Issue Ebook
cover story
Latest Issue
Volume 42 ， Issue 6 ， 2024
-
- Abstract：Large and shallow lakes are widely influenced by multiple anthropogenic stressors, including eutrophication. Normally, diverse strategies of eutrophication management are needed to restore the lake ecosystems. Dianchi Lake, a subtropical plateau lake in Yunnan Province, SW China, has long experienced the effects of eutrophication and cyanobacterial blooms. To mitigate the eutrophication of Dianchi Lake, various efforts have been implemented since 2000, including reducing nutrient inputs, re-establishing aquatic macrophytes in lakeside zones, manipulating fishes and so on. However, little is known about the changes in its ecosystem structure and function after long-term efforts of eutrophication management in the lake. Therefore, this study on such changes was conducted by comparing the field data-based Ecopath models between 2009 and 2019, a decade marked by a rapid implementation of eutrophication management policies. Results show that both top-down and bottom-up processes have influenced the ecosystem structure and function. First, over this decade, nutrient reduction significantly reduced phytoplankton biomass by 49.4%. Nutrient recycling and path length in food web began to decrease, as indicated by the decrease of Finn’s cycling index and Finn’s mean path length. Secondly, fishing management strategy has greatly changed the composition of fish assemblage, which was dominated by the small zooplantivorous fishes with ecological niche overlapping with shrimps. In general, the stability of the ecosystem has been decreasing, due to the dramatic decrease in zooplankton biomass (83.67%) and hence a collapse of the microbial loop in the food web. Therefore, we strongly advocate the persistent efforts to mitigate the risk of recurrent cyanobacteria blooms in Dianchi Lake, necessitating stricter regulation of nutrient levels and implementing effective fish population management techniques.Keywords：Dianchi Lake;Ecopath;ecosystem property;cyanobacterial bloom;nutrient reduction;fish manipulation36|15|0Updated：2024-12-24
- Abstract：Lake Kasumigaura, the second largest lake in Japan, has faced water quality challenges since the 1970s owing to rapid economic growth, land use changes, and increased wastewater discharge. Moreover, severe cyanobacterial blooms, particularly those of Microcystis, were observed in the 1980s, emphasizing the urgent need for comprehensive ecological monitoring. We present the results of phytoplankton monitoring by the Ibaraki Kasumigaura Environmental Science Center (IKESC) since 2005 and the publication of information on cyanobacterial blooms for citizens since 2012. Our monitoring surveys identified distinct phytoplankton communities in Nishiura and Kitaura, the two main water bodies of Lake Kasumigaura, emphasizing the need for monitoring surveys at various sites in Lake Kasumigaura. Analysis of long-term phytoplankton data from the Lake Kasumigaura Database (National Institute of Environmental Studies, NIES) revealed that Planktothrix is the predominant cyanobacteria in Lake Kasumigaura. At IKESC, we have responded to these potentially socially problematic phytoplankton blooms by releasing the “Bulletin of Cyanobacteria Blooms” in 2012 and the “Bulletin of Cyanobacteria Forecast” in 2020.Keywords：Microcystis;Planktothrix;monitoring;Nishiura;Kitaura;bulletin for citizens18|14|0Updated：2024-12-24
- Abstract：This study investigates the variations of microcystins (MCs) in water, cyanobacterial blooms, sediment, and aquatic organisms collected from the Dau Tieng Reservoir (DTR). Vietnam. High-performance liquid chromatography (HPLC) was employed to measure MC concentrations in various target samples. Results indicate that Microcystis spp. dominates as the primary MC producer in the DTR. The average concentrations of analyzed MCs in surface water ranged from 1.10 to 5.54 µg/L, temporally and spatially. In sediment, average concentrations varied from 0.15 to 1.13 µg/g wet weight (WW) temporally and from 0.41 to 0.72 µg/g WW spatially. MCs were detected in different organs of fish species (Oreochromis sp. and Labiobarbus sp.) and in the entire soft tissues of bivalve (Corbicula sp.) and gastropod (Assiminea sp.). The highest observed MC concentration in July was 0.83±0.22 µg/g WW in the intestines of fish Oreochromis sp. The presence of MCs in grass shrimp Palaemonetes sp. was observed solely in June, reaching a concentration of 0.28±0.19 µg/g WW. This is the first report of MC accumulation in the grass shrimp Palaemonetes sp. during field collection. For the bivalve Corbicula sp., the presence of analyzed MCs was consistent throughout the study period, except for March and September, with the highest concentrations in July at 0.77±0.1 µg/g WW. Pearson correlation analysis revealed significant positive correlations between MCs in water and sediment with MC concentrations in aquatic animals, indicating the potential transfer of MCs across different trophic levels. The estimated daily intake values for analyzed MCs indicate that fish collected from the DTR are considered safe for consumption, as long as only the edible organs, such as the muscle, are consumed. However, bivalves or gastropods collected from the DTR are not safe for human consumption. This study underscored the importance of monitoring MC accumulation in aquatic animals used as food to mitigate adverse effects on human health.Keywords：aquatic animal;bioaccumulation;cyanotoxin;health risk;toxic cyanobacteria21|14|0Updated：2024-12-24
- Abstract：Phytoplankton functional groups have gained increasing attention in recent years. To understand the composition of phytoplankton functional groups in Poyang Lake and their drivers, field investigations were conducted over three years: 2013, 2014, and 2016. Phytoplankton were dominated by diatoms, contributing from 20.19% to 57.57% of the total biomass, followed by cyanobacteria, 9.81%–39.98%. Microcystis sp. and Anabaena sp. were the dominant species among cyanobacteria. Twenty-six functional groups were identified among 72 genera or species, and fiver groups (P, B, MP, H1, and G) were categorized dominant. All of dominant groups except H1 were tolerate highly fluctuating mixing intensities and showed a typical monthly succession variation. Water temperature, water level, and nutrients are key drivers for the variation of phytoplankton communities at taxonomic and functional levels. Both of redundancy and variation partitioning analyses showed that environmental variables might explain functional groups better than taxonomic communities, implying that the functional groups were more advantageous in showing the effects of environmental conditions than taxonomic compositions. Hydrological conditions have a crucial influence on phytoplankton assemblage dynamics in highly variable water regime lakes, but not in the largest ones. The functional groups method is suitable for identifying the spatial and seasonal characteristics of aquatic environments that significantly affected by water regimes.Keywords：cyanobacteria bloom;light availability;nutrients dilution;water level;Poyang Lake20|15|0Updated：2024-12-24
- Abstract：Dolichospermum spp. and Microcystis spp. are two common cyanobacteria that form blooms in the Changjiang (Yangtze) River basin, but the environmental conditions for their succession in large lakes are still unclear. Based on daily monitoring data from Meiliang Bay in Taihu Lake from March to June, 2016–2018, we studied the environmental conditions necessary for the succession of these two cyanobacteria. Results show that from March to June, the dominant genera of cyanobacteria experienced succession and co-dominated with Microcystis. The succession process included three stages. In Stage Ⅰ, the biomass of Dolichospermum and Microcystis was similar (March), but Dolichospermum was dominant for most of the period. In Stage Ⅱ, dominance alternated between Dolichospermum and Microcystis (April to mid-May). In Stage Ⅲ, the biomass of Microcystis dominated (mid-May to June). In addition, temperature and nutrients across the three stages varied significantly. The average temperature increased continuously from 10.9 to 18.4, and to 24.2 °C. The total nitrogen content decreased from 2.87 to 2.40, and to 1.86 mg/L. The total phosphorus content increased from 0.08 to 0.09, and to 0.12 mg/L. Correlation analysis revealed that Microcystis biomass was positively correlated with temperature and total phosphorus. Dolichospermum biomass was positively correlated with total nitrogen. Classification and regression tree displays that when the temperature was below 18.1 °C, Dolichospermum dominated; above 18.1 °C, Microcystis took over. Further analysis revealed that when temperature reached 18 °C, the biomass of Microcystis increased exponentially, and the biomass of Dolichospermum exhibited a Gaussian distribution trend. This finding indicated that temperature was the key factor in the succession of Dolichospermum and Microcystis in nutrient-rich shallow lakes. As nitrogen and phosphorus concentrations decrease, the dominant species of cyanobacteria will diversify its development. The results of this study provide a foundation for risk prediction and control strategies for cyanobacterial blooms in lakes and reservoirs.Keywords：shallow lake;cyanobacteria bloom;advantage genera;meteorological condition;nutrient26|13|0Updated：2024-12-24
- Abstract：Taste and odor compounds (T&Os), which is often associated with plankton in water sources, pose significant challenges to water quality in the world. Identifying the potential producers and understanding the driving factors are critical for effective treatment. While most studies focused on outbreak of T&Os linked with summer cyanobacterial blooms, questions remain about the mechanisms and environmental factors driving spring outbreaks when cyanobacteria are typically in low abundance. Therefore, changes in the concentrations of T&Os, i.e., 2-methylisoborneol (2-MIB) and three others, in relation to the phytoplankton community, the physico-chemical and hydrological conditions in a mesotrophic reservoir surrounded by hills in East China were investigated from March to June 2023.Results show that 2-MIB was the main T&O during the spring outbreak of phytoplankton, and peaked at 96.10 ng/L, which is nearly 10 times of its odor threshold concentration (OTC) of 10 ng/L. The filamentous cyanobacterium Pseudanabaena sp. was identified as the primary producer of 2-MIB, and the cell concentration of 4 000 cells/mL of Pseudanabaena sp. could potentially result in 10 ng/L of 2-MIB in this reservoir. The abundance of Pseudanabaena sp. and 2-MIB were correlated significantly with turbidity, suggesting that a lower light environment might be critical to promote the dominance of Pseudanabaena sp. and the subsequent production of 2-MIB. Moreover, the combination of consistently decreased water level, moderate water stratification, optimal water temperature ranging ~14–23 °C, the increase of the chemical oxygen demand using permanganate as an oxidant (CODMn) and total nitrogen (TN) concentration were likely to drive the accumulation and outbreak of 2-MIB. The hydrodynamic disturbance (i.e., a sudden rapid flow of water) triggered the abrupt disappearance of both Pseudanabaena sp. and 2-MIB. This study suggests that proliferation of Pseudanabaena sp. in spring is important in contributing to 2-MIB outbreak, and flushing may be an effective approach to mitigate T&O issues in water sources.Keywords：2-methylisoborneol (2-MIB);cyanobacteria;hydrodynamic disturbance;Pseudanabaena sp.;thermal stratification21|14|0Updated：2024-12-24
- Abstract：Microcystinase (MlrA) is a key endopeptidase that catalyzes microcystin degradation without generating harmful byproduct. However, the application of MlrA in the field is primarily impeded by its limited productivity and short lifespan. Therefore, the MlrA’s function was studied by modelling its structure, which subsequently increased its heterologous expression and high-temperature stability. Results demonstrate that after the irregular sequence at the C-terminus of MlrA was removed, enzyme solubility was significantly decreased. In addition, three fusion tags, namely maltose-binding protein, glutathione S-transferase (GST), and N-utilization substance A (NusA) were used to enhance the overexpression of soluble recombinant MlrA, among which NusA-MlrA exhibited the highest solubility. Moreover, NusA-MlrA was active in pH 4–10 at 20–80 °C; even at 80 °C, approximately 35.8% of fusion protein remained active. NusA-MlrA retained 89% of MlrA’s activity even after 7 d of storage at 50 °C; and on day 7, the protein retained >90% of its activity at pH 7. Finally, a stable, soluble, and long-lasting heterologous MlrA was successfully constructed that could eliminate microcystins in Escherichia coli C43 (DE3). This study enriched the comprehension of MlrA’s structure and enzymatic properties, by particularly addressing the endopeptidase’s low expression and short lifespan, which improved its suitability for future applications.Keywords：microcystinase (MlrA);biodegradation;microcystin;Alphafold2;N-utilization substance A (NusA)-MlrA15|12|0Updated：2024-12-24
- Abstract：Using the Widdel medium with extracted microcystin (MC) as the sole carbon and nitrogen sources, the MC-degrading bacteria community S6 was enriched from the sediment of Litopenaeus vannamei pond, and a novel MC-degrading bacteria strain was isolated from S6. According to 16S rDNA gene sequence and biochemical characteristics, the isolated strain was identified and named Nitratireductor aquimarinus D1. Fulvic acid (FA), as a widely existing photosensitizer involved in MC photodegradation, coexists with MC-degrading bacteria in natural water. The synergistic effects of N. aquimarinus D1 and FA on MC degradation were evaluated via comparing the degradation rate of MC induced by N. aquimarinus D1 and FA alone and in combination under natural light conditions. Compared with the control group, the supplementation of N. aquimarinus D1 and FA alone or in combination could significantly increase the degradation rate of MC (P<0.05). In the first 36 h, the degradation effect of FA on MC was better than that of N. aquimarinus D1, but the degradation effect was opposite at 48 h. N. aquimarinus D1 and FA did not show synergistic effect on MC degradation until 48 h. In the application of N. aquimarinus and FA to degrade MC in aquaculture pond, there might be a time-lag effect in the synergistic degradation.Keywords：synergistic degradation;microcystin;N. aquimarinusD1;fulvic acid17|19|0Updated：2024-12-24
- Abstract：Aeration induced turbulence was considered as an important measure to control the occurrence of cyanobacterial blooms in many lakes. Different aeration intensities were set for the culture of Microcystis aeruginosa based on the formation of Microcystis colony at high iron concentrations. The turbulent dissipation rate was calculated using a computational fluid dynamics (CFD) model to evaluate the intensity of turbulence. The effects of turbulence on the formation of Microcystis colony and the release of microcystin were analyzed. Results show that turbulence produced by aeration promoted the growth of Microcystis compared to that in stagnant water. Low intensity turbulence (4×10-8–1×10-7 m2/s3) promoted the formation of Microcystis colonies, but high intensity turbulence (1.28×10-6–1.8×10-5 m2/s3) did not. The increase in the number of cells per colony was slower than that in total biomass, indicating that the low intensity turbulence induced colony formation via cell division, while the high level turbulence disaggregated colonies formed by both cell division and cell adhesion. Low aeration intensity induced more production of reactive oxygen species (ROS) and malondialdehyde (MDA) in the cells of Microcystis than those in high aeration intensity. In addition, the content of microcystin (MC)-LR in the cells was positively correlated with turbulence intensity, showing that turbulence affected not only the growth and aggregation of Microcystis colonies but also their toxin production. These findings provide a better understanding of the cyanobacterial bloom formation mechanisms and help to propose feasible methods to prevent the formation of Microcystis colonies in a natural environment.Keywords：aeration;turbulent;Microcystisaeruginosa;colony;microcystin20|5|0Updated：2024-12-24
- Abstract：Genus Microcystis is the most common dominant species of bloom-forming cyanobacteria. Growth and colony formation are critical processes for the occurrence of Microcystis blooms. To identify allelochemicals that can inhibit the growth and colony formation of Microcystis, Microcystis aeruginosa was cultivated and treated with various concentrations of gramine, catechol, berberine, and sanguinarine in laboratory. Results indicate that the growth, colony formation, and extracellular polysaccharides (EPS) content of Microcystis were significantly inhibited when treated with gramine, catechol, and berberine in appropriate concentrations at high iron level (6.8 mg/L). Microcystis growth was inhibited and colony formation and EPS content were promoted when treated with sanguinarine at high iron level. These findings suggest that cyanobacterial blooms can be controlled by regulating the input of gramine, catechol, and berberine. Furthermore, this study revealed that plant allelochemicals could affect the growth and morphology of algae in aquatic ecological restoration, which may be potentially important for improving water quality.Keywords：algal bloom;Microcystis;colony;plant allelochemicals;ecological restoration14|12|0Updated：2024-12-24
Special Section: Scientific control of cyanobacterial blooms and their secondary hazards
- Abstract：Deep-sea mining may disturb the water column environment, including the surface water and deep-sea, and these disturbances should be carefully treated. Remote sensing provides high-resolution and accurate long-term observations in the area around deep-sea mining. Discharge from mining ships can be identified within few days from satellite observations based on changes in reflectance. A pioneer two-month experimental deep-sea mining cruise was conducted by The Metal Company in the eastern Pacific Ocean from September 15 to November 17, 2022. A report from Greenpeace indicated incidents of surface discharge and leakage during this mining experiment. In this study, satellite observations captured a clear signal over the surface water from September 24 to October 28, indicating the location with discharged water from the mothership. The number of pixels where the potential discharged water was identified in the satellite imagery ranged from 4 to 13. The discharged water was transported by the combined effects of wind and currents, locating continuously to the downwind side of the mothership’s mooring location. Remote sensing provides a timely and accurate monitoring system for tracking water discharge during deep-sea mining.Keywords：remote sensing;deep-sea mining;chlorophyll-a concentration;water discharge;environmental monitoring18|5|0Updated：2024-12-24
Physics
- Abstract：Human perturbations such as dam regulation have led to significant changes in nutrient flux, structure, and spatiotemporal distribution through rivers and have greatly influenced coastal and estuarine ecological environments. Based on the data from 2001–2019, the impacts of the water-sediment regulation scheme (WSRS) in the Huanghe (Yellow) River on nutrient concentrations, forms, fluxes, and potential ecological effects on the Huanghe River estuary and Bohai Sea were analyzed. Nutrient concentrations and forms were significantly influenced by the different regulatory modes and were associated with hydrological and biogeochemical processes. The concentrations and forms of nutrients were strongly influenced by the riparian floodplains and scouring process of the downstream riverbed at the water draining stage, while they were influenced mainly by the mixing process in the Xiaolangdi Reservoir at the sediment desilting stage. Compared with those in non-WSRS years, the seasonal distributions of water discharge and nutrient fluxes in WSRS years significantly changed, with peaks occurring at least one month earlier than those in non-WSRS years. Nitrate (NO3-N), phosphate (PO4-P), and silicate (SiO3-Si) fluxes during the WSRS, which were strongly controlled by water discharge at Lijin (the nearest hydrological station to the river mouth), accounted for more than 20% of the annual fluxes; these fluxes were more than 5–9 times greater than those during the same period in non-WSRS years. WSRS exacerbated nutrient imbalances and increased Pyrrophyta/Bacillariophyta ratios by 231% in the Huanghe River estuary, resulting in chlorophyll-a peaks in the Bohai Sea shifting from spring to autumn in the 20th century to spring-summer in the 21st century.Keywords：water-sediment regulation scheme;nutrient form;nutrient flux;ecological effect;Huanghe (Yellow) River7|12|0Updated：2024-12-24
Chemistry
- Abstract：Hypoxia may cause severe disturbances to coastal ecosystems. The potential effects of summer hypoxia on zooplankton communities in Sishili Bay, China, was investigated in three cruises conducted during the summer from 2015 to 2017. Comparative analysis was performed on zooplankton communities at hypoxic and normoxic sites. Results show that the number and abundance of zooplankton species at hypoxic sites were lower than those at normoxic sites. Copepods exhibited greater dominance at the hypoxic sites compared to the normoxic sites, suggesting a higher tolerance to low oxygen concentrations than other taxonomic groups. Specifically, Oithona spp. was particularly prevalent at hypoxic sites and displayed a negative correlation with dissolved oxygen concentration at sea bottom. Additionally, the zooplankton community at hypoxic sites also exhibited lower Shannon-Wiener diversity and Margalef richness indices. The normalized biovolume size spectrum of the hypoxic sites showed steep slopes, suggesting a shift towards smaller species and lower transfer efficiency in pelagic food webs for the zooplankton community.Keywords：summer hypoxia;zooplankton community;comparative analysis;Sishili Bay12|9|0Updated：2024-12-24
- Abstract：The ecosystems in Southern Ocean (SO) are undergoing significant changes in the context of climate change. To identify environment-phytoplankton feedbacks in SO, seawater samples were collected in the Cosmonaut Sea (CS) during the 37th China Antarctic Research Expedition (Jan. 2021) (CHINARE-37) and subjected to analysis of particulate organic carbon (POC) and phytoplankton pigments. The remote sensing data, CHEMTAX community compositional modeling analysis, and physicochemical measurements were combined to explore the spatial variation of phytoplankton crops, taxonomic composition, and their environmental drivers. Historical phytoplankton community data from the area were also compared against those of this study to investigate inter-annual community differences and their potential causes. The column-integrated POC and chlorophyll-a (Chl-a) concentrations were 12.0±4.9 g/m2 and 73.8±50.5 mg/m2, respectively. The two most dominant taxa were haptophyte that are adapted to high Fe availability (Hapt-HiFe, mainly Phaeocystis antarctica) and Diatoms-A (Phaeodactylum tricornutum) that contributed to 33%±25% and 24%±14% to the total phytoplankton crops, respectively. Through cluster analysis, the study area was divided into two regions dominated by Hapt-HiFe and Diatoms-A, respectively. Spatially, Hapt-HiFe was mainly concentrated in the southwest coastal area that featured low temperatures, low salinity, and shallow euphotic zones. The coastal region southwest of the southern boundary of the Antarctic circumpolar current was experiencing a bloom of Hapt-HiFe during the study period that significantly contributed to the POC pool and Chl-a concentrations (R=0.46, P<0.01; R=0.42, P<0.01). Besides, the dominance of Hapt-HiFe in the CS suggests a high biological availability of dissolved Fe that is primarily associated with inputs from sea ice melt and upwellings.Keywords：Cosmonaut Sea;particulate organic carbon;phytoplankton crops;phytoplankton taxonomic composition;pigment;sea ice17|14|0Updated：2024-12-24
- Abstract：To understand the distribution of phytoplankton functional groups (PFGs) and key factors on their compositions in different watersheds of the Huanghe (Yellow) River basin, 25 river sites and 25 lake-reservoirs sites were selected. The contents of nephelometric turbidity (NTU), total nitrogen (TN), and total phosphorus (TP) were significantly higher in rivers than that in lakes or reservoirs, whereas the pH and CODMn (chemical oxygen demand or potassium permanganate index) were lower. Results show that, 27 PFGs, namely, assemblages A, B, C, D, E, F, G, H, J, K, LM, Lo, M, MP, N, P, S1, S2, T, TC, W1, W2, X1, X2, X3, XPh, and Y, were identified. Additionally, ANOSIM correlation analysis demonstrated significant differences in PFG composition between the riverine and lake-reservoir sections in the Huanghe River basin. In the riverine watersheds, the group MP was dominant, while assemblages B and J were prevalent in lakes and reservoirs. The Mantel correlation tests and RDA analysis showed that environmental variables, such as NTU, water temperature (WT), conductivity (Cond), and TP, were key driving factors of shaping the dominant PFGs of the study area. Using the Venn diagram based on variation partitioning analysis, PFGs were mainly influenced by WT and TP in lake-reservoir sites, while in the river sites were affected mainly by geo-climatic variables. This study helps understanding the PFGs in river ecosystems, and unraveling the key driving factors in different watersheds, which shall be important for the protection and management of entire Huanghe River basin.Keywords：Huanghe River;phytoplankton functional group;driving factor;riverine watershed;lake-reservoir region10|4|0Updated：2024-12-24
- Abstract：Understanding the relative impact of nutrients and related environmental variables on phytoplankton biomass changes in urban rivers is important for river management. In this study, we explored the long-term dynamic changes and driving factors of phytoplankton biomass in the process of urbanization from the perspective of time and space, and provided a scientific support to water ecological health assessment and management of urban rivers. From 2012 to 2021, the phytoplankton community composition in Taiyuan section of Fenhe River was found to be dominated by Cyanophyta, Chlorophyta, and Bacillariophyta. Among them, cyanobacteria were the main contributors to the total abundance, green algae ranked second, and diatoms were the least. The biomass of phytoplankton in different groups showed different decreasing trends. Based on 10 environmental factors to explain the changes of three main phytoplankton groups (cyanobacteria, green algae, diatoms), we found that chemical oxygen demand and water temperature had a high explanation rate for the abundance changes of the three main phytoplankton groups, which were important environmental factors affecting their biomass changes. The random forest model was used to analyze the changes in the total biomass of phytoplankton. It was found that the permanganate index had a higher contribution to the total biomass of phytoplankton in time. The contribution of air temperature to the total biomass of phytoplankton was higher in space.Keywords：phytoplankton biomass;environmental factor;urbanization13|2|0Updated：2024-12-24
Ecology
- Abstract：Assessment of population parameters and genetic diversity is critical for the economic and threatened species, including Oreochromis mossambicus. The morphometric and population parameters data for O. mossambicus were extracted based on the available literature from various countries. Phylogenetic and genetic diversity were analyzed based on cytochrome c oxidase Ⅰ (COⅠ) sequences of the mitochondrial DNA (mtDNA) gene. The population parameters (asymptotic length (L∞), growth constant (K), growth performance index (Ø), approximate maximum age (tmax), standard length (L), and weight (W)) results revealed a variation among the populations studied. The result categorized the population into two groups: South African populations located close to Zimbabwe, Mozambique, Namibia, Australia, and China, as Group Ⅰ, and the Indian population placed close to Thailand, the Philippines, Indonesia, America, and Mexico as Group Ⅱ. The meta-regression results reveal that temperature strongly correlated with weight. In contrast, other population factors showed no significant differences. The haplotype analysis based on COI of mtDNA displayed 21 haplotypes, which revealed low nucleotide (π=0.025) diversity. Haplotype diversity (HD) was 0.65. The haplotype analysis showed that Tajima (D) was negative (0.82) and Fu’s Fs was positive (2.2), and both tests were not significant (P>0.05), whereas the overall F-statistic (Fst) value was 0.40 (P<0.001). In conclusion, population parameters, and genetic analysis indices a high variation among the O. mossambicus from different locations. Additionally, the population parameters for O. mossambicus in America, Asia, and Australia were more influenced by ecological factors. At the same time, the population parameters in the African continent were influenced more by genetic factors.Keywords：tilapia fish;meta-regression;genetic diversity;mitochondrial DNA;population parameter;Oreochromismossambicus9|5|0Updated：2024-12-24
- Abstract：The growth and nutrients of photosynthetic organisms are significantly influenced by light spectra, yet this relationship is not well-understood in microalgae. Herein, we studied three microalgae species—Chaetoceros sp., Isochrysis galbana, and Tetraselmis helgolandica—distinguished by their pigments. We exposed them to seven light spectra, including white (control), red, orange, green, blue, violet, and full spectrum. The results showed distinct responses in the three microalgae to varying light spectra. Optimal growth occurred under blue, violet, and white lights for Chaetoceros sp., I. galbana, and T. helgolandica, respectively, while orange, red, and green lights inhibited growth. Notably, green light significantly increased the protein content in all three microalgae. Carbohydrate and lipid content exhibited species-specific responses: the highest carbohydrate accumulation was achieved for Chaetoceros sp. under red light (73.27±1.45 mg/g), I. galbana under orange light (122.89±12.28 mg/g), and T. helgolandica under blue light (43.62±2.79 mg/g). Meanwhile, the highest lipid content was obtained under violet light for Chaetoceros sp. and I. galbana (250.80±7.27 and 320.23±5.75 mg/g, respectively), and under green light for T. helgolandica (255.12±31.19 mg/g). Furthermore, violet light greatly promoted the accumulation of polyunsaturated fatty acids in all three microalgae. Specific pigment compositions also responded to variations in light spectra. For instance, the diadinoxanthin content in Chaetoceros sp. increased significantly under orange light (194.77±13.78 µg/g), while chlorophyll-a content in I. galbana increased significantly under violet and blue lights ((88.84±33.46)–(141.38±1.64) µg/g), and in T. helgolandica under red, green, and blue lights ((1 485.04±190.46)–(1 886.60±387.42) µg/g). Additionally, I. galbana exhibited the highest fucoxanthin, diadinoxanthin, and β-carotene contents under white light. In conclusion, our results highlight the species-specific impact of light spectra on microalgae growth and nutrients, providing valuable guidance for flexible application of light spectra in microalgal production to enhance yields and target specific nutrients.Keywords：microalgae;light spectrum;growth;biomass composition;fatty acids;pigment11|4|0Updated：2024-12-24
- Abstract：Marine natural products offer a promising source in the development of new antibiotic drugs. Two previously undescribed compounds, including one sulfur-bearing alkaloid named quinosumycin (1) along with one chromone derivative namely chromycone (2), were discovered from an ethyl acetate (EtOAc) extract of marine Streptomyces diastaticus NBU2966 through a bioactivity-guided isolation prioritized for antimicrobial potential. The analysis of nuclear magnetic resonance (NMR) spectroscopy, high resolution electrospray ionization mass spectroscopy (HRESIMS) data, and electronic circular dichroism (ECD) calculations enabled the elucidation of their structures and the determination of their absolute configurations. Quinosumycin (1) is the first heterodimer scaffold incorporating quinolinone and quinazolinone motifs coupled by a thioether bond. Interestingly, Compound 1 exhibited a relatively selective growth inhibition against methicillin-resistant Staphylococcus aureus (MRSA) with the minimal inhibitory concentration (MIC) value of 8 μg/mL.Keywords：marine natural product;marine Streptomyces;thioether;alkaloid;heterodimer;anti-methicillin-resistant Staphylococcus aureus (anti-MRSA)12|3|0Updated：2024-12-24
- Abstract：Alginate oligosaccharides (AOS) and fucoidan are two important bioactive carbohydrate which that can be prepared from brown seaweeds. We investigated a novel enzyme-assisted one-pot method on AOS and fucoidan extraction from Lessonia trabeculata, and found that the optimum extraction procedure was: first, using 10-g/L Na2CO3 solution to digest the seaweeds for 2 h at 80 °C with the material-liquid ratio 1꞉20 (g/mL), and then adding 4.0% fucoidan cleavage enzyme for reaction for 12 h at 45 °C. The yield of AOS and fucoidan was 21.36% and 14.40%, respectively, which was higher than those using traditional methods. The degree of polymerization of AOS was determined to be 3–5, confirming the results through thin layer chromatography (TLC) and electrospray ionization mass spectrometry (ESI-MS). The ratio of guluronic acid to mannuronic acid in AOS was found to be 1.97. Through anion-exchange column chromatography, four sulfated polysaccharide fractions (F0.5, F1.0, F1.5, and F2.0) were successfully isolated from fucoidan. Chemical analysis revealed that fucoidan and F0.5 were heteropolysaccharides, consisting mainly of mannuronic acid, fucose, and xylose, while the other fractions were predominantly composed of fucose and galactose. The sulfate group content increased from 8.74% to 18.76%, while the uronic acid content decreased from 23.79% to 5.58% across the fractions. All fractions of fucoidan exhibited significant antioxidant activity in various tests. There was a positive correlation between the sulfate content and the ability to scavenge superoxide radicals. Additionally, both AOS and the fucoidan fractions showed immunostimulation activity and were non-toxic to RAW264.7 cells. These results indicate that the novel enzyme-assisted one-pot method is a green and efficient approach for the extraction of fucoidan and alginate oligosaccharides from brown seaweeds. It has potential applications in the processing industry of brown seaweeds.Keywords：Lessoniatrabeculata;alkaline digestion-enzymatic hydrolysis;alginate oligosaccharides;fucoidan;antioxidant activity10|11|0Updated：2024-12-24
- Abstract：The marine green algae genus Chaetomorpha is a common source of “green tide” and is widespread on coasts around the world. In this study, based on invasive Chaetomorpha valida collected from the Shandong Peninsula, the morphogenesis and reproductive characteristics of two strains that are morphologically different from each other, were observed using experimental biology methods. The main results are as follows: (1) significant difference in the size of reproductive cells produced by Strains 1 and 2; (2) gametes produced by Strain 2 are isogamous and same gametangial during the binding process of gametes, whereas those of Strain 1 are isogamous but hetero-cystic; (3) progeny from Strain 1 has rhizoidal holdfast, whereas that of Strain 2 has discoid holdfast; (4) gametophytic “branching” was found in Strain 1. These results could validate the high phenotypic plasticity of macroalgae and offered an interpretation of habitat adaptation. Furthermore, this study innovatively provided fundamental research on the selection of macroalgal traits and explored competitive strategies for the dominant survival of macroalgae from a new perspective.Keywords：Chaetomorphavalida;individual difference;morphogenesis pattern;reproductive uniqueness12|5|0Updated：2024-12-24
- Abstract：Two new freshwater centric diatom species were described from the southwest of China based on light and scanning electron microscopy. Pliocaenicus weixiense sp. nov. has a transversely undulate valve face, marginal fultoportulae situated at the end of the hyaline strips, central fultoportulae forming a ring positioned in a circular pattern, each with 3–4 (usually 3) satellite pores, and a single rimoportula located at the base of the inner distal end of the costa. Tertiarius aspera sp. nov. has an uneven valve face with small granules that may be present on the marginal area and valve mantle, marginal fultoportulae situated on each costa close to the margin of the valve, 6–7 central fultoportulae forming a ring near the valve center each with two satellite pores, and one rimoportula located on the valve face/mantle junction in the middle of costa on the internal valve. T. aspera sp. nov. is the first reported extant species in the genus. This study played an important role in studying the taxonomic status and ecological information of the genus, and the establishment of the two new taxa will help demonstrate the unique nature of freshwater diatom flora in the southwest of China.Keywords：diatom;centric;new species;Pliocaenicus;Tertiarius;China11|8|0Updated：2024-12-24
Biology
- Abstract：Although the effects of diet on intestinal microbiotas have been well investigated, the effect of feeding time on the rhythm of gut microbiota remains uncertain. A 9-week feeding trial on Pelteobagrus fulvidraco was conducted. Two triplicate groups of fish were fed identically either at 8:00 (day) or at 20:00 (night). After 9 weeks, three fish from each cage were sacrificed every 4 h for 24 h. The intestinal contents were analyzed using high-throughput sequencing. Three phyla (Fusobacteria, Proteobacteria, and Verrucomicrobia), and three genera (Cetobacterium, Akkermansia, and Clostridium) were dominant at every time point. Moreover, 33.02% of detected amplicon sequence variants showed cyclical variations in fish fed at 20:00, and 3.47% in fish fed at 8:00. Among the top 20 genera, 17 showed cyclical variations in the 20:00 group, and only two in the 8:00 group. Rhodobacter, Ralstonia, Mycobacterium, Lactococcus, Halomonas, Akkermansia, and Acinetobacter contributed more to the predicted functional pathways. Moreover, 144 and 38 pathways exhibited daily cyclical fluctuations in fish fed at 20:00 and 8:00, respectively. Overall, certain intestinal microorganisms showed a circadian rhythm in P. fulvidraco, and this circadian rhythm was affected by shifted feeding times.Keywords：diurnal fluctuation;Pelteobagrusfulvidraco;gut microorganism;feeding time10|4|0Updated：2024-12-24
Aquaculture and Fisheries
- Address：Editorial Office of JOL, 88 Haijun Rd. Qingdao, 266000, China
- Tel：+86-532-82898754 Email：jol@qdio.ac.cn
- Technical support is provided by Beijing Founder electronics co., LTD 京ICP备09064830号-19
京公网安备11010802024621 - It is recommended to read the content of this site in Chrome&IE9+. Please switch to extreme mode in browser 360.
- Cookies We use cookies to help provide and enhance our service and tailor content. By continuing, you agree to the use of cookies.
0