Exploring seasonal variations, assembly dynamics, and relationships of bacterial communities in different habitats of marine ranching.

Offshore coastal marine ranching ecosystems provide habitat for diverse and active bacterial communities. In this study, 16S rRNA gene sequencing and multiple bioinformatics methods were applied to investigate assembly dynamics and relationships in different habitats. The higher number of edges in the water network, more balanced ratio of positive and negative links, and more keystone species included in the co-occurrence network of water. Stochastic processes dominated in shaping gut and sediment community assembly (R2 < 0.5), while water bacterial community assembly were dominated by deterministic processes (R2 > 0.5). Dissimilarity-overlap curve model indicated that the communities in different habitats have general dynamics and interspecific interaction (P < 0.001). Bacterial source-tracking analysis revealed that the gut was more similar to the sediment than the water bacterial communities. In summary, this study provides basic data for the ecological study of marine ranching through the study of bacterial community dynamics.

Whole-Transcriptome Analysis Reveals the RNA Profiles in Mouse Bone Marrow Mesenchymal Stem Cells or Zebrafish Embryos After Exposure to Environmental Level of Tributyltin.

To understand the underlying molecular mechanisms, mouse bone marrow mesenchymal stem cells (BMSCs) and zebrafish embryos were exposed to the control group and Tributyltin (TBT) group (10 ng/L, environmental concentration) for 48 h, respectively. The expression profiles of RNAs were investigated using whole-transcriptome analysis in mouse BMSCs or zebrafish embryos after TBT exposure. For mouse BMSCs, the results showed 2,449 differentially expressed (DE) mRNAs, 59 DE miRNAs, 317 DE lncRNAs, and 15 circRNAs. Similarly, for zebrafish embryos, the results showed 1,511 DE mRNAs, 4 DE miRNAs, 272 DE lncRNAs, and 28 circRNAs. According to KEGG pathway analysis showed that DE RNAs were mainly associated with immune responses, signaling, and cellular interactions. Competing endogenous RNA (ceRNA) network analysis revealed that the regulatory network of miRNA-circRNA constructed in zebrafish embryos was more complex compared to that of mouse BMSCs.

Micro(nano)plastics in marine medaka: Entry pathways and cardiotoxicity with triphenyltin.

The simultaneous presence of micro(nano)plastics (MNPs) and pollutants represents a prevalent environmental challenge that necessitates understanding their combined impact on toxicity. This study examined the distribution of 5 µm (PS-MP5) and 50 nm (PS-NP50) polystyrene plastic particles during the early developmental stages of marine medaka (Oryzias melastigma) and assessed their combined toxicity with triphenyltin (TPT). Results showed that 2 mg/L PS-MP5 and PS-NP50 could adhere to the embryo surface. PS-NP50 can passively enter the larvae and accumulate predominantly in the intestine and head, while PS-MP5 cannot. Nonetheless, both types can be actively ingested by the larvae and distributed in the intestine. 2 mg/L PS-MNPs enhance the acute toxicity of TPT. Interestingly, high concentrations of PS-NP50 (20 mg/L) diminish the acute toxicity of TPT due to their sedimentation properties and interactions with TPT. 200 µg/L PS-MNPs and 200 ng/L TPT affect complement and coagulation cascade pathways and cardiac development of medaka larvae. PS-MNPs exacerbate TPT-induced cardiotoxicity, with PS-NP50 exhibiting stronger effects than PS-MP5, which may be related to the higher adsorption capacity of NPs to TPT and their ability to enter the embryos before hatching. This study elucidates the distribution of MNPs during the early developmental stages of marine medaka and their effects on TPT toxicity, offering a theoretical foundation for the ecological risk assessment of MNPs.

Metagenomics analysis reveals the effects of norfloxacin on the gut microbiota of juvenile common carp (Cyprinus carpio).

Norfloxacin (NOR) is an early third-generation quinolone antibiotic that has been widely used in animal husbandry and aquaculture because of its bactericidal properties. As an emerging contaminant, NOR may have toxic effects on fish. This study assessed the chronic toxicity (6 weeks) of 0 (control group), 100 ng/L (environmental concentration), and 1 mg/L NOR to the gut microbiota of juvenile common carp (Cyprinus carpio) based on metagenomic sequencing. Metagenomic analysis revealed that the Proteobacteria, Bacteroidetes, Fusobacteria, Firmicutes, and Actinobacteria were the dominant bacteria in the gut of common carp. The relative abundance of Actinobacteria was highest in the control group. The alpha diversity of the environmental concentration NOR was significantly lower than the control group. Principal coordinates analysis (PCoA) indicated that the bacterial community between the different groups formed clear separate clusters. NOR exposure adversely could affect immune function and some substance metabolic pathways in the gut microbiota of common carp. Furthermore, environmental concentrations of NOR produce antibiotic resistance genes (ARGs) in the gut microbiota, enhancing resistance to drugs. In conclusion, environmental concentrations of NOR could alter the composition, structure, and abundance of ARGs in the gut microbiota, thereby affecting the intestinal health of fish.

Physiological and molecular responses in the silver carp (Hypophthalmichthys molitrix) larvae after acute mercury exposure.

The current study was performed to examine the acute toxicity of mercuric chloride (HgCl2) on the silver carp (Hypophthalmichthys molitrix) larvae. Probit analysis was used to determine the median lethal concentration (LC50). The LC50 values of Hg2+ for the fish larvae at 24, 48, 72, and 96 h were 267.72, 252.97, 225.57, and 97.80 µg/L, respectively. The safe concentration of Hg was 9.78 µg/L for fish larvae. Based on the 96 h LC50, fish were exposed to four different groups including 0, 6.11, 12.23, and 24.45 µg/L for 96 h to assess the effects of different concentrations of Hg2+ on antioxidant capacity, energy metabolism parameters, and related gene expression. The findings revealed that there were no significant differences in the activities of superoxide dismutase (SOD) and total antioxidant capacity (T-AOC) in fish larvae among all the groups (P < 0.05). In the 12.23 µg/L group, fish larvae had a maximum in catalase (CAT) activity. The creatine kinase (CK) activities of fish larvae in control and 6.11 µg/L groups were significantly lower than those groups (P < 0.05). A high concentration of Hg2+ significantly upregulated the mRNA levels of heat shock protein 70 (HSP70) and metallothionein (MT) genes in fish larvae. Furthermore, the IBR index value showed the highest value in the 24.45 µg/L group. Overall, this study provides an increased understanding of the effects of Hg-acute toxicity on silver carp larvae.

Acute Toxicity of a Novel anti-fouling Material Additive DCOIT to Marine Chlorella sp.

DCOIT (4,5-dichloro-2-n-octyl-4-isothiazolin-3-one) is the main ingredient in SeaNine-211, a new antifouling agent that replaces organotin compounds to prevent the growth of fouling organisms on board. Biocides from antifoulants can cause problems for marine ecosystems by destroying non-target algal species. This study evaluated the potential adverse effects DCOIT using the Marine Chlorella sp. The concentration of DCOIT were set according to the semi-inhibitory concentrations for acute exposure experiments, and relevant oxidative stress indicators were measured to assess the acute toxic effects. The results showed that the inhibition concentrations (IC50) of DCOIT against Marine Chlorella sp was 2.522 mg/L. The genes related to photosynthesis and antioxidant capacity showed the effect of promoting low concentration and inhibiting high concentration. In addition, based on the ultrastructural observation and the expression analysis of photosynthesis related genes, it was found that DCOIT had a significant effect on plant photosynthesis.

Exploring the interactions between the gut microbiome and the shifting surrounding aquatic environment in fisheries and aquaculture: A review.

The rise of "new" sequencing technologies and the development of sophisticated bioinformatics tools have dramatically increased the study of the aquaculture microbiome. Microbial communities exist in complex and dynamic communities that play a vital role in the stability of healthy ecosystems. The gut microbiome contributes to multiple aspects of the host's physiological health status, ranging from nutritional regulation to immune modulation. Although studies of the gut microbiome in aquaculture are growing rapidly, the interrelationships between the aquaculture microbiome and its aquatic environment have not been discussed and summarized. In particular, few reviews have focused on the potential mechanisms driving the alteration of the gut microbiome by surrounding aquatic environmental factors. Here, we review current knowledge on the host gut microbiome and its interrelationship with the microbiome of the surrounding environment, mainly including the main methods for characterizing the gut microbiome, the composition and function of microbial communities, the dynamics of microbial interactions, and the relationship between the gut microbiome and the surrounding water/sediment microbiome. Our review highlights two potential mechanisms for how surrounding aquatic environmental factors drive the gut microbiome. This may deepen the understanding of the interactions between the microbiome and environmental factors. Lastly, we also briefly describe the research gaps in current knowledge and prospects for the future orientation of research. This review provides a framework for studying the complex relationship between the host gut microbiome and environmental stresses to better facilitate the widespread application of microbiome technologies in fisheries and aquaculture.

Chronic toxic effects of polystyrene micro-plastics, DCOIT and their combination on marine Chlorella sp.

Polystyrene (PS) is one of the most dangerous polymers, mainly because of the mutagenic or carcinogenic risk of the monomers used to produce it. Sea-Nine 211 is a commercial antifouling agent; its active ingredient is the biocide 4,5-dichloro-2-octyl-4-isothiazolinone-3-one (DCOIT). Micro- and nano-plastics have different synergistic effects on marine organisms together with organic pollutants. To understand the toxic effects of DCOIT and PS alone and in combination, marine Chlorella sp was selected as the experimental organism. The exposure concentration of DCOIT was set at 50 µg/L, and that of PS was set at 10 µg/L. The results show that all exposed groups promoted the growth of marine Chlorella sp in the late stage of exposure, and the recovery time of marine Chlorella sp in the exposed group containing PS was earlier. Changing trend of chlorophyll a was consistent with the growth trend. On the 15th day of exposure, the gene expression of the photosynthesis system in the combined exposed group showed a significant difference, and the cells produced oxidative stress. Scanning electron microscope observation shows the algae adhered to each other. The volume of algae cells in DCOIT and PS exposed groups decreased, and the internal structure of algae cells in each exposed group was damaged.

Exposure to enrofloxacin and depuration: Endocrine disrupting effect in juvenile grass carp (Ctenopharyngodon idella).

This study aimed to determine the effects of Enrofloxacin (ENR) exposure and depuration on the disruption of thyroid function and growth of juvenile grass carp (Ctenopharyngodon idella) as well as to assess the risk of ENR exposure to human health. Juvenile grass carp were treated with ENR solutions at different concentration gradients for 21 days and then depurated for 14 days. The results indicated ENR accumulation in the juvenile grass carp muscles, which persisted after depuration. In addition, exposure to ENR could alter growth by regulating the expression of genes associated with growth hormone/insulin-like growth factor (GH)/IGF) axis and the hypothalamic-pituitary-thyroid (HPT) axis. During ENR exposure, no significant changes in growth hormone levels were observed; however, a significant increase in the growth hormone level was noted. GH/IGF axis-related genes were upregulated after ENR exposure, and their expression levels remained high after depuration. Notably, a significant increase in the serum triiodothyronine (T3) and thyroxine (T4) levels coincided with the upregulation of HPT axis-related genes in both exposure and depuration treatments, and their expression levels remained high after depuration. Therefore, juvenile grass carp exposure to ENR induces physiological stress through HPT and GH/IGF axes that cannot be recovered after depuration. ENR accumulates in the muscles of juvenile grass carp and may pose a threat to human health. Therefore, exposure of juvenile grass carp to ENR results in impaired thyroid function and impaired growth. In addition, consumption of ENR-exposed fish poses human health risks.

Transcriptomic and proteomic analysis of Chinese rare minnow (Gobiocypris rarus) larvae in response to acute waterborne cadmium or mercury stress.

In this study, Chinese rare minnow (Gobiocypris rarus) larvae were exposed to the control group, Cd concentrations (0.5 and 2.5 mg/L), and Hg concentrations (0.1 and 0.3 mg/L) for 96 h. Transcriptome analysis showed that 816 and 1599 significantly differentially expressed genes (DEGs) were identified in response to 2.5 mg/L Cd2+ and 0.3 mg/L Hg2+, respectively. Functional enrichment analysis revealed that DEGs were mostly associated with immune responses after Cd exposure, such as antigen processing and presentation, phagosome, apoptosis, and lysosome. Similarly, functional enrichment analysis showed that many pathways were mostly involved in metabolism after Hg exposure, such as glutathione metabolism and starch and sucrose metabolism. Results of two-dimensional electrophoresis (2-DE) showed that the abundance of 10 protein spots was significantly altered in the Cd2+ treatments. The proteomic analysis demonstrated that Cd toxicity might impair cytoskeletal and cell motility-related protein activity in the liver of G. rarus. Similarly, the abundance of 24 protein spots was significantly altered in the Hg2+ treatments. Hg toxicity regulates the expression of proteins belonging to several functional categories, including cytoskeleton, oxidative stress, digestive system, and energy metabolism. This study provides valuable relevant insight into the molecular mechanisms in response to Cd or Hg toxicity in aquatic organisms and will help screen for potential biomarkers to respond to Cd and Hg pollutants.