Flavor and nutritional value are important qualities of freshwater fish products, but the key factors affecting these quality parameters remain unclear. In this study, four typical aquaculture modes, including the commercial feed treatment (control), faba bean treatment (FBT), grass powder treatment (GPT), and waving water treatment with commercial feed (WWT), were used to explore the regulatory effect of water quality and feed (eaten and uneaten) on the flesh flavor and nutrition in grass carp (Ctenopharyngodon idella), a freshwater fish of the largest global production. During the culture period (90 days), water quality parameters of the four modes were measured every 15 days, and the flavor quality was evaluated by volatile flavor compounds detection and electronic nose analyzer. Flesh crude protein, crude fat, free fatty acid and free amino acid profiles were also determined. The results showed that, in the late period, the FBT mode had the poorest water quality with highest concentrations of nitrite and nitrate, while the GPT mode has the best water quality among the four modes. Most flesh flavor compounds found in the flesh of the control, GPT and WWT modes were pleasant. In the FBT mode with the poorest water quality, on the other hand, we found lower flavor quality (higher contribution of fishy compounds), higher water content, and lower contents of crude protein, crude fat, free fatty acids and free amino acids, compared to the other three modes. Correlation analyses showed that nitrite and nitrate are probably key water quality factors affecting the flavor quality and nutritional values besides eaten feed and uneaten feed factors. This study can serve as an important reference for ecological regulation and feeding administration of flesh quality in freshwater aquaculture fish.

Marine ranching is an important strategy for restoring marine habitats and replenishing aquatic populations. However, the effects of marine ranching on phytoplankton dynamics remain unclear. In this context, this study takes the Bailong Pearl Bay National Marine Ranching Demonstration Zone as an example to evaluate the influence of marine ranching on the spatial and temporal variation in phytoplankton abundance and community structure. A total of 101 phytoplankton species, spanning 44 genera and 26 families, were documented in the Bailong Pearl Bay National Marine Ranching Demonstration Zone, with 19 of these species identified as harmful algal blooms (HABs) or potential HABs. In spring, phytoplankton abundance remained relatively uniform across sampling stations, with community structure characterized by varying combinations of co-dominant species. In summer, phytoplankton density within the demonstration zone was higher than in adjacent regions. In contrast, lower phytoplankton abundance was observed within the demonstration zone during autumn and winter, periods marked by phytoplankton blooms in surrounding areas (autumn: Chaetoceros lorenzianus, Rhizosolenia alata, and Skeletonema costatum; winter: Nitzschia pungens). Correlation analysis indicated that phytoplankton abundance was positively correlated with nitrate and negatively correlated with phosphate, suggesting nutrient availability as a key driver of phytoplankton dynamics. These findings provide baseline information on how phytoplankton communities vary spatially and seasonally in relation to a marine ranching zone and offer insights to support the management and rehabilitation of marine ecosystems.

Hemibagrus guttatus is a large omnivorous fish of significant economic value, listed as a Class II protected species in the National Key Protected Wildlife List in 2021 in China. To provide a theoretical foundation for the artificial breeding of H. guttatus, this study employs high-throughput transcriptome sequencing of testes and ovaries to elucidate the molecular regulatory pathways involved in sex differentiation. Because H. guttatus exhibits no obvious sexual dimorphism even during the breeding season, the distinctive contribution of this study compared with previous gonadal-transcriptomic investigations in other Siluriformes lies not only in documenting sex-biased genes but also in providing a molecular foundation for developing non-lethal sex-identification methods for this morphologically indistinguishable species. A total of 303,192,896 raw reads were obtained, with an effective data rate of 98.4%, indicating high sequencing quality. Differential expression analysis identified 8694 genes, including 6369 upregulated in testes and 2325 upregulated in ovaries. Among these, 88 genes were functionally annotated as sex-related, with 62 testis-biased genes such as spata17, sox9, and dmrt1, and 26 ovary-biased genes including cyp19a, wnt8, and sox12. KEGG pathway enrichment analysis revealed that the TGF-β signaling pathway, insulin secretion, and steroid hormone biosynthesis may play crucial roles in gonadal development and differentiation in H. guttatus. The expression patterns of key genes such as hsd11b1, amh, and insl3 were validated by quantitative real-time PCR, showing consistency with the transcriptome results. These findings lay a molecular foundation for understanding the regulatory mechanisms of sex differentiation in H. guttatus, and provide candidate genes for further investigation into the genetic basis of gonadal development, which is essential for improving artificial reproduction and selective breeding practices.

The Marine Microbial Carbon Pump (MCP) theory proposes a novel mechanism for long-term carbon sequestration in the ocean, wherein microbial processes convert labile dissolved organic carbon (LDOC) into recalcitrant dissolved organic carbon (RDOC). This review synthesizes recent advancements in technologies aimed at enhancing carbon sinks based on the MCP, with a specific emphasis on coastal ecosystems. Through a structured literature review, this paper evaluates the mechanisms of action, key environmental regulatory factors, and negative emissions technologies associated with utilizing the MCP to bolster the ocean carbon sink. Research indicates that the MCP significantly contributes to the global ocean carbon reservoir, with coastal systems accounting for 40–60% of RDOC production. However, this contribution is constrained by nutrient availability, temperature, light, and anthropogenic pollutants that suppress microbial activity. Current strategies for enhancing carbon sinks encompass nutrient addition, microbial community engineering, and integrated ecological engineering approaches, such as artificial upwelling and macroalgae cultivation. Major challenges remain—particularly low RDOC conversion efficiency (<5%), inadequate monitoring methods, and ecological risks such as harmful algal blooms—that must be addressed before MCP technologies can be deployed at scale. The MCP framework offers a novel and useful perspective for understanding the ocean carbon cycle and presents a potential pathway that requires further validation for achieving negative emissions. Among the strategies reviewed, integrated artificial upwelling with macroalgae cultivation appears most immediately actionable, with pilot studies demonstrating 15–25% increases in sediment carbon storage, though verification at environmentally relevant scales is still required.