Transcriptome analysis of response mechanism to Microcystin-LR and microplastics stress in Asian clam (Corbicula fluminea).

In this study, we analyzed the hepatopancreas tissues of Asian Clam (Corbicula fluminea) exposed to three different adverse environmental conditions from the same batch using RNA-seq. The four treatment groups included the Asian Clam group treated with Microcystin-LR (MC), the Microplastics-treated group (MP), the Microcystin-LR and Microplastics-treated group (MP-MC), and the Control group. Our Gene Ontology analysis revealed 19,173 enriched genes, and the Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis identified 345 related pathways. The KEGG pathway analysis demonstrated that the MC vs control group and the MP vs control group were significantly enriched in immune and catabolic pathways such as Antigen processing and presentation, Rheumatoid arthritis, Lysosome pathway, Phagosome pathway, and Autophagy pathway. We also evaluated the effects of Microplastics and Microcystin-LR on the activities of eight antioxidant enzymes and immune enzymes in Asian clams. Our study enriched the genetic resources of Asian clams and provided valuable information for understanding the response mechanism of Asian clams to microplastics and microcystin in the environment, through the identification of differentially expressed genes and related pathway analyses from the large number of transcriptome sequences obtained.

Transcriptome Analysis of Different Aquaculture Substrates on the Immune Response of Babylonia areolata.

To assess the impact of different substrates in a recirculating water system on the immune response and antioxidant capacity of Babylonia areolata, we conducted a comparative analysis of the transcriptomes and antioxidant performance of the digestive glands in three substrate environments (sand-S group, ceramic granules-C group, and PVC breeding nest-P group). Transcriptome results revealed that the S group and P group exhibited the highest number of differentially expressed genes (DEGs), with a total of 2218 DEGs, including 928 upregulated and 1290 downregulated DEGs. The C group and P group had 1055 DEGs in common, with 316 upregulated and 739 downregulated DEGs. The C group and S group had the fewest DEGs, with 521 in total, including 303 upregulated and 218 downregulated DEGs. GO enrichment analysis showed that in the S vs P group, terms such as catalytic activity, membrane part, and cellular process were enriched with 287, 262, and 180 DEGs, respectively. In the C vs P group, binding, cellular process, and cell part were enriched with 146, 135, and 127 DEGs, respectively. In the C vs S group, catalytic activity, membrane part, and metabolic process were enriched with 90, 83, and 59 DEGs, respectively. Kegg enrichment analysis revealed significant changes in immune-related pathways in the S vs P group, including lysosome, phagosome, and leukocyte transendothelial migration, with 30, 13, and 10 enriched DEGs, respectively. In the C vs P group, phagosome, drug metabolism-other enzymes, and N-Glycan biosynthesis showed significant changes in immune-related pathways, with 9, 6, and 4 enriched DEGs, respectively. In the C vs S group, lysosome, PPAR signaling pathway, and fatty acid degradation exhibited significant changes in immune-related pathways, with 8, 4, and 3 enriched DEGs, respectively. Regarding antioxidant capacity, the S group showed significantly higher total T-AOC than the other experimental groups, while CAT, SOD, POD, and AKP were lower than in the C and P groups. The ACP level in the Sand group was not significantly different from the P group but significantly lower than the C group. In conclusion, substrate environments significantly influence the immune-related genes and key antioxidant enzyme activities in B. areolata.

The biomass of bloom-forming colonial Microcystis affects its response to aeration disturbance.

The algal succession in Microcystis blooms of varying biomass under continuous aeration was studied in a greenhouse. There were four treatments (control, Low, Medium, and High) with initial chlorophyll a (Chl-a) of 32.5, 346.8, 1413.7, and 14,250.0 µg L-1, respectively. During the experiment, Cyanophyta biomass was the lowest in the Medium treatment (P < 0.05), while its Chlorophyta biomass was the highest (P < 0.05). Both Chlorophyta and Bacillariophyta biomass were the lowest in the High treatment (P < 0.05). Bacillariophyta biomass, particularly the diatom Nitzschia palea was the highest in the Low treatment (P < 0.05), and Nitzschia palea cells were attached to the Microcystis colonies. Thus, the algal shift in Microcystis blooms under aeration disturbance depends on its initial biomass, and it shift to green algae or/and diatom dominance in the control, Low, Medium treatments. Diatom cells, particularly N. palea, grew in an attached form on Microcystis colonies in treatment Low, in which the colonies provided media for the adherence. The mechanism of the algal shift with different biomass must be related to the nutrient level, low light and aerobic conditions under aeration disturbance as well as the aeration itself, which destroyed the Microcystis colonies' advantage of floating on the water.

Anaerobic Ammonium Oxidation Bacteria in a Freshwater Recirculating Pond Aquaculture System.

Anaerobic ammonium oxidation (anammox) is a key biochemical process to reduce nitrogen pollution in aquaculture, especially in water recirculating pond aquaculture system (RPAS). We used 16S RNA and quantified PCR to study the distribution and environmental impacts of anammox bacteria in RPAS. The results show that the anammox bacterial community distributions and diversities that are apparently unit-specific and seasonal have significant (p < 0.05) difference variation in the RPAS. Most of the anaerobic ammonium oxidation bacteria sequences (77.72%) retrieved from the RPAS belong to the Brocadia cluster. The abundance of anammox bacterial in the RPAS ranged from 3.33 × 101 to 41.84 × 101 copies per ng of DNA. The environmental parameter of temperature and nitrogen composition in water could have impacted the anammox bacterial abundance. This study provides more information on our understanding of the anammox bacteria in the RPAS, and provides an important basis for RPAS improvement and regulation.

Culture of attached and suspended Rhodopseudomonas faecalis in the presence of decomposing fish feed.

An approach to culturing attached and suspended forms of Rhodopseudomonas faecalis by using compound fish feed with tap water in transparent containers is reported in this study. The ratio of fish feed to tap water was 14.3-50.8 g/L, and no other inoculum or substances were added during the culture process. When the ratio of fish feed to tap water was 14.3 g/L, the highest total nitrogen, total phosphorus, and total dissolved carbon content recorded in the water in the containers were approximately 730 mg/L, 356 mg/L, and 1,620 mg/L, respectively, during the process of feed decay. Comamonas, Rhodopseudomonas, and Clostridium successively dominated during the culture process. Rhodopseudomonas was the most common dominant genus in both the attached and suspended forms when the water was dark red, and the relative operational taxonomic unit abundance reached 80-89% and 24.8%, respectively. The dominant species was R. faecalis. The maximum thickness of attached bacteria and the biomass of attached Rhodopseudomonas reached up to 0.56 mm and 7.5 mg/cm2 , respectively. This study provides a method for the mass culture of Rhodopseudomonas by using the fermentation of aquatic compound fish feed.

Effects of portable solar water quality control machines on aquaculture ponds.

The effects of a portable solar water quality control machine (PSWM) on water quality and sediment of aquaculture ponds were studied in bream aquaculture ponds in Shanghai, China. PSWM operation reduced the temperature and dissolved oxygen (DO) differences between upper and lower water levels. Concentrations of NH4+-N, NO2--N, TN, TP, COD and TSS increased rapidly and reached maximums at 12 h. The density and biomass of phytoplankton and levels of chlorophyll a reached maximums after 40 h of PSWM operation. In a 165-day study, the mean concentrations of NH4+-N, NO2--N and the available phosphorous (AP) in the PSWM ponds were significantly lower than in the control ponds, but the TP was significantly greater than the control ponds. Compared with the test began, the thickness of the sediment in PSWM ponds declined by 12.4 ± 4.3 cm, the control ponds increased by 5.0 ± 2.3 cm and the TN and AP levels in sediment significantly declined. PSWM treatment increased the production of bream and silver carp by 30 and 25%, respectively, and the feed coefficient was reduced by 24.2%. Use of PSWM in bream aquaculture ponds improved water quality, reduced sediment, reduced aquaculture pollution emissions and increased production.

Vertical Segregation and Phylogenetic Characterization of Ammonia-Oxidizing Bacteria and Archaea in the Sediment of a Freshwater Aquaculture Pond.

Pond aquaculture is the major freshwater aquaculture method in China. Ammonia-oxidizing communities inhabiting pond sediments play an important role in controlling culture water quality. However, the distribution and activities of ammonia-oxidizing microbial communities along sediment profiles are poorly understood in this specific environment. Vertical variations in the abundance, transcription, potential ammonia oxidizing rate, and community composition of ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA) in sediment samples (0-50 cm depth) collected from a freshwater aquaculture pond were investigated. The concentrations of the AOA amoA gene were higher than those of the AOB by an order of magnitude, which suggested that AOA, as opposed to AOB, were the numerically predominant ammonia-oxidizing organisms in the surface sediment. This could be attributed to the fact that AOA are more resistant to low levels of dissolved oxygen. However, the concentrations of the AOB amoA mRNA were higher than those of the AOA by 2.5- to 39.9-fold in surface sediments (0-10 cm depth), which suggests that the oxidation of ammonia was mainly performed by AOB in the surface sediments, and by AOA in the deeper sediments, where only AOA could be detected. Clone libraries of AOA and AOB amoA sequences indicated that the diversity of AOA and AOB decreased with increasing depth. The AOB community consisted of two groups: the Nitrosospira and Nitrosomonas clusters, and Nitrosomonas were predominant in the freshwater pond sediment. All AOA amoA gene sequences in the 0-2 cm deep sediment were grouped into the Nitrososphaera cluster, while other AOA sequences in deeper sediments (10-15 and 20-25 cm depths) were grouped into the Nitrosopumilus cluster.