Unusual hydrocarbon waxes detected in <Emphasis Type="Italic">Salix oritrepha</Emphasis> leaf from Nianbaoyeze Mountains,eastern Qinghai-Tibetan Plateau

Plant biomarkers, such as hydrocarbon waxes, are frequently found in various sediments and could be adopted as paleovegetation and paleoclimate indicators. Nevertheless, scarce researches have focused on leaf waxes in higher plants of alpine region. Herein, hydrocarbon leaf wax components of Salix oritrepha, which flourish in Nianbaoyeze Mountains in eastern Tibetan Plateau were fully discussed. The n-alkane distribution in leaves ranges from n-C₂₁ to n-C₂₉ with maxima at n-C₂₅, which were entirely different with Salix taxa displayed in previous surveys in non-alpine regions. The unusual even carbon nalkenes from n-C_22:1 to n-C_30:1, which were thought to appear only in aquatic organisms, were firstly reported in an alpine plant. Additionally, iso-(2-methyl) alkanes, ranging from i-C₂₃ to i-C₂₉ with maxima at i-C₂₅, which have been commonly reported in microorganisms, were also identified in an alpine plant for the first time. Unusual hydrocarbon distribution detected in Salix oritrepha leaf from Nianbaoyeze Mountains is most likely due to the extreme environment in such alpine region.     

Changes of Biogenic Elements in <Emphasis Type="Italic">Phragmites australis</Emphasis> and <Emphasis Type="Italic">Suaeda salsa</Emphasis> from Salt Marshes in Yellow River Delta,China

Little information is available on biogenic elements (carbon, nitrogen, phosphorus and sulfur) and the ecological stoichiometric characteristics of plants in coastal wetlands. To investigate the contents of carbon, nitrogen, phosphorus and sulfur of plants, and their ecological stoichiometric characteristics in the Yellow (Huanghe) River Delta, plant samples were collected from two typical salt marshes (Suaeda salsa and Phragmites australis wetlands) during the period of from August to October in 2007, and the ratios of C/N, C/P, N/P, C/N/P and C/N/P/S were calculated. Results showed that during the studying period, plant C, N and P were lower than the global average values, and plant N and P were lower than the China’s average values. Leaf C and S in Suaeda salsa were significantly lower than those in Phragmites australis (P < 0.05), and leaf N and P in Suaeda salsa and Phragmites australis showed no significant differences (P > 0.05). Average C/N ratios were 23.75 in leaf, 73.36 in stem, 65.67 in root of Suaeda salsa, and 33.77 in leaf, 121.68 in stem, 97.13 in root of Phragmites australis. Average C/N ratios of Suaeda salsa and Phragmites australis were all great than 25, indicating the salt marsh in the Yellow River Delta is an N limitation system. Average C/P ratios were 276.78 in leaf, 709.28 in stem and 1031.32 in root of Suaeda salsa, and 536.94 in leaf, 768.13 in stem and 875.22 in root of Phragmites australis. The average N/P ratios of Suaeda salsa were 12.92 in leaf, 10.77 in stem and 10.91 in root, and the average N/P ratios of Phragmites australis were 16.40 in leaf, 7.40 in stem and 6.92 in root, indicating the Suaeda salsa wetlands were N limited and Phragmites australis wetlands were N limited in August and P limited in October in 2007. The average C/N, C/P and C/N/P ratios in Suaeda salsa and Pragmites australis were higher than the global average values, indicating the lower quality of organic matter provided by wetland plants in the Yellow River delta.     

Effects of a Potential Autochthonous Probiotic <Emphasis Type="Italic">Bacillus subtilis</Emphasis> 2-1 on the Growth and Intestinal Microbiota of Juvenile Sea Cucumber, <Emphasis Type="Italic">Apostichopus japonicus</Emphasis> Selenka

The effects of Bacillus subtilis 2-1 from the intestine of healthy sea cucumber on the growth, digestive enzyme activities and intestinal microbiota of juvenile sea cucumber (Apostichopus japonicus) were determined in the present study. Sea cucumber was fed with Sargassum thunbergii powder supplemented with B. subtilis 2-1 at different concentrations varying among 0 (control), 10⁵, 10⁷, and 10⁹ CFU g^?1 for 8 weeks. Results showed that the growth performance and intestinal amylase and trypsin activities were significantly increased by dietary B. subtilis 2-1 at 10⁹ CFU g^?1 (P < 0.05). However, dietary B. subtilis 2-1 had no significant influence on the lipase activity in sea cucumber (P > 0.05). The polymerase chain reaction denaturing gradient gel electrophoresis and 16S rRNA gene sequencing analysis indicated that dietary B. subtilis 2-1 at 10⁵ and 10⁷ CFU g^?1 inhibited most of the Proteobacteria including those in genus Vibrio. Dietary B. subtilis 2-1 at 10⁹ CFU g^?1 not only decreased the abundance and species of genus Vibrio, but also increased the intensity of genera Psychrobacter and Bacillus. A specific dosage of dietary B. subtilis 2-1 could increase the growth and modulate the intestinal microbiota of sea cucumber; thus it might be a novel probiotic for keeping the health of sea cucumber.     

Genotype and Phylogenetic Diversity of <Emphasis Type="Italic">Symbiodinium</Emphasis> ITS2 Sequences Within Clade C in Three Typical Coral Species from Luhuitou Fringing Reef of the South China Sea

Dinoflagellates in the genus Symbiodinium, including nine clades (A–I), mainly form mutualistic symbioses with corals. More than 100 Symbiodinium molecular types have been identified by the ITS2-based genotype method within any given clade, and specifically within Symbiodinium clade C. However, the genotype identification method using the ITS2 sequence is likely to lead to high diversity estimates due to the intra-genomic variations in the ITS2 space; thus, further validation is essential for a correct identification. In this study, the molecular diversity of Symbiodinium ITS2 sequences cloned from two stone corals, Acropora sp. SY-01 and Pocillopora sp. SY-05, and one soft coral, Sarcophyton sp. SY-07, living in the northern part of South China Sea (SCS), were analyzed and compared using the ITS2-based genotype identification method, coupled with ITS2-based secondary structural and phylogenetic analyses. As the result, 12 Symbiodinium ITS2 genotypes were identified, while only six and three Symbiodinium ITS2 genotypes were supported by ITS2-based secondary structural and phylogenetic analyses, respectively. In addition, no shared Symbiodinium ITS2 genotypes were observed among the three coral species, suggesting coral species-dependent Symbiodinium genotypes were within clade C. In summary, the present study provides a theoretical basis for validating the molecular diversity of Symbiodinium ITS2 genotypes in corals.     

Trophic Interaction in a <Emphasis Type="Italic">Portunus rituberculatus</Emphasis> Polyculture Ecosystem Based on Carbon and Nitrogen Stable Isotope Analysis

Trophic interaction among various biomass groups in a swimming crab Portunus trituberculatus polyculture pond was investigated using carbon and nitrogen stable isotope analysis. The polycultured animal species also included white shrimp Litopenaeus vannamei, short-necked clam Ruditapes philippinarum, and redlip mullet Liza haematochila. The mean δ¹³C value for all the biomass groups in polyculture ecosystem ranged from ?25.61‰ to ?16.60‰, and the mean δ¹⁵N value ranged from 6.80‰ to 13.09‰. Significant difference in the δ¹³C value was found between particulate organic matter (POM) and sediment organic matter (SOM) (P < 0.05), indicating that these two organic matter pools have different material sources. Assuming that a ¹³C-enrichment factor of 1.00‰ and a ¹⁵N-enrichment factor of 2.70‰ existed between consumer and prey, diets of the four cultured animals were estimated using a stable isotope mixing model. The estimated model results indicated that P. trituberculatus mainly feed on Aloidis laevis; L. vannamei mainly feed on shrimp feed; while A. laevis, R. philippinarum and L. haematochelia mainly feed on POM. Shrimp feed was also an important food source of R. philippinarum and L. haematochelia. The diets of P. trituberculatus, L. vannamei, R. philippinarum, and L. haematochila showed complementary effects in this polyculture ecosystem. Our finding indicated that the polyculture of these four organisms with suitable farming density could make an effective use of most of the food sources, which can make a highly efficient polyculture ecosystem.     

Taxonomy,Morphology and Phylogeny of a New Oligotrich Ciliate–<Emphasis Type="Italic">Omegastrombidium hongkongense</Emphasis> n. sp. (Protozoa: Ciliophora) from Clear Water Bay,Hong Kong

One new marine oligotrich ciliate, Omegastrombidium hongkongense n. sp., was isolated from a bloom of Noctiluca scuntillans near Port Shelter, Hong Kong. The morphology and infraciliature of this new species were studied on both living and protargol-stained specimens. Its phylogenetic position was discussed based on the sequence of the small subunit rRNA gene. O. hongkongense is different from its congeners with special characters. The cells are usually heart-shaped, and the cell size usually is (20–35) × (20–30) μm in vivo. Its deep buccal cavity extends obliquely to about 1/2 of cell length. It shows prominent apical protrusion. The adoral zone of membranelles is divided into 17–19 collar membranelles and four buccal membranelles. It has one ball-like macronucleus. The girdle kinety forms a closed loop which obliquely surrounds the body. The ventral kinety and thigmotactic membranelles are not observed. The SSU rRNA sequence of O. hongkongense was close to those of Strombidium paracalkinsi and Varistrombidium kelum with approximately 99% similarity. In the phylogenetic trees, O. hongkongense can be grouped with O. elegans and V. kielum species with very low support (16% ML).     

The mycobiota of discoloured needles of the Swiss stone pine (<Emphasis Type="Italic">Pinus cembra</Emphasis> L.) in the Tatra Mountains (Poland)

The Swiss stone Pine (Pinus cembra L.) is an alpine species, fairly commonly occurring in the Alps and the Carpathians, close to the timberline. Natural sites of the Swiss stone pine in Poland are found exclusively in the Tatra Mountains, within the area of the Tatra National Park (TNP). In 2017, the health status of the needles of P. cembra was determined and their mycological analysis was carried out. As a result, 11 species of fungi were isolated from the needles showing disease symptoms, manifested by various shades of discoloration. The most frequently observed species was Fusarium oxysporum. It probably does not bring on disease symptoms, but may affect the development of other frequently isolated species (such as Sydowia polyspora, Lophodermium sp. and Lophodermium conigenum) that are pathogenic to Pinus spp.     

Spatial variations of <Emphasis Type="Italic">b</Emphasis>-values in the coastal area of Guangdong

We used earthquake catalogs recorded by Guangdong Seismological Network from 2008 to 2014 to resolve the spatial variations of b-values in the coastal area of Guangdong, particularly in three key research areas (Yangjiang, Heyuan, and offshore Nanao Island) with strong seismicity. Our results revealed that b-values exhibited significant spatial variations, and zones with low b-values could indicate the most likely seismogenic area of large earthquakes. We observed three clear low b-value patches in the offshore Nanao Island. We found a distinct high b-value peak at the depth of 11 km and two minimum peaks at about 14 and 7–8 km in the Yangjiang area. The overall b-values generally decrease with depth in the Heyuan area. The spatial variations of b-values reflect tectonic anomalies; that is, the ‘low-high-low’ distribution of b-values in the offshore Nanao Island and the Yangjiang area may indicate the anomaly of the crustal structure with a weak layer. The b-values of reservoir-induced seismicity are obviously lower than that induced by tectonism. This finding indicates that the reservoir area is generally at high stress state under the condition of high pore pressure. We inferred that large earthquakes might be prone to occur at 10–12 km depth in the offshore Nanao Island, at 12–15 km depth in the Yangjiang area, and at the lower part of the seismic activity zone in the Heyuan area. Moreover, the upstream area of the Xinfengjiang reservoir is the most likely area of future large earthquakes in the Heyuan area.     

Effects of <Emphasis Type="Italic">Trichoderma harzianum</Emphasis> YC459 and soil types on seed germination and seedling growth in rock slope restoration

We carried out experiments with various concentrations of Trichoderma harzianum YC459 in different soil types (forest soil, mixed soil, merchantable soil, and leaf mold soil) to evaluate its effect on seed germination and seedling establishment of four species (Festuca arundinacea Schreb., Dianthus barbatus var. asiaticus Nakai, Lespedeza cyrtobotrya Miq., and Parthenocissus tricuspidata Planch) for rock slope restoration. We also investigated the use of drilled slanted holes on the rock slopes for seedling establishment. The results showed that T. harzianum concentration had significant effects on seed germination, seedling growth, and seedling survival for all the species with different soil types. Seed germination and survival rates peaked at 5% T. harzianum concentration with leaf mold soil and decreased as T. harzianum concentration increased from 5% to 10%. Seedling survival rates of all four species were generally lowest at 0% T. harzianum concentration in all soil types. The height of F. arundinacea and L. cyrtobotrya peaked at 5% T. harzianum concentration whereas that of D. barbatus and P. tricuspidata peaked at 10% T. harzianum concentration. We concluded that 5% T. harzianum concentration with leaf mold soil is appropriate for seed germination and seedling survival rates of most species, thus enhancing seedling establishment. Practical application of the findings of this study will contribute in the vegetation restoration of steep rocks in mountain environments     

Soil Organic Carbon Contents and Stocks in Coastal Salt Marshes with <Emphasis Type="Italic">Spartina alterniflora</Emphasis> Following an Invasion Chronosequence in the Yellow River Delta,China

Plant invasion alters the fundamental structure and function of native ecosystems by affecting the biogeochemical pools and fluxes of materials and energy. Native (Suaeda salsa) and invasive (Spartina alterniflora) salt marshes were selected to study the effects of Spartina alterniflora invasion on soil organic carbon (SOC) contents and stocks in the Yellow River Delta. Results showed that the SOC contents (g/kg) and stocks (kg/m²) were significantly increased (P < 0.05) after Spartina alterniflora invasion of seven years, especially for the surface soil layer (0–20 cm). The SOC contents exhibited an even distribution along the soil profiles in native salt marshes, while the SOC contents were gradually decreased with depth after Spartina alterniflora invasion of seven years. The natural ln response ratios (LnRR) were applied to identify the effects of short-term Spartina alterniflora invasion on the SOC stocks. We also found that Spartina alterniflora invasion might cause soil organic carbon losses in a short-term phase (2–4 years in this study) due to the negative LnRR values, especially for 20–60 cm depth. And the SOCD in surface layer (0–20 cm) do not increase linearly with the invasive age. Spearman correlation analysis revealed that silt + clay content was exponentially related with SOC in surface layer (Adjusted R2 = 0.43, P < 0.001), suggesting that soil texture could play a key role in SOC sequestration of coastal salt marshes.     

Coccolith Assemblages and Primary Productivity Variations in the Central Western Pacific Warm Pool Over the Last 380 kyr

Coccolith assemblages in two gravity cores(KX21-2 and KX12-1) from the central Western Pacific Warm Pool(WPWP) have been analyzed with SYRACO. The variations of nutricline and primary productivity(PP) have been reconstructed based on these assemblages. The results show that the coccolith assemblages were dominated by Florisphaera profunda, Gephyrocapsa and Emiliania huxleyi over the last 380 kyr. Variations of nutricline and primary productivity can be divided into three intervals. Interval I(about 380–300 kyr): PP was high and nutricline was shallow; Interval II(about 300–160 kyr): PP decreased dramatically for a short time after the acme of G. caribbeanica in Mid-Brunhes while nutricline became deeper; Interval III(about 160 kyr–present): PP fluctuated at low levels and nutricline was deep. Variations of each coccolith taxon and PP were highly correlated in the two cores, which means that the geological environment is similar in the two cores. Spectrum analysis is performed for all coccolith taxons and PP, and the 19-kyr cycle is the most prominent. It means that the production of coccolithophores in the WPWP is mainly controlled by precession.     

<Emphasis Type="Italic">GST</Emphasis> (<Emphasis Type="Italic">phi</Emphasis>) gene from Macrophyte <Emphasis Type="Italic">Lemna minor</Emphasis> is involved in cadmium exposure responses

Reactive oxygen species (ROS) scavengers, including ascorbate peroxidase, superoxide dismutase, catalase and peroxidase, are the most commonly used biomarkers in assessing an organisms’ response to many biotic and abiotic stresses. In this study, we cloned an 866 bp GST (phi) gene in Lemna minor and investigated its characteristics, expression and enzymatic activities under 75 μmol/L cadmium concentrations in comparison with other ROS scavengers. GST (phi) gene expression patterns were similar to those of other scavengers of ROS. This suggests that GST (phi) might be involved in responding to heavy metal (cadmium) stress and that its expression level could be used as a bio-indicator in monitoring cadmium pollution.     

Distribution patterns of chlorophyll <Emphasis Type="Italic">a</Emphasis> in spring and autumn in association with hydrological features in the southern Yellow Sea and northern East China Sea

Two field studies were conducted to measure pigments in the Southern Yellow Sea (SYS) and the northern East China Sea (NECS) in April (spring) and September (autumn) to evaluate the distribution pattern of phytoplankton stock (Chl a concentration) and the impact of hydrological features such as water mass, mixing and tidal front on these patterns. The results indicated that the Chl a concentration was 2.43±2.64 (Mean ± SD) mg m^?3 in April (range, 0.35 to 17.02 mg m^?3) and 1.75±3.10 mg m^?3 in September (from 0.07 to 36.54 mg m^?3) in 2003. Additionally, four areas with higher Chl a concentrations were observed in the surface water in April, while two were observed in September, and these areas were located within or near the point at which different water masses converged (temperature front area). The distribution pattern of Chl a was generally consistent between onshore and offshore stations at different depths in April and September. Specifically, higher Chl a concentrations were observed along the coastal line in September, which consisted of a mixing area and a tidal front area, although the distributional pattern of Chl a concentrations varied along transects in April. The maximum Chl a concentration at each station was observed in the surface and subsurface layer (0–10 m) for onshore stations and the thermocline layer (10–30 m) for offshore stations in September, while the greatest concentrations were generally observed in surface and subsurface water (0–10 m) in April. The formation of the Chl a distributional pattern in the SYS and NECS and its relationship with possible influencing factors is also discussed. Although physical forces had a close relationship with Chl a distribution, more data are required to clearly and comprehensively elucidate the spatial pattern dynamics of Chl a in the SYS and NECS.     

Spatio-temporal Variation of Soil Respiration and Its Driving Factors in Semi-arid Regions of North China

Soil respiration (SR) is the second-largest flux in ecosystem carbon cycling. Due to the large spatio-temporal variability of environmental factors, SR varied among different vegetation types, thereby impeding accurate estimation of CO₂ emissions via SR. However, studies on spatio-temporal variation of SR are still scarce for semi-arid regions of North China. In this study, we conducted 12-month SR measurements in six land-use types, including two secondary forests (Populus tomentosa (PT) and Robinia pseudoacacia (RP)), three artificial plantations (Armeniaca sibirica (AS), Punica granatum (PG) and Ziziphus jujuba (ZJ)) and one natural grassland (GR), to quantify spatio-temporal variation of SR and distinguish its controlling factors. Results indicated that SR exhibited distinct seasonal patterns for the six sites. Soil respiration peaked in August 2012 and bottomed in April 2013. The temporal coefficient of variation (CV) of SR for the six sites ranged from 76.98% to 94.08%, while the spatial CV of SR ranged from 20.28% to 72.97% across the 12-month measurement. Soil temperature and soil moisture were the major controlling factors of temporal variation of SR in the six sites, while spatial variation in SR was mainly caused by the differences in soil total nitrogen (STN), soil organic carbon (SOC), net photosynthesis rate, and fine root biomass. Our results show that the annual average SR and Q₁₀ (temperature sensitivity of soil respiration) values tended to decrease from secondary forests and grassland to plantations, indicating that the conversion of natural ecosystems to man-made ecosystems may reduce CO₂ emissions and SR temperature sensitivity. Due to the high spatio-temporal variation of SR in our study area, care should be taken when converting secondary forests and grassland to plantations from the point view of accurately quantifying CO₂ emissions via SR at regional scales.