Response of methanotrophic activity and community structure to plant invasion in China’s coastal wetlands

Abstract

Coastal wetlands are critical in the global carbon budget while vulnerable to plant invasion. Spartina alterniflora (S. alterniflora), a typical invasive plant species, has rapidly expanded in China’s coastal area since 1979, which disturbed the carbon cycle of the coastal wetland ecosystems. However, until now, the effect and underlying mechanisms of S. alterniflora invasion on methanotrophs are poorly known in coastal wetlands. Here, a large-scale investigation of the activity, abundance and community structure of methanotrophs was conducted in seven wetlands under both native (dominated by Phragmites australis, Kandelia candel or Avicennia marina) and invasive plants (dominated by S. alterniflora) across the southeast coast of China. Compared with the native community, S. alterniflora invasion led to a significant (p < 0.05) increase in activity and abundance of methanotrophs, which increased by 62.1% and 64.0% in average, respectively. The invasion of S. alterniflora did not greatly alter the methanotrophic community structure in most of the examined wetlands. However, the relative abundance of type I methanotrophs decreased under P. australis community, while type II methanotrophs (Methylocystis) increased after S. alterniflora invasion. In addition, the soil organic carbon content, ammonium content and salinity were identified as important environmental factors affecting the activity and community structure of methanotrophs. Overall, our results demonstrated that the activity and abundance of methanotrophs responded positively to S. alterniflora invasion, suggesting the important role of methanotrophs in reducing methane emissions from China’s coastal wetlands.