Labyrinthulomycetes thrives in organic matter-rich waters with ecological partitioning in the Pearl River Estuary.

Labyrinthulomycetes play an important role in marine biogeochemical cycles, but their diversity, distribution patterns, and key regulatory factors remain unclear. This study measured the abundance and diversity of Labyrinthulomycetes in the Pearl River Estuary (PRE) to understand its distribution pattern and relationship with environmental and biological factors. The abundance of Labyrinthulomycetes ranged from 24 to 500 cells·mL-1, with an average of 144.37 ± 94.65 cells·mL-1, and its community composition showed obvious ecological partitioning in the PRE. The results of statistical analysis indicated that CDOM, salinity, and chlorophyll a contributed significantly (P < 0.01) to the community composition, explaining 46.59%, 11.34%, and 4.38% of the variance, respectively. The Labyrinthulomycetes distribution pattern combined with the niches of dominant species was revealed; low-salinity species mainly use terrigenous organic matter occupied dominant positions in the upper estuary and showed the highest abundance; moderate-salinity species that can use phytoplankton-derived resources thrived in the middle estuary; and seawater species dominated the lower estuary with the highest diversity but the lowest abundance. In addition, the results of phylogenetic tree analysis indicated that the existence of a novel lineage, and further study on the diversity and ecological functions of Labyrinthulomycetes is needed.IMPORTANCELabyrinthulomycetes play important roles in organic matter remineralization, carbon sinks, and food webs. However, the true diversity of Labyrinthulomycetes is still unclear due to limitations in isolation and culture methods. In addition, previous studies on their relationship with environmental factors are inconsistent and even contradictory, and it is speculated that their community composition may have spatial heterogeneity along the environmental gradient. In this study, the distribution pattern and key regulators of Labyrinthulomycetes in the PRE were revealed. Combining the niche of dominant species, it is suggested that salinity determines the spatial differences in Labyrinthulomycetes diversity, and the resources of substrate (terrestrial input or phytoplankton-derived) determine the dominant species, and its abundance is mainly determined by organic matter concentrations. Our study provided new information on the Labyrinthulomycetes diversity and verified the spatial heterogeneity of Labyrinthulomycetes community composition, providing reliable explanations for the inconsistencies in previous studies.

[Long-term Variation Characteristics of Zooplankton Community Structure in Meiliang Bay, Lake Taihu].

Zooplankton, as an important part of the water food chain, plays an important role in lake ecosystems. It is an important monitoring indicator for water bodies. However, due to the lack of long-term monitoring data of zooplankton community structure, there is a lack of understanding about its long-term characteristics. Based on monthly monitoring data from 1997 to 2017 of Meiliang Bay in Lake Taihu, the long-term trends of zooplankton community structure and its relation to the environment were examined. The results showed that the abundance and biomass of zooplankton in Meiliang Bay significantly decreased from 1997 to 2017 (P<0.05). In particular, the abundance and biomass of rotifer and copepod slowly declined, and the abundance of cladocerans fluctuated but its biomass presented a significant decreasing trend (P<0.05). The cladocerous biomass contributed the most to the zooplankton biomass in Meiliang Bay. The dominance of smaller cladocerans and copepods increased with decreasing rotifer density, significantly decreasing the average body size of zooplankton (P<0.05). This study indicated that zooplankton were becoming smaller, potentially weakening the top-down control on phytoplankton. In addition, zooplankton abundance and biomass showed an upward trend in spring and decreased in autumn and winter, and reached maximum values of 1406.70 ind.·L-1 and 25.64 mg·L-1, respectively, in September. In the summer, their changes were the opposite. Pearson correlation analysis showed that zooplankton community structure was significantly related to water physical characteristics (alkalinity, electrical conductivity, water depth, suspended substance, and water temperature), chlorophyll a, and nitrogen (P<0.05). This indicated that the eutrophication of Meiliang Bay in Lake Taihu had a significant impact on the community structure of zooplankton.

Response of photosynthesis to different concentrations of heavy metals in Davidia involucrata.

Lead (Pb) and cadmium (Cd) are highly toxic and are widespread in agricultural soils, representing risks to plant and human health. In this study, Davidia involucrata was cultivated in soil with different concentrations of Pb and Cd and sampled after 90 days. We used ANOVA to analyse the photosynthesis of D. involucrata and the ability of Pb and Cd to enrich and migrate in roots, stems and leaves. Various results are described here. 1) Under individual and combined Pb and Cd stress, the accumulation factors in the roots were greater than 1, which was significantly greater than those in the stems and leaves (P < 0.05), and the translocation factors both were less than 1. The Pb and Cd enrichment ability of D. involucrata roots was significantly higher than that of stems and leaves, and the migration ability of the two heavy metals in D. involucrata was weak. 2) The Mg-dechelatase activities of chlorophyll degradation products increased under stress due to high concentrations of Pb and Cd. However, chlorophyllase activity was higher at relatively low concentrations of the two heavy metals (P < 0.05). δ-Aminolevulinic acid and porphobilinogen of chlorophyll synthesis products are easily converted to uroporphyrinogen III under low concentrations of Cd, which promotes the synthesis of chlorophyll. 3) The effect of Cd stress alone on the chlorophyll concentration was not significant. Under combined stress, concentrations of Pb and Cd in the range of 400~800 mg·kg-1 and 5~20 mg·kg-1 significantly promoted an increase in photosynthetic pigments (P < 0.05). 4) Inhibition of the net photosynthetic rate increased with increasing Pb and Cd concentrations under both individual and combined stress. In addition, the root of D. involucrata had a strong absorption and fixation effect on heavy metals, thereby reducing metal toxicity and improving the tolerance of D. involucrata to heavy metals.

[Wind Field Influences on the Spatial Distribution of Cyanobacterial Blooms and Nutrients in Meiliang Bay of Lake Taihu, China].

Wind field is a very important physical factor controlling the formation of cyanobacteria blooms. A surface particle tracking drift experiment was carried out to study the influence of wind field on the surface current in Meiliang Bay of Lake Taihu during the algal bloom season. For this, chlorophyll-a, nitrogen, phosphorus, the permanganate index, dissolved organic carbon (DOC), and dissolved oxygen (DO) were measured in surface, middle, and bottom waters of the Meiliang Bay during the cyanobacteria bloom period to test how wind field affects the temporal and spatial distribution of cyanobacterial blooms and biomass stock in the water column. The results showed that the average drift velocities of surface particles were 3.0 cm·s-1 and 5.0 cm·s-1 when wind speed averaged 1.9 m·s-1 and 2.3 m·s-1, respectively. The wind field determined the spatial distribution of cyanobacterial blooms in surface waters and led to a high spatial heterogeneity of cyanobacterial blooms. The spatial redistribution of cyanobacterial blooms exerted an important influence on water quality indexes such as particulate nitrogen, phosphorus, organic matter, and dissolved oxygen. The concentrations of particulate nitrogen, phosphorus, the permanganate index, and chlorophyll-a showed a similar vertical distribution pattern. Cyanobacterial blooms were less influenced by the distribution of dissolved nitrogen and dissolved organic carbon from external pollution, while long-term legacy loading played a more important role. This meant that the spatial distributions of dissolved nitrogen and dissolved organic carbon were different from that of chlorophyll-a. Because the redistribution of cyanobacterial blooms, as affected by wind fields, has a complex effect on the dissolved oxygen in the water column, the dissolved oxygen concentration decreased with depth, which may affect the release of soluble nutrients from the sediment. The cyanobacterial biomass stock in the surface water was estimated according to the survey of high-density sites. The dry matter of cyanobacteria in the surface 20 cm of Meiliang Bay was approximately 396 tons on the day of sampling. The results from the present study indicated that the factors influencing cyanobacterial blooms should be considered in sampling methods and the analysis of lake water quality due to the significant influence of wind fields on bloom drift. The collection of cyanobacteria has limited effect on the removal of the algal bloom biomass in whole lake, only being effective at prevention of the event of black spots in lake shore.

Pollinator effectiveness and importance between female and male mining bee (Andrena).

Bees are often considered to be effective pollinators in both agricultural and natural ecosystems but could be ineffective pollinators in that they collect large quantities of pollen for food provision but deliver little to stigmas. Male bees do not collect pollen to feed larvae, and their pollination role has been underappreciated. Here we compare pollination effectiveness, visit frequency and pollen foraging behaviour between female and male individuals of a mining bee, Andrena emeishanica, visiting a nectariferous spring flower (Epimedium pubescens). Female bees were observed to forage for both pollen and nectar, but male bees foraged only for nectar. Female bees had large hairy hind tibiae with conspicuous scopae, and nearly 90% of the pollen grains they collected went onto the hind legs. Male bees removed less pollen from anthers than female bees but deposited more pollen on stigmas per visit. The higher pollen transfer efficiency of male bees was due to 48.4% of pollen grains remaining ungroomed on the thorax and abdomen, available for stigma contact, but their visitation rate to flowers was much lower. Our results indicate that male solitary bees could transfer more pollen on the stigma per visit but were less important (transferred less pollen in total, because they made fewer visits per unit time) than females.

[Effects of Cyanobacterial Blooms in Eutrophic Lakes on Water Quality of Connected Rivers].

The location at which the Liangxi River meets Meiliang Bay of Lake Taihu was selected to explore the influence and controlling factors of algal blooms on the connected rivers. The cyanobacterial particulates and water quality parameters including nitrogen, phosphorus, and dissolved oxygen were monitored daily during the summer bloom season. The spatial variation in water quality parameters along the river were also surveyed, and data from hydrological and meteorological factors such as discharge, temperature, and wind field characteristics over the same period were collected to help investigate the effects of cyanobacterial blooms on the water quality of connected rivers. The results showed that the total fresh biomass of algal blooms entering Liangxi River for three months during the summer cyanobacterial bloom period in Meiliang Bay was 9733 t, which was similar to the amount harvested from the entire lake throughout the year. The flux of water bloom particles to the river varied widely, ranging from 75-496 t·d-1, with an average of 105 t·d-1. The flux was primarily controlled by hydrological and meteorological conditions. Water volume, temperature, and wind direction were the most important influencing factors. Lake water with a large amount of cyanobacterial particles entering the river can significantly improve the dissolved oxygen, ammonia-nitrogen, and other qualities of the river water in the city. It also significantly increased the concentrations of nutrients such as particulate nitrogen and phosphorus in the river, while it had a relatively weak effect on dissolved nitrogen and phosphorus. Spatially, the chlorophyll a concentration rapidly decreased with increasing distance from the lake, and the concentration of nitrogen and phosphorus exist as particulate cyanobacteria also declined. Upon being discharged into the canal 7 km away, the cyanobacterial particles were largely decomposed, and chlorophyll a content from the phytoplankton collected from the river by a 67 µm net decreased from 152.93 µg·L-1 to 1.99 µg·L-1. The results indicated that lakes plagued with cyanobacterial blooms have a great impact on the water quality of surrounding rivers. Although the connection between rivers and lakes can effectively relieve black spots and solve the black and odorous phenomenon in urban rivers, it had a great impact on nutrients concentration in the rivers. Depending on the different protection targets of rivers and lakes, lake water blooms and hydro-meteorological factors should be considered during water transfer management to optimize the water ecological services of lakes and rivers.

Pollen competition between morphs in a pollen-color dimorphic herb and the loss of phenotypic polymorphism within populations.

Flower color polymorphism is relatively uncommon in natural flowering plants, suggesting that maintenance of different color morphs within populations is difficult. To address the selective mechanisms shaping pollen-color dimorphism, pollinator preferences and reproductive performance were studied over three years in Epimedium pubescens in which some populations had plants with either green or yellow pollen (and anthers). Visitation rate and pollen removal and receipt by the bee pollinator (Andrena emeishanica) did not differ between the two color morphs. Compared to the green morph, siring success of the yellow morph's pollen was lower, but that of mixtures of pollen from green and yellow morphs was lowest. This difference, corresponding to in vivo and ex vivo experiments on pollen performance, indicated that pollen germination, rather than tube growth, of the green morph was higher than that of the yellow morph and was seriously constrained in both morphs if a pollen competitor was present. A rare green morph may invade a yellow-morph population, but the coexistence of pollen color variants is complicated by the reduced siring success of mixed pollinations. Potential pollen competition between morphs may have discouraged the maintenance of multiple phenotypes within populations, a cryptic mechanism of competitive exclusion.

Effects of clonal integration on the proximal and distal ramets of Cynodon dactylon under shade stress

ABSTRACT In a pot experiment, clonal ramets of Cynodon dactylon, a stolon herbaceous plant, were treated with heterogeneous lighting. Proximal ramets (elder ramets) were subjected to shade stress at three different degrees, and stolons between proximal and distal ramets of each pair were treated in a connected or severed manner. Results showed that in moderate shade stress, the number of ramets and leaves, biomass, net photosynthetic rate (Pn), maximum quantum yield (Fv/Fm), effective quantum yield of PSII (ФPSII), and soil and plant analysis development values (SPAD) of proximal ramets were significantly reduced, regardless of whether stolons were kept intact or severed. However, the growth of distal ramets was not significantly influenced, and keeping the stolons intact also did not bring apparent benefits for the whole clonal fragments. These results show that clonal integration does not help alleviate the shade stress suffered by proximal ramets and the costs of distal ramets and does not significantly influence the whole clonal fragments. The possible reasons are that distal ramets may be at the cost of metabolism for resource transportation when the proximal ramets suffer from shade stress; thus, clonal integration is not favorable.

Development of 15 polymorphic microsatellite markers for Ficus virens (Moraceae).

PREMISE OF THE STUDY: Ficus virens (Moraceae) is distributed widely in South and Southeast Asia, Melanesia, and northern Australia, and it is also cultivated outside its original northern range limit in southwestern China. Therefore, the species is well suited to explore the mechanism of range limits of Ficus species. However, little is known about its genetic background. METHODS AND RESULTS: Fifteen polymorphic microsatellite markers were developed using the biotin-streptavidin capture method. Polymorphism was tested in 85 F. virens individuals sampled from three populations. The number of alleles ranged from three to 17. The observed and expected heterozygosity of each population varied from 0.0667 to 0.9286 and 0.0650 to 0.8890, respectively. Cross-species amplification was also carried out in eight other Ficus species. CONCLUSIONS: These 15 markers will be valuable for studying the genetic variation and population structure of F. virens and related Ficus species.

Exploring the best model for describing light-response curves in two Epimedium species.

Photosynthetic responses to light environment can be useful measurements to determine favorable habitat conditions for the conservation and cultivation of medicinal species. The nonrectangular hyperbola model, rectangular hyperbola model, modified rectangular hyperbola model, exponential model, modified exponential model are used to explore the best model for describing light-response curves in two Epimedium species. The results show that the light-response curves of E. wushanense and E. acuminatum were best described by the modified exponential model, the test MSE and MAE of the modified exponential model were smaller, and the LSP and Pmax calculated by the modified exponential model were more accurate than those calculated by other models in E. wushanense and E. acuminatum. This model may be widely applicable to light-response curves of other Epimedium species.

Genome-Wide Survey and Analysis of Microsatellite Sequences in Bovid Species.

Microsatellites or simple sequence repeats (SSRs) have become the most popular source of genetic markers, which are ubiquitously distributed in many eukaryotic and prokaryotic genomes. This is the first study examining and comparing SSRs in completely sequenced genomes of the Bovidae. We analyzed and compared the number of SSRs, relative abundance, relative density, guanine-cytosine (GC) content and proportion of SSRs in six taxonomically different bovid species: Bos taurus, Bubalus bubalis, Bos mutus, Ovis aries, Capra hircus, and Pantholops hodgsonii. Our analysis revealed that, based on our search criteria, the total number of perfect SSRs found ranged from 663,079 to 806,907 and covered from 0.44% to 0.48% of the bovid genomes. Relative abundance and density of SSRs in these Bovinae genomes were non-significantly correlated with genome size (Pearson, r < 0.420, p > 0.05). Perfect mononucleotide SSRs were the most abundant, followed by the pattern: perfect di- > tri- > penta- > tetra- > hexanucleotide SSRs. Generally, the number of SSRs, relative abundance, and relative density of SSRs decreased as the motif repeat length increased in each species of Bovidae. The most GC-content was in trinucleotide SSRs and the least was in the mononucleotide SSRs in the six bovid genomes. The GC-contents of tri- and pentanucleotide SSRs showed a great deal of similarity among different chromosomes of B. taurus, O. aries, and C. hircus. SSR number of all chromosomes in the B. taurus, O.aries, and C. hircus is closely positively correlated with chromosome sequence size (Pearson, r > 0.980, p < 0.01) and significantly negatively correlated with GC-content (Pearson, r < -0.638, p < 0.01). Relative abundance and density of SSRs in all chromosomes of the three species were significantly negatively correlated with GC-content (Pearson, r < -0.333, P < 0.05) but not significantly correlated with chromosome sequence size (Pearson, r < -0.185, P > 0.05). Relative abundances of the same nucleotide SSR type showed great similarity among different chromosomes of B. taurus, O. aries, and C. hircus.

[Research on growth state and physiological changes of Tianquan Bergenia purpurascens under different shade conditions].

OBJECTIVE: To study the growth index and physiological index of Tianquan Bergenia purpurascens under different shade conditions (100%, 80%, 60%, 40%, 20%), and investigate its adaptation mechanism to shade environment so that it can provide theoretical basis for cultivation and production. METHOD: The growth index such as the length, the width and the number of new leaves, and leaf area, fresh weight, dry weight and specific leaf weight of the samples which were collected from the beginning of March to late May under different shade conditions were measured. The physiological index including the contents of photosynthetic pigments, MDA, soluble sugar, soluble protein, proline and the activity of SOD were measured all together. RESULT: The growth and morphological index under light intensity 100%-60% were higher than those under light intensity 40%-20%. And except specific leaf weight, the growth and morphological index were significantly higher under light intensity 60% than those under the other shade conditions; The contents of Chla, Chlb, Chl (a + b) and Car under light intensity 100%-60% were higher than those under light intensity 40%-20%, while Chla/b was higher under light intensity 40%-20%; The activity of SOD, soluble sugar, soluble protein and proline contents were higher under light intensity 100%-60%, while MDA content was higher under light intensity 40%-20%. Chl(a+b) content, soluble sugar content and activity of SOD were the highest under light intensity 60%, but MDA content was the lowest. CONCLUSION: Sixty percent irradiance treatment was the most favorable to the growth of Tianquan B. purpurascens; 100%-80% irradiance treatments were favorable to its growth; 40%-20% irradiance treatment was negative for its growth.

[Behavior ethogram and PAE coding system of Cervus nippon sichuanicus].

A monthly 5-day periodic observation at 06:00-18:00 from March to November 2007 was conducted to record the behavioral processes, contents, and results, and the surrounding habitats of Sichuan sika deer (Cervus nippon sichuanicus) in Donglie, Chonger, and Reer villages of Tiebu Natural Reserve of Sichuan Province. The behavioral ethogram, vigilance behaviors ethogram and its PAE (posture, act, and environment) coding system of the Sichuan sika deer were established, which filled the gap of the PAE coding of ungulates vigilance behaviors. A total of 11 kinds of postures, 83 acts, and 136 behaviors were recorded and distinguished, with the relative frequency of each behavior in relation to gender, age, and season described. Compared with other ungulates, the behavioral repertoire of Sichuan sika deer was mostly similar to that of other cervid animals.

[Research on growth state and physiological changes of Epimedium wushanense under different shade conditions].

OBJECTIVE: To study the growth state and physiological changes of Epimedium wushanense under different light conditions (100%, 80%, 60%, 40%, 20%), and investigate its adaptation mechanism to shade environment so that it can provide theoretical basis for cultivation and production. METHOD: The growth index, the content of photosynthetic pigments, proline content, MDA content, soluble sugar content, soluble protein content and antioxidant enzymy activity of E. wushanense under different shade conditions were measured. RESULT: Except for length/width, the other form index of E. wushanense changed significantly. The E. wushanense grew well between light intensity 80%-40%, besides, the biomass above the earth was relatively high. The chlorophyll a, chlorophyll b, total chlorophyll content and carotenoids cotent were enhanced after shaded, the values of chlorophyll a\chlorophyll b increased between light intensity 100% -60% and reduced between light intensity 60% -20%. The proline and MDA content decreased after shading, the soluble sugar and soluble protein content increased respectively between light intensity 100% -60%, 100% -40% and reduced respectively between light intensity 60% -20%, 40% -20%. The SOD activity, CAT activity decreased after shading, and the POD activity, APX activity reduced between light intensity 60% -40%, raised under 20% treatment. CONCLUSION: 80% 40% irradiance treatment was favorable to the growth of E. wushanense.

[Total flavonoids and icariin contents of Epimedium pubescens in different types of communities and their relationships with soil factors].

Epimedium pubescens and soil samples were collected from the Betula albosinensis community (community I ), Cyclobalanopsis glauca var. gracilis community (community II), and Cinnamomum longepaniculatum community (community III) in Tangjiahe Nature Reserve in August 2009, with the total flavonoids and icariin contents in E. pubescens samples measured by high performance liquid chromatography and UV-spectrophotometer, and the relationships between these contents and soil parameters analyzed. Among the plant organs of E. pubescens, leaf had the highest contents of total flavonoids and icariin, while stem had the lowest one. The total flavonoids and icariin contents of E. pubescens were significantly higher in community I [(5.32 +/- 0.23)%, (0.47 +/- 0.05)%] than in communities II [(4.06 +/- 0.03)%, (0.32 +/- 0.01)%] and III [(4.15 +/- 0.07)%, (0.28 +/- 0.09)%] (P<0.05), and negatively correlated with soil total nitrogen and alkali-hydrolyzable nitrogen (P<0.05) but positively correlated with soil pH (P<0.01), suggesting that the soil with lower level of nitrogen and higher level of acidity in community I could enhance the total flavonoids and icariin contents of E. pubescens.

[Studies on purification of total saponins from the leaves of Acanthopanax trifoliatus by macroporous adsorption resin].

OBJECTIVE: To study the enrichment and purification of total saponins from the leaves of A. trifoliatus. METHODS: Using the total saponins from the leaves of A. trifoliantus as the standard index, we examinad the capability of static adsorption and desorption to select the optimum macroporous adsportion resin. Then we studied the purification technological parameters such as pH value, the dynamic adorption speed of flow, the best type quantity, the eluent density and so on. RESULTS: The optimum purification conditions were as follows: the type of macroporous adsorption resin was AB-8, the pH value of absorbing solution was 5-6, the absorbing velocity of flow was 1.0 mL/min, the concentration of ethanol as elutent was 70%, the proportion of the amount of absorbing solution and resins was 4:1, the proportion of the amount of elutent and resins was 4:1, the eluting velocity of flow was 2.0 mL/min.

[The contents changes of polysaccharides and total flavonoids during flower bud differentiation of Epimedium sagittatum].

OBJECTIVE: To study the dynamic changes of the contents of polysaccharides and total flavonoids Daring flower bud differentiation of Epimedium sagittatum. METHODS: The polysaccharides and total flavonoids from Epimedium sagittatum were extracted by Microwave-assisted method. The content of polysaccharides was determined by anthrone sulphuric acid colorimetry and that of total flavonoids was determined at 270 nm by ultraviolet spectrophotometry. RESULTS: The polysaccharides content in leaf decreased during the initial stages of floral bud differentiation and then increased, while the content in stem and fibrous root decreased steadily until floral bud differentiation completed. The content in rhizome kept invariant. In the flower bud physiological differentiation period,the content of total flavonoids in leaf and stem decreased and then kept invariant, while the content in rhizome increased and kept invariant. The content of total flavonoids in fibrous root increased during the initial stages of floral bud differentiation and then decreased. CONCLUSION: The contents of polysaccharide and total flavonoids have relation with the flower bud differentiation of Epimedium sagittatum.