Since the mud snail Bullacta exarata was introduced for economic aquaculture in the Huanghe River (Yellow River) Delta in 2001, its quick population growth and expanded distribution make it a key-species in the intertidal zone of this area. This significantly contributed to the economic income of the local people, but its potential ecological impact on the benthic ecosystem remains unknown. A mesocosm study was conducted to test whether its bioturbation activities affect the microphytobenthos (MPBs; i.e., sedimentary microbes and unicellular algae) productivity and the nutrient exchange between the sediment-water interface. Our results show that the mud snail significantly impacted the dissolved oxygen (DO) flux across the sediment-water interface on the condition of normal sediment and light treatment, and significantly increased the ammonium efflux during recovery period in the defaunated sediment and dark treatment. The presence of micro- and meiofauna significantly increased the NH₄-N flux in dark treatment. Whereas, in light treatment, these small animals had less effects on the DO and NH₄-N flux between sediment-water interface. Our results provide better insight into the effect of the mud snail B. exarata on the ecosystem functioning via benthic fluxes.

Located in the intertidal zone of the tropical and subtropical coasts, mangrove forests are an important ecosystem in the global carbon cycle and serve as a protector of local seashores. Under the double impacts of climate change, especially sea-level rise, and human activity, mangrove forests around the world have faced degradation, against which the reconstruction of the historical development of mangrove forests using an effective indicator has been regarded as a necessary strategy for designing a predictable model. As the primary product of mangrove forest, it is reasonable that the content of leaf fragments of mangrove (CLFM) buried in sediments in the form of sub-fossils potentially has the same indicative function for the development of mangrove forests as that of widely-used mangrove pollen. In this study, the leaf fragments of mangrove in two sediment cores (YLW02 and YLW03) drilled in the Yingluo Bay in Guangxi, Southwest China were picked out and weighted for calculation of CLFM, which was used as an indicator of mangrove development after examination of parallelism and a statistical correlation of the CLFM with the concentration of mangrove pollen. The results clearly show that the vertical distribution of the CLFM for the core taken from the landward margin of mangrove forests (YLW03) only parallels that of the local mangrove species (Rhizophora. stylosa) with a significantly positive correlation (R=0.56, P=0.05), while the vertical distribution of the CLFM for the core taken from the interface between seaward margin of mangrove forest and the trunk of tidal creeks of the bay (YLW02) parallels the summed concentration of mangrove pollen (SCMP) with a more positive correlation than that of YLW03 (R=0.85, P=0.01), indicating that the trunk outlet of tidal creeks must have been the site where mangrove production gathered from the overall forest rather than from local production. The variations in the CLFM of both cores indicate that overall the mangrove forests in the Yingluo Bay have increasingly flourished over the last 130 years except for the interval of 1940–1950 AD in response to an increase in air temperature and decrease in rainfall, which would have resulted in an increase in seawater salinity; while the coupled extreme increases in air temperature and in rainfall in summer, which would have resulted in extreme decreases in seawater salinity, would be responsible for the relative degradation of mangrove forests in the interval of 1940–1950 AD.

Water salinity condition is an important factor for artificial propagation of the swimming crab (Portunus trituberculatus). Low salinity (LS)-resistant strains are preferred by crab industries. Single nucleotide polymorphism (SNP), the third generation of molecular markers, can be utilized in the breeding of LS-resistant species of P. trituberculatus. Our earlier study identified 615 genes differentially expressed in low-salinity stress compared to the controls. Although thousands of SNP loci have been found, it is hard to identify a SNP marker in correlation with a desired trait. In this study, time-of-flight mass spectrometry (TOF-MS), as an efficient method to select SNPs for the tolerance of LS challenge, was utilized for SNP typing. Fifty gene segments were amplified based on comparative transcriptomics in our earlier study, a total of 18 511 bp DNA fragments were amplified, and eighty-five SNP markers were found. The frequency of the SNPs was estimated to be 0.46 per 100 base pairs of DNA sequences. The rate of the conversion mutation was 81%, while the transversion mutation was 19%. The mutation rate of the G/T (C/A), A/T and G/C was 26%, 12% and 7%, respectively. Eight SNP markers were found to significantly correlate with the adaption of low salinity. Of the eight SNP markers, three linked-SNPs were found in the cuticle proportion gene, and another three SNPs were found in three new genes, and the rest two were found in aquaporin gene and chloride channel gene. The development of these SNP markers found in our study could be primarily used for breeding LS-resistant strains of P. trituberculatus.

Dimethylsulfoniopropionate (DMSP) is mainly produced by marine phytoplankton as an osmolyte, antioxidant, predator deterrent, or cryoprotectant. DMSP is also an important carbon and sulfur source for marine bacteria. Bacteria may metabolize DMSP via the demethylation pathway involving the DMSP demethylase gene (dmdA) or the cleavage pathway involving several different DMSP lyase genes. Most DMSP released into seawater is degraded by bacteria via demethylation. To test a hypothesis that the high gene frequency of dmdA among major marine taxa results in part from horizontal gene transfer (HGT) events, a total of thirty-one bacterial strains were isolated from Arctic Kongsfjorden seawater in this study. Analysis of 16S rRNA gene sequences showed that, except for strains BSw22118, BSw22131 and BSw22132 belonging to the genera Colwellia, Pseudomonas and Glaciecola, respectively, all bacteria fell into the genus Pseudoalteromonas. DmdA genes were detected in five distantly related bacterial strains, including four Arctic strains (Pseudoalteromonas sp. BSw22112, Colwellia sp. BSw22118, Pseudomonas sp. BSw22131 and Glaciecola sp. BSw22132) and one Antarctic strain (Roseicitreum antarcticum ZS2–28). Their dmdA genes showed significant similarities (97.7%–98.3%) to that of Ruegeria pomeroyi DSS–3, which was originally isolated from temperate coastal seawater. In addition, the sequence of the gene transfer agent (GTA) capsid protein gene (g5) detected in Antarctic strain ZS2–28 exhibited a genetically closely related to that of Ruegeria pomeroyi DSS–3. Among the five tested strains, only Pseudomonas sp. BSw22131 could grow using DMSP as the sole carbon source. The results of this study support the hypothesis of HGT for dmdA among taxonomically heterogeneous bacterioplankton, and suggest a wide distribution of functional gene (i.e., dmdA) in global marine environments.

The parameter inversion of internal solitary waves (ISWs) based on optical remote sensing images is a key work. A new approach is proposed and demonstrated for simulating the optical remote sensing images of ISWs with a smooth surface in the laboratory. An optical remote sensing simulation system used to detect ISWs is constructed by a two-dimensional ISW flume, a LED (light emitting diode) light source and two CCD (charge coupled device) cameras. The optical remote sensing images of the horizontal surface and ISWs propagation images of a vertical side are detected simultaneously, which aims to explore the response of optical remote sensing corresponding to ISWs with the smooth surface. The results show that during the propagation of ISWs, dark pattern images are obtained by CCD 1 camera. The characteristics of the dark patterns vary along with the incident angle of the light source. The characteristic parameters of the optical remote sensing images correspond to the wave factors of vertical profiles. The experiment also shows a positive correlation between the dark pattern width and the half wave width under different amplitudes of ISWs. The system has the advantages of clear phenomenon and high repeatability, which provides the scientific basis for quantitative investigation on imaging mechanism of ISW by optical remote sensing.

Seven bacterial clones with alginate-utilizing activity were isolated from rotten kelp. By activity test, the Vibrio sp. QD-5 with the potential alginate-degrading capability was chosen to carry out the draft genome sequencing, and the result showed that the Vibrio sp. QD-5 containing an alginate lyase gene cluster. One of these genes, aly-IV, was cloned and characterized for the first time. After overexpression, Aly-IV, with a molecular mass of about 62 kDa and a theoretical isoelectric point (pI) of 5.12, was purified to a specific activity of 1 256.78 U/mg and showed highest activity at 35°C in the Tris-HCl buffer at pH of 8.9. Moreover, the enzyme activity was enhanced by the metal ions of Na⁺, K⁺ and Mg²⁺ under certain concentration. Aly-IV degraded favorably polyG blocks in an endo-type, yielding monomer and dimer as the main products. Due to its high substrate specificity, Aly-IV could be used as a potential tool for production of polyG oligosaccharides with low degree of polymerization (DP) and for determining the fine structure of alginate.

The hydrodynamic efficiencies of caisson-type vertical porous seawalls used for protecting coastal areas were calculated in this study. Physical models were developed to compare the wave reflection from vertical plane, semi-porous, and porous seawalls caused by both regular and random waves. Tests were carried out for a wide range of wave heights, wave periods, and different water depths (d=0.165, 0.270 and 0.375 m). The performance regarding the reflected waves from porous and semi-porous seawalls showed improvement when compared with those from the plane seawall. The reflection coefficients of the porous and semi-porous seawalls were calculated as 0.6 and 0.75, respectively, while the coefficient for the fully reflecting plane vertical wall was significantly higher (0.9). It was also observed that the reflection coefficient decreases with increase in wave steepness and relative water depth. In addition, the reduction in the reflection coefficient of porous and semi-porous seawalls, as compared to that of a plane seawall, was observed for both regular and random waves. New equations were also proposed to calculate the reflection coefficient of different types of seawalls with the aid of laboratory experiments. By verifying the developed equations using some other experimental data, it was validated that the equations could be used for practical situations. The results of the present study can be applied to optimize the design of vertical seawalls and for coastal protecting schemes.

A great deal of oil contaminated the shoreline by the Qingdao oil pipeline explosion in 2013. The four oil-degrading consortia were enriched from sediment samples with crude oil as sole carbon and energy sources. The biodiversity and community analysis showed that the Luteibacter, Parvibaculum and a genus belonging to Alcanivoracaceae were found predominant bacteria in the four consortia, which belonged to Proteobacteria. Nine strains exhibiting distinct 16S rRNA gene sequences were isolated from the consortia. These strains were identified to eight genera based on 16S rRNA gene sequences. Five of the nine strains degraded more than 30% of the crude oil in two weeks by gravimetric method. From the analysis of GC-MS, most of the isolated strains tended to degrade n-alkanes rather than PAHs. Five strains showed high degrading ability of the total n-alkanes. Only Strain D2 showed great PAHs degrading ability and the degrading rates ranged from 34.9% to 77.5%. The sequencing analysis of the oil-degrading consortia confirmed that the genus of Alcanivorax was one of the dominant bacteria in Consortia A and E and Strain E4 might be one of the dominant bacteria. The strains obtained in this study demonstrated the potential for oil bioremediation in oil-contaminated beach ecosystems.

In this study, the method of lines (MOLs) with higher order central difference approximation method coupled with the classical fourth order Runge-Kutta (RK(4,4)) method is used in solving shallow water equations (SWEs) in Cartesian coordinates to foresee water levels associated with a storm accurately along the coast of Bangladesh. In doing so, the partial derivatives of the SWEs with respect to the space variables were discretized with 5-point central difference, as a test case, to obtain a system of ordinary differential equations with time as an independent variable for every spatial grid point, which with initial conditions were solved by the RK(4,4) method. The complex land-sea interface and bottom topographic details were incorporated closely using nested schemes. The coastal and island boundaries were rectangularized through proper stair step representation, and the storing positions of the scalar and momentum variables were specified according to the rules of structured C-grid. A stable tidal regime was made over the model domain considering the effect of the major tidal constituent, M₂ along the southern open boundary of the outermost parent scheme. The Meghna River fresh water discharge was taken into account for the inner most child scheme. To take into account the dynamic interaction of tide and surge, the generated tidal regime was introduced as the initial state of the sea, and the surge was then made to come over it through computer simulation. Numerical experiments were performed with the cyclone April 1991 to simulate water levels due to tide, surge, and their interaction at different stations along the coast of Bangladesh. Our computed results were found to compare reasonable well with the limited observed data obtained from Bangladesh Inland Water Transport Authority (BIWTA) and were found to be better in comparison with the results obtained through the regular finite difference method and the 3-point central difference MOLs coupled with the RK(4,4) method with regard to the root mean square error values.

Acorn barnacles are important model species in researches on intertidal ecology, larval development and bio-fouling. At present, with the development of mitochondrial genomics, it is helpful to understand the phylogenetic relationship from the mitogenomic level. The complete mitochondrial genome of Chthamalus challengeri was presented. The genome is a circular molecule of 15 358 bp. Compared with other species in Balanomorpha, the non-coding region is longer, while the length of the genes is similar to the other species. The overall A+T content of the mitochondrial genome of C. challengeri is 70.5%. There are variations of initiation and stop codons in the known Balanomorpha mitochondrial genomes. The C. challengeri and C. antennatus within the same genus share the identical gene arrangement. However, the gene arrangement of different genera in Chthamalidae is different, as there is a translocation between two tRNA genes and an inversion involving a large gene block. In particular, both srRNA and lrRNA of the two species in Chthamalus are encoded in the heavy strand, differing from the former Balanomorpha species. The topology and gene arrangement in Chthamalidae support each other. Phylogenetic analysis indicates that the Chthamalidae is monophyletic, while the Balanidae and Archaeobalanidae are polyphyletic.