Methane seepage is the signal of the deep hydrocarbon reservoir. The determination of seepage is significant to the exploration of petroleum, gas and gas hydrate. The seepage habits microbial and macrofaunal life which is fueled by the hydrocarbons, the metabolic byproducts facilitate the precipitation of authigenic minerals. The study of methane seepage is also important to understand the oceanographic condition and local ecosystem. The seepage could be active or quiescent at different times. The geophysical surveys and the geochemical determinations reveal the existence of seepage. Among these methods, only geochemical determination could expose message of the dormant seepages. The active seepage demonstrates high porewater methane concentration with rapid SO₄^2– depleted, low H₂S and dissolved inorganic carbon (DIC), higher rates of sulfate reduction (SR) and anaerobic oxidation of methane (AOM). The quiescent seepage typically develops authigenic carbonates with specific biomarkers, with extremely depleted ¹³C in gas, DIC and carbonates and with enriched ³⁴S sulfate and depleted ³⁴S pyrite. The origin of methane, minerals precipitation, the scenario of seepage and the possible method of immigration could be determined by the integration of solutes concentration, mineral composition and isotopic fractionation of carbon, sulfur. Numerical models with the integrated results provide useful insight into the nature and intensity of methane seepage occurring in the sediment and paleo-oceanographic conditions. Unfortunately, the intensive investigation of a specific area with dormant seep is still limit. Most seepage and modeling studies are site-specific and little attempt has been made to extrapolate the results to larger scales. Further research is thus needed to foster our understanding of the methane seepage.

Stocking density is widely recognized as a critical factor in aquaculture and a potential source of long-term stress. The influence of stocking density on growth and stress response of juvenile turbot (Scophthalmus maximus, ~3–75 g, initial to final weight) was examined in fish held under low (LD, ~0.21–5.31 kg/m², initial to final density), medium (MD, ~0.42–10.81 kg/m²) and high stocking density (HD, ~0.63–14.27 kg/m²) for 120 days in a recirculating aquaculture system (RAS). In this trial, the growth curve for weight of juvenile turbot in RAS, all fitted by the Schnute model. No significant difference was found in growth performance among the three densities until at the final sampling (Day 120). The final weight and body weight increase (BWI) in the HD group were significantly lower than in other groups (P<0.05, weight: (75.83±2.49) g, (75.39±2.08) g, (65.72±2.86) g and BWI: (2 436.12±28.10)%, (2 421.29±4.64)%, (2 097.88±20.99)% in LD, MD and HD groups, respectively). Similarly, the specific growth rate (SGR), feed conversion ratio (FCR) and coefficient of variation for weight (CV_w) were adversely affected by high stocking density (P<0.05). However, there was no difference in survival and Fulton’s condition factor (K) of turbot among the different groups. Physiological analyses demonstrated a clear increase in the plasma cortisol level and an obvious decrease in growth hormone (GH) concentration in the HD group on Day 120 (P<0.05). There was no significant effect of stocking density on plasma glucose, Cl^– and protein levels. All these findings would provide a reference for selecting the optimal stocking density of juvenile turbot in RAS.

Bayesian and restricted maximum likelihood (REML) approaches were used to estimate the genetic parameters in a cultured turbot Scophthalmus maximus stock. The data set consisted of harvest body weight from 2 462 progenies (17 months old) from 28 families that were produced through artificial insemination using 39 parent fish. An animal model was applied to partition each weight value into a fixed effect, an additive genetic effect, and a residual effect. The average body weight of each family, which was measured at 110 days post-hatching, was considered as a covariate. For Bayesian analysis, heritability and breeding values were estimated using both the posterior mean and mode from the joint posterior conditional distribution. The results revealed that for additive genetic variance, the posterior mean estimate ($\sigma _a^2$=9 320) was highest but with the smallest residual variance, REML estimates ($\sigma _a^2$=8 088) came second and the posterior mode estimate ($\sigma _a^2$=7 849) was lowest. The corresponding three heritability estimates followed the same trend as additive genetic variance and they were all high. The Pearson correlations between each pair of the three estimates of breeding values were all high, particularly that between the posterior mean and REML estimates (0.996 9). These results reveal that the differences between Bayesian and REML methods in terms of estimation of heritability and breeding values were small. This study provides another feasible method of genetic parameter estimation in selective breeding programs of turbot.

Lectins are sugar-specific binding proteins or glycoproteins that play important physiological roles in cellular recognition and regulation. And they are also valuable in medicine and pharmacy. Tubeworm is the representative species around the hydrothermal vent in the deep sea. They have developed unique mechanisms to adapt to the harsh environment. In this study, a 1 092 bp cDNA, designed as rpgal, was first cloned and characterized from the tubeworm Ridgeia piscesae. Sequence analysis showed that RPGAL had low homology with the known galectin. And it had two homologous carbohydrate-recognition domains, which is the characteristic of the tandem-repeat type galectins. The RPGAL was successfully recombinant expressed in Escherichia coli and purified. Analysis of biological activity revealed that RPGAL was metal ion independent and it could agglutinate all the vertebrate erythrocytes tested. It was stable at 10–50°C and pH 5–10. And the hemagglutinating activity of RPGAL was strongly inhibited by D-Lactose and lipopolysaccharide. Although RPGAL had no effect on the microorganisms tested, it showed anti-tumor activity towards HeLa cells and HT1080 cells, which was accomplished by apoptosis. The study demonstrated that RPGAL was a novel galectin and provided a potential candidate for therapy of anti-tumor.

As one of the most common and dominant species in the Southern Ocean, Antarctic krill (Euphausia superba) play a significant role in food web structure and the process of energy flow. The diet of Antarctic krill in the Prydz Bay during austral summer of 2012/2013 was investigated and the ontogenetic shift in krill diet was evaluated using the stable isotope method. The nitrogen stable isotope values (δ¹⁵N) of adults ((2.78±0.58)‰) were much higher than those of juveniles ((1.69±0.70)‰), whereas the carbon stable isotope values (δ¹³C) of adults (–(28.26±1.08)‰) were slightly lower than those of juveniles (–(27.48±1.35)‰). Particulate organic matter (POM) from 0, 25, and 50 m depth combined (0/25/50 m) represented phytoplankton food items. The results showed that phytoplankton food items in surface water and mesozooplankton were two essential food items for Antarctic krill in the Prydz Bay during summer. POM (0/25/50 m) contributes 56%–69% and 26%–34% to the diet of juvenile and adult krill, respectively, whereas mesozooplankton composes 13%–34% and 58%–71% of the diet of juvenile and adult krill, respectively. Thus, an ontogenetic diet shift from POM (0/25/50 m), which consists mainly of phytoplankton, to a higher trophic level diet containing mesozooplankton, was detected. The capacity for adults to consume more zooplankton food items may minimize their food competition with juveniles, which rely mostly on phytoplankton food items. This suggests “diet shift with ontogeny” which may somehow help krill keep their dietary energy budget balanced and well adapted to the Antarctic marine ecosystem as a dominant species.

Copepods are a key trophic link between primary producers and predatory animals at higher trophic levels in the marine ecosystem. Knowledge of the in situ composition of the copepod diet is critical for the accurate evaluation of trophic relationships and energy transfer in marine food webs. In this study, we applied a PCR-based cloning technique developed previously to investigate the in situ diet of Calanus sinicus, an ecologically important large-sized calanoid copepod that dominates in the shelf waters around China, Japan and Korea. Analyses of the 18S rDNA sequences obtained from the copepod diet revealed the diverse food composition of C. sinicus from two stations (Y19 in the South Yellow Sea and B49 in the Bohai Sea). A total of 43 operational taxonomic units (OTUs) were detected, which belonged to 13 diverse lineages: Bacillariophyta, Dinoflagellata, Dictyochophyceae, Chrysophyta, Katablepharidophyta, Pelagophyceae, Apusozoa, Hydrozoa, Ctenophora, Echinodermata, Tunicata, Chaetognatha and marine fungi. The results indicate that during an algae bloom, C. sinicus can graze on the bloom causative species. When the abundance of phytoplankton in ambient water is relatively low, C. sinicus can choose eggs, larvae, or organic particles/detritus of various metazoans, especially hydrozoans and ctenophores, as alternative food sources. Our result suggests that C. sinicus is an omnivorous species, and its prey choice may depend on the food availability in the ambient waters.

The effects of nitrogen (N) addition on microbial biomass, bacterial abundance, and community composition in sediment colonized by Suaeda heteroptera were examined by chloroform fumigation extraction method, real-time quantitative polymerase chain reaction, and denaturing gradient gel electrophoresis (DGGE) in a salt marsh located in Shuangtai Estuary, China. The sediment samples were collected from plots treated with different amounts of a single N fertilizer (urea supplied at 0.1, 0.2, 0.4 and 0.8 g/kg (nitrogen content in sediment) and different forms of N fertilizers (urea, (NH₄)₂SO₄, and NH₄NO₃, each supplied at 0.2 g/kg (calculated by nitrogen). The fertilizers were applied 1–4 times during the plant-growing season in May, July, August, and September of 2013. Untreated plots were included as a control. The results showed that both the amount and form of N positively influenced microbial biomass carbon, microbial biomass nitrogen, and bacterial abundance. The DGGE profiles revealed that the bacterial community composition was also affected by the amount and form of N. Thus, our findings indicate that short-term N amendment increases microbial biomass and bacterial abundance, and alters the structure of bacterial community.

Prevalence of bacterial species involved in biomineralization of manganese on titanium (Ti) surfaces in marine environment was revealed in this research work. This study involves one year sea water exposure of Ti and their periodical biofilm characterization was carried out to quantify the manganese oxidizing bacterial (MOB) presence in the biofilm formed on titanium surfaces. The total viable count study of Ti coupons exposed to sea water for one year resulted in 60% of the MOB in overall biofilm population. The biochemical characterization of MOB isolates were performed for the genus level identification of the seven bacterial isolates. Further, the seven strains were subjected to 16S rRNA gene sequencing. Evolutionary analysis was performed using MEGA 7 to obtain closely related strains within the groups. The manganese oxidizing ability of the bacterial isolates were determined with Leucoberbelin Blue Assay (LBB) and Atomic Absorption Spectroscopy studies (AAS). The results show that among the isolated marine MOB species, Bacillus sp. and Leptothrix sp. have the maximum Mn oxidizing property. The microtitre plate assay was performed to determine the biofilm forming ability of the isolated marine MOB species. All the results have confirmed the prevalence of Bacillus sp. among the biofilm colonizers on Ti surfaces when exposed in sea water.

To understand the distribution of aluminum (Al) under the influence of mesocale eddies in the western South China Sea (SCS), sea level anomaly, geostrophic current, environmental parameters and reactive Al were investigated in the western SCS in August 2013. The highest reactive Al concentration ((180±64) nmol/L) was observed in the surface waters, indicating a substantial atmospheric input. Vertically, the reactive Al decreased from the surface high concentration to the subsurface minima at the depth of chlorophyll a (Chl a) maxima and then increased again with depth at most of the stations. The average concentration of reactive Al in the upper 100 m water column was significantly lower in the cyclonic eddy ((137±6) nmol/L) as compared with that in the non-eddy waters ((180±21) nmol/L). By contrast, the average concentrations of Chl a and silicate in the upper 100 m water column were higher in the cyclonic eddy and lower in the anticyclonic eddy. There was a significant negative correlation between the average concentrations of reactive Al and Chl a in the upper 100 m water column. The vertical distribution of reactive Al and the negative correlation between reactive Al and Chl a both suggest that the reactive Al in the upper water column was significantly influenced by biological removal processes. Our results indicate that mesoscale eddies could regulate the distribution of reactive Al by influencing the primary production and phytoplankton community structure in the western SCS.

A three-dimensional time-domain potential flow model with second-order nonlinearity was applied to simulate the wave resonance in a gap between two side-by-side rectangular barges. In the model, the velocity potential was decomposed into the incident potential and unknown scattered potential which was obtained by solving the boundary integral equation. The fourth-order predict-correct method was applied to enforce the free surface conditions in the time integration. The influence of the wave direction on the first and second-order gap surface elevations was investigated. The results reveal that the incident wave angle does not affect the resonant wave frequency and the maximum surface elevation at resonance always occurs at the middle location along the gap. However, the corresponding maximum wave surface elevation at resonance varies with the incident wave angle. The location of the maximum wave elevation shifts either upstream or downstream along the gap, depending on the relative magnitude of incident wave frequency to the resonant frequency.