Improving Water Quality and Microbial Health in Integrated Aquaculture Ponds

Greg Howard
4th June, 2024

Improving Water Quality and Microbial Health in Integrated Aquaculture Ponds

Image Source: Natural Science News, 2024

Key Findings

  • Researchers at Shanghai Ocean University studied nitrogen removal in integrated multi-trophic aquaculture (IMTA) ponds
  • Denitrification and anammox rates increased with longer cultivation periods and greater sediment depth
  • The flux of nitrous oxide at the water-air interface remained stable regardless of cultivation periods
Nitrogen pollution in aquaculture systems is a significant environmental issue. Excess nitrogen can lead to eutrophication, which depletes oxygen in water bodies and harms aquatic life. To address this, researchers at Shanghai Ocean University have conducted a study to assess the nitrogen removal potential of integrated multi-trophic aquaculture (IMTA) ponds[1]. This study explores the efficacy of denitrification and anaerobic ammonium oxidation (anammox) in reducing nitrogen levels in marine aquaculture ponds. The study focused on the denitrification and anammox rates, nitrous oxide (N2O) flux at the water-air interface, sediment microbial community structure, and gene expression associated with nitrogen removal in IMTA ponds. These ponds contained a mix of Apostistius japonicus, Penaeus japonicus, and Ulva, cultivated over different periods. Denitrification and anammox are processes where nitrogen compounds are converted into nitrogen gas (N2) or nitrous oxide gas (N2O), effectively removing nitrogen from the water. Denitrification involves bacteria that convert nitrates (NO3-) into nitrogen gas, while anammox bacteria convert ammonium (NH4+) and nitrites (NO2-) into nitrogen gas. The findings revealed that both denitrification and anammox rates increased with longer cultivation periods and greater sediment depth. Interestingly, the flux of nitrous oxide at the water-air interface did not significantly vary with cultivation periods, suggesting a stable release of this gas regardless of the duration. Microbial analysis indicated significant changes in the abundance of nitrogen-removing microorganisms with depth and cultivation period. The concentration of particulate organic nitrogen (PON) in sediments was a key factor influencing these changes. The expression of denitrification genes (narG, nirS, nosZ) was higher in surface sediments than in deeper layers and showed a negative correlation with the denitrification rate. This suggests that while the genes are more actively expressed at the surface, the actual denitrification process might be more efficient at greater depths. The study also identified an anammox capacity in all samples, although no known anammox bacteria were detected. The expression of the hzsB gene, related to the anammox process, was extremely low. This could indicate the presence of an unknown anammox bacterium, a finding that warrants further investigation. These results align with earlier studies that have explored various methods for enhancing nitrogen removal in aquatic systems. For instance, a study on mix-cultured aerobic denitrifying bacterial communities (Mix-CADBCs) demonstrated significant nitrogen and carbon removal in polluted lake water[2]. The addition of these bacteria promoted denitrification and organic degradation, showcasing a similar potential for biological treatment in aquatic environments. Another study highlighted the benefits of integrating constructed wetlands (CWs) with microalgae-based technologies for wastewater treatment[3]. This integrated system improved pollutant removal efficiencies and promoted denitrification, emphasizing the complementary effects of combining different biological processes. The current study by Shanghai Ocean University builds on these findings by specifically examining the IMTA system's potential for nitrogen removal in marine aquaculture ponds. The results suggest that IMTA ponds have a significant capacity for nitrogen removal, although the presence of unknown anammox bacteria and the varying gene expressions indicate that further research is needed to fully understand and optimize these processes. In summary, the study provides valuable insights into the microbial mechanisms and gene expressions involved in nitrogen removal in IMTA ponds. It highlights the potential of such systems to mitigate nitrogen pollution in aquaculture, contributing to more sustainable and environmentally friendly practices. Future research and practical evaluations will be crucial in determining the full impact and effectiveness of these findings in real-world applications.

EnvironmentEcologyMarine Biology

References

Main Study

1) Nitrogen Removal Performance and Microbial Community Structure of IMTA Ponds (Apostistius japonicus-Penaeus japonicus-Ulva)

Published 3rd June, 2024

https://doi.org/10.1007/s00248-024-02378-z

Related Studies

2) Novel insights into aerobic denitrifying bacterial communities augmented denitrification capacity and mechanisms in lake waters.

https://doi.org/10.1016/j.scitotenv.2022.161011

3) Microalgae-based constructed wetland system enhances nitrogen removal and reduce carbon emissions: Performance and mechanisms.

https://doi.org/10.1016/j.scitotenv.2023.162883


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