Nitrogen cycling and microbial community dynamics in lake sediments

Nitrogen is an essential element in all living organisms and a limiting nutrient in some terrestrial and aquatic ecosystems. Due to increasing anthropogenic nitrogen input, many aquatic systems face changes in the nitrogen cycle that may result in eutrophication of coastal ecosystems. Lakes play a crucial role as nitrogen sinks. Up to 90% of the nitrogen input is reduced through several processes, such as denitrification, anammox, and nitrogen burial. The transformations between the different nitrogen forms are driven by microbial processes, which take place simultaneously in different sections of the lake and are controlled by several environmental parameters.Microbes play a crucial role in the nitrogen transformation processes. Thus, we want to find the key players for the nitrogen transformation processes using a modern microbiological method called metagenomics. The community composition and the abundant key players are analyzed using the entire DNA from a lake sediment sample. Furthermore, we extract and analyze mRNA form the same sample to quantify the activity of gene transcription for each nitrogen transformation process.This study is part of a multidisciplinary project. Several environmental parameters, organic matter and nitrogen transformation rates are measured simultaneously. This will help to better understand the main drivers of microbial community structure and microbial nitrogen transformation processes that influence lake-internal nitrogen removal.