Conversion of coastal marsh to aquaculture ponds altered soil ammonia oxidiser community and decreased ammonia oxidation potential

Introduction

As a crucial component of the nitrogen cycle, ammonia oxidation in soil can be driven by canonical ammonia-oxidising archaea (AOA) and bacteria, as well as complete ammonia oxidiser (CMX Nitrospira). Land use change can disrupt and alter the soil microbial community and the nitrogen cycle.

Materials & Methods

We compared the soil ammonia-oxidising microorganisms and ammonia oxidation potentials in a coastal marsh and nearby reclaimed aquaculture ponds, monthly over a 10-month period in southeastern China. The abundance of ammonia oxidisers was assessed by real-time quantitative PCR and the community structure of CMX Nitrospira was evaluated by high-throughput sequencing.

Results

The ammonia oxidiser community was dominated by AOA in the marsh (91%) and was made up of similar proportions of AOA and CMX Nitrospira in the aquaculture ponds (46%–47%). The CMX Nitrospira community structure changed significantly between habitat types, mainly driven by opposite change in relative abundance of clade B versus clades A.2 and A.3. Aquaculture reclamation decreased the soil potential ammonia oxidation rate (PAO) by an order of magnitude, and AOA was the only significant predictor of PAO among all ammonia oxidiser groups.

Conclusion

Our results suggest that aquaculture reclamation from coastal marshes would significantly alter the soil ammonia oxidiser community and decrease ammonia oxidation rate, and CMX Nitrospira appear to play a relative larger role in nitrogen cycling in aquaculture ponds.