The deep-sea floor covers 67% of the Earth’s surface, and is in most places characterized by cold temperatures, permanent darkness, high pressure and food limitation. The surface sediments host a distinct microbial biome, which is dominated by bacteria with on average a billion cells per milliliter. Benthic bacteria are highly relevant to the Earth’s element cycles as they remineralize most of the organic matter sinking from the productive surface ocean, and return nutrients, thereby promoting ocean primary production. What passes the bacterial filter is a relevant sink for carbon on geological time scales, influencing global oxygen and carbon budgets, and fuelling the deep subsurface biosphere. Despite the relevance of deep-sea sediment bacteria to climate, geochemical cycles and ecology of the seafloor, their genetic and functional diversity, niche differentiation and biological interactions remain unknown.

Within the ABYSS project, we want to develop a systematic understanding of abyssal sediment bacterial community distribution, diversity, function and interactions, by bridging biogeochemistry, ecology, microbiology and marine biology, and by combining in situ flux studies and different visualization techniques with a wide range of molecular tools. One of our main study sites is the LTER observatory HAUSGARTEN in Fram Strait.

The main tasks of the ABYSS are: 

• to identify the most common bacterial taxa in deep-sea surface sediments and characterize their distribution in space and time. Classify organic matter size, age, and compound classes.
• to compare bacterial communities of surface sediments with those of sinking and suspended particles and those of subsurface sediments.
• to investigate which microbial taxa associate with freshly deposited algal detritus, how rapidly they respire and assimilate carbon, and which types of bacterial and molecular profiles remain in the aged particulate and organic matter.
• to measure variations in cell and community level element stoichiometry, carbon respiration, hydrolysis and assimilation efficiencies of a range of bacterial types by in situ incubation with isotope-labeled substrates.
• to improve insights into bacterial interactions with temporal and spatial variations in POC export, by using a modeling approach.
• to decipher the long-term fate of surface communities and deposited organic matter by high-resolution analysis of vertical sediment layers into the past/subsurface.
• to adapt and improve our existing deep-sea technology pool for targeted and quantitative biogeochemical sampling.

Contact: A. Boetius, C. Bienhold

Paper featuring results from the ABYSS project

Conference contributions of the ABYSS project

Theses written in the framework of ABYSS