As the aquaculture capacity of S. paramamosain in southern China nears saturation, northern coastal regions, which are characterized by abundant water resources, ample feed availability, and favorable climatic conditions, have emerged as ideal areas for aquaculture expansion. This study investigates the aquatic environment of S. paramamosain cultured in seawater and saline-alkali ponds in northern China. Over the course of a five-month aquaculture experiment, water samples were collected from seawater and saline-alkali ponds and subsequently analyzed using 16S rRNA gene sequencing technology to examine the bacterial community composition and its relationship with physicochemical water quality parameters. Sensitive bacterial species were identified as well. The results revealed that seawater ponds exhibited higher salinity and dissolved oxygen levels, but lower pH, ammonia nitrogen, and nitrite nitrogen concentrations. In contrast, saline-alkali ponds exhibited elevated pH, ammonia nitrogen, and nitrite nitrogen levels, accompanied by reduced salinity and dissolved oxygen. Bacterial communities in seawater ponds demonstrated greater species richness, evenness, and diversity indices, whereas those in saline-alkali ponds were characterized by reduced diversity and distinct dominant bacterial groups. Redundancy analysis (RDA) identified salinity, pH, and dissolved oxygen as the principal environmental factors influencing bacterial community structure. Using the IndVal method, we identified strong associations between specific bacterial species and pond types, such as Sphingoaurantiacus and Cobetia in seawater ponds, and Roseivivax, Tropicimonas, and Thiobacillus in saline-alkali ponds. Environmental factors exerted distinct effects on bacterial communities in the two pond types, with sensitive bacterial species demonstrating significant specificity and strong correlations with water quality parameters. Functional predictions indicated that microbes in saline-alkali ponds prioritized resource acquisition and stress resistance, whereas those in seawater ponds emphasized nitrogen metabolism and protein synthesis. This study demonstrated significant differences in bacterial community characteristics between seawater and saline-alkali ponds, which were strongly influenced by water quality parameters. These findings are crucial for optimizing the growth environment of S. paramamosain, providing essential data for improving aquaculture conditions and promoting the development of northern S. paramamosain farming.

Investigating hypoxia tolerance and growth trait single nucleotide polymorphisms (SNPs) in Macrobrachium nipponense is conducive to cultivating prawns with hypoxia tolerance and good growth characteristics. The glutathione S-transferase-2 gene (GST-2) has been shown to regulate hypoxia responses in M. nipponense. In this study, we identified a single GST-2 SNP in M. nipponense, and analyzed its regulatory relationship with hypoxia tolerance and growth. The GST-2 sequence was amplified with a polymerase chain reaction from 197 “Taihu Lake No. 3”, “Taihu Lake No. 2”, and Pearl River population samples to identify SNP loci. The full-length Mn-GST2 sequence was 2317 bp, including three exons and two introns. In total, 38 candidate SNP loci were identified from GST-2 using Mega11.0 comparisons, with most loci moderately polymorphic in terms of genetic diversity. Locus genotypes were also analyzed, and basic genetic parameters for loci were calculated using Popgene32 and PIC_CALC. The expected heterozygosity of the 38 SNP loci ranged from 0.2334 to 0.4997, with an average of 0.4107, while observed heterozygosity ranged from 0.1929 to 0.4721, with an average of 0.3401. The polymorphic information content ranged from 0.21 to 0.37. From SPSS analyses, the G+256A locus was significantly correlated with hypoxia tolerance across all three M. nipponense populations, while the SNP loci A+261C, C+898T, A+1370C, and G+1373T were significantly associated with growth traits. Further analyses revealed that the T+2017C locus was significantly correlated with hypoxia tolerance in “Taihu Lake No. 2” populations, G+256A, A+808T, C+1032T, and A+1530G loci were significantly correlated with hypoxia tolerance in “Taihu Lake No. 3” populations, while no SNP loci were correlated with hypoxia tolerance in Pearl River populations. A+1370C and G+1373T loci, which were associated with growth traits, exhibited a high degree of linkage disequilibrium (r² = 0.89 and r² > 0.8), suggesting potential genetic linkage. Our data suggest associations between hypoxia tolerance and growth trait SNP loci in M. nipponense, and provide valuable evidence for the genetic improvement of growth and hypoxia tolerance in this prawn species.