Intra-habitat Differences in the Composition of the Methanogenic Archaeal Community between the Microcystis-Dominated and the Macrophyte-Dominated Bays in Taihu Lake

A regime shift between a macrophyte-dominated clear state and a phytoplankton-dominated turbid state can have considerable impact on ecosystem structure and function of shallow lakes. However, very little is known about the response of the methanogenic archaeal community in the sediment during this regime shift. We investigated the methanogenic archaeal community at two sites in the large, shallow, eutrophic Taihu Lake over the course of one year. One site is located in Meiliang Bay and is dominated by Microcystis blooms, and the other site is located in East Taihu Bay and is dominated by aquatic macrophytes. Terminal restriction fragment length polymorphism (T-RFLP) and phylogenetic analyses of archaeal 16S rRNA genes were used to analyze the methanogenic community. Higher ratio of methanogens in Archaea was observed in East Taihu Bay than in Meiliang Bay. The methanogenic archaeal community was dominated by the Methanobacteriales and the LDS cluster in macrophytes-dominated East Taihu Bay, while it was dominated by the Methanosarcinaceae, Methanobacteriales, and the LDS cluster in Microcystis-dominated Meiliang Bay. Clustering analysis of all of the samples revealed differences in the composition of the methanogenic archaeal communities between the two sites that were independent of seasonal variations. Further statistical analysis indicated that the chlorophyll a (Chla) concentration had a profound impact on the composition of the methanogenic archaeal community in Meiliang Bay, whereas it was primarily influenced by total organic carbon (TOC) levels in East Taihu Bay. Overall, this investigation demonstrates that intra-habitat differences in the composition of methanogenic archaeal communities are likely driven by changes in the available organic materials.