Effect of salinity on the community structure and ecological functions of Archaea in Liaohe Estuary

Abstract Archaea plays an important role in biogeochemical processes. Using the quantitative polymerase chain reaction (qPCR) and Illumina high-throughput sequencing, eight sediment samples collected in Liaohe Estuary were used to investigate the effects of salinity gradient on the archaeal community structure and ecological functions. The results showed that archaeal abundance ranged from 5.1 × 105 to 1.3 × 106 copies/g. Archaeal community included the classes of Thaumarchaeota (69%), Euryarchaeota (29%), and Crenarchaeota (0.01%), respectively. Methanogens in the genera Methanococcoides, Methanoregula, and Methanosaeta and Marine Group I, Candidatus Nitrososphaera, and Nitrososphaera within the ammonia-oxidizing archaea were abundant in freshwater sediments, whereas Marine Benthic Group B and Marine Benthic Group D were abundant in seawater sediments. The positive correlation was observed in between the abundances of Euryarchaeota and salinities (P < 0.05). Physico-chemical analysis in the sediments showed that the temperature and salinity were impacted on the abundance and distribution of archaea significantly (P < 0.05). In general, these results have broadened our understanding on the changes of the archaeal abundance and community structure in estuarine sediment along the salinity gradient.