Bacterial diversity patterns in deep sea sediments

The deep seafloor covers almost 70% of the Earth’s surface and therefore presents the largest continuous ecosystem on Earth, but also one of the least understood. Bacteria dominate deep-sea sediments in terms of abundance and biomass, and play an integral part in the recycling of organic matter and nutrients. However, little is known about bacterial diversity patterns at the deep seafloor and its main environmental drivers. Here, we analyzed globally distributed pelagic surface sediment samples from all major oceans. Using 454 massively parallel tag sequencing, our goal was to provide a first comprehensive description of bacterial communities in pelagic deep-sea surface sediments, and to further determine their specific distribution patterns in a spatial and environmental context. In the Arctic Ocean we specifically analyzed links between phytodetritus input (measured as chlorophyll pigment content), diversity and activity (extracellular enzyme activity) of bacterial communities of the Siberian continental margin (37 to 3472 m water depth). As the main source of energy, phytodetritus flux to the deep sea strongly impacts the abundance, biomass and biodiversity of various size classes of organisms. It has also been shown to influence bacterial biomass and activity, but studies linking energy availability at the seafloor to bacterial diversity patterns are rare. Here we tested for the first time bacterial energy -diversity relationships for complex natural bacterial communities in Arctic seafloor.