Diversity and ecology of bacterial communities at the deep seafloor

Abstract

Understanding biodiversity and its distribution across space, time, and along environmental gradients, is crucial in order to assess the ecological functions of groups of organisms in the environment and gain insights into overall ecosystem functioning. In contrast to the distribution patterns of larger organisms, little is known about the structuring of bacterial communities in the environment. The reason being, that appropriate tools for the study of microbial ecology have only become available during the last decades. Today, molecular tools like fingerprinting or next-generation sequencing enable a time- and cost-effective, high-throughput processing of environmental samples to study bacterial diversity patterns. The application of such tools has revealed non-random patterns of bacterial diversity across space and time, and along environmental gradients in a variety of habitats. However, research on microbial community ecology is just starting to pick up pace, and entire ecosystems, such as the deep seafloor, remain largely uncharted. The deep sea represents the largest ecosystem on Earth and at the same time remains one of the least explored regions on our planet. Bacterial communities play an essential role for carbon and nutrient cycling in deep-sea sediments, and are thus an important component of benthic deep-sea ecosystems. Therefore, the specific investigation of bacterial diversity and its distribution at the deep seafloor in the context of environmental parameters were major objectives of this thesis. The influence of both spatial distance, as an indicator for dispersal limitation, and contemporary environmental factors on bacterial communities were investigated at different spatial scales.