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Volume 40 ， Issue 5 ， 2022
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- Abstract：Microcystisspecies identification is essential for ecological studies and water bloom control. Immunoassays are more specific and convenient and several approaches have been used to develop for diagnosing harmful red tide algae. However, investigations onMicrocystisidentification using immunological approaches are still in the initial stage. In this study,Microcystis aeruginosaPCC7806 lysates were utilized as coated antigens to enrich and screen specificMicrocystisnanobodies from a human domain antibody display library. After three rounds of enrichment, 10 positive monoclonal particles were isolated from the library and the most two positive nanobodies (DAb2 and Dab3) were effectively produced inEscherichia coliBL21. Finally, the DAb2 showed specific immune binding to differentMicrocystisby the immuno-dot blot assay. This antibody could be used to establish an immunological method to identifyMicrocystis.Keywords：Microcystis;phage display library;nanobody;immuno-dot blot assay6|0|1Updated：2023-05-19
- Abstract：Bound extracellular polymeric substances (bEPS) play an important role in the proliferation ofMicrocystis. However, the understanding of bEPS characterization remains limited. In this study, three-dimensional fluorescence excitation-emission matrix (3D-EEM) spectroscopy and zeta potentiometer were used to characterize the loosely bound EPS (LB-EPS) and tightly bound EPS (TB-EPS) from two dominantMicrocystismorphospecies from Taihu Lake (China) at different light intensities. Physiochemical analysis showed that the growth and TB-EPS or bEPS contents inMicrocystis aeruginosawere higher than those inMicrocystis flos-aquaeat each light intensity. The 3D-EEM contour demonstrated that the intensities of peak B (tryptophan-like substances) in the TB-EPS fromM.aeruginosawere stronger than those fromM.flos-aquaewhen the light intensity was higher than 10 μE/(m2ds). Zeta potential analysis showed that the absolute values of the zeta potential of TB-EPS in the two species both increased with rising light intensity, except those of TB-EPS inM.aeruginosaat 105 μE/(m2ds). Moreover, the absolute values of the zeta potential ofM.aeruginosawere higher than those ofM.flos-aquaeat each light intensity. All these results indicated thatM.aeruginosamay more quickly proliferate thanM.flos-aquaethrough increased negative charges, bEPS contents, growth, and tryptophan-like substance contents at certain light intensities.Keywords：Microcystis;bound extracellular polymeric substances;light intensity;zeta potential7|0|3Updated：2023-05-19
- Abstract：Colony formation of cyanobacteria is crucial for the formation of surface blooms in lakes. However, the underlying mechanisms of colony formation involving in physiological and cell surface characteristics remain to not well be established. Six cyanobacterialMicrocystisstrains (including both unicellular and colonial ones) were employed to estimate the influences of their physiological traits and the composition of extracellular polymeric substances (EPS) on colony or aggregate formation. Results show that raising the number of the photosynthetic reaction center and light-harvesting antenna in the PSII and reducing the growth rate were the major physiological strategies ofMicrocystisto produce excess EPS enhancing colony formation. Tightly bound EPS (T-EPS) was responsible for colony formation, which approximately accounted for 50% of the total amount of EPS. Five fluorescent components (protein-, tryptophan-, and tyrosine-like components and two humic-like components) were found in the T-EPS, although the amounts of these components varied with strains. Importantly, colonial strains contained much higher tyrosine-like substances than unicellular ones. We suggest that tyrosine-like substances might serve as a crosslinking agent to connect other polymers in EPS (e.g., proteins or polysaccharides) for colony formation. Our findings identified key physiological traits and chemical components of EPS for colony formation inMicrocystis, which can contribute to a better understanding on the formation ofMicrocystisblooms.Keywords：colony formation;physiological properties;extracellular polymeric substances (EPS) composition;cyanobacterial blooms9|0|1Updated：2023-05-19
- Abstract：To explore how decomposedMicrocystis-dominant cyanobacterial blooms affect submerged macrophytes, the submerged plantMyriophyllum spicatumwas exposed to cell extracts from microcystin (MC)- and non-MC-producingMicrocystisstrains in a laboratory experiment. Results showed that bothMicrocystiscell extracts exerted obvious damages to plant biomass, photosynthesis, primary and secondary metabolism measures, and resistance of plant antioxidant systems, with MC-producingMicrocystishaving stronger effects due to the presence of MCs. Cyanotoxins other than MCs responsible for the negative effects from bothMicrocystisstrains needs further identification. The Shannon diversity and Chao1 indices of epiphytic and planktonic bacteria were decreased by the cell extracts from bothMicrocystisstrains. However, epiphytic and planktonic bacterial communities responded differently toMicrocystiscell extracts at the genus level. The dominant genera of planktonic bacteria includingEnterobacter,Pseudomonas, andNovosphingobiumfrom phylum Proteobacteria,Chryseobacteriumfrom phylum Bacteroidetes, andMicrobacteriumfrom Actinobacteriota in the treatments with cell extracts were previously reported to have strains with algicidal and MC-degrading capabilities. Bacterial genes associated with energy production and conversion, amino acid transport and metabolism, and inorganic ion transport and metabolism, were more abundant in both treatments than the control for planktonic bacteria, but less abundant for epiphytic bacteria. We speculate that planktonic bacterial communities have the potential to use and degrade substances derived fromMicrocystiscell extracts, which may be beneficial forM.spicatumto alleviate damages fromMicrocystis. Further research is needed to verify the structure and function dynamics of epiphytic and planktonic bacteria in the interaction between cyanobacteria and submerged macrophytes.Keywords：microcystins;Microcystis;Myriophyllum spicatum;dissolved organic carbon;epiphytic and planktonic bacteria6|0|3Updated：2023-05-19
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The impact of the accumulation of algal blooms on reed wetlands in the littoral zones of Chaohu Lake
Abstract：In a large eutrophic lake, the littoral zone is normally an area with high-density elevated aquatic plant life, including algal blooms, where the presence of reed wetlands allows the accumulation of algae. In this study, the impact of accumulated algal blooms in reed wetlands in the littoral zones of Chaohu Lake was investigated seasonally from 2018 to 2019. The concentrations of chlorophylla(Chla), total nitrogen (TN), and total phosphorus (TP) were much higher in the reed-covered littoral zones (RCLZ) than in the unvegetated littoral zones (ULZ), indicating that more algal biomass was trapped and accumulated in the RCLZ. Algal biomass could be horizontally transported to downwind littoral zones under low wind speeds, favoring the establishment of blooms. Algal accumulation levels were highest in summer due to high water temperatures and algal biomasses. Likewise, the northern littoral zones were conducive to the development of large algal blooms because of the wind pattern. The values of TN, TP, Chla, and loss on ignition in surface sediments were higher in the RCLZ than in the ULZ. Moreover, the diffusive fluxes of ammonium and soluble reactive phosphorus were also higher in the RCLZ than in the ULZ. Considering the capability of reed wetlands to trap algae, mechanical salvage and other physical methods should be adopted to eliminate algal biomass when massive blooms accumulate in the RCLZ.Keywords：Chaohu Lake;littoral zone;reed wetlands;algal blooms6|0|1Updated：2023-05-19 - Abstract：Cyanobacteria can accumulate as a heavy biomass on the leeward side of large eutrophic lakes, posing a potential threat to public health. The mitigating capacity of three flocculants and their potential impacts on the major environmental features of water and sediments was evaluated. Results indicate that polyaluminum chloride (PAC) and ferric chloride (FeCl3) are efficient flocculants that can rapidly mitigate cyanobacterial blooms with chlorophyll-aconcentrations higher than 1 500 µg/L within 15 min. In comparison, cationic starch with chitosan could only treat cyanobacterial blooms in chlorophyll-aconcentrations of less than 200 µg/L. The addition of FeCl3caused a decline in the pH value, while dissolved oxygen in the water column dropped to 2 mg/L during cationic starch with chitosan treatment for a high cyanobacterial biomass group. Thus, a combination of flocculants and oxygenators should be considered when treating high-concentration cyanobacterial blooms for emergency purposes. Additionally, the cell lysis of cyanobacteria caused by cationic starch with chitosan can result in an increase in total dissolved phosphorus and total dissolved nitrogen. Furthermore, the high accumulation of nutrients in sediments after the settling of cyanobacteria can cause high internal phosphorus pollution. The increase in the total organic carbon of the sediments can threaten lake restoration achieved by planting submerged macrophytes.Keywords：Cyanobacterial bloom;emergency control;flocculants;lake restoration6|0|1Updated：2023-05-19
- Abstract：Raphidiopsis raciborskiiis a notorious bloom-forming and filamentous cyanobacterium that has been extensively investigated into its toxicity, phylogeny, and spreading potential. Studies have demonstrated that this species has spanned different climates from tropical zones to temperate regions, suggesting thatR. raciborskiiis becoming a cosmopolitan species in freshwater systems around the world. In fact, it has been proposed that several characteristics ofR. raciborskiimay explain its spread and dominance. In particular,R. raciborskiiis known to display a high extent of physiological plasticity regarding nutrients, light regimes, and temperatures. Moreover, this species illustrates different ecotypes with distinct environmental requirements. Here, we present an overview ofR. raciborskii's global distribution and adaptation strategy based on the recent findings from genome variance, toxicity, and ecophysiology. The expansion of its geographical distribution can be linked to its genome, toxicity, and ecophysiology. The variable genes are mainly associated with the stress response, phage defense, DNA repair, cell cycle control, and membrane transport, illustrating the species' adaptability in response to changing environments. In fact, the species shows rapid adaptability to low and/or variable nutrient availability, especially changing phosphorus availability. Moreover, the variabilities of strains within the population extend their flexibility to adapt and acclimate to ambient environment. In addition, cylindrospermopsins (CYN) appear to have a potential biological role in facilitating theirs dominance or bloom. These strategies ofR. raciborskiimake it a challenge to manage in a freshwater system, reflecting the management of its bloom from further evidence of the complex ecophysiology, toxicity, and genome of this species.Keywords：distribution;ecophysiology;genome variance;Raphidiopsis raciborskii;toxicity9|0|5Updated：2023-05-19
- Abstract：Raphidiopsis raciborskiican cause harmful cyanobacterial blooms when concentrations of environmental phosphorus (P) are very low, thus the physiological and molecular mechanisms involved in the acclimation to P need to be characterized better. The growth, chlorophyll fluorescence, alkaline phosphatase, and expression of genes directly involved in P assimilation were compared in theR. raciborskiiFACHB 1496 strain grown with and without inorganic P. The specific growth rate (μ), Chla, and six fluorescence parameters (minimal fluorescence (F0), maximal fluorescence (Fm), maximal variable fluorescence (Fv), electron transport flux (further thanQA) per RC (ET0/RC), quantum yield of the electron transport in PSII (ØE0), and the probability that an electron from a trapped exciton is moved into the electron transport chain beyondQA−(ψ0)) markedly decreased inR. raciborskiiin response to experimental P-deficiency. In contrast, the relative variable fluorescence at the J-step (VJ), trapped energy flux (leading toQAreduction) per RC (TR0/RC), and alkaline phosphatase activity significantly increased. In addition, gene expressions involved in the alkaline phosphatase (phoA1andphoA2), high-affinity inorganic P transporter (pstS1), phosphonate transporter and metabolism (phnDandphnM), and nucleotidase (nucH) were significantly upregulated under P deficiency. However, physiological and molecular responses were resumed rapidly after P re-supplementation following P-deficient conditions. Our results highlight thatR. raciborskiican perform coordinated and complex cellular and physiological responses to cope with P deficiency, reflectingR. raciborskii's multi-faceted machinery to respond to environmental P fluctuationsKeywords：phosphorus deficiency;Raphidiopsis raciborskii;gene expression;chlorophyll fluorescence;alkaline phosphatase7|0|1Updated：2023-05-19
- Abstract：Microcystis aeruginosahas always been regarded as the main culprit of cyanobacterial blooms in freshwater. However, in recent years,Raphidiopsis raciborskiihas gradually replacedM. aeruginosaas the culprit of cyanobacterial blooms in some tropical and subtropical shallow lakes. To reveal which one plays a more dominant role, interactions between cylindrospermospin (CYN)-producingR. raciborskiiand microcystins (MCs)-producing or non-MCs-producingM. aeruginosastrains were studied using bialgal cultures at different initial ratios of biomasses of the two species at 25 ℃. During the co-cultivation, theM. aeruginosastrains inhibited the growth and heterocyst formation ofR. raciborskiifilaments, and thus occupied a dominant position during the co-cultivation regardless of the initial biomass ratios in the cultures. In addition, the MCs-producingM. aeruginosastrain contributed to a higher portion of the total biomass and exerted a stronger inhibitory effect onR. raciborskiicompared with the non-MCs-producing strain. However, the growth of both MCs-producing and non-MCs-producingM. aeruginosastrains was stimulated byR. raciborskiiin the co-cultures compared withM. aeruginosamonoculture, indicating thatM. aeruginosacould outcompeteR. raciborskiiif given enough time, enabling it to develop into the dominant species even in very low initial concentration. To our best knowledge, this is the first report on the loss of heterocyst formation by a species of cyanobacteria that resulted from interactions between two different species of cyanobacteria. These findings indicate that it is difficult forR. raciborskiito replace the dominant position ofM. aeruginosaunder the experimental environmental condition, and the allelopathic effects ofM. aeruginosaonR. raciborskiicould significantly contribute to the success ofM. aeruginosa.Keywords：competition;growth;heterocyst;Microcystis aeruginosa;morphology;Raphidiopsis raciborskii6|0|1Updated：2023-05-19
- Abstract：Cyanobacterial blooms have become a serious global environmental issue due to their potential risk for releasing detrimental secondary metabolites into aquatic ecosystems, posing a great threat to water quality management for public health authorities.Aphanizomenon, a common filamentous cyanobacterial genus belonging to Nostocales, is under particular concern because its several members are able to form harmful blooms. Furthermore, succession of bloom betweenA. flos-aquaeandMicrocystisoccurs in many natural lakes. To evaluate the competitiveness ofA. flos-aquaevs.M. aeruginosa, two sets of experiments at different ratios of biomass at 15 ℃ and 25 ℃ were conducted. Results show that at 15 ℃, the two species were able to coexist, andA. flos-aquaeshowed a specific higher growth rate, and its growth was promoted by the presence ofM. aeruginosa. At 25 ℃, the growth ofA. flos-aquaewas inhibited by the biomass ofM. aeruginosa, andM. aeruginosasuppressedA. flos-aquaein competition. Additionally, the vegetative cell size ofA. flos-aquaewas significantly influenced by the co-culture withM. aeruginosa, whereas the filament length ofA. flos-aquaewas not significantly affected. This study confirms that temperature is the dominating factor on the succession ofA. flos-aquaeandM. aeruginosaof a different biomass.Keywords：Cyanobacterial bloom;Aphanizomenon flos-aquae;Microcystis aeruginosa;succession;temperature;biomass6|0|1Updated：2023-05-19
- Abstract：Eutrophication and climate warming have intensified the global expansion of invasive cyanobacteria such asCylindrospermopsisspp. andChrysosporumspp. Cylindrospermopsin (CYN) produced by species of the latter two genera may harm phytoplankton, zooplankton, and fishes. However, effects of CYN on the bacterioplankton community have not been studied. Based on high-throughput sequencing, we explored the effect of CYN on the structure and function of the bacterioplankton community by adding pure CYN to in-situ water collected from a brackish coastal shallow lake: Dishui Lake, China. We found that most bacterioplankton taxa had a certain tolerance potential to CYN, but that high concentrations of CYN (40 µg/L) caused a significant decrease in microbial abundance and functional groups. Of the dominant phyla, Actinobacteria had the strongest tolerance to CYN. Network analysis indicated that CYN caused shifts in the community structure of the bacterioplankton, reducing community stability and structural complexity. High CYN concentrations also reduced the correlation between the different bacterioplankton groups, and the abundances of some bacterial taxa associated with the denitrification function and the process of carbon transfer in the microbial food web were inhibited. Our study provides new insight into the response of the bacterioplankton communities to harmful algal toxins produced by cyanobacteria.Keywords：cylindrospermopsin;bacterioplankton;denitrification function;carbon cycles;Dishui Lake6|0|1Updated：2023-05-19
- Abstract：Dissolved inorganic phosphorus is an important form of directly bioavailable phosphorus for cyanobacteria in natural water. Dissolved organic phosphorus could be used by cyanobacteria via alkaline phosphatase, which is produced mainly by bacteria and also cyanobacteria itself. Herein, we review the current knowledge of extracellular phosphatase excreted by cyanobacteria, highlighting the development of detection method and its ecological roles in regulating phosphorus cycling in freshwater systems, which is based on reports for around 100 species of cyanobacteria. Recommendations are suggested concerning the extracellular phosphatase produced by bloom-forming cyanobacteria in terms of the ecological role, followed by a discussion of the future prospects for the study.Keywords：alkaline phosphatase;phosphate;dissolved organic phosphorus;cyanobacteria;ecological role6|0|1Updated：2023-05-19
- Abstract：Aerobic anoxygenic phototrophic bacteria (AAPB) represent a major group of bacterioplankton assemblages in many water systems and some are assumed to be closely associated with phytoplankton. However, studies on relationships between AAPB and cyanobacterial blooms are in scarcity. The dynamics of the abundance and diversity of AAPB was compared based onpufMgene in Meiliang Bay (featured by cyanobacterial blooms) and East Bay (featured by macrophyte) of Taihu Lake, a shallow subtropical lake in the East China plain. AAPB abundance was not significantly different between the two sites, and they were positively correlated with dissolved organic carbon (DOC) concentration. The ratios of AAPB to total bacteria varied from 3.4% to 11.5% and peaked in winter in both sites. No significant differences of AAPB community compositions were detected between the two sites, but there was a separation between warm seasons (June, August, and October) and cold seasons (December, February, and April). Rhizobiales andLimnohabitans-likepufMsequences were significantly contributors for the difference between two seasons, and specially enriched in cold seasons. Chlorophylla(Chla) and DOC were the most significant variables influencing the AAPB community structure. Furthermore,Porphyrobacterand Rhodospirillales-likepufMsequences were positively correlated with Chla, indicating potential influence of cyanobacterial blooms on these AAPB taxa. These results suggested that diverse AAPB ecotypes coexisted in Taihu Lake, and their ecological role in carbon cycling in the lake may not be ignored.Keywords：aerobic anoxygenic phototrophic bacteria;cyanobacterial blooms;dissolved organic carbon;Alphaproteobacteria;chlorophylla6|0|1Updated：2023-05-19
- Abstract：For estuaries, inland lakes play a vital role in the ecological balance under the impact of tides. The effect of tides-induced water exchange on phytoplankton community in a semi-closed lake was studied and compared with that of an adjacent closed lake in the Oujiang River mouth in Zhejiang, East China Sea, from June 29, 2020 to June 14, 2021. Results show that the dominant species, abundance, dominance, and diversity of the phytoplankton species between the two lakes were significantly different. In the closed lake, cyanobacteria were the dominant species during the study period. However, in the semi-closed lake, the diversification of the dominant species was greater, and some species of diatoms and green algae became dominant. The average phytoplankton abundance in the closed lake was 6 times of that in the semi-closed lake. The average dominance of cyanobacteria in the closed lake was 0.96, and those in the semi-closed lake and the Oujiang River were 0.51 and 0.22, respectively. Cyanobacterial blooms occurred throughout the study time in the closed lake but not in the semi-closed one. Furthermore, the species diversity richness of the phytoplankton in the semi-closed lake was higher than that of the closed one, and the phytoplankton community between the closed lake and semi-closed lake could be divided into distinctly different groups based on non-metric multidimensional scaling analysis (NMDS) and analysis of similarities (ANOSIM) analysis. The salinity of the water was significantly greater and the transparency significantly smaller in the semi-closed lake than those in the closed lake. Therefore, water exchange driven by local tidal movement increased salinity and decreased transparency of water, which consequently shaped the community structures of different phytoplankton and reduced the risk of a cyanobacterial bloom outbreak in the semi-closed lake.Keywords：estuary;harmful cyanobacterial blooms;phytoplankton community;water exchange;tidal movement;environmental parameters6|0|1Updated：2023-05-19
Special Section: Cyanobacterial blooms in China: ecology, toxicity, and treatment
- Abstract：To achieve better observation for sea surface, a new generation of wide-swath interferometric altimeter satellites is proposed. Before satellite launch, it is particularly important to study the data processing methods and carry out the detailed error analysis of ocean satellites, because it is directly related to the ultimate ability of satellites to capture ocean information. For this purpose, ocean eddies are considered a specific case of ocean signals, and it can cause significant changes in sea surface elevation. It is suitable for theoretical simulation of the sea surface and systematic simulation of the altimeter. We analyzed the impacts of random error and baseline error on the sea surface and ocean signals and proposed a combined strategy of low-pass filtering, empirical orthogonal function (EOF) decomposition, and linear fitting to remove the errors. Through this strategy, sea surface anomalies caused by errors were considerably improved, and the capability of satellite for capturing ocean information was enhanced. Notably, we found that the baseline error in sea surface height data was likely to cause inaccuracy in eddy boundary detection, as well as false eddy detection. These abnormalities could be prevented for "clean" sea surface height after the errors removal.Keywords：interferometric altimetry;baseline error;random error;ocean eddy;theoretical and systematic simulation;error removal strategy6|0|0Updated：2023-05-19
- Abstract：Based on mooring observations from Aug. 1, 2016 to Dec. 14, 2017, the characteristics and underlying mechanisms of near-inertial waves (NIWs) observed east of the Philippines were studied. Three strong NIW events were investigated in detail. The NIWs in Event Ⅰ were induced by typhoon Lan and had the strongest magnitudes of 0.35 m/s. The maximum near-inertial kinetic energy (NIKE) was shown at the ocean surface. The NIW in Event Ⅱ was stimulated by a moderate cyclonic wind with the extreme NIKE located at about 110-m depth. The existence of a cyclonic eddy during Events Ⅰ and Ⅱ led to a blue shift of near-inertial frequencies. For Event Ⅲ, the surface near-inertial signals were also induced by local weak wind, whereas the real generation mechanisms for the subsurface NIWs remain unclear. In particular, during Event Ⅲ, there was a nonlinear wave-wave interaction between NIWs and semidiurnal (D2) tides, which further induced strong D2±fwaves. Overall, the NIWs in the three events exhibited distinct vertical structures. The NIWs in Events Ⅰ and Ⅱ were dominated by lower modes with elevated NIKE well confined to the upper 250 m and 270 m, respectively. In contrast, the NIW Event Ⅲ was dominated by higher modes and the NIWs penetrated downward beyond 360 m. Such deep penetration of NIWs could be attributed to the weak wind stress curl and positive sea level anomalies associated with an anticyclonic eddy. In addition, the three NIW events hade-folding timescales of less than 7 days.Keywords：near-inertial wave (NIW);generation mechanism;dynamic characteristic6|0|1Updated：2023-05-19
- Abstract：The occurrence of rogue waves is closely related to the non-Gaussianity of sea states, and this non-Gaussianity can be estimated using corresponding two-dimensional wave spectra. This paper presents an approach to non-Gaussianity estimation based on a phase-resolving model called the high-order spectral method (HOSM). Based on numerous HOSM simulations, a set of precalculated non-Gaussianity indicators was established that could be applied to real sea states without any calibration of spectral shapes. With a newly developed extraction approach, the indicators for given two-dimensional wave spectra could then be conveniently extracted from the precalculated dataset. The feasibility of the newly developed approach in a real wave environment is verified. Using the estimation approach, phase-resolved non-Gaussianity can now be illustrated throughout the evolution of sea states of interest, not just at a few specific times; and the level of non-Gaussianity at any time in a duration can be identified according to the statistics (e.g., quantities) of the phase-resolved indicators, that are obtained throughout the duration concerned.Keywords：rogue wave;sea state non-Gaussianity;high-order spectral method;spectral geometry;wave-wave nonlinearity6|0|0Updated：2023-05-19
Physics
- Abstract：Shallow marine sand waves are formed on the seabed and are widely distributed within tidal environments. However, the use of multibeam echo sounding (MBES) is costly to obtain the bathymetric mapping of large complex sand waves. Therefore, we propose a new method that employs a combination of multiangle sun glint images and sparse MBES data to achieve comprehensive bathymetric mapping of large and complex sand waves. This method involves estimating sea surface roughness, automatically extracting sand-wave crests, conducting adaptive subregion partitioning, estimating the water depth at auxiliary points, and generating digital bathymetric models. The method was employed in a case study of sand waves on the Taiwan Bank. Bathymetric mapping was implemented for large complex sand waves over an area spanning approximately 350 km2using multiangle sun glint images from the Advanced Spaceborne Thermal Emission and Reflection Radiometer and MBES data. The results show that mapped and measured water depths were well-matched; the root-mean-square error of water depths was 1.77 m, and the relative error was 5.03%. These findings show that bathymetric mapping of large complex sand waves can be effectively conducted using the new method, and as such, the workload of MBES is reduced and efficiency is improved.Keywords：bathymetric mapping;sand waves;submarine topography;sun glint images;multibeam echo sounding (MBES)6|0|0Updated：2023-05-19
- Abstract：The wobble errors caused by the imperfect integration of motion sensors and transducers in multibeam echo-sounder systems (MBES) manifest as high-frequency wobbles in swaths and hinder the accurate expression of high-resolution seabed micro-topography under a dynamic marine environment. There are many types of wobble errors with certain coupling among them. However, those current calibration methods ignore the coupling and are mainly manual adjustments. Therefore, we proposed an automatic calibration method with the coupling. First, given the independence of the transmitter and the receiver, the traditional georeferenced model is modified to improve the accuracy of footprint reduction. Secondly, based on the improved georeferenced model, the calibration model associated with motion scale, time delay, yaw misalignment, lever arm errors, and soundings is constructed. Finally, the genetic algorithm (GA) is used to search dynamically for the optimal estimation of the corresponding error parameters to realize the automatic calibration of wobble errors. The simulated data show that the accuracy of the calibrated data can be controlled within 0.2% of the water depth. The measured data show that after calibration, the maximum standard deviation of the depth is reduced by about 5.9%, and the mean standard deviation of the depth is reduced by about 11.2%. The proposed method has significance in the precise calibration of dynamic errors in shallow water multibeam bathymetries.Keywords：multibeam echo-sounder systems;footprint reduction;wobble errors;genetic algorithm;automatic calibration6|0|0Updated：2023-05-19
Geology
- Abstract：Intertidal macroalgae can cope with the dual effects of UV-B irradiation and allelopathy. To study the impacts of the two stressors, we co-culturedCorallina piluliferawithSargassum thunbergiiin 1:1 and 1:10 ratios under different doses of UV-B radiation. The response of the antioxidant defense system, focusing on activities of superoxide dismutase (SOD), ascorbate peroxidase (APX), peroxidase (POX) and glutathione reductase (GR), was monitored. In addition, isoenzyme patterns were analyzed using non-denaturing polyacrylamide gel electrophoresis. The results show that the activities of SOD, APX, and GR were all significantly affected by both UV-B radiation and allelopathy, and the effect of their interaction was significant. However, POX activity was only influenced by UV-B radiation. The enzymatic assay revealed four distinct bands of SOD. The SODIII band weakened significantly when the co-cultures were exposed to extremely high dosage of UV-B irradiation under both co-culturing ratios of 1:1 and 1:10. When the co-culturing ratio was 1:10, both POXII and APXII enzyme activities increased with different UV-B doses. GR activity was at its greatest when the co-culture ratio was 1:10 and exposure was to the higher UV-B doses. The activities of GRIII and GRIV were elevated under all UV treatments whereas the activities of GRI and GRII were reduced under the lower UV-B treatments but were elevated under the higher UV-B treatments. However, lipid peroxidation, as indicated by the thiobarbituric acid-reacting substance (TBARS) assay, increased significantly under the dual stressors. Our data suggest that allelopathy and UV-B radiation stress can each affect the antioxidant enzyme activities ofC.pilulifera. Critically, the adverse effects of UV-B onC.piluliferawere intensified by the compounding effects of allelopathy.Keywords：Corallina pilulifera;antioxidant system;isoenzymes;UV-B radiation;allelopathy8|0|1Updated：2023-05-19
- Abstract：Diatoms are important contributors to global net primary productivity, and play a crucial role in the biogeochemical cycles of carbon, phosphorus, nitrogen, iron, and silicon. Currently in some regions in the ocean, there's a trend that carbon content is high while oxygen concentration is low, and the underlying mechanisms of diatoms' response to low oxygen environments are worth investigating.Phaeodactylum tricornutumis a model diatom whose genome has been sequenced; it provides a universal molecular toolbox and a stable transgenic expression system. Therefore, the study of the responses ofP.tricornutumto low oxygen has not only fundamental research significance but also important ecological significance. In this study, growth rates were determined and proteomic analysis and metabolomic analysis were performed to examineP.tricornutumresponses under different oxygen concentrations (2% oxygen concentration for hypoxic condition and 21% oxygen concentration for the normal condition (sterilized air)). Results show that the hypoxic environment inhibited the growth ofP.tricornutum. In the hypoxic conditions,P.tricornutumcould reset its metabolism pathways, including enhancement in lipid utilization, replenishment of tricarboxylic acid (TCA) cycle through the glyoxylic acid cycle, and down-regulation of photorespiration to reduce energy waste. Additionally, the stress resistance mechanism was activated to facilitate the adaptation to low oxygen conditions. This study helps to reveal the different metabolic changes to hypoxia of diatom from that of higher plants, which might be ascribed to their different habitats and needs further exploration in the future.Keywords：Phaeodactylum tricornutum;hypoxia;metabolomics;proteomics6|0|0Updated：2023-05-19
- Abstract：Several studies have suggested the pivotal roles of eutrophic lakes in carbon (C) cycling at regional and global scales. However, how the co-metabolism effect on lake sediment organic carbon (OC) mineralization changes in response to integrated inputs of labile OC and nutrients is poorly understood. This knowledge gap hinders our ability to predict the carbon sequestration potential in eutrophic lakes. Therefore, a 45-day microcosm experiment was conducted to examine the dominant mechanisms that underpin the co-metabolism response to the inputs of labile C and nutrients in lacustrine sediments. Results indicate that the labile C addition caused a rapid increase in the positive co-metabolism effect during the initial stage of incubation, and the co-metabolism effect was positively correlated with the C input level. The positive co-metabolism effect was consistently higher under high C input, which was 152% higher than that under low C input. The higher β-glucosidase activity after nutrient addition, which, in turn, promoted the OC mineralization in sediments. In addition, different impacts of nutrients on the co-metabolism effect under different C inputs were observed. Compared with the low nutrient treatments, the largest co-metabolism effect under high C with high nutrient treatment was observed by the end of the incubation. In the high C treatment, the intensity of the co-metabolism effect (CE) under high nitrogen treatment was 1.88 times higher than that under low nitrogen condition. However, in the low C treatment, the amount of nitrogen had limited impact on co-metabolism effect. Our study thus proved that the microorganisms obviously regulate sediment OC turnover via stoichiometric flexibility to maintain a balance between resources and microbial requirements, which is meaningful for evaluating the OC budget and lake eutrophication management in lacustrine sediments.Keywords：co-metabolism effect;stoichiometric;carbon cycling;eutrophic lake;decomposition;organic carbon6|0|0Updated：2023-05-19
- Abstract：Identifying seasonal shift in phytoplankton community is essential for understanding the significance of eutrophication and finding biological indicators of ecological health of a lotic system. Phytoplankton communities, as well as the seasonal changes in the Ashi River Basin (ASRB) of Heilongjiang Province were investigated from April 2018 to January 2019. A survey in April (spring), July (summer), October (autumn), and January (winter) at 16 sampling sites was conducted. The composition, abundance, and biodiversity indices of phytoplankton were studied and 127 taxa of phytoplankton were identified. Among them, Bacillariophyta dominated the phytoplankton communities in the whole year. There were significant spatio-temporal changes in the structures of the phytoplankton communities during the study period. Trophic state index (TSI) show that the nutritional status of the ASRB was at mesotrophic-middle eutrophic levels. Redundancy analysis (RDA) revealed that total nitrogen (TN), water temperature (WT), oxidation reduction potential (ORP), pH, and dissolved oxygen (DO) were the critical factors in the dynamic phytoplankton community structure. The multivariate regression tree (MRT) analysis showed thatChlamydomonas microsphaerellaPascher et Jahoda,Melosira granulata(Ehrenberg) Ralfs,Merismopedia tenuissimaLemmermann, andAsterionella formosaHassall were valuable indicators in the determination of water quality in ASRB. Our findings provide a scientific basis for water quality protection and management at basin scale.Keywords：Ashi River Basin;eutrophication;community structure;succession;indicator6|0|1Updated：2023-05-19
Ecology
- Abstract：Glutamate dehydrogenase (GDH) plays an important role in the ammonium assimilation and nitrogen metabolism by catalyzing the reversible oxidative deamination of L-glutamate to α-ketoglutarate. In the present study, the potential functions of GDH in response to heat stress were explored in the scleractinian coralPocillopora damicornis(designated as PdGDH). The cDNA of PdGDH contained an open reading frame of 1 611 bp encoding a polypeptide of 536 amino acids, which exhibited the highest sequence identity to GDH ofStylophora pistillata(96% identity), and the deduced PdGDH protein was predicted to contain one GdhA domain (from Val95 to Tyr525). The recombinant protein of PdGDH (rPdGDH) was expressed inEscherichia coliBL21 (DE3)-Transetta, and its catalytic activity was measured under different temperatures, pH conditions and epigallocatechin-3-gallate (EGCG, a GDH inhibitor) concentrations. The purified rPdGDH only used reduced coenzyme nicotinamide adenine dinucleotide (NADH) as coenzyme, and its highest activity was observed at 35 ℃ and pH 7.5, respectively. The rPdGDH activity was negatively correlated with the concentration of EGCG, and was inhibited by more than half (65%,P<0.05) at 10-4 mol/L EGCG. No significant alteration of PdGDH mRNA expression was detected at 12 h after exposure to heat and ammonium (P>0.05). Furthermore, the activities of NADH-GDH in the scleractinian coralP.damicornisincreased significantly at 12 h after the heat and ammonium stress, and the NADH-GDH activity in the heat stress group (32.66 U/mg,p<0.05) was significantly higher than that in the heat and ammonium stress group (11.26 U/mg). These results collectively suggested that PdGDH, as a homologue of glutamate dehydrogenase in the scleractinian coralP.damicornis, could respond to heat stress at the protein level, which would have ability to further promote ammonium assimilation to increase the heat acclimatization of the coral-Symbiodiniaceae symbiotic association.Keywords：scleractinian coral;glutamate dehydrogenase;ammonium assimilation;global warming;heat response6|0|0Updated：2023-05-19
- Abstract：Photoperiod is a key environmental indicator for regulating embryonic development, individual growth and physiological processes in aquatic animals. In this study, differences in embryonic development and performance of newly hatched cuttlefish juvenile exposed to five different cycles of light: dark (L: D): constant light, 18L: 6D, 12L: 12D, 6L: 18D cycles, and constant darkness were evaluated. Prolonged exposure to light induced an accelerated rate of embryonic development, particularly after the red-bead stage. Principal component analysis (PCA) revealed that red-bead stage, heartbeat, endoskeleton formation, pigment appear, and six increments of cuttlebone were the main factors contributing to the embryonic development. Meaning that the duration time of these five stages were significantly different when exposed to photoperiod regimes, which may determine the duration of the incubation period of the embryos. Long term light has also affected the incubation parameters with an increased rate in hatching and shortened the incubation and hatching periods in the 12—24-h day length range. However, constant light and darkness environment appeared to have a greater effect on the stress of embryonic development, mainly reflected in the yolk shed ratio and the inking rate in the egg capsule. Moreover, the increase in the day length has contributed to improve the growth and survival of juveniles in the 12—18-h day length range; however, juveniles exposed to constant light and darkness experienced worse results in terms of growth, tissue glycogen content, digestive enzymes of the digestive glands, and metabolic enzymes of the muscles. These finding suggest that prolonged light exposure accelerates the process of embryonic development, maximum feeding time is not necessarily a condition of optimal growth, and inappropriate light cycles can disturb the body's endogenous controls. Therefore, the optimal photoperiod for the embryos development and juvenile growth ofSepia pharaoniswere 12 h and 12—18 h of day length, respectively. These results are useful for increasing the production of this species during embryo incubation and juveniles rearing in aquaculture practice.Keywords：photoperiod;embryonic development;growth;physiological changes;cuttlefish6|0|0Updated：2023-05-19
- Abstract：The Polian vesicle is the main accessory structure in the water vascular system of sea cucumbers. It can function to hold water vascular fluid under slight pressure and act as a hematopoiesis, excretory, and inflammatory response organ. Being the only organ to remain after evisceration, the Polian vesicle may function in the survival and regeneration of sea cucumber. We performed Tandem Mass Tag (TMT)-based proteomics to identify how proteins in the Polian vesicle ofApostichopus japonicusrespond to evisceration. Among the 8 453 proteins identified from vesicle samples before evisceration (PV0h) and at 6-h post-evisceration (PV6h) and 3-d post-evisceration (PV3d), we detected 222 differentially abundant proteins (DAPs). Most of the annotated DAPs were associated with cell growth and proliferation, immune response and wound healing, substance transport and metabolism, cytoskeleton/cilia/flagella, extracellular matrix, energy production and conversion, protein synthesis and modification, and signal recognition and transduction. Compared with PV0h, fewer DAPs were identified at PV6h, and more DAPs were found at PV3d, and these DAPs were widely distributed among multiple biological processes. Our results indicate that a wide range of biological processes was induced in Polian vesicles in response to evisceration. In particular, Polian vesicles may play important roles in the restoration of coelomocytes, immune defense, and wound healing in sea cucumber. We propose that the Polian vesicle may be involved in visceral regeneration through nutrition and energy supply and by promoting dedifferentiation and migration. Together, these results provided new insights into the function of the Polian vesicle inA.japonicuspost-evisceration.Keywords：sea cucumber;Polian vesicle;evisceration;proteomics;differentially abundant protein6|0|0Updated：2023-05-19
- Abstract：Portunus trituberculatusis an ideal model for elucidating crustacean genetic networks. Here we combined single molecule real-time (SMRT) sequencing and Illumina RNA-seq to characterize the coding genes, non-coding RNAs and pseudogenes and further to improve the genome annotation information ofP.trituberculatus. In this study, we assembled 9 694 non-redundancy full-length transcripts, and 658 737 307-bp repetitive sequences were identified in theP.trituberculatusfull-length transcriptome. We also predicted theP.trituberculatusgenome structure based on full-length transcripts, including 18 602 genes, 28 686 non-coding RNAs, 1 407 pseudogenes, 740 motif, and 26 434 domain. Meanwhile, 14 460, 10 211, 5 412, 7 314, and 14 448 genes had significant matches with sequences in the NR, KOG, GO, KEGG, and TrEMBL database, respectively. Overall, our work firstly provided the long-read transcriptome and we believed that these data are very necessary to improve the annotation information ofP.trituberculatusgenome structure, and useful information for the future studies on evolution and physiological regulation ofP.trituberculatus.Keywords：Portunus trituberculatus;full-length transcripts;single molecule real-time (SMRT) sequencing6|0|0Updated：2023-05-19
- Abstract：Haematococcus pluvialisis an ideal natural source of strong antioxidant astaxanthin. Sodium acetate (NaAc) was proven an effective organic carbon source for improving algal growth and astaxanthin production; however, the underlying mechanism remains obscure. To reveal the mechanism of NaAc at the green vegetative stage ofH.pluvialis, the physiochemical characteristics and the global protein expression profiles obtained using a tandem mass tag labeling approach were compared between the control (CK) and two NaAc-addition groups. Results show that after NaAc addition, the biomass, nitrate consumption rate, and activities of three carbohydrate metabolism enzymes ofH.pluvialiswere significantly increased, and the net photosynthetic rate and chlorophyll content decreased. In addition, astaxanthin, total carbohydrates, and total lipids were accumulated, and some red cells appeared in the NaAc5 group. Moreover, 317 differentially expressed proteins (DEPs) with the most altered expression patterns were screened out in the CK vs. NaAc5 comparison in our proteomics study. All the DEPs involved in carbohydrate metabolism and lipid metabolism were significantly increased, while most of the photosynthesis-related proteins were depressed in the two NaAc-treated groups. The proteomics results were verified and supported by parallel reaction monitoring approach and physiochemical data. Our findings demonstrate that NaAc promoted the tricarboxylic acid cycle, glyoxylate cycle, and amino acid and lipid synthesis, and inhibited the photosynthesis-related activities, which consequently speeded up the growth and astaxanthin accumulation in this alga.Keywords：Haematococcus pluvialis;sodium acetate (NaAc);growth;differentially expressed protein;proteomics approach7|0|0Updated：2023-05-19
Biology
- Abstract：The morbidity and mortality peak of farmedProcambarus clarkiioccurs around May every year, a phenomenon known as "Black May" disease (BMD). Increasing evidence shows that the intestinal flora is closely related to host health. We analyzed and compared the microbiota of healthy and BMD-affectedP.clarkiiintestines. The results show that there was no significant difference in bacterial α-diversity (richnessP=0.59; evennessP=0.43; and diversityP=0.052) between the diseased group and the control group. Four dominant phyla in the intestines of crayfish in the control group, namely Tenericutes (30.86%), Bacteroidetes (29.99%), Firmicutes (22.23%), and Proteobacteria (15.23%), were identified. However, a striking shift in the microbial composition were found in the intestines ofP.clarkiiwith BMD. Bacteroidetes was a dominant phylum in healthyP.clarkii, whereas the prevalence was low in diseasedP.clarkii(1.87%). By contrast, the prevalence of Proteobacteria was significantly higher (P< 0.05) inP.clarkiiwith BMD than inP.clarkiiwithout BMD.Candidatus Bacilloplasma,Bacteroides,Vibrio, andAeromonasshowed significant differences (P< 0.05) at the genus level. Tax4Fun function prediction indicated that the relative abundance of genes involved in energy metabolism in the intestinal flora ofP.clarkiiwith BMD was significantly reduced (P< 0.05). Therefore, BMD can change the composition of the intestinal microbiota ofP.clarkii. This study contributes to the understanding of the relationship between intestinal flora and host especially in aquatic animals.Keywords：Procambarus clarkii;"Black May" disease (BMD);intestinal flora;high-throughput sequencing7|0|1Updated：2023-05-19
Aquaculture and Fisheries
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