Molecular identification and population differentiation of Aurelia spp. ephyrae in sea cucumber aquaculture ponds of northern China

Aurelia spp. ephyrae have been reported to form blooms in sea cucumber aquaculture ponds in the Bohai and Yellow Seas. To identify the species, we carried out a genetic analysis of Aurelia spp. ephyrae and medusae based on mitochondrial 16S rRNA gene. Samples of four Aurelia sp. ephyrae populations were collected in sea cucumber aquaculture ponds and samples of four Aurelia sp. medusae populations were collected in coastal waters. Using a BLASTn search, we found that both the ephyrae collected in the aquaculture ponds and medusae collected in coastal waters belong to Aurelia coerulea. Seventeen haplotypes were recovered from the 16S rRNA gene. The overall haplotype diversity and nucleotide diversity of the 166 A. coerulea individuals were 0.686 and 0.329%, respectively, indicating high haplotype diversity and low nucleotide diversity. Moreover, the haplotype diversity of ephyrae populations were generally lower than that of medusae populations with close sampling points. The genetic differentiation between ephyrae populations collected in the sea cucumber aquaculture ponds and A. coerulea medusae collected in coastal waters was not significant, suggesting the ephyrae populations in the sea cucumber culture ponds were part of the same genetic group as the medusae populations in the coastal waters. Phylogeographic analysis of the 16S rRNA region revealed that there was no significant correlation between the haplotypes and the geographic distribution of populations. Pairwise fixation index values showed significant genetic differentiation and limited gene flow between A. coerulea population of Weifang and other locations

Composition and Potential Functions of Bacterial Communities Associated With Aurelia Polyps

Jellyfish and their associated microbes form an ecological unit called the holobiont. Changes in the composition of dominant microbial assemblages may influence the environmental resilience and function of the holobionts. Differentiating the microbial communities from diverse jellyfish is essential for characterizing the functional contributions of microorganisms but has not been fully explored. In this study, based on 16S rRNA gene sequencing, we investigated the composition of microbial communities associated with two Aurelia polyp species (Aurelia coerulea and Aurelia solida) obtained from seven locations, which were maintained under the same environmental conditions. Sequence analysis showed that the genera Sphingomonas, Phyllobacterium, and Ralstonia were the most abundant members of the Aurelia-associated microbial communities and dominated the core microbiome of the Aurelia polyps in this study. Functional prediction revealed that chemoheterotrophy and aerobic chemoheterotrophy, based on the FAPROTAX dataset, were the primary functions of the associated microbes of Aurelia polyps. In addition, the comparison of microbial communities from different Aurelia polyp populations revealed interspecific instead of intraspecific variation, indicating a correlation between the composition of the symbiotic microbiota and genetic background of Aurelia polyps

Bacterial Communities Associated With Four Blooming Scyphozoan Jellyfish: Potential Species-Specific Consequences for Marine Organisms and Humans Health

Cnidarians have large surface areas available for colonization by microbial organisms, which serve a multitude of functions in the environment. However, relatively few studies have been conducted on scyphozoan-associated microbial communities. Blooms of scyphozoan species are common worldwide and can have numerous deleterious consequences on the marine ecosystem. Four scyphozoan species, Aurelia coerulea, Cyanea nozakii, Nemopilema nomurai, and Rhopilema esculentum, form large blooms in Chinese seas. In this study, we analyzed the bacterial communities associated with these four jellyfish based on 16S rRNA gene sequencing. We found that the bacterial communities associated with each scyphozoan species were significantly different from each other and from those of the surrounding seawater. There were no significant differences between the bacterial communities associated with different body parts of the four scyphozoan jellyfish. Core bacteria in various compartments of the four scyphozoan taxa comprised 57 OTUs (Operational Taxonomic Units), dominated by genera Mycoplasma, Vibrio, Ralstonia, Tenacibaculum, Shingomonas and Phyllobacterium. FAPROTAX function prediction revealed that jellyfish could influence microbially mediated biogeochemical cycles, compound degradation and transmit pathogens in regions where they proliferate. Finally, Six genera of potentially pathogenic bacteria associated with the scyphozoans were detected: Vibrio, Mycoplasma, Ralstonia, Tenacibaculum, Nautella, and Acinetobacter. Our study suggests that blooms of these four common scyphozoans may cause jellyfish species-specific impacts on element cycling in marine ecosystems, and serve as vectors of pathogenic bacteria to threaten other marine organisms and human health

Bacterial communities associated with hydromedusa Gonionemus vertens in different regions in Chinese coastal waters

Bacteria communities in cnidarian jellyfish can be harmful to many important aquaculture species, as they can be key vectors of bacterial pathogens. However, our knowledge of bacterial communities associated with jellyfish in culture ponds and their potential roles in the regulation of aquaculture species remains unclear. In this study, sequencing based on the bacterial 16S rRNA gene was used to investigate the composition and variation of the bacterial communities associated with hydromedusa Gonionemus vertens in sea cucumber culture ponds and natural marine environment. The associated bacterial communities of G. vertens from the culture ponds in the Yellow Sea and Bohai Sea had significantly different compositions, when compared with those from ambient seawater environment. Furthermore, bacterial communities associated with G. vertens had similar diversity and composition in culture ponds and natural marine environment in the Yellow Sea. There were 31 unique bacterial biomarkers identified in three locations. The major communities were highly abundant in Kiloniellales, Octadecabacter, Polynucleobacter, and Polaribacter, and are related to the environmental information processing. Pathogen candidates such as Vibrionales and Chlamydiales had notably low relative abundances (<1%). The venom of the jellyfish was considered responsible for damage to the aquaculture. This study provides important data to help assess the impact of cnidarians-associated bacterial communities on pond aquaculture and the influences on material cycling and energy flow in marine ecosystems

Adsorption of Sb(III) from Solution by Immobilized <i>Microcystis aeruginosa</i> Microspheres Loaded with Magnetic Nano-Fe₃O₄

In this study, a renewable and reusable immobilized Microcystis aeruginosa microsphere loaded with magnetic Nano-Fe3O4 composite adsorbent material is designed to study the treatment of wastewater containing heavy metal Sb(III). Through static absorption experiments combined with various characterization methods, this article studies the absorption process and mechanism of Sb(III), and investigates the optimal preparation conditions and environmental influencing factors. The results show that the optimal preparation conditions for immobilized Microcystis aeruginosa microspheres loaded with magnetic Nano-Fe3O4 adsorbent materials are 50.0% mass fraction of Microcystis suspension, 1.5% mass fraction of Nano-Fe3O4, and 2.5% mass fraction of sodium alginate. When the pH of the solution is 4, the reaction temperature is 25 °C, and the adsorbent dosage is 8.5 g/L, the removal rate of Sb(III) is the highest, reaching 83.62% within 120 min. The adsorption process conforms to the pseudo-second order kinetic model and Langmuir adsorption isotherm model, mainly characterized by chemical adsorption and surface complexation. Therefore, the composite material has been proven to be an efficient Sb (III) adsorption material

Abundance, Diversity and Functional Potentials of Planktonic Bacteria and Microeukaryotes in the Coral-Reef System of Xisha Islands, China

Corals influence microorganisms within the surrounding seawater, yet the diversities and functions of seawater bacteria and microeukaryotes in coral-reef systems have not been well addressed. We collected 40 seawater samples in outer coral reef flats and semi-closed inner lagoons from the surface, middle and bottom layers in the pristine coral-reef system of Xisha Islands, South China Sea. We detected the abundance, composition and distribution of bacteria and microeukaryotes using flow cytometry, qPCR and high throughput sequencing techniques, and profiled the potential ecological roles based on the information of 16S and 18S rDNA sequencing. In terms of flow cytometry, Prochlorococcus dominated the autotrophs with cell abundance ranging from 5.8 x 10(2) to 5.44 x 10(3) cells mL(-1) seawater. Based on qPCR, the 16S rDNA copies were much higher in coral reef flats than in lagoons (P=0.003). The bacterial communities held significantly lower diversity in bottom waters compared with surface and middle waters (P < 0.05), which were dominated by SAR11, Flavobacteriales, and Synechococcus. Alveolata represented most of the microeukaryotic communities with Dinophyceae and Syndiniales well represented in all samples. Neither bacterial nor microeukaryotic community exhibited distinct layer or niche pattern, however, Haptophyta and Picozoa decreased with depth and SAR 86, MAST-3 and Picozoa were enriched in lagoons (P <0.05). To adapt the nutrient-poor and organic matter-rich environment, bacterial nitrogen fixation and assimilatory/dissimilatory nitrate reduction were active in the system, and mixotrophy was the most important trophic strategy among microeukaryotes. The study highlighted the ecological adaptability of seawater microbes to the unique coral-reef environments

Environmental and molecular regulation of diapause formation in a scyphozoan jellyfish

Understanding the mechanisms underlying diapause formation is crucial for gaining insight into adaptive survival strategies across various species. In this study, we aimed to uncover the pivotal role of temperature and food availability in regulating diapausing podocyst formation in the jellyfish Aurelia coerulea. Furthermore, we explored the cellular and molecular basis of diapause formation using single-cell RNA sequencing. Our results showed cell-type-specific transcriptional landscapes during podocyst formation, which were underscored by the activation of specific transcription factors and signalling pathways. In addition, we found that the heat shock protein-coding genes HSC70 and HSP90a potentially act as hub genes that regulate podocyst formation. Finally, we mapped the single-cell atlas of diapausing podocysts and identified cell types involved in metabolism, environmental sensing, defence and development that may collectively contribute to the long-term survival and regulated excystment of diapausing podocysts. Taken together, the findings of this study provide novel insights into the molecular mechanisms that regulate diapause formation and contributes to a better understanding of adaptive survival strategies in a variety of ecological contexts

Application of environmental DNA metabarcoding and quantitative PCR to detect blooming jellyfish in a temperate bay of northern China

Abstract Frequently occurring jellyfish blooms have severe impacts on the socioeconomics of coastal areas, which stress the importance of early detection and assessments of blooming jellyfish taxa. Environmental DNA (eDNA) techniques (quantitative PCR and eDNA metabarcoding) have the advantage of high sensitivity and are an emerging powerful tool for investigations of target species. However, a comprehensive analysis of the biodiversity and biomass of jellyfish taxa in the target area by combining the two eDNA techniques is still lacking. Here, we developed eDNA metabarcoding and quantitative PCR for the detection and assessment of jellyfish taxa in the temperate Yantai Sishili Bay (YSB) and estimated the spatial distribution of Aurelia coerulea. Species‐specific quantitative PCR assays targeting the mitochondrial cytochrome c oxidase subunit I gene of A. coerulea were developed. Additionally, eDNA metabarcoding based on the mitochondrial 16S rDNA sequences identified six jellyfish species in YSB. Moreover, our results indicate that A. coerulea aggregations were more likely to occur in the inner part of the bay than in the outer part, and they gathered in the bottom layer of seawater rather than in the surface layer. Our results demonstrate the potential of two eDNA techniques in jellyfish biomass investigation and jellyfish taxa detection. These eDNA techniques may contribute to the discovery of jellyfish aggregation so as to achieve early warning of large‐scale jellyfish blooms in coastal areas