Seasonal variation in the function and diversity of methanotrophs in the littoral wetland of a boreal eutrophic lake

Littoral wetlands are responsible for most of the total methane (CH₄) emissions from lake ecosystems. We show that seasonally variable hydrological and temperature conditions in the littoral wetland of a eutrophic boreal lake affect the community composition and gene transcription of methanotrophs measured by a particulate methane monooxygenase (pmoA) gene-targeted microarray. Type Ib freshwater-cluster methanotrophs were favoured by the high water level, and CH₄ oxidation was positively correlated with their pmoA gene transcripts. In the dry subsite of the wetland, the more stagnant hydrological conditions in summer and autumn induced the dominance of type II methanotrophs over type I methanotrophs (community composition and pmoA gene transcripts). The relative abundance of type II methanotrophs increased in winter. The results provide new insight into the variation of methanotroph communities across seasons in littoral wetlands.