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Volume 41 ， Issue 6 ， 2023
- Abstract：Sea surface salinity (SSS) is an essential variable of ocean dynamics and climate research. The Soil Moisture and Ocean Salinity (SMOS), Aquarius, and Soil Moisture Active Passive (SMAP) satellite missions all provide SSS measurements. The European Space Agency (ESA) Climate Change Initiative Sea Surface Salinity (CCI-SSS) project merged these three satellite SSS data to produce CCI L4 SSS products. We validated the accuracy of the four satellite products (CCI, SMOS, Aquarius, and SMAP) using in-situ gridded data and Argo floats in the South China Sea (SCS). Compared with in-situ gridded data, it shows that the CCI achieved the best performance (RMSD: 0.365) on monthly time scales. The RMSD of SMOS, Aquarius, and SMAP (SMOS: 0.389; Aquarius: 0.409; SMAP: 0.391) are close, and the SMOS takes a slight advantage in contrast with Aquarius and SMAP. Large discrepancies can be found near the coastline and in the shelf seas. Meanwhile, CCI with lower RMSD (0.295) perform better than single satellite data (SMOS: 0.517; SMAP: 0.297) on weekly time scales compared with Argo floats. Overall, the merged CCI have the smallest RMSD among the four satellite products in the SCS on both weekly time scales and monthly time scales, which illustrates the improved accuracy of merged CCI compared with the individual satellite data.Keywords：sea surface salinity (SSS);South China Sea (SCS);Argo;multi-satellite merged data;validation38|4|0Updated：2024-10-12
- Abstract：China’s Bohai Bay has experienced large-scale land reclamation since 2000. These reclamation projects create a nearshore ecological imbalance and shift sediment transport by changing the tidal current. However, these tidal current changes are not comprehensively understood. In this paper, the coastline changes in Bohai Bay due to reclamation are investigated and the responses of the tidal current are calculated through numerical methods. The results show that the coastline length of the bay increases by more than 500 km from 2000 to 2015 with the largest reclamation rate of 150.9 km2/a. Consequently, the current velocity changes with an uneven distribution near the reclamation due to construction masking and dike protrusion. The tidal symmetry also changes in most nearshore areas, with opposite variations in the current velocity at peak flood and ebb tide. In addition, the tide direction deflects to bypass the reclamation and is usually consistent with the coastline. Harmonic analysis of the dominant M2 tidal constituent shows that the range of the reciprocating current is widely extended. The total influence of the reclamation can reach the -8-m isobaths in Bohai Bay. Changes in the tidal current are the main causes of water environment deterioration. Therefore, the arrangement and structural optimization of reclamation projects should be considered in the future.Keywords：Bohai Bay;reclamation;coastline;tidal current16|0|1Updated：2024-10-12
- Abstract：Track density function (TDF) was computed for all Western North Pacific tropical cyclones (WNP TCs) tracks from 1950 to 2018, and the TDFs were further investigated using principal component analysis (PCA) to analyze their inter-annual spatial and temporal variability. Then, the relationships between each empirical orthogonal function (EOF) mode and the typhoon count, typhoon landfall count, track pattern, and the Qinghai-Xizang Plateau snow cover (QXPSC) were examined, and the possible physical mechanisms implied by the statistical relationship were explored. The results show the QXPSC significantly affected the surface-atmosphere heat exchange through snow cover (SC) level, then changed the East Asian summer monsoon regional circulation pattern, influenced the subtropical high-pressure system strength and location, and ultimately affected the WNP TCs track patterns and thus changed their landfall locations.Keywords：Tropical Cyclone;Qinghai-Xizang Plateau snow cover;track pattern;landfall location10|0|0Updated：2024-10-12
Physics
- Abstract：Submarine micro-geomorphology is a geo-morphological type occurring in shallow and surface areas of seabed. The combined relationships and distribution of the micro-geomorphology indirectly reflect coupling relationships among the sediment deposition, dynamic environment, and geomorphologic evolution. Spatial differentiation and dynamic changes in micro-geomorphology were studied based on acoustic data interpretation from a wide range (3 200 km2) of the Huanghe (Yellow) River delta (HRD). The combination of the sub-bottom profiler and the side-scan sonar methods allowed for the identification of submarine shallow micro-geomorphologic types, as well as their scale and spatial distributions. There were seven typical micro-geomorphologic features in the shallow and surface areas of the HRD, including buried ancient channels, stratigraphic disturbances, scour troughs, sand waves, pits, erosional remnants, and sand spots. The coupling and superposition of the sediment, sediment characteristics, seabed scouring and silting, and hydrodynamic conditions of the Huanghe River had combined effects on the patterns of micro-geomorphologic types, characteristics, and ranges. From the perspective of acoustic profile interpretations, the scale, range, and spatial locations of the micro-geomorphology in the HRD revealed seasonal variation characteristics, and the spatial distributions displayed significant regional differentiation characteristics. In addition, strong stratigraphic disturbances and areas with densely distributed buried ancient channels reflected the activity and instability of the submarine shallow strata. Through the interpretation of the sub-bottom profile detection data, the diversion processes of the flow paths in the lower reaches of the Huanghe River were obtained for a certain historical period in the coastal waters of the HRD. This study further clarified the relationships between the micro-geomorphologic features and spatial combinations, which is important for research on micro-geomorphologic features and their dynamic mechanisms.Keywords：Huanghe (Yellow) River delta (HRD);micro-geomorphology;acoustic reflection characteristics;spatial differentiation;dynamic mechanisms11|0|0Updated：2024-10-12
- Abstract：With the consumption of terrestrial metal resources, the exploitation of deep-sea polymetallic nodule minerals has been widely concerned around the world. Therefore, the environmental impact of deep-sea polymetallic nodule mining cannot be ignored. However, duo to the lacks in stable and safe deep-sea (the depth >1 000 m) vertical profile observation systems and consequently in long-term in-situ observation data, the sound speed and dissolved oxygen and the other water environment factors in the deposition areas of polymetallic nodules remains poorly understood. In this study, a deep-sea in-situ observation system was designed and deployed, and the water environment data of the polymetallic nodule deposition area were collected and analyzed. Result shows that the dissolved oxygen in the depth of 0–600 m was mainly affected by biological factors, while that in the area deeper than 600 m was affected by physical factors. The sound speed in the water body was mainly affected by temperature and pressure. At depths below 840 m, the sound speed is mainly controlled by temperature, and at depths between 840 m and 5 700 m, the sound speed is mainly controlled by pressure. The correlations of sound speed vs. pressure and vs. temperature were regressed into equation. The resuspension of sediments rich in various metals may result in the reduction of dissolved oxygen and the improvement of redox potential. This environmental impact caused by a single sediment resuspension could last for 24 h or more. These findings enrich the understanding of the background value of the water environment in the polymetallic nodule deposition area.Keywords：deep sea;dissolved oxygen;redox potential;sound speed;conductivity8|0|0Updated：2024-10-12
Geology
- Abstract：Methane (CH4) and dimethylsulphoniopropionate (DMSP) are major carbon and sulfur sources for bacterioplankton in the ocean. We investigated the characteristics of CH4 and DMSP in the southern Yap Trench from sea surface to hadal zone in June 2017. We found that concentrations of CH4 varied from 1.5 to 4.5 nmol/L with saturation between 94% and 204% in the euphotic layer. Concentrations of dissolved DMSP (DMSPd) ranged from 0.5 to 3.7 nmol/L with higher values in surface water and decreased with depth. Concentrations of particulate DMSP (DMSPp) varied from 0 to 13.6 nmol/L. Concentrations of total DMSP (DMSPt) ranged 2.0–15.2 nmol/L. Their concentrations decreased slightly and reached consistent levels in 200–3 000-m depth due probably to heterotrophic bacterial production in marine aphotic and high-pressure environments. An exception occurred around 4 000-m depth where their concentrations increased considerably and then decreased in deeper water. This previously unrecognized phenomenon sheds light on the elevated concentrations of DMSP in the abyssal layer that might be affected by the Lower Circumpolar Deep Water (LCPW). Concentrations of CH4 in seawater of the Benthic Boundary Layer of the southern Yap Trench were slightly higher than those in the water column at approximate depth, and concentrations of DMSP in seawater of the Benthic Boundary Layer of the southern Yap Trench were not much higher than those in the water column at the approximate depth, indicating that sediment was a weak source of CH4 but was not a source of DMSP for seawater in the study area. This study presented clear correlations between CH4 and DMSP from sea surface to sea bottom, proving that DMSP might be a potential substrate for CH4 not only in oxic surface seawater but also in deep water.Keywords：methane;dimethylsulphoniopropionate (DMSP);hadal zone;Jiaolong submersible;Yap Trench;oceanic methane paradox12|0|0Updated：2024-10-12
- Abstract：2,4,6-Tripyridine-s-triazine (TPTZ) spectrophotometric method was applied to determine the concentrations of dissolved monosaccharides (MCHO), polysaccharides (PCHO), and total carbohydrate (TCHO) in seawater samples collected from sea surface to hadal zone and sediment-seawater interface of the Southern Yap Trench in the Western Pacific Ocean. Results show that the concentrations of MCHO, PCHO, and TCHO ranged from 6.3 to 22.3 μmol C/L, 1.1 to 25.4 μmol C/L, and 12.1 to 44.9 μmol C/L, respectively, from the euphotic layer to the hadal zone of the trench. At different sampling stations, the concentrations of MCHO, PCHO, and TCHO in the seawater showed complex vertical variation characteristics, but the overall variation trends were decreasing with water depth. In the Southern Yap Trench, the maximum concentration of MCHO in the seawater appeared in the euphotic layer, and the minimum in the hadal zone. The maximum concentration of PCHO appeared in the euphotic layer, and the minimum in the bathypelagic layer. The water layer where the maxima and minima of the average concentration of TCHO appeared was consistent with that of PCHO. PCHO was the major component of TCHO in the seawater of the Southern Yap Trench. In the seawater from the sediment-seawater interface, the concentrations of MCHO, PCHO, and TCHO ranged from 8.4 to 10.6 μmol C/L, 3.8 to 5.8 μmol C/L, and 12.2 to 15.2 μmol C/L, respectively, and MCHO was the major component of TCHO. The key factors affecting the concentration and existing forms of dissolved sugars in the seawater of the Southern Yap Trench included photosynthesis, respiration, polysaccharide hydrolysis, adsorption and desorption of particulate matter, trench “funnel effect”, deep ocean currents, sediment resuspension, and etc. This study provided fundamental data about labile organic matter in abyss and hadal zone of marine environment, which is significant for further understanding of deep-sea organic carbon cycle.Keywords：deep sea;Yap Trench;abyss;hadal zone;monosaccharides;polysaccharides9|0|0Updated：2024-10-12
- Abstract：Salt marshes are important carbon and nutrient sinks that are threatened by climate changes and human activities. In this study, the accumulation rates of sedimentary total organic carbon (TOC), total nitrogen (TN), and total phosphorus (TP) from two cores in the Andong salt marsh, Hangzhou Bay, were investigated to determine whether TOC, TN, and TP show increasing or decreasing trends toward the present. The TOC accumulation rates at the relatively lower marsh were lower during 1990–1996 (1.63–2.37 g/(cm2·a)) than 1997–2014 (1.15–4.30 g/(cm2·a)). The TN accumulation rates increased from 1990 (0.14 g/(cm2·a)) toward 2012 (0.40 g/(cm2·a)), then decreased toward 2014 (0.16 g/(cm2·a)). The TP accumulation rates were lower during 1990–1999 (0.10–0.21 mg/(cm2·a)), and decreased from 2000 (0.32 mg/(cm2·a)) toward 2014 (0.15 mg/(cm2·a)). The TOC accumulation rates along the relatively upper marsh during 1982–1992 (1.18–3.25 g/(cm2·a)) were lower than during 1998–2010 (2.30–4.20 g/(cm2·a)), and then decreased toward 2015 (2.15 g/(cm2·a)). TN increased from 1982 (0.18 g/(cm2·a)) to 2005 (0.41 g/(cm2·a)), then decreased toward 2015 (0.22 g/(cm2·a)). TP accumulation rates fluctuated within a narrow range during 1982–1997 (0.21–0.41 mg/(cm2·a)), increased from 1998 (0.50 mg/(cm2·a)) to 2004 (0.87 mg/(cm2·a)), then decreased to 2015 (0.38 mg/(cm2·a)). Thus, increases in accumulation rates of TOC, TN, and TP from the 1980s to 1990s indicates that the marsh likely served as carbon and nutrient sinks, then the rates decreased during 2000–2015 due probably to the reduced sediment inputs from rivers and intensified sea level rise.Keywords：wetland;climate change;anthropogenic activity;marsh degradation10|0|0Updated：2024-10-12
- Abstract：Colloidal particles, heterogeneous mixture with various organic components and continuous molecular weight (MW) distribution, is omnipresent in lake sediments and substantially influence the retention, transportation, and fate of contaminants in lake ecosystem. We sampled and extracted sedimentary colloids from different ecology regions in Taihu Lake, Jiangsu, East China, in June 2020, and they were further separated into four different particle size ranges by tangent ultrafiltration, and the properties of colloids were studied in various methods, including zeta potential analysis, transmission electron micrograph images (TEM), Fourier transformation infrared (FTIR), and 3D fluorescence. Results show that the surface of the colloids is covered with organic macromolecular substances, such as humus-like substances and protein-like substances. There were significant differences in molecular weight and fraction content of colloids in the sediments from macrophyte-dominant (MD) area and algae-dominant (AD) area in the lake. Colloids from MD area are mainly composed of humic acid, protein, and fulvic acid; the content of fulvic acid is lower than that of humic acid and protein. The humic acid exists mainly in small molecular weight (10–100 kDa), protein exists in mainly large molecular weight colloids (0.45–1 μm). Colloids from AD area are mainly composed of humic acid, and mainly distributed in the molecular weight (10 kDa–0.45 μm). The presence of humic acid inhibits effectively the agglomeration of the colloids. Especially, the stability of colloids is closely related to the molecular weight, with low molecular weight from MD area show higher stability. The existence of humic acid in colloids increases the electrostatic repulsion between colloidal particles, which can effectively inhibit the agglomeration of colloids, thus enhancing the stability of colloids. Furthermore, both monovalent and divalent electrolytes enhance colloidal aggregation, and the low-molecular-weight (LMW) colloid fraction exhibits higher stability efficiency than the high-molecular-weight (HMW) colloidal.Keywords：sediment colloid;molecular weight;electrolyte ion;characterization;aggregation behavior8|0|0Updated：2024-10-12
Chemistry
- Abstract：The giant jellyfish Nemopilemanomurai is the largest and most dangerous jellyfish species in East Asian waters, and the N. nomurai bloom causes serious problem in coastal industries, fisheries, and tourism. In the previous surveys, we found N. nomurai could not be observed in the south of 30°N. In this paper, we analyzed the mechanism of this phenomenon. After exploring the possible impacts of different environmental factors, we found that physical processes are essential to the distribution pattern of N. nomurai rather than biological or chemical factors in the East China Sea. The combination of the location of the initial breeding places of N. nomurai and the current system determine the distribution pattern. This study could provide important insights to the potential control of the giant jellyfish in the Chinese coastal waters.Keywords：giant jellyfish;Nemopilemanomurai;distribution pattern;physical process;East China Sea8|0|1Updated：2024-10-12
- Abstract：Western Subarctic Gyre (WSG), which possesses distinctive differences in oceanographic and biogeochemical processes, is situated in the northwest subarctic Pacific. The WSG is characterized by high nutrient and low chlorophyll. We carried out a field investigation in this area in summer 2020 and performed microscopic observation, cytometric counting, and RuBisCO large subunit (rbcL) gene analysis to understand the community structure and spatial distribution of chromophytic phytoplankton better. Microscopic method revealed that total phytoplankton (>10 μm, including Bacillariophyta, Dinoflagellata, Ochrophyta, and Chlorophyta) abundances ranged (0.6×103)–(167.4×103) cells/L with an increasing trend from south to north. Dinoflagellates and Pennatae diatoms dominated the phytoplankton assemblages in the southern and northern stations, respectively. Major chromophytic phytoplankton groups derived from rbcL genes included Haptophyta, Ochrophyta, Bacillariophyta, as well as rarely occurring groups, such as Xanthophyta, Cyanobacteria, Dinoflagellata, Rhodophyta, and Cryptophyta. At the phylum level, Haptophyta was the most abundant phylum, accounting for approximately 30.80% of the total obtained operational taxonomic units in all samples. Ochrophyta and Bacillariophyta were the second and third most abundant phylum, and their relative abundance was 20.26% and 19.60%, respectively. Further, redundancy analysis showed that high proportion of diatoms (e.g., microscopic and rbcL methods) was positively correlated with nutrients (e.g., dissolved inorganic nitrogen (DIN), dissolved inorganic phosphorous, and dissolved silicate (DSi)) and negatively correlated with temperature and salinity. The proportion of Ochrophyta, Rhodophyta, and Cyanobateria identified by rbcL genes was positively correlated with salinity and temperature and showed negative correlation to nutrients. This work is the first molecular study of phytoplankton accomplished in the WSG, and our results show some discrepancies between morphological observation and rbcL gene sequences, which highlight the necessity of combining the microscopic and molecular methods to reveal the diversity of phytoplankton in marine environment.Keywords：flow cytometry;microscopic counting;phytoplankton;rbcL;Western Subarctic Gyre10|0|0Updated：2024-10-12
- Abstract：Based on 10 multidisciplinary investigations conducted from February 2015 to January 2016, the phytoplankton community and its association with ambient seawater physicochemical parameters in the Changjiang (Yangtze) River estuary (CE) and its adjacent waters were comprehensively examined. In total, 265 taxa were identified, belonging to 5 phyla and 94 genera. Diatoms (63.78%) and dinoflagellates (33.21%) were the dominant groups. The variation of diatom abundance showed a positive relationship with the nutrient concentrations while the dinoflagellate abundance showed a negative relationship. Two algal bloom events occurred during the investigation period. The Changjiang Diluted Water (CDW) induced environmental gradients in the upper layer, favoring the diatom bloom in July. The invasion of the nearshore Kuroshio branch current could affect the formation of a bloom of Prorocentrum donghaiense. With the blooming and senescence of phytoplankton, low dissolved oxygen (DO) and hypoxia occurred in the bottom waters. The bottom DO concentration displayed a significantly negative correlation with phytoplankton carbon flux. The present study provides straightforward evidence for the source of organic matter for oxygen consumption in the CE and its adjacent waters.Keywords：phytoplankton;community structure;algal blooms;carbon flux;hypoxia13|1|0Updated：2024-10-12
- Abstract：Phaeocystis is an important bloom-forming species and over 100 blooms have occurred since 1997 along the Chinese coasts, while only the species P. globosa was described. In this project, a total of 246 phytoplankton samples collected from the Bohai Sea, the Yellow Sea, and the East China Sea in April 2021 were analyzed to evaluate the species diversity and geographical distribution of the genus Phaeocystis based on metabarcoding 18S rDNA sequence. Four described Phaeocystis species were recognized, including P. globosa, P. pouchetii, P. jahnii, and P. cordata, and each has distinguished geographical distribution characteristics. P. globosa was the most widespread and abundant species, and P. pouchetii was found in the Bohai Sea and the northern Yellow Sea with substantially elevated abundance. P. cordata was also a widespread species, but its abundance was relatively low, while P. jahnii gathered only in the southeastern East China Sea. Water temperature, phosphate as well as ammonium contents were found to be associated with the abundance of P. globosa, P. pouchetii, and P. jahnii significantly. Moreover, two uncharacterized Phaeocystis species were detected in the Chinese seas, indicating the diversity of the genus remains underestimated worldwide.Keywords：Haptophyta;Phaeocystis;species diversity;distribution;Chinese Seas;amplicon sequence variant8|0|0Updated：2024-10-12
- Abstract：Dolichospermum, a typical model filamentous of cyanobacteria, has the potential to cause severely bloom. Extracellular polymeric substances (EPSs) are considered to influence the aggregation of the algae, and temperature is a significant factor affecting EPSs secretion. However, the mechanism of how EPSs affects the aggregation of Dolichospermum is still unclear because the structure and composition of EPSs are complex. In this study, the effects of EPSs on the aggregation of Dolichospermum during the rise of temperature (7–37 °C) were determined. The results showed that the concentration of extracellular polysaccharides and proteins changed significantly with increasing temperature (P<0.01). Firstly, during the increasing temperature, the polysaccharide content of EPSs increased from 20.34 to 54.64 mg/L, and the polysaccharides in the soluble EPS (S-EPS) layer changed significantly. The protein content reached maximum value at 21 °C (14.52 mg/L) and varied significantly in S-EPS and loosely bound EPS (LB-EPS). In the EPSs matrix, humus substances and protein were main components of S-EPS and LB-EPS, and protein was the main component of tightly bound EPS (TB-EPS). Secondly, the cell density of Dolichospermum increased during the temperature rise while the aggregation ratio decreased. Moreover, zeta potential and surface thermodynamic analysis of Dolichospermum revealed that the interfacial free energy and electrostatic repulsion increased gradually with increasing temperature, which further reduced the aggregation of Dolichospermum. Finally, principal component analysis (PCA) analysis showed the aggregation of Dolichospermum was directly related to the changes of protein in EPSs (especially S-EPS and LB-EPS) and zeta potential, and polysaccharides in EPSs inhibited the aggregation of Dolichospermum. Based on these results, it was illustrated that the composition and concentration of EPSs affected the cell surface properties of Dolichospermum with the change of temperature and thus affected the aggregation of Dolichospermum.Keywords：temperature;Dolichospermum;extracellular polymeric substances;aggregation12|0|0Updated：2024-10-12
- Abstract：Using allelochemicals to suppress cyanobacteria growth is a prospective method for its high efficiency and ecological safety. However, the suppression efficiency is affected inevitably by the extracellular polymeric substances (EPS) produced by cyanobacteria, and the knowledge about the roles of EPS in resistance to allelochemical stress is scarce. For the study, two typical anti-cyanobacterial allelochemicals were adopted to investigate the role of EPS in resistance to allelochemical stress on Microcystis aeruginosa. Results show that EPS was crucial in alleviating the toxicity of allelochemicals to algae, especially in stabilizing the metabolism and photosynthetic activity of algal cells. The aggregation rate of algal cells increased with the increase of EPS secretion, which alleviated the stress of allelopathy. Tryptophan proteins and humic acids in EPS provided a binding site for allelochemicals, and the EPS-allelochemicals complex were formed by chemical bonding. This study improved our comprehension of the role of EPS in algal inhibition by allelochemicals.Keywords：allelochemicals;extracellular polymeric substances;cyanobacteria;Microcystis aeruginosa;allelopathy14|0|0Updated：2024-10-12
- Abstract：The economic alga Neopyropia, which holds significant value in China for its edibility and economic potential, harbors diverse epiphytic bacteria on its surface. The epiphytic bacteria on Neopyropia yezoensis and Neopyropia katadae, two nori species of Neopyropia living at the same tidal level but with distinct physiological states and living habits, were investigated to understand the differences between them and the effects of epiphytic bacteria on their differential characteristics. Analysis of 16S rRNA gene sequences and real-time quantitative PCR (qPCR) of thalli and seawater samples (n=24) revealed notable differences in microbial diversity and community structure between the two species. Bacteroidetes dominated the bacterial communities in association with N. yezoensis, whereas Proteobacteria were predominant in N. katadae. Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt2) analysis revealed enriched genes that related to the ABC transport system, iron complex outer membrane receptor proteins, and proliferation in N. yezoensis, whereas N. katadae exhibited enrichment of genes that related to energy supply as well as cell wall and cell membrane production.The results of qPCR indicate a higher abundance of epiphytic bacteria on surface of N. yezoensis than those on surface of N. katadae. The findings indicate that differences in the living environments of N. yezoensis and N. katadae may result in distinct structural composition and abundance of epiphytic bacteria on their surfaces, thereby conferring specific biological functionalities to each microbial community, and the epiphytic bacteria may shape the living habits of hosts to some extents. This study provided a basis for understanding the close association between surface microorganisms and algal bodies, and the physiological and ecological characteristics of nori species.Keywords：Neopyropia yezoensis;Neopyropia katadae;epiphytic bacteria;16s rRNA;quantitative PCR (qPCR)8|0|0Updated：2024-10-12
- Abstract：The pollution of microplastics (MPs) in the ocean has become a serious matter of concern. The farmed seaweeds (Caulerpa lentillifera and Gracilaria tenuistipitata) were selected to study their ability of adsorption with two typical classes of MPs (polyamides and polystyrene), thereby revealing the interaction between MPs and macroalgae and exploring novel methods of removing MPs from macroalgae. The results demonstrate that polyamides (PA) fibers had no effect on the various physiological parameters of both seaweeds (e.g., relative growth rate, photosynthetic oxygen evolution rate, the contents of malondialdehyde and extracellular polymeric substances) after 7 days of exposure, except for the chlorophyll-a concentration. However, the effects of polystyrene (PS) particles on the algae were strongly associated with the concentration of MPs exposure. Exposed to the high concentration (100 mg/L) of PS particles, the relative growth rate of C. lentillifera and G. tenuistipitata decreased by 54.56% and 30.62%, respectively, compared to the control, while no significant (P>0.05) harmful effect of PS particles on seaweeds was observed in an environment with a low content of PS particles (25 mg/L). The PS particles in concentration of 100 mg/L significantly (P<0.05) inhibited photosynthetic oxygen evolution rate and extracellular polymeric substances (EPS) contents in both seaweeds, but increased malondialdehyde (MDA) contents. When exposed for 72 h, the MPs adhesion rate of G. tenuistipitata is higher than that of C. lentillifera, which might be due to the higher EPS content of G. tenuistipitata. The MPs desorption experiment indicated that the combination of dewatering and washing had the highest desorption rate of MPs which could reach to 91.45% and 87.23% for C. lentillifera and G. tenuistipitata, respectively. This research demonstrates the potential of macroalgae as a vector for MPs in aquatic environment and provides methodological insights into decontamination procedures for removing the MPs from macroalgae.Keywords：decontamination;interaction;macroalgae;microplastics8|0|2Updated：2024-10-12
- Abstract：To understand the effect of regime shift in Caohai Lake in Yunnan-Guizhou Plateau, SW China from submerged macrophyte dominance to phytoplankton dominance on the specification and distribution of phosphorus and on ecological and environmental states, changes in phosphorus specification in the sediments and water were studied. The form, composition, and distribution of phosphorus in sediment were sampled in July 2020 (before regime shift) and July 2021 (after regime shift) were analyzed. Results reveal that phosphorus content in sediment was lower than that those of Erhai Lake and Dianchi Lake, Yunnan, SW China, on the same plateau, and was lower than those of Taihu Lake, Chaohu Lake, and Poyang Lake in the middle-lower Changjiang (Yangtze) River Plain. Organic phosphorus (Or-P) was the main form (up to 60%), followed by inactive phosphorus (Ina-P), and the active phosphorus (Act-P), the least, which is opposite to those of Taihu Lake and Poyang Lake in the middle-lower Changjiang River Plain in the eastern China. Or-P content was high, indicating a high potential risk of phosphorous release. After the regime shift, the total phosphorus in sediment decreased from 0.87±0.13 to 0.70±0.13 g/kg. The proportion of Or-P and Act-P decreased from 68.23% to 65.32% and from 5.35% to 4.69%, respectively. In contrast, the proportion of Ina-P increased from 26.42% to 29.99%. The Moran’s I index revealed that the heterogeneity of the spatial distributions of the total phosphorus (S-TP) and Act-P in the sediments before regime shift was significant (P<0.1). However, the heterogeneity of the spatial distributions of S-TP and the various forms of phosphorus after regime shift was not significant (P>0.05). The regime shift aggravated the eutrophication of the lake, the trophic level index (TLI) increased from 48.42 to 54.49 (P<0.01), and the previously mesotrophic lake became a mildly eutrophic lake. The results of this study revealed the impact of regime shift in the lake from submerged macrophyte dominance to phytoplankton dominance on the composition and spatial distribution of phosphorus in sediments and provided a basis for the restoration of eutrophicated and aquatic ecosystem degraded lakes.Keywords：Caohai Lake;sediment;phosphorus specification;regime shift8|0|0Updated：2024-10-12
- Abstract：Denitrifying bacteria in epiphytic biofilms play a crucial role in nitrogen cycle in aquatic habitats. However, little is known about the connection between algae and denitrifying bacteria and their assembly processes in epiphytic biofilms. Epiphytic biofilms were collected from submerged macrophytes (Patamogeton lucens and Najas marina L.) in the Caohai Lake, Guizhou, SW China, from July to November 2020 to: (1) investigate the impact of abiotic and biotic variables on denitrifying bacterial communities; (2) investigate the temporal variation of the algae-denitrifying bacteria co-occurrence networks; and (3) determine the contribution of deterministic and stochastic processes to the formation of denitrifying bacterial communities. Abiotic and biotic factors influenced the variation in the denitrifying bacterial community, as shown in the Mantel test. The co-occurrence network analysis unveiled intricate interactions among algae to denitrifying bacteria. Denitrifying bacterial community co-occurrence network complexity (larger average degrees representing stronger network complexity) increased continuously from July to September and decreased in October before increasing in November. The co-occurrence network complexity of the algae and nirS-encoding denitrifying bacteria tended to increase from July to November. The co-occurrence network complexity of the algal and denitrifying bacterial communities was modified by ammonia nitrogen (
- Abstract：The co-occurrence of bacteria and microeukaryote species is a ubiquitous ecological phenomenon, but there is limited cross-domain research in aquatic environments. We conducted a network statistical analysis and visualization of microbial cross-domain co-occurrence patterns based on DNA sampling of a typical subtropical bay during four seasons, using high-throughput sequencing of both 18S rRNA and 16S rRNA genes. First, we found obvious relationships between network stability and network complexity indices. For example, increased cooperation and modularity were found to weaken the stability of cross-domain networks. Secondly, we found that bacterial operational taxonomic units (OTUs) were the most important contributors to network complexity and stability as they occupied more nodes, constituted more keystone OTUs, built more connections, more importantly, ignoring bacteria led to greater variation in network robustness. Gammaproteobacteria, Alphaproteobacteria, Bacteroidetes, and Actinobacteria were the most ecologically important groups. Finally, we found that the environmental drivers most associated with cross-domain networks varied across seasons (in detail, the network in January was primarily constrained by temperature and salinity, the network in April was primarily constrained by depth and temperature, the network in July was mainly affected by depth, temperature, and salinity, depth was the most important factor affecting the network in October) and that environmental influence was stronger on bacteria than on microeukaryotes.Keywords：co-occurrence network;cross-domain;network stability;network complexity;subtropical bay8|0|0Updated：2024-10-12
- Abstract：The Western Subarctic Gyre (WSG) is one of the two gyre-systems in the subarctic North Pacific known for high nutrient and low-chlorophyll waters. However, the bacterioplankton in marine water of this area, either in terms of the taxonomic composition or functional structure, remains relatively unexplored. A total of 22 sampling sites from two water layers (surface water, SW and 50-m layer water, FW) were collected in this area. The physiochemical parameters of waters, Synechococcus, and bacterial density, as well as the bacterioplankton community composition and distribution pattern, were analyzed. The nutrient concentrations of DIN, DIP, and DSi, Chl-a concentration, and the average abundance of heterobacteria in FW were higher than those in SW. However, temperature and the average abundance of Synechococcus and pico-eukaryotes were higher in SW. A total of 3 269 OTUs were assigned, and 2 123 OTUs were commonly shared; moreover, similar alpha diversity patterns were observed in both SW and FW. The bacterioplankton community showed significantly obvious correlation with salinity, DIP, DIN, and Chl a in both SW and FW. Proteobacteria, Cyanobacteria, Bacteroidota, Actinobacteriota, and Firmicutes were the main phyla while Synechococcus_CC9902, Psychrobacter, and Sulfitobacter were the dominant genera in each sampling site. Most correlations that happened between the OTUs in the co-occurrence network were positive and inter-module. Higher edges and graph density were found in SW, indicating that more correlations occurred, and the community was more complex in SW. This study provided novel knowledge on the bacterioplankton community structure and the correlation characteristics in WSG.Keywords：Western Subarctic Gyre (WSG);marine water;bacterioplankton;community;co-occurrence network8|0|0Updated：2024-10-12
Ecology
- Abstract：Hildenbrandia is an early diverged lineage in Florideophyceae, Rhodophyta. The species diversity of this genus is still unresolved due to the simple morphology and limited molecular information. The mitochondrial genome of freshwater H. jigongshanensis was determined in this study. The freshwater H. jigongshanensis had a larger mitochondrial genome than the marine H. rubra and GC content was higher. Collinear alignment structure was observed between the mitochondrial genomes of H. jigongshanensis and H. rubra, except for one block that was encoded on the complement strand. More introns were found in mitochondrial genome of H. jigongshanensis than in H. rubra, and H. jigongshanensis shares the common feature with Bangiophyceae that two introns were distributed in cox1. Comparison of mitochondrial genome organization suggests that H. jigongshanensis preserves characters that could be hypothetically more similar to the ancestor of Bangiophyceae and Florideophyceae, which differ with previous studies based on chloroplast, and nuclear markers. More mitochondrial genomes and phylogenetic analyses combing nuclear, chloroplast and mitochondrial genomes are needed to clarify this discrepancy. Mitochondrion-based phylogeny in this study resulted in better solution at both the deep and recent derived nodes than single-gene phylogenies. Most protein-coding genes between H. jigongshanensis and H. rubra were identical except atp8, which was present in H. jigongshanensis while absent from H. rubra. This finding follows the trend that high Ka/Ks ratio genes are more frequently lost than low Ka/Ks ratio ones in red algae.Keywords：red algae;organelle genome;freshwater species;phylogenomics13|1|0Updated：2024-10-12
- Abstract：Species in genus Nannochloropsis, especially N. oceanica and N. gaditana, have been evolving as the model microalgae for both application and theory studies. The position effect of genome integration, the carrying capability limitation of integrative vectors and the instability of non-integrative vectors have hindered Nannochloropsis genetic modification with concatenate genes and extremely long DNA fragments. The molecular tools including genetic transformation, homologous recombination, gene edition, gene stacking and episome vectors for transient gene expression and diverse reporters and selection markers have been rapidly developing in Nannochloropsis species. The construction of animal and plant artificial chromosomes with “top down” strategy has set fine examples for the construction of Nannochloropsis artificial chromosomes (NannoACs). It seems that the methods and materials to set the foundation for constructing NannoACs are at hands. In this review, we outlined the current status of transgenes in Nannochloropsis species, summarized the limitations of both integrative and non-integrative vectors, and proposed a tentative approach to construct NannoACs by doubling and stabilizing the genome first, and then truncating the natural chromosomes. NannoACs once constructed will facilitate transferring the desired traits and concatenate genes into Nannochloropsis genetic backgrounds, thus contributing towards its genetic improvement and synthetic biological studies.Keywords：Nannochloropsis;artificial chromosome;microalgal genetic improvement;gene stacking;concatenate gene;trait transfer9|1|0Updated：2024-10-12
- Abstract：Mitogen-activated protein kinases (MAPKs) play pivotal roles in response to environmental stresses and bacterial infections. Compared with those in the higher vertebrates, studies of mapk gene family are still limited in teleost. Identification, characterization, classification, and expression profiling of totally 15 mapk genes in black rockfish (Sebastes schlegelii) were conducted. Phylogenetic relationships show that these mapk genes could be divided into extracellular signal-regulated kinase (ERK), c-Jun N-terminal kinase (JNK), and p38 sub-families. In addition, gene structures, syntenic analysis, and selective pressure analysis are performed to confirm their annotations. Results of selective pressure analysis indicate that mapk1, mapk3, mapk7, mapk10, mapk11, and mapk12 underwent significantly-positive selections, while the others genes such as mapk4, mapk6, mapk15, mapk8a, mapk8b, mapk9, mapk13, mapk14a, and mapk14b were under purifying selections. Moreover, results of qRT-PCR indicate that mapk genes in 8 healthy tissues displayed different expression patterns. The expression patterns of several mapk genes including mapk12, mapk13, mapk14a, mapk14b, and mapk15 were significantly changed in mucosal tissues after Edwardsiella piscicida infection. This study demonstrates that mapk genes in black rockfish play vital prevention roles against bacterial infection, which not only helps us understand the structure and function of mapk genes in black rockfish, but also provides a reference to understand the role of mapk genes in teleost immune responses.Keywords：Sebastes schlegelii;mitogen activated protein kinases (mapk);Edwardsiella piscicida;expression profiles12|2|0Updated：2024-10-12
- Abstract：Ocean warming is altering the habitats of marine invertebrates, which has resulted in an increased physiological stress to marine molluscs, especially those intertidal bivalves, such as the ark shell Scapharcabroughtonii. We investigated the physiological and transcriptional responses of ark shells to acute and chronic thermal stress results showed that at 33 °C, a significantly higher cumulative mortality (55.7%) occurred under acute thermal stress than chronic thermal stress. The apoptosis rate of hemocytes was sustained at higher levels and the necrosis rate was increased significantly in a time-dependent manner under acute thermal stress. However, under chronic thermal stress, the apoptosis and necrosis rates exhibited similar change trends: a rapid increase followed by a gradual decline and sustained at a relatively high level until the end of the experiment. The expressions of heat shock protein genes (HSP20 and HSP90), apoptosis-related genes (TRAF6, GRP78, NIX, and Casp-3), antioxidative-related genes (GST and MRP) and cellular detoxification-related genes (HbⅡB, NOS-1, HO-1, and ENO-1) were up-regulated significantly under both acute and chronic thermal stresses. These results demonstrated that the anti-apoptotic system, antioxidant defense system, cellular detoxification system, and heat shock proteins (HSPs) played vital roles for ark shells in response to thermal stress. As acute thermal stress can result in irreversible damage to marine molluscs, it is thus advised that chronic thermal stress should be used to select thermal-resistant ark shell strains.Keywords：Scapharcabroughtonii;thermal stress;apoptosis;necrosis;gene expression8|0|0Updated：2024-10-12
- Abstract：Solemyidae is an ancient group of protobranch bivalves, and most solemyids are symbiotic with chemoautotrophic and gill-hosted bacteria, enabling them to survive in unusual habitats such as deep-sea chemosynthetic environments. However, evolution of the mitogenomes in this family and their phylogenetic relationships remain poorly understood. The complete mitogenome of Acharax sp. was determined and compared with other available mitogenomes of solemyids. The mitogenome of Acharax sp. is 18 970 bp in length and consists of 13 protein-coding genes, 2 ribosomal RNA genes, and 22 transfer RNA genes. The gene arrangement was identical to those of other sequenced solemyids. For the present five mitogenomes of Solemyidae species, all protein-coding genes were initiated with the typical ATD (ATA, ATG, and ATT) codon and terminated with the TAA/TAG codon. Furthermore, the incomplete termination codon was detected. The Ka/Ks ratio analyses indicated that 13 protein-coding genes of five Solemyidae mitogenomes suffered strong purifying selection. Compared to 45 existing shallow water equivalents, the 18 available mitogenomes from the deep-sea, including the Acharax sp. in this study, show significantly more nonpolar amino acids in the 13 protein-coding genes, which indicates the adaptation to the deep-sea environment. The phylogenetic tree based on 48 Bivalvia complete mitogenomes provided further information to support the scientific classification of protobranchs. The relationships among Solemyidae were assessed based on 2 mitochondrial (16S rRNA and COX1) and 3 nuclear (18S rRNA, 28S rRNA, and histone H3) gene sequences from 17 in-group species. The two genera Acharax and Solemya formed a monophyletic clade each, and Acharax sp. clustered with previously reported Acharax bivalves with high support values.Keywords：Solemyidae;Acharax;mitogenome;deep sea;adaptation;phylogeny9|2|0Updated：2024-10-12
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Makinoella parva ,Makinoella (Oocystaceae, Trebouxiophyceae, Chlorophyta)Abstract：Makinoella Okada is a genus of coccoid green algae belonging to the family Oocystaceae with typical morphological characteristics. Reports to date included only one type species. Since the genus is rarely reported, there is a lack of taxonomic research. In this study, 17 strains of this genus were collected from several different places in China, and their taxonomic studies were conducted based on morphological and molecular phylogenetic analysis. The phylogenetic results based on the analysis of ITS, chloroplast genes rbcL and tufA showed that the genus was divided into two branches. One of the branches comprised newly collected algae. Compensatory base changes (CBCs) and hemi-compensatory base changes (hemi-CBCs) within the secondary structure of the ITS-2 confirmed the branches as two species. Compared with the type species of Makinoella tosaensis, the cell size of this new branch was only about 50%, and included 2–4 colonial cells. Therefore, based on the smaller cell size, simpler colony composition, independent phylogenetic position and CBCs and hemi-CBCs, we suggest that the new clade should be designated as a new taxon of Makinoella, namely Makinoella parva. Among the four molecular markers using in this study, the rbcL and newly introduced ITS are recommended for species separation, which can help further studies to revise the species and generic concepts of the family.Keywords：coccoid green algae;Makinoella;morphology observation;Oocystaceae;phylogenetic analysis10|0|0Updated：2024-10-12 - Abstract：The xanthid genus Medaeops Guinot, 1967 currently contains seven species reported from the Indo-West Pacific region. However, only one species, Medaeops granulosus (Haswell, 1882), has been recorded from China seas and was once thought to be widespread in the Indo-West Pacific region. In this study, two species of the Medaeops granulosus species-group were identified during the analysis on Medaeops crabs from China seas. Medaeops japonicus (Rathbun, 1898), which had previously been considered a junior synonym of M. granulosus, is shown to be a distinct species that can be distinguished from M. granulosus by the lower first anterolateral tooth, the larger and concentrated granules on carapace dorsally, and the different shape of the male’s first gonopod. In addition, a new recorded species, Medaeops edwardsi Guinot, 1967, was reported from China seas for the first time. A molecular analysis was conducted to determine the status of each species, and an updated key for species of the genus Medaeops was provided.Keywords：euxanthine;Xanthoidea;crab;Decapoda;DNA barcode9|0|0Updated：2024-10-12
Biology
- Abstract：Reproduction is subtlety regulated by the hypothalamic-pituitary-gonad (HPG) axis in vertebrates. Pituitary gland is the center of the HPG axis, while pituitary gonadotropins follicle stimulating hormone (FSH) and luteinizing hormone (LH) were identified the key elements of the HPG axis in teleost and mammal. Morphology, cell lines, and gonadotropins cell localization of female turbot and mouse pituitary were determined at mature stage to illustrate the anatomical difference and cell characteristics in this study. Results show that turbot pituitary is chicken heart-shaped, dorsoventral, located on the ventral surface of the diencephalon. The mouse pituitary is oval, located in the pituitary fossa of the sella turcica at the skull base. Two well-distinguished areas adenohypophysis (AH) and neurohypophysis (NH) in pituitary were identified in turbot and mouse. Turbot AH comprised the rostral pars distalis (RPD), proximal pars distalis (PPD), and pars intermedia (PI). NH was not pronounced and with finger-like protrusions into PPD. However, mouse AH only comprised the pars distalis (PD) and PI. NH distribution was semicircular. Three main types of cells (acidophilic, basophilic, and chromophobic cells) were distributed in the mouse PD region, whereas appeared in the turbot PPD, RPD, and PI. Moreover, the percentage of mouse chromophobic and basophilic cells was higher and lower than that of turbot, respectively. The diameter of the aforementioned three cells in the mouse was significantly higher than turbot. fshβ- and lhβ-immunoreactive signals were identified in turbot-distinct pituitary cells that primarily occupied the peripheral and central regions of AH. However, mouse fsh- and lh-immunoreactive cells were expressed in the same cells and present in the PD. These results demonstrate the significantly difference of pituitary morphology, cell lines and gonadotropins (fshβ and lhβ) location in female turbot and mouse. These differences help for fully understand the evolution and endocrinological functions of pituitary.Keywords：turbot;mouse;pituitary gland;cell line;gonadotropins8|0|0Updated：2024-10-12
- Abstract：Hypoxia has become an unfavorable factor affecting the sustainable development of the large yellow croaker Larimichthyscrocea, an economically important mariculture fish in China. Apoptosis is a consequence of hypoxia on fish. However, the effects of hypoxia stress on apoptosis in L. crocea remain largely unknown. We investigated the effect of environmental hypoxia on apoptosis in L. crocea. Results show that hypoxia induced apoptosis in L. crocea both in vivo and in vitro. The mitochondrial membrane potential was significantly reduced in large yellow croaker fry (LYCF) cells. The expression levels of B-cell lymphoma/leukemia-2 (Bcl-2) mRNA and protein were also significantly decreased in the liver and LYCF cells during 96 h and 48 h of hypoxia stress, respectively, whereas the expression level of Bcl-2 associated X (Bax) mRNA, Casp3 mRNA, and activity of caspase-3/7/9 were significantly increased, indicating that hypoxia induced caspase-dependent intrinsic apoptosis in L. crocea. The expression level of the apoptosis-inducing factor (AIF) protein was significantly increased in the liver and LYCF cells. The level of AIF protein was significantly decreased in the cytoplasm but increased in the nuclei of L. crocea, demonstrating that hypoxia induced the AIF-mediated caspase-independent intrinsic apoptosis. In addition, the activity of caspase-8 was significantly increased, indicating that hypoxia stress induced extrinsic apoptosis in L. crocea. Therefore, hypoxia induced apoptosis in L. crocea through both the intrinsic and extrinsic pathways. The present study accumulated basic biological information to help elucidate the mechanism of hypoxia response in marine fish.Keywords：hypoxia;large yellow croaker;mitochondrial apoptosis pathway;death receptor apoptosis pathway8|0|0Updated：2024-10-12
- Abstract：Information on survival and growth during the early life stage is essential to understand the mechanism of interannual variations in fish recruitment. Chub mackerel Scomberjaponicus is a commercially important pelagic fish widely distributed in the northwestern Pacific. Its catch showed large fluctuations with changes in distribution and migration under climate change and strong fishing. We determined the hatch dates and growth rates of young-of-the-year of chub mackerel through otolith microstructure using samples collected in the Oyashio water in autumn 2018. Results show that the ages of young chub mackerel ranged between 120 and 180 d, and the estimated hatch date lasted from mid-January to late May with a peak from mid-March to mid-April. Average otolith daily increment width during the early life stages (from hatching to 25 d) showed an increasing trend. Chub mackerel grows slowly in the first 10 d, and then grows faster during the 10th to 25th d. Three groups with dissimilar growth histories and migration routes were identified using unsupervised random forest clustering analysis, but all eventually converge on the same nursery ground. The faster growth of young-of-the-year chub mackerel leads to better recruitment due to the hypothesis of growth-dependent mortality. Most chub mackerels hatched in March and April, the spawning period is longer and earlier, which could lead to strong year classes. These findings on population composition and life history traits of young-of-the-year of chub mackerel provide valuable information on its recruitment processes during the period of stock recovery.Keywords：Scomberjaponicus;otolith microstructure;growth history;unsupervised random forest clustering;recruitment10|0|0Updated：2024-10-12
Aquaculture and Fisheries
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