Transformation and drive mechanism of nitrogen functional genes at estuaries in dry and wet seasons.

The nitrogen cycle plays a vital role in maintaining ecological health and biodiversity. In aquatic systems, nitrogen transformation genes significantly contribute to biological nitrogen cycling. Although the function of these genes is known to be influenced by environmental factors, there is limited research exploring the relationship between nitrogen transformation genes and environmental factors. Therefore, the correlations, between nitrogen transformation genes and environmental factors, were investigated at the estuaries of Chaohu lake (China) in different seasons. The results showed that the values of temperature, pH, organic compounds, nitrogen, and dissolved oxygen were higher in dry season, whereas the abundance of the genes was lower in dry season. In addition, the abundance of the anaerobic ammoxidation gene was much lower than the nitrification gene and denitrification gene. The results indicated that biological nitrification and denitrification were the primary mechanisms for nitrogen removal at estuaries in different seasons, and the reduction of nitric oxide may be a limiting step in the denitrification process. The Co-occurrence Network and Mantel test indicated that, during the dry season, the temperature was the primary driver of ammonification and nitrification functions, the NO and NO were the primary drivers of denitrification, and the total nitrogen (TN) and NH were the main drivers of anaerobic ammonia oxidation. During the wet season, the dissolved oxygen was the primary driver of ammonification and nitrification functions, the chemical oxygen demand was the primary driver of denitrification, and the TN was the main driver of anaerobic ammonia oxidation. This study provides valuable insights into nitrogen cycling in surface water, contributing to a better understanding of this important process.