Aegiceras corniculatum is one of the pioneering mangroves. The coupling process involving A. corniculatum development and tidal flat geomorphological evolution is one of the core contents of mangrove bio-morphodynamic and ecological restoration research. Based on high-resolution remote sensing images between 2005−2019, monthly sediment and A. corniculatum population samples from October 2019 to October 2020, the variation characteristics of A. corniculatum distributed over the tidal flat of the Nanliu River Estuary were analyzed. Meanwhile, the coupling mechanism between the morphological changes of tidal flat erosion/accretion and the population expansion of A. corniculatum was discerned. The main results can be shown as follows: (1) it is found that the main grown area of A. corniculatum is the outer sides of the levees of Nanliu River Estuary. The distribution of the adult, youth and embryos of A. corniculatum presented bandy features along the high tidal flat, middle tidal flat and the area near mean sea level, respectively. Furtherly, tidal flat elevation of 0.07 m above the mean sea level is the growth limit of annual seedling. (2) A. corniculatum of the Nanliu River Estuarine flat expanded rapidly from northwest to southeast, which is in coincidence with development tendency of tidal flat. Tidal flat height is elevated with possibility for mangrove habitation, which should be necessary for A. corniculatum promoted seaward progradation. (3) A. corniculatum that induced wave attenuation can mitigate hydrodynamics forcing with benefit to tidal flat sedimentation, which can furtherly have tidal flat accreted seaward. Moreover, the low tidal flat can be elevated into the middle-high tidal flat by silting, which provides growth and development conditions for A. corniculatum.

Salinity is an important parameter to characterize physical and biogeo-chemical processes. Optical satellite images with high resolution can avoid radio frequency interference, and provide a feasible way to monitor sea surface salinity (SSS) in coastal regions. Using an extensive dataset of ship-based SSS and MODIS estimated remote sensing reflectance (Rrs) at 412 nm, 443 nm, 488 nm, 555 nm and 667 nm and sea surface temperature (SST) a random forest (RF) model has been utilized to retrieve the SSS. Based on the predicted SSS, we analyze the spatiotemporal heterogeneity of SSS in the Gulf of Mexico and contribution of each factor with correlations coefficient. The results show that: (1) the RF model can accurately estimate the SSS in the Gulf of Mexico (RMSE=0.335, R²=0.931); (2) the spatial distribution pattern of SSS shows a ring-shaped inward value increase, which is affected by river discharge, wind forcing and circulation; (3) there is a strong correlation between SSS and SST, and SST significantly impact in retrieving SSS; (4) the correlation between SST, Rrs and SSS appears spatial heterogeneity.

In order to understand the population dynamics of ichthyoplankton and the changing laws of biodiversity in the Laizhou Bay, four investigations (respectively in spring, summer, autumn and winter) of 20 positions in the Laizhou Bay from 2014 to 2015, the seasonal variations of species composition and community structure of ichthyoplankton in this area, involving its dominant species, community diversity and seasonal turnover rate were studied in this paper. The results showed that 135275 fish eggs and 2456 larvae were collected, total 22 species. Main species of ichthyoplankton changed significantly with the seasons, from Engraulis japonicus and Liza haematocheilus in spring, to Thryssa kammalensis and Allanetta bleekeri in summer, to Protosalanx hyalocranius in autumn, to Zoarces elongates in winter. The richness index (D) and diversity index (H′) were the highest in summer, and the evenness index (J′) was the highest in autumn. The species turnover rate from spring to summer was the lowest. Analysis of the results of clustering using R language with the highest likelihood suggest the existence of three assemblages of ichthyoplankton in the surveyed waters: spring group, summer and autumn group, winter group. The main divergent species of spring group and summer-autumn group, spring group and winter group were Engraulis japonicus. While the main divergent species of summer autumn group and winter group were Zoarces elongates and Thryssa kammalensis. This study shows that there are significant seasonal differences in the species composition, quantity distribution and biodiversity of ichthyoplankton in the Laizhou Bay. The research results supplement the basic data of fish early replenishment resources in the Laizhou Bay and provide basis for fishery resources conservation in the Laizhou Bay.

In order to study the growth, death, transport and distribution of early life history of winter-spring cohort of neon flying squid Ommastrephes bartramii in the Northwest Pacific Ocean, parameterized early biological processes, such as growth and death. Used the physical model (FVCOM-Global) to simulate and generate three-dimensional physical field of the North Pacific Ocean (10°−60°N, 120°E−110°W), and adopted the Lagrangian particle tracking method to couple the physical model and the biological model (individual-based model), and constructed an individual-based ecological model of early life history of winter-spring cohort of O. bartramii in the Northwest Pacific Ocean, and used this model to numerically simulate the transport distribution of winter-spring cohort from 1997 to 2010. The simulation results showed that within a certain temperature range, the closer to the optimum water temperature, the faster the growth rate of winter-spring cohort. When the age was 38 days, the mantle length could reach 11.76 millimeters, and then gradually changed from exponential growth to linear growth. The simulative recruitment had interannual fluctuation from 1997 to 2010. Considering the different number of winter-spring cohort parents, the years with the most and the least actual recruitment were 1999 and 2009, respectively. In the simulation stage, the winter-spring cohort was mainly located in the spawning ground, transported to the west in the south of 25°N, and gradually transported to the north and northeast in the north of 25°N, especially affected by the strong current in the later period of transport. In the vertical direction, the larvae within 100 meters water depth accounted for nearly half. This study can lay a foundation for further study of ecological dynamics of winter-spring cohort of O. bartramii in the Northwest Pacific Ocean.

As a typical high-turbidity bay, the carbonate systems in the Hangzhou Bay are not well documented. In this paper, the spatial distributions of inorganic carbonate paramenters in the Hangzhou Bay were analyzed based on data collected from two summer surveys in 2018 and 2019. The results showed that dissolved inorganic carbon (DIC) concentration and total alkalinity (TA) in surface layer of the Hangzhou Bay ranged from 1 553 μmol/kg to 1 964 μmol/kg and from 1 577 μmol/kg to 2 101 μmol/kg, respectively, which were lower than that of the Changjiang River Estuary (1 407−2 110 μmol/kg and 1 752−2 274 μmol/kg). The spatial distributions of DIC concentration and TA were controlled by the mixing of fresh water and offshore sea water. They were affected by strong tide, which gradually increased DIC concentration from inner bay to outlet of the bay. Air-sea carbon exchange and biological respiration led to decrease and increase of DIC concentration, with the contributions of (−42.3±11.7)% and (34.2±14.3)%, respectively. Such two compensate processes resulted in a net balanced state. The average surface pCO₂ in the Hangzhou Bay was 799 μatm (675−932 μatm), indicating that bay waters were source of atmospheric CO₂. The revelle factor in the Hangzhou Bay varied from 12.8 to 23.8, suggesting a weaker CO₂ buffering capacity than the adjacent East China Sea (the mean value was 11.9). Compared with other estuaries/gulfs, the characteristics of high turbidity and strong tides in the Hangzhou Bay made the spatial distributions of the carbonate system in the bay water had regional specificity.

Phycobilisomes are photosynthetic light-harvesting antenna complexes unique to red algae and cyanobacteria. Allophycocyanin (APC) is the main component of the core structure of phycobilisomes. In this experiment, recombinant allophycocyanin (rAPC) was used as the material, and the structure conformation and energy transfer process of rAPC were studied through steady-state spectroscopy, circular dichroic spectroscopy, and ultrafast time-resolved spectroscopy. The results show that rAPC can maintain the same spectral characteristics and active conformation as natural APC under the test conditions; after rAPC monomers are assembled into trimer, the results confirmed that α84PCB and β84PCB can form an exciton pigment pair which can improve the energy transfer efficiency of the rAPC trimer through exciton splitting; ultrafast time-resolved spectroscopy results show that the energy transfer time from 620 nm to 650 nm is 300−600 fs, and there is also a 19 fs exciton state electronic decoherence process. These results provide a data basis for revealing the efficient energy transfer mechanism of phycobilisomes.

Ten strains of bacteria were isolated from the gut of Mytilus coruscus to study its role in the settlement of larvae and plantigrade by forming biofilms. Results showed that the inducing ability of the biofilms formed by ten bacteria were different, although all of them could induce the settlement of larvae and plantigrade. In larvae, Bacillus sp.4 showed high inducing activity, while Phaeobacter sp.1 had low inducing activity. In plantigrades, Phaeobacter sp.1 showed high inducing activity, while Bacillus sp.4 showed low inducing activity. The polysaccharides and proteins from biofilms formed by Bacillus sp.4 and Phaeobacter sp.1 impacted larval settlement and metamorphosis, and the cell density, thickness and extracellular lipids of biofilm showed no effect on inducing activity of larval settlement and metamorphosis. For plantigrades, biofilm’s bacterial density, thickness and extracellular α-polysaccharide could induce plantigrades to the settlement, and the extracellular lipids and proteins of biofilms did not affect the settlement. This study is helpful for improving the healthy ecological culture of M. coruscus and to understand the settlement mechanism of M. coruscus.

To investigate the changes in mercury (Hg) speciation in vegetated sediments of the wetlands in Changjiang River Estuary, China, following the invasion of Spartina alterniflora, we determined total mercury (THg), methylmercury (MeHg), toatal organic carbon (TOC), reduced sulfur (S) and grain size in core sediments (0−40 cm) vegetated with different plants in wetlands. The results showed that: (1) the mean concentrations of THg were 49.9−100.9 μg/kg in sediments vegetated by S. alterniflora, Phragmites communis, Scirpus mariqueter and Scirpus tabernaemontani had a significant positive correlation with the fraction of fine particles (<16 µm) and TOC content (r²=0.85, p<0.01; r² =0.58, p<0.01), indicating that the distribution of Hg levels in sediments could be dominated by the spatial differentiation of the mineral-organic complexes in fine particles. The invasion of S. alterniflora promoted the deposition of fine particles, and thus could facilitate Hg storage indirectly in wetland sediments. (2) The mean concentrations MeHg and average values of MeHg/THg (%) in vegetated sediments were 0.3−1.4 μg/kg and 0.4%−1.4%, respectively. The profiles of MeHg and MeHg/THg exhibited decrease with increasing depth across all sites. There was no significant difference in the content of MeHg and the values of MeHg/THg in vegetated sediments dominated by S. alterniflora, P. australis and S. mariqueter, indicating that the impact of S. alterniflora invasion on Hg methylation may be limited. In addition, there was no significant positive correlation between MeHg/THg and THg, TOC and acid volatile sulfur (AVS). S-K edge XANES further revealed that the reduced sulfur (S) (e. g., thoil and sulfide) changed greatly in depth profiles. These results suggested that the changes in reduced sulfur could have limited impacts on MeHg production. The values of MeHg/THg was higher in surface horizon (0～8 cm) than in deeper horizon, indicating that the higher rates of Hg methylation in surface sediments and the degradation of fresh organic matter (e. g., algae and plant litter) could be the key biogeochemical process on controlling MeHg production in surface sediments of wetland in Changjiang River Estuary.

DNA barcoding technology is a tool for rapid and accurate species identification using short orthologous DNA sequence. In this study, both traditional morphology and DNA barcoding technology was used to accurately identify ichthyoplankton species in the Changjiang River Estuary and its adjacent waters. Morphological description was carried out at the same time. The results showed that in spring and summer of 2016 and summer of 2017, 55 species of ichthyoplankton were obtained, belonging to 9 orders and 19 families. Among them, there were 35 species of Perciformes at most. The seasonal variation of ichthyoplankton in fish group was not obvious, while there was significant seasonal variation in species. Only Coilia mystus, Engraulis japonius and Larimichthys polyactis appeared both in spring and summer. It was the first time to describe the morphological characteristics of Harpadon nehereus larva and juvenile. In addition, the quantifiable characters, fin development and melanin distribution of larvae and juvenile of Harpadon nehereus, Chelon affinis, Eleutheronema tetradactylum, Sillago japonica and Paraplagusia japonica, were described and drew. The research could provide a scientific basis for the study of fish nursery in estuaries, and also provide a new way for the accumulation of taxonomic data in the early stage of fish development.

Transparent exopolymer particles (TEP) play an important role in the marine micro-food web and the marine carbon cycle. The distribution patterns and influencing factors of TEP in the coast of eastern Fujian in summer are investigated in this research. The results show that the contents of TEP (calculated with xanthan gum as the standard substance, the same below) in the coast of eastern Fujian ranged from 25.2 μg/L to 935.5 μg/L, with an average value of (201.8±177.9) μg/L. The level of TEP is high in the near-shore and low in the far-shore, which in surface layer is lower than that in bottom layer. Correlation analysis shows that TEP in the research area are positively correlated with turbidity, silicate, phosphate, nitrite, nitrate and ammonium concentration, negatively correlated with pH, DO concentration and Net-level phytoplankton. The results of chlorophyll a fractions show that Net-level phytoplankton in the area may contribute more to TEP than other size phytoplankton. Comparing with phytoplankton as the main controlling factor of TEP in the open ocean, TEP in the coast of eastern Fujian in summer are mainly produced by phytoplankton in the decline stage, and its distribution is mainly affected by the resuspension of particles. The results can not only further clarify the differences between the influencing factors of TEP in the coastal waters and the open ocean, but also supplement the gaps in the study of TEP distribution in different regions of coastal waters in China.