Archaeal communities in sponge, sediment and water from marine lakes and open water habitats
Marine lakes are characterized by higher temperatures and lower pH and salinity values compared to open-water environments. Microbial communities in these habitats are, thus, subjected to distinct environmental conditions. Understanding how these conditions influence marine lake microbial composition and function can be illuminating since global phenomena such as ocean acidification are predicted to profoundly affect the marine environment. Here we investigated the archaeal community composition and putative function in three biotopes (water, sediment, the sponge Biemna fortis) in three distinct habitats (Kakaban and Haji Buang Lakes and the surrounding open-water habitat of Berau, Indonesia). Both biotope and habitat were shown to be important predictors of variation in archaeal composition and higher taxon abundance, but habitat only proved to be a significant factor for water and sediment. The compositional differences among habitats were mainly driven by differences in sediment archaea. These differences were not only prevalent at a higher taxonomic level, but also at the level of OTU identity, suggesting a degree of environmental specialization of distinct Cenarchaeum symbiosum phylotypes. There were also differences in the abundance of predicted relative gene counts among biotopes and habitats with functions that favour the adaptation to stressful environmental conditions enriched in samples from marine lakes.