Effects of Trophic Status and Temperature on Communities of Sedimentary Ammonia Oxidizers in Lake Taihu

To probe the responsiveness of ammonia oxidizers to environmental factors along different seasons in eutrophic lakes, we investigated the seasonal distribution of community structure and abundance of ammonia oxidizers in relation to the environmental factors in sediments within eutrophic Lake Taihu. We used terminal restriction fragment length polymorphism and real-time PCR to target the molecular biomarker gene of ammonia monooxygenase subunit A. Both phylogenetic analyses and the dominant terminal restriction fragments showed that archaeal ammonia oxidizers belonged to the Crenarchaeota Group I.1a and Crenarchaeota Group I.1b, while bacterial ammonia oxidizers included both Nitrosomonas-like and Nitrosospira-like species. The bacterial ammonia oxidizers were more diverse but less abundant than the ammonia-oxidizing archaea. Significant spatial differences in the ammonia-oxidizing archaeal community structure and abundance were found between the algae-dominated and the macrophyte-dominated regions, which suggest sedimentary trophic status is an important influence. In contrast, there was no significant correlation between bacterial ammonia oxidizer communities and sedimentary trophic status. There were pronounced seasonal variations in ammonia-oxidizing bacterial community structures, reflected by the absence of the Nitrosospira-like species in August and their presence in other months. Both the abundances of archaeal and bacterial ammonia oxidizers were highest in February. The correlation analyses between prokaryotic ammonia oxidizer communities and the investigated physicochemical variables demonstrated that the overlying water temperature was the dominant factor influencing the seasonal variations in ammonia oxidizer community structure and abundance. Supplemental materials are available for this article. Go to the publisher's online edition of Geomicrobiology Journal to view the supplemental file.