AUTHOR=Sun Dongyao , Huang Jiafang , Luo Min , Chen Cheng , Lan Xue , Hu Weifang TITLE=Dissimilatory nitrate reduction processes in surface sediments of shrimp ponds during the culture period JOURNAL=Frontiers in Marine Science VOLUME=9 YEAR=2022 URL=https://www.frontiersin.org/journals/marine-science/articles/10.3389/fmars.2022.1082768 DOI=10.3389/fmars.2022.1082768 ISSN=2296-7745 ABSTRACT=

Intensive aquaculture in estuaries and coasts has resulted in several ecological and environmental problems. Among various nitrogen transformation pathway, dissimilatory nitrate (NO₃^-) reduction is considered to be highly important in regulating reactive nitrogen. However, there are relatively few studies on the processes and contribution of NO_x^- reduction in sediment during the shrimp pond culture period. Three sediment NO₃^- reduction processes, denitrification (DNF), anaerobic ammonium oxidation (ANA), and dissimilatory NO₃^- reduction to ammonium (DNRA), were surveyed in eight shrimp ponds across three subtropical estuaries using ¹⁵N isotope tracing experiments. The rates of DNF, ANA and DNRA ranged from 2.87–18.11, 0.10–1.92, and 0.21–1.25 nmol N g ^-1 h ^-1, respectively. DNF was responsible for 64.2–91.6% of the total NO₃^- reduction. Regarding environmental factors, C and N substrates, as well as salinity, significantly affected NO₃^- reduction. In general, the N losses were approximately 32.43–131.64 g N m^-2 yr^-1 for DNF and 2.38–15.85 g N m^-2 yr^-1 for ANA in this study, indicating that coastal reclamation is a nonnegligible way to remove nitrogen. Our results provide a scientific foundation for understanding the mechanism of nitrogen cycling in the artificial aquatic environment of shrimp ponds.