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Volume 39 ， Issue 4 ， 2021
- Abstract：Impact factors on the salinity budget, especially the eddy salt fluxes and smaller-scale diffusive salt fluxes for the upper 50 m of the Bay of Bengal (BoB) in 2014 are investigated using a box model based on the Regional Ocean Modeling System (ROMS) daily outputs. The model results reproduce that the precipitation and river runoffs are the dominant factors modulating the sharp salinity decrease during the summer monsoon season. The analysis shows that the salinity increase after the summer monsoon is mostly due to the meridional advective and diffusive salt fluxes. The vertical advective salt flux, which is sensitive to the different signals of the wind stress curl, plays an important role in balancing the salinity change induced by the meridional advective salt flux during both the summer and winter monsoon seasons. Distinctive spatial mesoscale structures are presented in the eddy salt flux throughout the year, and their contributions are sizeable (over 30% in the meridional direction and about 10%-30% in the vertical direction). The meridional eddy salt flux is larger in the monsoon seasons than that in the inter-monsoon seasons, and in a positive pattern near the western boundary during the winter monsoon and autumn inter-monsoon. The vertical eddy salt flux makes an important contribution to the salinity budget, especially along the coastal area and around the Andaman and Nicobar Islands. The vertical eddy salt flux becomes large when a tropical cyclone passes the area.Keywords：salinity budget;Bay of Bengal;Regional Ocean Modeling System (ROMS);monsoon;eddy flux4|0|0Updated：2023-05-20
- Abstract：The accurate calculation of marine environmental design parameters depends on the probability distribution model, and the calculation results of different distribution models are often different. It is very important to determine which distribution model is more stable and reasonable when extrapolating the recurrence level of the studied sea area. In this paper, we constructed an evaluation method of the overall uncertainty of the calculation results and a measurement of the uncertainty of the design parameters derivation model, by incorporating the influence of sample information on the model information entropy, such as sample size, degree of dispersion, and sampling error. Results show that the sample data size and the degree of dispersion are directly proportional to the information entropy. Within the same group of data, the maximum entropy distribution model has the lowest overall uncertainty, while the Gumbel distribution model has the largest overall uncertainty. In other words, the maximum entropy distribution model has good applicability in the accurate calculation of marine environmental design parameters.Keywords：uncertainty;information entropy;extreme value distribution model4|0|2Updated：2023-05-20
- Abstract：Marine oil spills are among the most significant sources of marine pollution. Synthetic aperture radar (SAR) has been used to improve oil spill observations because of its advantages in oil spill detection and identification. However, speckle noise, weak boundaries, and intensity inhomogeneity often exist in the oil spill regions of SAR imagery, which will seriously affect the accurate identification of oil spills. To enhance marine oil spill segmentation of SAR images, a fast, edge-preserving framework based on the distance-regularized level set evolution (DRLSE) model was proposed. Specifically, a bilateral filter penalty term is designed and incorporated into the DRLSE energy function (BF-DRLSE) to preserve the edges of oil spills, and an adaptive initial box boundary was selected for the DRLSE model to reduce the operation time complexity. Two sets of RadarSat-2 SAR data were used to test the proposed method. The experimental results indicate that the bilateral filtering scheme incorporated into the energy function during level set evolution improved the stability of level set evolution. Compared with other methods, the proposed improved BF-DRLSE algorithm displayed a higher overall segmentation accuracy (97.83%). In addition, using an appropriate initial box boundary for the DRLSE method accelerated the global search process, improved the accuracy of oil spill segmentation, and reduced computational time. Therefore, the results suggest that the proposed framework is effective and applicable for marine oil spill segmentation.Keywords：level sets;bilateral filter;marine oil spill segmentation;synthetic aperture radar (SAR) imagery4|0|1Updated：2023-05-20
- Abstract：The resolution of ocean reanalysis datasets is generally low because of the limited resolution of their associated numerical models. Low-resolution ocean reanalysis datasets are therefore usually interpolated to provide an initial or boundary field for higher-resolution regional ocean models. However, traditional interpolation methods (nearest neighbor interpolation, bilinear interpolation, and bicubic interpolation) lack physical constraints and can generate significant errors at land-sea boundaries and around islands. In this paper, a machine learning method is used to design an interpolation algorithm based on Gaussian process regression. The method uses a multiscale kernel function to process two-dimensional space meteorological ocean processes and introduces multiscale physical feature information (sea surface wind stress, sea surface heat flux, and ocean current velocity). This greatly improves the spatial resolution of ocean features and the interpolation accuracy. The effectiveness of the algorithm was validated through interpolation experiments relating to sea surface temperature (SST). The root mean square error (RMSE) of the interpolation algorithm was 38.9%, 43.7%, and 62.4% lower than that of bilinear interpolation, bicubic interpolation, and nearest neighbor interpolation, respectively. The interpolation accuracy was also significantly better in offshore area and around islands. The algorithm has an acceptable runtime cost and good temporal and spatial generalizability.Keywords：Gaussian process regression;sea surface temperature (SST);machine learning;kernel function;spatial interpolation4|0|0Updated：2023-05-20
- Abstract：The chlorophylla(Chla) is an important indicator of marine ecosystems. The spatiotemporal variation of the Chlagreatly affects the mariculture and marine ranching in coastal waters of the Shandong Peninsula. In the current study, the climatology and seasonal variability of surface Chl-aconcentration around the Shandong Peninsula are investigated based on 16 years (December 2002-November 2018) of satellite observations. The results indicate that the annual mean Chl-aconcentration is greater in the Bohai Sea than in the Yellow Sea and decreases from coastal waters to offshore waters. The highest Chl-aconcentrations are found in Laizhou Bay (4.2-8.0 mg/m3), Haizhou Bay (4.2-5.9 mg/m3) and the northeast coast of the Shandong Peninsula (4.4-5.0 mg/m3), resulting from the combined effects of the intense riverine input and long residence time caused by the concave shape of the coastline. The seasonal Chl-aconcentration shows a significant spatial variation. The Chl-aconcentrations in these three subregions generally exhibit an annual maximum in August/September, due to the combined effects of sea surface temperature, river discharge and sea surface wind. In the southeast coast region, however, the Chl-aconcentration is lowest throughout the year and reaches a maximum in February with a minimum in July, forced by the seasonal evolution of the Yellow Sea Cold Water and monsoon winds. The interannual Chl-aconcentration trends vary among regions and seasons. There are significant increasing trends over a large area around Haizhou Bay from winter to summer, which are mainly caused by the rising sea surface temperature and eutrophication. In other coastal areas, the Chl-aconcentration shows decreasing trends, which are clearest in summer and induced by the weakening land rainfall. This study highlights the differences in the Chl-adynamics among regions around the Shandong Peninsula and is helpful for further studies of coupled physical-ecological-human interactions at multiple scales.Keywords：chlorophyll-aconcentration;Shandong Peninsula;climatology;seasonal variability;Yellow Sea Cold Water4|0|4Updated：2023-05-20
Physics
- Abstract：The growth of tidal flats off Zhejiang coasts in southwestern China has provided substantial areas for local agriculture and construction activities. To evaluate modern and future development of tidal flats in the region, a good understanding of sediment sources is necessary. Previous research has concluded that the Changjiang (Yangtze) River is the dominant supplier of sediments to this part of the southeast Chinese coast, despite the fact that sediment delivery from this source has been decreased markedly in the past two decades. In this study, we investigated the sources of tidal flat sediments, and the magnetic and geochemical properties of recent tidal flat sediments along the Zhejiang coast were compared with those discharged from rivers. Magnetic and geochemical properties of the tidal flat samples reveal statistically distinct sediment provenance groups. The magnetic and geochemical scatter plots show that the suspended sediment samples are naturally divided into two different groups, one including the Changjiang River and Qiantang River material, and the other including the Jiaojiang, Oujiang, and Feiyun Rivers that located in the central and southern parts of the study areas. At last, a binary source of tidal flat sediments along the Zhejiang coast was determined, with the substantial majority originating from local rivers, while a much smaller proportion emanates from the Changjiang River to the north. We conclude that the sediment contribution of the Changjiang River to tidal flat development in the region has been markedly overestimated, with important implications for management.Keywords：tidal flats;Zhejiang coastal area;magnetic and geochemical characteristics;sediment source tracing4|0|1Updated：2023-05-20
Geology
- Abstract：Dissolved organic matter (DOM) plays a crucial role in both the carbon cycle and geochemical cycles of other nutrient elements, which is of importance to the management and protection of the aquatic environments. To achieve a more comprehensive understanding the characteristics of DOM in the Changjiang (Yangtze) River basin, water samples from four natural lakes (Xiandao, Baoan, Daye, and Qingshan) in southeastern Hubei Province in China with different eutrophication levels were collected and analyzed. The optical characteristics were analyzed using ultraviolet-visible spectrophotometry and excitation-emission matrix spectroscopy coupled with parallel factor analysis. The results show that: (1) two humic-like components (C1 and C2) and two protein-like substances (C3 and C4) of DOM were identified in all waterbodies; (2) C3 originated primarily from the degradation of microalgae and contributed substantially to humic-like components during transformation. C4 was widely present in the Changjiang River basin and its formation was related to microbial activity, rather than algal blooms or seasons. Influenced by the water mixing, the protein-like components were more likely to be transformed by microorganism, whereas humic-like components were more easily to be photobleached; (3) the concentration of DOM and the fluorescence intensity of humic-like components gradually increased with rising lake eutrophication levels. With respect to protein-like components, only C3 showed changes along the eutrophication gradients; (4) DOM showed a high affinity with permanganate index (CODMn) and chlorophylla(chla) while the relationship was variable with phosphorus. This study helps us systematically understand the DOM characteristics, microbial activities, and pollutant transformation in the Changjiang River basin and provides reference to the ecological restoration of aquatic environments.Keywords：Hubei;eutrophic lake;dissolved organic matter (DOM);excitation-emission spectra;parallel factor analysis5|0|11Updated：2023-05-20
- Abstract：Metal species and the degree of environmental pollution are related to the hydrogen sulfide (H2S), an important product of early diagenesis that can react with metals to form stable compounds. To investigate the effects of H2S to metals and evaluate metal environment effect in the sediments of the East China Sea (ECS) and Yellow Sea (YS), geochemical characteristic and spatial distribution of nine heavy metals and H2S profile were studied. Higher H2S content and lower metal content was observed in the sediments 10 cm in depth in the North Yellow Sea and the west coast of South Korea. The pollution load index (Ipl) indicates that the southern coast of Shandong Peninsula underwent moderate pollution (Ipl=1) of heavy metals and no heavy metal pollution appeared in other areas (Ipl< 1). To some extents, the ecological risk of Cd and As enrichment was moderately severe in all stations. The chance of heavy metal combination to be toxic in ECS and YS during summer was 21%. In addition, correlation between H2S content and metals in both solid and porewater phases was obvious, corroborating important effect of H2S on metal distribution. Moreover, H2S could affect the spatial distributions of heavy metals in porewater directly and be indicative of potential biological effects of combined toxicant groups in the study region.Keywords：hydrogen sulfide;heavy metal;East China Sea and Yellow Sea;sediment;porewater;risk assessment4|0|1Updated：2023-05-20
Chemistry
- Abstract：Harmful algal blooms (HABs), such as dinoflagellate blooms, have adverse effects on coastal water environments, causing seafood contamination and aquaculture economic losses. Based on historical HAB records data (1983-2017) and phytoplankton data (1982-2008), field investigation and laboratory experiments on frequently bloomed dinoflagellate species, we analyzed the possible mechanisms of high frequency dinoflagellate blooms in Daya Bay, South China Sea. The HAB records data show that the proportion of dinoflagellate blooms increased from 15% before 1994 to 77.27% after 2011. The bloom occurred mostly in summer (57.58%) in Yaling Bay (76.92%). The species inducing dinoflagellate blooms tended to be singular over time, with high proportion ofScrippsiella trochoidea(42.86%-88.88%). Laboratory experiment and field investigation ofS. trochoideabloom showed that this species grew rapidly at 30℃ and 32.1℃ (r=0.47,P< 0.05), respectively. Results indicate that temperature rise in Yaling Bay was affected by nearby nuclear plant effluent, which favored theS. trochoideabloom. Coincidently, nearly 70% ofS. trochoideablooms occurred in about 7 days after local spring tide and strong wind (wind velocity >7 m/s), which disturbed the resting cysts in the sediment and bring them into surface layer. Taking into account of environmental parameters, algae source, and atmospheric conditions, the probable mechanism ofS. trochoideabloom could be explained. The cysts were resuspended by the spring tide or strong wind, germinated at the bottom layer, reproduced rapidly at higher temperature, and then aggregated in the inner bay (Yaling Bay), resulting the frequentS. trochoideabloom. Considering the influences of global warming and human activities, it should be taken more attention that dinoflagellate blooms might increase along the coastal waters.Keywords：harmful algal blooms;dinoflagellate;Daya Bay;Scrippsiella trochoidea4|0|0Updated：2023-05-20
- Abstract：The dinoflagellatesAlexandrium pacificumandProrocentrum donghaienseare two wellknown harmful algal blooms (HABs)-forming species, both were usually found in the same sea areas in form of HABs in China. To date, there is no mechanistic model that can fully explain the occurrence ofP. donghaienseblooms withA. pacificum. We found that different strains ofP. donghaiensehad different intrinsic growth rates of 0.107-0.215/d, and these strains exhibited different responses to the allelopathic action fromA. pacificum. Some strains ofP. donghaiensecould grow well despite some degrees of inhibition in a short period, suggesting the two algal speciesP. donghaienseandA. pacificumcould coexist, even ifA. pacificumwas allelopathic. Our findings may advance the understanding of phenotypes inP. donghaienseand provide a potential mechanism involved in the coexistence ofP. donghaienseandA. pacificumin the same area.Keywords：Prorocentrum donghaiense;allelopathy;Lotka-Volterra model;algal bloom;phenotype4|0|0Updated：2023-05-20
- Abstract：Marine picophytoplankton (Pico) as a major contributor to primary productivity in oligotrophic waters, play a very important role in marine material cycle and energy conversion, and their key role in the carbon cycle and global climate change is increasingly emphasized. To study the factors affecting the dynamic distribution ofSynechococcus, Prochlorococcus, and picoeukaryotes in the East China Sea (ECS), a marginal sea of the Northwest Pacific, we investigated 27 stations in May 2017, and collected 148 samples of Pico and nutrients from the surface to the bottom. By means of flow cytometry, the abundance of Pico was measured, and then we estimated the carbon biomass and analyzed the distribution of Pico. Finally, combined with the ECS unique geographical situation and hydrological regime, we evaluated various factors affecting the Pico in the ECS. In Pico community, the picoeukaryotes cell abundance was between 0.49×102-1.44×104cells/mL.Prochlorococcusranged from 1.36×103-3.47×104cells/mL andSynechococcusranged from 0.69×103-1.15×105cells/mL.Synechococcuswas the most, both in abundance and in carbon biomass.Picoeukaryoteswere the least in abundance, but has larger contribution to carbon biomass thanProchlorococcus. Water temperature, salinity, and stability of water column influenced Pico distribution. Picoeukaryotes were abundant in the shelf sea, whereasSynechococcusandProchlorococcuswere detected in the northeast of Taiwan, China. This study provided basic information for the study of Pico communities in the ECS and its adjacent marine ecosystem.Keywords：picophytoplankton;distribution;East China Sea;physicochemical condition4|0|1Updated：2023-05-20
- Abstract：Carbon biomass, carbon-to-chlorophyllaratio (C: Chla), and the growth rate of phytoplankton cells were studied during four seasonal cruises in 2017 and 2018 in Jiaozhou Bay, China. Water samples were collected from 12 stations, and phytoplankton carbon biomass (phyto-C) was estimated from microscope-measured cell volumes. The phyto-C ranged from 5.05 to 78.52 μg C/L in the bay, and it constituted a mean of 38.16% of the total particulate organic carbon in the bay. High phyto-C values appeared mostly in the northern or northeastern bay. Diatom carbon was predominant during all four cruises. Dinoflagellate carbon contributed much less (< 30%) to the total phyto-C, and high values appeared often in the outer bay. The C: Chlaof phytoplankton cells varied from 11.50 to 61.45 (mean 31.66), and high values appeared in the outer bay during all four seasons. The phyto-C was also used to calculate the intrinsic growth rates of phytoplankton cells in the bay, and phytoplankton growth rates ranged from 0.56 to 1.96/d; the rate was highest in summer (mean 1.79/d), followed by that in fall (mean 1.24/d) and spring (mean 1.17/d), and the rate was lowest in winter (mean 0.77/d). Temperature and silicate concentration were found to be the determining factors of phytoplankton growth rates in the bay. To our knowledge, this study is the first report on phytoplankton carbon biomass and C: Chlabased on water samples in Jiaozhou Bay, and it will provide useful information for studies on carbon-based food web calculations and carbon-based ecosystem models in the bay.Keywords：phytoplankton;carbon biomass;carbon-to-chlorophylla(C: Chla) ratio;growth rates;Jiaozhou Bay4|0|0Updated：2023-05-20
- Abstract：Ecological purification in a reservoir is an important strategy to control the level of nutrients in water. The bacterial community of such a reservoir is the main agent for pollutant degradation, which has not been fully documented. Taking the Jinze Reservoir, a freshwater source for Shanghai, China as the case, its spatial distributions of water and sediment bacteria were determined using 16S rRNA gene-based Illumina MiSeq sequencing, and the environmental parameters were analyzed. The reservoir takes natural river water and functions as an ecological purification system, consisting of three functional zones, i.e., pretreatment zone, ecological purification zone, and ecological sustaining zone. Results show that the concentrations of both total nitrogen (TN) and total phosphorus (TP) decreased considerably after the ecological treatment, and the concentration of dissolved oxygen (DO) in the ecological purification zone was boosted from that before pretreatment. In addition, patterns of bacterial communities in both water and sediment were similar and consisted of mainly Proteobacteria, Actinobacteria, and Bacteroidetes. However, difference in water bacterial composition was distinct in each functional zone, whereas the bacterial communities in sediment changed only slightly among sediment samples. Network analysis revealed nonrandom co-occurrence patterns of bacterial community composition in water and sediment, andPseudomonas, unclassified Comamonadaceae,Variovorax, andDechloromonaswere the key taxa in the co-occurrence network. The bacterial taxa from the same module of the network had strong ecological connections, participated in C-cycles, and shared common trophic properties. PICRUSt analysis showed that bacteria were involved potentially in various essential processes; and the abundance of predicted xenobiotic biodegradation genes showed a decreasing trend in water samples from the inlet to the outlet of the reservoir. These results improve our current knowledge of the spatial distribution of bacteria in water and sediment in ecological purification reservoirs.Keywords：ecological purification reservoir;bacterial community;Illumina MiSeq sequencing;network analysis;PICRUSt analysis4|3|0Updated：2023-05-20
- Abstract：Over the past decades, jellyfish occurred increasingly and abundantly in coastal areas worldwide. Usually, biomass of jellyfish, especially when they bloom, can be determined by visual counting. However, tiny individuals of jellyfish (e.g., planulae, polyps, and ephyrae) are difficult to detect in the field. In this study, species-specific quantitative real-time PCR assays (qPCR) (SYBR Green I) targeting the mitochondrial 16S rDNA (mt-16S rDNA) of jellyfish were developed and were used to estimate the distribution and seasonal fluctuations of four jellyfish species (Nemopilema nomurai, Cyanea nozakii, Rhopilema esculentum, andAurelia coerulea) in Jiaozhou Bay (JZB), China in 2013. The mt-16S rDNA ofA. coeruleaandN. nomuraiwas detected in most of the survey months and it peaked in July (1.03×104copies/L) and September (1.08×106copies/L), respectively. The mt-16S rDNA ofC. nozakiioccurred from August to October only with monthly mean values of 7.18-46.17 copies/L and was mainly located from the middle part to the outer part of the bay. The mt-16S rDNA ofR. esculentumwas the least abundant among the four species and was detected in only one sample (B2 station in March), with a value of 88.49 copies/L. The Spearman correlation test revealed that phytoplankton biomass was significantly and positively correlated with the mt-16S rDNA abundance ofA. coerulea(R=0.37,P< 0.01) and negatively with the mt-16S rDNA ofN. nomurai(R=-0.36,P< 0.01). The qPCR assay will enable the identification and quantification of jellyfish species in their whole life history and can be used as an approach in combination of the traditional jellyfish survey.Keywords：jellyfish bloom;Aurelia coerulea;Nemopilema nomurai;Cyanea nozakii;Rhopilema esculentum;mitochondrial 16S rDNA4|0|3Updated：2023-05-20
Ecology
- Abstract：The Yellow Sea Cold Water Mass (YSCWM), one of the most vital hydrological features of the Yellow Sea, causes a seasonal thermocline from spring to autumn. The diel vertical migration (DVM) of zooplankton is crucial to structural pelagic communities and food webs, and its patterns can be affected by thermocline depth and strength. Hence, we investigated zooplankton community succession and seasonal changes in zooplankton DVM at a fixed station in the YSCWM. Annual zooplankton community succession was affected by the forming and fading of the YSCWM. A total of 37 mesozooplankton taxa were recorded. The highest and lowest species numbers in autumn and spring were detected. The highest and lowest total densities were observed in autumn (14 464.1 inds./m3) and winter (3 115.4 inds./m3), respectively. The DVM of the dominant species showed obvious seasonal variations. When the YSCWM was weak in spring and autumn, most species (e.g.Paracalanus parvus, Oithona similis, andAcartia bifilosa) stayed above the thermocline and vertically migrated into the upper layer.Calanus sinicusandAidanosagitta crassacrossed the thermocline and vertically migrated. No species migrated through the stratification in summer, and all of the species were limited above (P. parvusandA. crassa) or below (C. sinicusandCentropages abdominalis) the thermocline. The YSCWM disappeared in winter, and zooplankton species were found throughout the water column. Thus, the existence of thermocline influenced the migration patterns of zooplankton. Cluster analyses showed that the existence of YSCWM resulted in significant differences between zooplankton communities above and below the thermocline.Keywords：mesozooplankton;diel vertical migration;Yellow Sea Cold Water Mass;North Yellow Sea;thermocline4|0|0Updated：2023-05-20
- Abstract：To explore genetic diversity and estimate the genetic differences among populations ofLutraria maximain the coastal waters off south to southeast China, the morphology of the species of five different geographical populations (Beihai, Weizhou Island, Zhanjiang, Xiamen, and Fuzhou) in Guangxi, Guangdong, and Fujian provinces was studied statistically in combination with the microsatellite markers. As revealed by morphological principal component analysis (PCA), the cumulative contribution rate of the first three principal components was 72.596%. The discrimination accuracy ranged from 47.5% to 80.0%, and the scatter plots of principal component and discriminant analysis were consistent in overall, showing that the Xiamen and Fuzhou populations were overlapped obviously. For microsatellite markers, 10 pairs of polymorphic primers were obtained by high-throughput transcriptome sequencing, and used for genetic diversity analysis. It was showed that the average number of alleles and effective alleles observed in each population ranged from 8.100 to 10.900, and from 3.497 to 4.228, respectively. The average observed heterozygosity (Ho) and expected heterozygosity (He) in the five populations ranged from 0.541 to 0.615, and from 0.642 to 0.733, respectively. The genetic distance (DA) ranged from 0.078 to 0.523, and the population genetic differentiation index (FST) ranged from 0.027 to 0.139. The unweighted pair-population method with arithmetic means (UPGMA) and structure analysis showed that the five populations could be divided into two main clusters, the Beibu Gulf group (Beihai and Weizhou Island) and the Southeast China Sea group (Zhanjiang, Xiamen, and Fuzhou), suggesting thatL. maximahas been separated geographically by the barrier of the Leizhou Peninsula into two groups in evolution, which provided us with a scientific clue to better protect the bioresource and establish an appropriate fishery management stocks forL. maximapopulations in south China.Keywords：Lutraria maxima;morphological difference;microsatellite markers;genetic diversity;genetic differentiation;transcriptome4|0|0Updated：2023-05-20
- Abstract：With the increase in the need for flood prevention and lake resource used by humans, the construction of floodgates and sluices has changed the hydrological connection between rivers and lakes, and between adjacent lakes. In river-disconnected lakes, exploitation and use of lake resources have resulted in water quality decline and mechanical disturbance intensification to a different degree. Of the large number of river-disconnected lakes in the middle-lower reaches of the Changjiang (Yangtze) River, the Futou Lake, and the Xiliang Lake lie close together and are, historically, directly connected, and so do Liangzi Lake and Baoan Lake. The extent of human disturbance is severe in the Futou Lake and the Baoan Lake, but relatively mild in the Xiliang Lake and Liangzi Lake. The freshwater rosette-forming submerged plantVallisneria natansis one of the dominant species in the four lakes. Using microsatellite markers, we studied the genetic variation ofV. natanssubpopulations in lakes with different intensities of human disturbance and historical direct hydrological connections. Our results showed that human disturbance decreased plant density and clonal growth inV. natans, but might increase genetic and clonal diversity at a subpopulation level and enhance gene flow among subpopulations by sexual propagule movement. Under similar climatic conditions, different intensities of disturbance seem to have such a high selective potential to differentiate genetically adjacent lake populations that they outperform the forces of gene flow through historical direct hydrological interconnection, which tends to produce genetic homogeneity. Our findings imply that human disturbance has a profound effect on the evolutionary process of natural populations of submerged plants. Moreover, increased subpopulation genetic diversity can enhance resistance and resilience to environmental disturbances. To a certain degree, we could expect that disturbed populations have the possibility of restoring spontaneously if humans cease to perturb natural ecosystems in the future.Keywords：river-disconnected lakes;annual plant;microsatellite marker;clonal diversity;gene flow4|0|0Updated：2023-05-20
- Abstract：Ichthyoplankton samples were collected from Changjiang (Yangtze) River estuary in May 2016. Species composition was studied by DNA barcoding and morphological identification. To make better use of the estuarine biotic integrity index (EBI) to assess the ecosystem health of the Changjiang River estuary over the past 30 years, we collected the data of a spring ichthyoplankton survey in the estuary from 1986 to 2016. The EBI was calculated using 12 evaluation metrics, namely, the number of total ichthyoplankton species, estuarine spawning species, estuarine nursery species, estuarine resident species, benthic species, pelagic species, and intolerant species, and the percentages of tolerant species, omnivores, insectivores, carnivores, and natural hybrid species. EBI was calculated in spring in four periods (1986, 1999, 2007, and 2016) by assigning points of 1, 3 or 5, giving values of 50, 38, 36, and 32, respectively, corresponding to "Good", "Fair-Poor", "Fair-Poor", and "Poor" EBI levels, respectively. Changes in species composition were the primary reason for the significant decreases in EBI between 1986 and 1999, and for the large differences between 1986 and 2007 and between 2007 and 2016. The changes in species composition were influenced by declines in ichthyoplankton species, pollution sensitive species, estuarine nursery species and estuarine sedentary species, and an increase in pollution resistant species. An analysis of EBI interdecadal variability showed that the health status of the Changjiang River estuary ecosystem over the last 30 years first declined and then stabilized at a lower level. This result further settled the argument for urgent protection and restoration of the Changjiang River estuary.Keywords：ichthyoplankton;estuarine ecological restoration;interdecadal variability4|0|1Updated：2023-05-20
- Abstract：Microgels are plankton-derived transparent exopolymer particles (TEP) and have a significant impact on global marine carbon cycle. We investigated the influence of biogeochemical variables on the pattern of TEP abundance and its associated carbon (TEPC) distribution through a vertical transect of the northern South China Sea (nSCS) during summer, 2014. The average TEP concentration was 58.32±30.56 μg Xeq./L. Vertically, it was higher in the subsurface water column and lower at 200-m water depths. As chlorophylla(chla), TEP, and TEPCwere highly concentrated at the bottom of the study transect, mainly on the continental shelf bottom and slope regions. Among biotic factors, cyanobacteria, especiallyTrichodesmium thiebautiishowed significant positive correspondences with TEP through studied water columns in nSCS. In addition, TEP showed a positive correlation with chl-adistribution and clustered closely with diatom as well. It indicates a combined contribution of them on TEP sourcing accordingly. Nutrient concentrations were also high due to estuarine diluted water from Zhujiang (Pearl) River in the season that may intrigue those scenarios. Significant positive correlation (P< 0.05) among biotic and abiotic parameters also supported the statement. Furthermore, mentionable contribution of TEP-derived TEPCwas found after comparing the particulate organic carbon data, which may signify the importance of TEP in local carbon cycle in the nSCS.Keywords：South China Sea;transparent exopolymer particles (TEP);carbon with TEP;monsoon4|0|0Updated：2023-05-20
- Abstract：The genusPyropiacontains several important cultivated species. Genetic research in nori species has mainly focused on the cell nucleus, with few studies on organelles (chloroplast and mitochondria). Due to the high copy numbers of organelles in cells, which influence the development and traits of algae, it is necessary to study their genetic mechanism. In this study, the marine red algaPyropia yezoensis, an important economic macroalga, was selected as the study object. To investigate organelle (chloroplast and mitochondria) inheritance inP. yezoensis, the wild type RZ (maternal strain) was crossed with the red mutant HT (paternal strain) and 30 color-sectors from 11 F1 gametophytic blades were examined. The complete chloroplast and mitochondrial genomes of the red mutant (HT) were assembled for the first time. One reliable and stable single nucleotide polymorphism (SNP) loci filtrated by bioinformatics analysis was used as a molecular marker for chloroplast and mitochondrial DNA, respectively, in subsequent experiments. PCR amplification and sequence analysis showed that the haplotypes of color-sectors detected were consistent with those of the maternal parent, confirming that both chloroplast and mitochondrial genomes were inherited maternally inP. yezoensis. The inheritance pattern of organelles inP. yezoensiscan be used to guide the hybridization and breeding of nori. Additionally, the organelle SNP markers developed in this study can be applied in subsequent genetic research.Keywords：Pyropia yezoensis;organelle single nucleotide polymorphism (SNP) markers;chloroplast;mitochondrial;organelle inheritance;maternal inheritance4|0|0Updated：2023-05-20
- Abstract：The genome of green microalgae has rarely been reported.Ulva proliferais a green microalga that has received much attention. Despite research articles aboutU. proliferain recent years, we know very little about its genome. Therefore, the 87.9-Mb haploid genome (containing 10 311 protein-coding genes) ofU. proliferawas studied, and the genome was compared with that ofU. mutabilis, which is the only publishedUlvaspecies. Results showed that the two species are closely related. A phylogenetic tree was constructed amongU. proliferaand other green algae available in GenBank, revealing the evolutionary status ofU. proliferain Chlorophyta. To understand whyU. proliferacould grow rapidly, we identified some genes related to growth, such as those involved in cell division, phosphorylation, and cell proliferation. In addition, genes related to stress resistance were found, which supports the notion thatU. proliferagrows vigorously in nature. These results help to characterize green tides from a new perspective and reveal some important insight into the biology ofU. prolifera.Keywords：Ulva prolifera;genome;fast grow;evolution4|0|2Updated：2023-05-20
- Abstract：When megalopa molting to the first juvenile crab stage, the crabs undergo carcinization morphogenesis. To study the key physiological and morphological processes in carcinization, we performed a comparative transcriptomic analysis between the cephalothoraxes and the pleons of megalopa and the first juvenile crab stage in Chinese mitten crab. The results reveal that the major physiological and morphological changes in the pleon were related to energy metabolism (oxidative phosphorylation and AMPK pathways), ventral nerve cord fusion (apoptosis-related pathways), and metamorphosis (transcription factors, Hedgehog and Hippo pathways). We also discovered that the key Hox genes abdominal-B and abdominal-A might regulate morphological changes, especially in the degeneration of the fifth pair of pleopods, and ganglion fusion, respectively. Studying the regulatory mechanisms of carcinization may help us better understand the developmental biology of the juvenile crabs.Keywords：Eriocheir sinensis;carcinization;pleon;physiology;morphology4|0|0Updated：2023-05-20
- Abstract：Fish embryos are widely used as models in toxicology, drug development, and human disease research because of their high sensitivity, observability, and operability, providing the basis for an in-depth understanding of the embryogenesis. Increasing studies have indicated that birth defects are hereditary. In this study, we usedOryzias melastigmaas a model to conduct a study of 185-day embryogenesis and observed self-induced non-pathological abnormal embryogenesis.O. melastigmaexperienced pre-puberty stage, adolescence stage, and senescence stage, and individuals produced up to 102 eggs per day. However, the fecundity was markedly reduced during the senescent stage. During the active egg and blastodisc stages, pseudo-fertilization and pseudo-blastocysts were observed. During cleavage at the 4-to 32-cell stages, we observed blastomeres separation or dislocation. Excessively separated blastomeres formed double blastoderms, eventually resulting in conjoined twins. During the blastula stage, we observed abnormally increased cell volume, narrowed and elongated blastocysts, and abnormally coated blastoderms. At the organogenesis stage, we observed abnormal numbers of Kupffer's vesicles and conjoined twins. Abnormality in the location and number of oil droplets were observed in various development stages. Abnormal development was more commonly observed in fertilized eggs produced by broodstock in prepuberty or senescence stages, which is probably related to the age of fish and the egg quality. This study can provide the materials for comparative analysis in toxicological and molecular studies ofO. melastigma, and may provide evidence for other economic fish that produce sticky eggs.Keywords：marine fish model;abnormal embryogenesis;blastomeres separation;Kupffer's vesicle;conjoined twins4|2|1Updated：2023-05-20
- Abstract：Mandarin fish (Siniperca chuatsi) is an economically important freshwater fish cultured in China. In this species, females grow faster than males. However, due to the lack of available genomic and transcriptome information, the mechanisms of sex differentiation remain poorly understood. In this study, Illumina high-throughput sequencing technology was used to sequence four cDNA libraries; the tissues examined included hypothalamus, pituitary gland, ovary, and testis. A total of 134 124 high-quality unigenes were obtained on average length of 1 361 bp and N50 of 3 312 bp. A search of all-unigene sequences against NR, NT, SwissProt, KOG, KEGG, GO, and InterPro databases resulted in 59 688 (44.50%), 76 329 (56.91%), 50 432 (37.60%), 45 741 (34.10%), 48 760 (36.35%), 5 241 (3.91%), and 46 099 (34.37%) annotations, respectively. In a comparison of ovarian and testicular libraries, 15 289 ovary-biased genes and 10 035 testis-biased genes were identified, including a series of genes related to sex determination and differentiation, such ascyp19a1a,foxl2,sox9,dmrt1,amh, and others. In addition, 49 495 SSRs and 85 899 SNPs were detected in transcriptome data. Quantitative real-time PCR results of 15 sex-related functional genes indicated that RNA-seq data was reliable. This study will contribute to a better understanding of the molecular mechanisms of sex differentiation and development in Mandarin fish.Keywords：transcriptome;mandarin fish;HPG axis;female and male4|0|0Updated：2023-05-20
- Abstract：Psilorhynchus homalopteramainly inhabits turbulent waters in the lower reach of the Yarlung Zangbo River,Tibet,China,and it is the only species ofPsilorhynchusin China. However,many important aspects of its biology remain poorly documented,which hinders the conservation efforts. Therefore,we studied its reproduction using 801 specimens from the Motuo sector of the lower Yarlung Zangbo River from December 2015 to November 2016. The sex ratio was 0.68:1 (male: female) for the overall population. Females reached a larger total length and weight (134 mm and 18.6 g) than males did (113 mm and 12.2 g). Lengths at maturity were estimated 80.0 mm for males and 93.1 mm for females. Our analyses of gonad development and the size distribution of oocytes suggest thatP. homalopterais a single spawner with the peak spawning period between September and October. Furthermore,the estimated mean absolute fecundity was 557±204 eggs per fish,and mean relative fecundity was 50.9±10.9 eggs per g of female weight. The fecundity ofP. homalopteraincreased linearly with increasing total length,total weight,ovary weight,and age. This study on the reproductive biology ofP. homalopterademonstrates that the fish was in a vulnerable state due to the increasing anthropogenic activities in the lower Yarlung Zangbo River.Keywords：reproductive biology;maturity;spawning period;fecundity;environmental adaptation4|0|0Updated：2023-05-20
- Abstract：Uncoupling protein 2 (UCP2) is a proton transporter located in the inner mitochondrial membrane,and inhibits the formation of adenosine triphosphate and reactive oxygen species by uncoupling oxidative phosphorylation. To provide a theoretical basis for the role ofSiUCP2in lipid metabolism,a 2 341-bp full-length cDNA ofSiUCP2from sea urchinStrongylocentrotus intermedius,which encodes 323 amino acids (predicted MW 36.11 kDa) was obtained,and the structure and function of theSiUCP2gene and its expression at the mRNA and protein level were studied.SiUCP2had high homology withUCP2of other species. Expression ofSiUCP2was detected in the order of tube feet > gonads > coelomocytes > intestines. The expression level was the highest in prismatic larvae and lowest in the two-cell stage. Moreover,using in-situ hybridization,we found that SiUCP2 protein was expressed in the gonads and intestine. This study provided a theoretical basis for subsequent studies on the role ofSiUCP2and its regulatory mechanism in lipid metabolism,and for the improvement of gonad quality to obtain a higher economic value from sea urchins.Keywords：Strongylocentrotus intermedius;SiUCP2;gene cloning;lipid metabolism;in-situ hybridization;western blot4|0|0Updated：2023-05-20
- Abstract：Virescentia guangxiensis,a new species ofVirescentiafrom Guangxi,South China,is described and illustrated based on morphological observations and phylogenetic analysis. This species was distinguished morphologically from other species by the presence of special expansion cells with a variable shape,obovoid,spherical,pear-shaped,located in the penultimate cells of primary or secondary fascicles,rarely terminal on primary fascicles,as well as by small whorls (250-350-μm wide) and short primary fascicles (5-7 cell stories). Phylogenetic analysis of molecular data from therbcL and COI-5P loci supported the separation of the proposed new species from other species in the genusVirescentia. This is the first species of the order Batrachospermales reported in Guangxi and the second species of the genusVirescentiareported in China. This study expands the known species diversity and geographical distribution of freshwater Rhodophyta in China.Keywords：Virescentia;new species;rbcL;COI-5P;China4|0|0Updated：2023-05-20
- Abstract：Two new species of genusDiplopeltoidesGerlach,1962and two new species of genusMinolaimusVitiello,1970were described based on recently collected specimens from marine sediments of the South China Sea and the East China Sea,respectively.Diplopeltoides conoicaudatussp. nov. is characterized by annulated cuticle; tiny terminal buccal cavity; short cephalic setae about 2-μm long; loop-shaped amphideal fovea without sclerotized plate; slender and arcuate spicules; triangular gubernaculum possessing a small dorso-caudal apophysis; female with two opposed and reflexed ovaries.Diplopeltoides longifoveatussp. nov. is characterized by its papilliform cephalic sensilla; long and narrow amphideal fovea with fine transverse striations; inverse S-shaped spicules with a dorsally bent manubrium; gubernaculum with dorso-caudal apophysis; cylindrical tail with round terminal end.Minolaimus multisupplementatussp. nov. is characterized by cuticle with lateral differentiation of three longitudinal rows of large dots,spiral amphideal fovea with seven turns,pharynx cylindrical without posterior bulb,spicules arcuated with central lamella,gubernaculum arcuate and parallel to spicule,without dorso-caudal apophysis,a papilliform and 29 cup-shaped precloacal supplement; tail conical with long flagelliform portion.Minolaimus apicalissp. nov. is characterized by cuticle with lateral differentiation of three longitudinal rows of larger dots from the middle of pharynx to the conical portion of tail and a longitudinal row of pores in the pharyngeal region and precloacal region; spiral amphidial fovea with four turns and close to anterior end; pharynx cylindrical with oval posterior bulb,spicules arcuated and proximal end bent dorsally,gubernaculum with a broad curved dorsal apophysis; two sucked-like and six cup-shaped cuticularized precloacal supplements; tail conico-cylindrical with slightly enlarged tip. Updated keys to species ofDiplopeltoidesandMinolaimuswere provided.Keywords：Diplopeltoides conoicaudatussp. nov.;Diplopeltoides longifoveatussp. nov.;Minolaimus multisupplementatussp. nov.;Minolaimus apicalissp. nov.;East China Sea;South China Sea4|0|1Updated：2023-05-20
Biology
- Abstract：Skin ulceration syndrome (SUS) is the main diseases affected the development of sea cucumber (Apostichopus japonicus) culture industries. To better observe the changes in the sea cucumberA. japonicuswith SUS and understand the pathogenesis of the disease,activities of superoxide dismutase (SOD),catalase (CAT),and level of malondialdehyde (MDA) in coelomic fluid were detected using the Assay Kit and metabolites in the body wall were assessed using ultra-performance liquid chromatography and quadrupole-time of flight mass spectrometry. The results indicated that level of MDA was increased during SUS compared with healthy individuals (P< 0.01),but activities of SOD and CAT were reduced (P< 0.05). In metabolomics analysis,metabolites,such as adenosine,choline,betaine aldehyde,palmitic acid,and taurine,were found to be upregulated and 2-oxoadipic acid,anthranilic acid (vitamin L1),thioetheramide-PC,cholesterol-3-sulfate,and pentadecanoic acid were downregulated (VIP>1 andP< 0.1). Pathway enrichment analysis indicated most enrichment of KEGG pathways were mainly related to energy metabolism,immunity,and osmoregulation such as ABC transporters,glycine,serine and threonine metabolism,tryptophan metabolism and neuroactive ligand-receptor interaction. Our study reflected the difference in enzyme activity and metabolites betweenA. japonicuswith SUS and those without,which will provide reference data for investigating SUS.Keywords：Apostichopus japonicus;skin ulceration syndrome (SUS);metabolome;differential metabolites4|0|1Updated：2023-05-20
- Abstract：A habitat model has been widely used to manage marine species and analyze relationship between species distribution and environmental factors. The predictive skill in habitat model depends on whether the models include appropriate explanatory variables. Due to limited habitat range,low density,and low detection rate,the number of zero catches could be very large even in favorable habitats. Excessive zeroes will increase the bias and uncertainty in estimation of habitat. Therefore,appropriate explanatory variables need to be chosen first to prevent underestimate or overestimate species abundance in habitat models. In addition,biotic variables such as prey data and spatial autocovariate (SAC) of target species are often ignored in species distribution models. Therefore,we evaluated the effects of input variables on the performance of generalized additive models (GAMs) under excessive zero catch (>70%). Five types of input variables were selected,i.e.,(1) abiotic variables,(2) abiotic and biotic variables,(3) abiotic variables and SAC,(4) abiotic,biotic variables and SAC,and (5) principal component analysis (PCA) based abiotic and biotic variables and SAC. Belanger's croakerJohnius belangeriiis one of the dominant demersal fish in Haizhou Bay,with a large number of zero catches,thus was used for the case study. Results show that the PCA-based GAM incorporated with abiotic and biotic variables and SAC was the most appropriate model to quantify the spatial distribution of the croaker. Biotic variables and SAC were important and should be incorporated as one of the drivers to predict species distribution. Our study suggests that the process of input variables is critical to habitat modelling,which could improve the performance of habitat models and enhance our understanding of the habitat suitability of target species.Keywords：generalized additive model;principal component analysis;biotic variables;spatial autocovariate4|0|1Updated：2023-05-20
Aquaculture and Fisheries
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