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 study the effect of hypoxia on immune function of juvenile cobia (Rachycentron canadum), the transcription level of immune related genes were detected in gills, liver, intestines, and spleen after exposing to (3.15±0.21) mg/L hypoxia stress for 28 d. The results showed: (1) in gills, the transcription level of tumor necrosis factor α (TNFα) and type 2 interleukin-1 receptor (IL-1R2) extremely decreased (p<0.01) on 1 d and 14 d of stress. On 28 d of stress, TNFα extremely decreased (p<0.01) while IL-1R2 significantly decreased (p<0.05). Tumor necrosis factor alpha induced protein 3 (TNFAIP3) extremely increased (p<0.01) on 1 d and then significantly decreased (p<0.05) on 7 d and extremely decreased (p<0.01) on 14 d. Interleukin-1β (IL-1β) extremely decreased (p<0.01) on 1 d and then extremely increased (p<0.01) . Interleukin-17C (IL-17C) extremely decreased (p<0.01) on 7 d and 14 d, while heat shock protein 70 (HSP70) significantly decreased (p<0.05) on 1 d and extremely decreased (p<0.01) on 14 d and 28 d. (2) In liver, the transcription level of TNFα and IL-1R2 significantly decreased (p<0.05) on 1 d and 28 d and extremely decreased (p<0.01) on 14 d. TNFAIP3 extremely increased (p<0.01) on 1 d and extremely decreased (p<0.01) on 14 d and 28 d. IL-1β extremely increased (p<0.01) at all stress time points, while IL-17C extremely decreased (p<0.01) on 7 d, 14 d and 28 d. HSP70 continued to increase and reached the maximum on 28 d (p<0.01). (3) In the intestine, the transcription level of TNFα, IL-1β, IL-1R2, IL-17C and HSP70 genes were higher (p<0.01) than those in the control group at all stress time points. TNFAIP3 extremely increased (p<0.01) on 1 d and significantly decreased (p<0.05) on 7 d and extremely decreased (p<0.01) on 14 d. (4) In spleen, the transcription level of TNFα and IL-17C extremely decreased (p<0.01) on 1 d, 7 d, 14 d and significantly decreased (p<0.05) on 28 d. IL-1β extremely decreased (p<0.01) on 1 d, 28 d and significantly decreased (p<0.05) on 7 d and 14 d. IL-1R2 extremely decreased (p<0.01) on 1 d, 7 d, 28 d and significantly decreased (p<0.05) on 14 d, while HSP70 extremely decreased (p<0.01) on 1 d, 7 d and 28 d. The results indicated that immune genes of transcription level in juvenile cobia showed significantly change after 28 d of hypoxia stress, suggesting that long-term hypoxia may inhibit the immune function, cause intestinal inflammation, and increase the risk of pathogen infection in cobia.

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.

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.

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.

The composition and distribution of mangrove species are crucial to the protection and restoration of mangrove wetland ecosystems. In this study, mangrove species distribution was identified by unmanned aerial vehicle (UAV) hyperspectral images from Zhangjiangkou mangrove national nature reserve. Spectral characteristics, spectral differential, and spectral continuum removal were analyzed, 17 spectral parameters of 911 group spectral data from different vegetation species were obtained. Furthermore, 13 parameters for decision tree construction were selected by stepwise discriminant analysis. As a result, an accurate distribution map of mangrove species in the study area was obtained through C5.0 decision tree classification model. The vegetation species present different distribution types from top to bottom in the Zhangjiangkou mangrove national nature reserve. The upper part of the study area was dominated by the mixed type of Aegiceras corniculatum and Kandelia obovata. The middle area showed symbiosis status of three different mangrove species Avicennia marina, Aegiceras corniculatum and Kandelia obovata. The lower part of the study area was dominated by Avicennia marina, and a small amount of Kandelia obovata. Through the confusion matrix, the overall classification accuracy is 87.95% and the Kappa coefficient is 83.81%, showed a satisfactory precision. Therefore, our mangrove species identification results from UAV hyperspectral images could be used as a reference for ecological protection of regional mangrove wetland, and also as a identification method reference for mangrove species.

The cumulative human impact assessment of marine ecosystems is an ecological method to scientifically recognize the response and feedback laws of the system to external disturbances. In order to explore and reveal the inherent mechanisms, the region of coastal seas of China as the research scope in this article, selecting 16 ecological factors in four aspects, marine fishery, marine shipping, land-based and offshore pressures, and climate change. And by spatial quantization and standardization, the cumulative exposure and impact assessment of the 9 marine habitat types in the study area are carried out under the 1 km×1 km spatial grid scale. The results show that the cumulative exposure in the study area is generally higher in the coastal seas than in the pelagic, and gradually decreases to the far ocean; the coastal seas ecosystem is mainly affected by land-based pollution and fishing, and overall climate change contributes the most; 22.8% and 7.6% of China’s coastal seas are respectively highly and extremely highly affected, among which the Changjiang River Delta is the most affected by human activities.

A high resolution numerical model based on a proven FVCOM with a Lagrangian particle tracking module was introduced to simulate water particle movement under differences controlling conditions, including the tide, wind, boundary circulation flow, temperature, salinity, wave coupling etc. Combined with simulate results and the actual drift bottles movement paths, factors influencing Ulva prolifera were discussed. The results showed that the migration path of U. prolifera firstly migrated northward along the coast of northern Jiangsu to the sea area near the abandoned Huanghe River Estuary and then continued its migration to the sea area south of Shandong Peninsula. The external forces that affecting the migration of U. prolifera is mainly wind. It is an order of magnitude higher than anything else and followed by temperature-salinity, wave, tidal, circulation, the tidal current can cause the cyclic movement of U. prolifera in the local area, and it has no influence on Enteromorpha for drifting to the north more distant. During the simulation period, the surface temperature, salinity of drifting sea area were between 18−24℃, 28−31, respectively. These temperature and salinity conditions are close to the most suitable growth conditions of U. prolifera, indicating that U. prolifera would fast reproduce during its drifting.

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.

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.