℃,dissolved oxygen 7.07–7.15 mg L−1 and salinity 31.8–31.9.The results of this study are beneficial to resource conservation and fishery management.

Analysis of effect of nicotine on microbial community structure in sediment using PCR-DGGE fingerprinting

Solid or liquid waste containing a high concentration of nicotine can pollute sediment in rivers and lakes, and may destroy the ecological balance if it is directly discharged into the environment without any treatment. In this study, the polymerase chain reaction （PCR） and denaturing gradient gel electrophoresis （DGGE） method was used to analyze the variation of the microbial community structure in the control and nicotinecontaminated sediment samples with nicotine concentration and time of exposure. The results demonstrated that the growth of some bacterial species in the nicotine-contaminated sediment samples was inhibited during the exposure. Some bacteria decreased in species diversity and in quantity with the increase of nicotine concentration or time of exposure, while other bacteria were enriched under the effect of nicotine, and their DGGE bands changed from undertones to deep colors. The microbial community structure, however, showed a wide variation in the nicotine- contaminated sediment samples, especially in the sediment samples treated with high-concentration nicotine. The Jaccard index was only 35.1% between the initial sediment sample and the sediment sample with a nicotine concentration of 0.030 μg/g after 28 d of exposure. Diversity indices showed that the contaminated groups had a similar trend over time. The diversity indices of contaminated groups all decreased in the first 7 d after exposure, then increased until day 42. It has been found that nicotine decreased the diversity of the microbial community in the sediment.