Rapid changes on nutrient supply and CO₂ concentration that occurred in the northern South China Sea (SCS) during the Early Oligocene, provides an ideal natural laboratory, allowing us to peer into the coccolithophores’ physiology in the geological records. In this study, we established a new nannofossil assemblage index, termed as E* ratio, which is calculated by the relative abundance of eutrophic taxa and meso-oligotrophic taxa (${E^*}=\frac{e}{{e + c}}\times100$, where e is eutrophic taxa, and c is meso-oligotrophic taxa). Eutrophic taxa include small Reticulofenestra, Reticulofenestra lockeri group, Reticulofenestra bisecta group and Coccolithus pelagicus group, while meso-oligotrophic taxa include Cyclicargolithus spp. The E* ratio is well correlated with nutrient proxy during the Early Oligocene, while with different covarying patterns under the higher and lower CO₂ condition. By comparing the assemblage changes to the published data, we suggest that coccolithophores may change the way they use carbon source and nutrient with the decline of CO₂. Furthermore, this implies a possible initiation of the carbon concentrating mechanism.

Triacylglycerols (triglycerides, TAGs) are the major carbon and energy storage forms in various organisms, and important components of cellular membranes and signaling molecules; they have essential functions in multiple physiological processes and stress regulation. Acyl-CoA: diacylglycerol acyltransferase (DGAT) catalyzes the final and only committed acylation step in the synthesis of TAGs in eukaryotes. The present work identified and isolated a novel gene, UpDGAT1, from the green tide alga Ulva prolifera. The activity of UpDGAT1 was confirmed by heterologous expression in a Saccharomyces cerevisiae TAG-deficient quadruple mutant. Results of thin-layer chromatography and BODIPY staining indicated that UpDGAT1 was able to restore TAG synthesis and lipid body formation in the yeast. Lipid analysis of yeast cells revealed that UpDGAT1 showed broad substrate specificity, accepting saturated as well as mono- and polyunsaturated acyl-CoAs as substrates. High salinity and high temperature stresses increased UpDGAT1 expression and TAG accumulation in U. prolifera. The present study provides clues to the functions of UpDGAT1 in TAG accumulation in, and stress adaptation of, U. prolifera.

The Nankai Trough subduction zone is a typical subduction system characterized by subduction of multiple geological units of the Philippine Sea Plate (the Kyushu-Palau Ridge, the Shikoku Basin, the Kinan Seamount Chain, and the Izu-Bonin Arc) beneath the Eurasian Plate in the southwest of Japan. This study presents a geophysical and geochemical analysis of the Nankai Trough subduction zone in order to determine the features and subduction effects of each geological unit. The results show that the Nankai Trough is characterized by low-gravity anomalies (–20 mGal to –40 mGal) and high heat flow (60–200 mW/m²) in the middle part and low heat flow (20–80 mW/m²) in the western and eastern parts. The crust of the subducting plate is 5–20 km thick. The mantle composition of the subducting plate is progressively depleted from west to east. Subduction of aseismic ridges (e.g., the Kyushu-Palau Ridge, the Kinan Seamount Chain, and the Zenisu Ridge) is a common process that leads to a series of subduction effects at the Nankai Trough. Firstly, aseismic ridge or seamount chain subduction may deform the overriding plate, resulting in irregular concave topography along the front edge of the accretionary wedge. Secondly, it may have served as a seismic barrier inhibiting rupture propagation in the 1944 M_w 8.1 and 1946 M_w 8.3 earthquakes. In addition, subduction of the Kyushu-Palau Ridge and hot and young Shikoku Basin lithosphere may induce slab melting, resulting in adakitic magmatism and the provision of ore-forming metals for the formation of porphyry copper and gold deposits in the overriding Japan Arc. Based on comparisons of their geophysical and geochemical characteristics, we suggest that, although the Izu-Bonin Arc has already collided with the Japan Arc, the Kyushu-Palau Ridge, which represents a remnant arc of the Izu-Bonin Arc, is still at the subduction stage characterized by a single-vergence system and a topographic boundary with the Japan Arc.

As the largest genus of Halymeniaceae, Grateloupia has been widely reported. Here, we observed the life history and early development of Grateloupia constricata Li et Ding and investigated the effects of temperature, irradiance, and photoperiod on the discoid crust and sporeling development of G. constricata under laboratory conditions. We observed that the type of carpospore development was “mediate discal type”. The life history included homotypic gametophyte (haploid), carposporophyte (diploid), and tetrasporophyte (diploid), with typical isomorphic alternation of generations. The results of double factorial analysis showed that both single factorial effects and interaction among temperature, photoperiod, and irradiance were obviously significant on the discoid crust and sporeling development. Furthermore, we found that the optimum combination of condition for the early growth and development of G. constricata was temperature 20°C, irradiance 80 μmol photons/(m²·s) and photoperiod 16L:8D. This study provides the theoretical basis and technical support for the conservation of the Grateloupia germplasm, artificial breeding, large-scale cultivation and sustainable development.

Rapid and accurate identification of Vibrio species has been problematic because phenotypic characteristics are variable within species and biochemical identification requires two or more days to complete. Matrix-assisted laser desorption ionization–time of flight mass spectrometry (MALDI-TOF MS) has become a powerful tool for rapidly distinguishing between related bacterial species. However, its accuracy depends on the number of strains in a database. In the current study, we extend and apply the Vibrio database based on MALDI-TOF MS. A total of 74 strains of Vibrio representing 28 species were identified and included in new database. A phylogenetic tree based on rpoB sequence and dendrograms were constructed. We analyzed 30 clinical Vibrio of three species to evaluate the new database and carried out PCA dendrogram analyses for differences of strains. We created a new database that offered fast and accurate Vibrio identification. MSP and PCA dendrogram analyses provided technical support to track sources and incidences of Vibrio infection. In addition, the discovery of characteristic and differential peaks is useful for the future identification of Vibrio. This represents a powerful tool for the rapid and accurate classification and identification of Vibrio and closely related species.

Transparent exopolymer particles (TEPs) are ubiquitous throughout the oceans, and their sedimentation is considered an efficient biological carbon sink pathway. To investigate the role of coastal TEPs in sinking carbon from the upper layer, samples were collected in the spring and summer of 2011 in the Changjiang River (Yangtze River) Estuary, a typical coastal water. The concentrations and sinking rates of TEPs were measured, and potential sedimentation flux of TEPs was estimated. TEPs concentrations ranged from 40.00 μg/L to 1 040.00 μg/L (mean=(209.70±240.93) μg/L) in spring and 56.67 μg/L to 1 423.33 μg/L (mean=(433.33±393.02) μg/L) in summer, and they were higher at bloom stations than at non-bloom stations during both cruises. A significant positive correlation between TEPs concentration and chlorophyll a (Chl a) concentration was detected, suggesting that phytoplankton was the primary source of TEPs in this area. TEPs sinking rates ranged from 0.08 m/d to 0.57 m/d with a mean of (0.28±0.14) m/d in spring and 0.10 m/d to 1.08 m/d with a mean of (0.34±0.31) m/d in summer. The potential sedimentation flux of TEP-C ranged from 4.95 mg/(m²·d) to 29.40 mg/(m²·d) with a mean of (14.66±8.83) mg/(m²·d) in spring and 6.80 mg/(m²·d) to 30.45 mg/(m²·d) with a mean of (15.71±8.73) mg/(m²·d) in summer, which was ~17.81% to 138.27% (mean=65.15%±31.75%) of sedimentation flux of phytoplankton cells in the study area. Due to the increase of TEPs concentrations and their sinking rates, sedimentation fluxes of TEPs at the bloom station were obviously higher than at the non-bloom station during both cruises. This study indicates that TEPs serve as a carbon sink in the Changjiang River Estuary, especially during bloom events, and their sedimentation should be taken into account when we study the carbon sedimentation in the coastal sea.

Investigating the spatiotemporal variability of biogeochemical processes and ecological responses under multiple physical controls in shelf seas is of great importance for obtaining an in-depth understanding of marine ecosystem. Based on a compiled data set of historical observations and remote sensing data, the spatiotemporal variability and heterogeneity of physical-biogeochemical processes in the semi-enclosed South Yellow Sea (SYS) are investigated, and the intrinsic connectivity among different subregions and the associated mechanisms are examined. The results show that the seasonal alternation between southward transport in cold seasons and upwelling-induced vertical delivery in warm seasons is the primary physical control of the biogeochemical processes and primary production off Shidao and in the area adjacent to the Haizhou Bay. The northeastward expansion of coastal waters in the Subei Shoal constitutes an important physical driver for the offshore transport of Ulva prolifera in summer. Stratification significantly affects the biogeochemical processes in the Yellow Sea Cold Water Mass (YSCWM)-dominated area during warm seasons, and nutrients can accumulate in bottom waters from spring to autumn, making the Yellow Sea Cold Water Mass (YSCWM) be an important nutrient pool. Upwelling around the YSCWM boundary in the stratified season leads to consistency among the high chlorophyll a (Chl a) area, high primary productivity region and low-temperature upwelling zone. During cold seasons, the interactions of the southward cold waters in the western nearshore area and the northward warm waters in the central region lead to an “S”-shaped front in the SYS. In summer, upwelling can extract nutrients from the YSCWM; thus, the biogeochemical-ecological processes inside the cold-water mass and in the frontal zone are well connected via upwelling, and three typical physical-biogeochemical coupling regions are generated, namely, the Shidao coast, the area beyond the Haizhou Bay and the area off the Subei Shoal. This work refines and integrates studies on regional oceanography in the SYS and provides a comprehensive and systematic framework of physical-biogeochemical-ecological processes.

Ulva prolifera is a green alga that plays an important role in green tides. Carotenoid biosynthesis is a basic terpenoid metabolism that is very important for maintaining normal life activities in algae. In this study, we first reported the complete sequences of all genes in the 2-C-methyl-D-erythritol 4-phosphate (MEP) pathway, which is the only carotenoid synthesis pathway in U. prolifera. Then, we compared these genes with those of other species. Additionally, by detecting the carotenoid contents and expression levels of key genes participating in carotenoid biosynthesis in U. prolifera under three different light (1 000 lx, 5 000 lx and 12 000 lx) and salinity (12, 24 and 40) regimes, we found that carotenoid synthesis could be influenced by light and salinity, such that low light and high salinity could promote the synthesis of carotenoids. The results showed that the expression levels of genes involved in the MEP and the downstream pathway could affect the biosynthesis of carotenoids at the molecular level. This study contributes to a better understanding of the roles of genes participating in carotenoid biosynthesis in U. prolifera and the environmental regulation of these genes.

As one of the top four commercially important species in China, yellow croaker (Larimichthys polyactis) with two geographic subpopulations, has undergone profound changes during the last several decades. It is widely comprehended that understanding its population dynamics is critically important for sustainable management of this valuable fishery in China. The only two existing population dynamics models assessed the population of yellow croaker using short time-series data, without considering geographical variations. In this study, Bayesian models with and without hierarchical subpopulation structure were developed to explore the spatial heterogeneity of the population dynamics of yellow croaker from 1968 to 2015. Alternative hypotheses were constructed to test potential temporal patterns in yellow croaker’s population dynamics. Substantial variations in population dynamics characteristics among space and time were found through this study. The population growth rate was revealed to increase since the late 1980s, and the catchability increased more than twice from 1981 to 2015. The East China Sea’s subpopulation witnesses faster growth, but suffers from higher fishing pressure than that in the Bohai Sea and Yellow Sea. The global population and two subpopulations all have high risks of overfishing and being overfished according to the MSY-based reference points in recent years. More conservative management strategies with subpopulation considerations are imperative for the fishery management of yellow croaker in China. The methodology developed in this study could also be applied to the stock assessment and fishery management of other species, especially for those species with large spatial heterogeneity data.

microRNAs (miRNA) families play a critical role in plant growth, development, and responses to abiotic stress. In this study, we characterized Up-miR-843 and its targets genes in Ulva prolifera responses to nitrogen depravation and heat stress. The data demonstrated that 184 target genes of Up-miR-843 could be successfully validated. N deficiency not heat stress stimulus induced increase in abundance of the Up-miR-843 while exhibited reverse expression of target genes, including cyclin A3 and cyclin L, which were strictly required for cell cycle progression. In addition, U. prolifera with highly expression of Up-miR-843 showed improved biomass, and photosynthesis compared with that under normal growth conditions. Thus, the N deprivation and heat responsive miRNAs might be a possible member mediating the expression of these target genes, which further regulated the growth of U. prolifera.