To improve the quality of natural seawater to meet the needs of aquaculture production, a large-scale subsurface-flow constructed wetland (HSFCW) was constructed and operated stably for 2 years to understand the reasons for its purification effect on natural seawater. The results of the study showed that the system could maintain a high purification effect on natural seawater during aquaculture; the average removal rates of COD, TSS, TN, NH₄⁺-N, and DON (organic nitrogen) were 22.29%, 49.33%, 36.94%, 10.88%, and 44.08%, respectively. Additionally, the HSFCW could effectively remove harmful algae such as Cyanobacteria; the removal rate of dominant algae species in Cyanobacteria was 90.33–97.93%. The pyrosequencing of 16S ribosomal DNA revealed that Proteobacteria, Nitrospirae, and Chloroflexi were the main and key bacterial phyla in the system. Members of these key gates are regarded as playing important roles in resisting water purification. The study results suggest that the subsurface-flow wetland system can effectively improve seawater quality and reduce the density of harmful algae cells.

Microsporidia are obligate intracellular parasites with extensively reduced genomes, yet substantial genomic variation occurs among lineages. Glugea plecoglossi infects ayu (Plecoglossus altivelis) and forms conspicuous xenomas, but its genome characteristics and evolutionary position remain poorly resolved. We generated a genome assembly of G. plecoglossi and compared it with 42 additional microsporidian taxa using phylogenomics, functional profiling, repeat analysis, and multi-copy orthogroup analysis. The 16.71 Mb assembly comprised 59 scaffolds, with a scaffold N50 of 557.5 kb and 78.5% complete BUSCOs, and contained 4331 predicted protein-coding gene loci. Phylogenomic analysis recovered G. plecoglossi as the sister taxon to Pseudoloma neurophilia. Compared with closely related taxa, G. plecoglossi had a substantially larger genome and more predicted protein-coding genes. Major Gene Ontology profiles were broadly similar across taxa, whereas metabolism-related profiles varied considerably. Among 11 genomes, repetitive-sequence composition differed markedly, with G. plecoglossi showing particularly high long terminal repeat coverage and substantial DNA-transposon coverage. The retained multi-copy orthogroups showed highly heterogeneous member distributions across taxa, with relatively high member numbers in G. plecoglossi restricted to a limited subset. These findings highlight genomic and functional variation among microsporidian lineages and provide a comparative genomic resource for future studies of fish-infecting microsporidia.

Low-density SNP panels are widely used to reduce genotyping costs in genomic selection (GS) in aquaculture, but sparse marker density can constrain prediction accuracy, particularly in species with rapid linkage disequilibrium decay. In this study, we evaluated a locally enriched multi-SNP (mSNP) strategy derived from a conventional 1K SNP panel in a family-based breeding population of Pacific white shrimp (Penaeus vannamei). Targeted sequencing was used to recover multiple nearby variants surrounding each marker locus, and conventional SNP and mSNP panels were compared for genomic features, imputation performance, and genomic prediction accuracy for body weight. The mSNP panel exhibited higher polymorphism and broader gene-region coverage than the corresponding SNP panel. The original mSNP panel improved prediction accuracy by 11.6% over the original 1K SNP panel. This advantage was maintained or slightly improved when mSNPs were restricted to on-target variants within ±300 bp of the target markers. A locus-matched comparison further showed that enriched mSNPs consistently outperformed conventional SNPs derived from the same target loci, with a 12.0% improvement at the full 961-locus panel. Although imputation improved the 1K SNP panel, the original mSNP panel already outperformed the imputed SNP panel and reached 0.509 after imputation. These findings demonstrate that locally enriched mSNP markers provide an effective and practical strategy for improving low-density GS in aquaculture species with rapid LD decay.