Carl von Ossietzky University Oldenburg – Institute for Chemistry and Biology of the Marine Environment
Sven Emig

Background

Marine biogeochemical cycles are largely driven by microbial processes. In the deep ocean, elevated hydrostatic pressure influences both microbial physiology and the kinetics of enzymatic reactions. However, the extent to which these pressure effects shape global biogeochemical cycling remains poorly understood.

A major challenge is that microbiological and biogeochemical experiments are commonly performed at atmospheric pressure, where pressure-dependent processes are not adequately represented. This can lead to underestimation of microbial activity and biased assessments of carbon and oxygen turnover in deep-sea environments.

Understanding how microbial communities process this material under natural pressure conditions is essential for improving estimates of deep-sea carbon cycling.

To overcome this limitation, a pressure-stable incubation system is currently being developed to investigate microbial activity under in-situ conditions. The system integrates PyroScience optical oxygen sensors to continuously monitor oxygen consumption within sealed incubation chambers throughout the deployment. This approach enables high-resolution observation of respiratory processes and provides a basis for assessing microbial metabolism under realistic deep-sea conditions.

System Set-Up

The system utilizes three PICO-O₂-SUB oxygen meters from PyroScience, each connected to an OXROB3-SUB optical oxygen probe. This configuration enables simultaneous oxygen measurements in three independent incubation bottles.

The pressure-neutral incubation bottles are designed to allow continuous monitoring of oxygen concentration and temperature throughout the entire incubation period. In addition, a CTD unit records ambient temperature, conductivity, and depth outside the incubation chambers during deployment.

An integrated chemical fixation mechanism allows samples to be preserved directly at depth before recovery, minimizing alterations caused by decompression and maintaining conditions close to the original in-situ environment.

Expected Benefits

The integration of PyroScience optical oxygen sensing technology enables continuous, high-resolution monitoring of microbial oxygen consumption during deep-sea incubations. Combined with pressure-neutral incubation chambers, the system is designed to quantify respiration rates under in-situ conditions while reducing artifacts associated with sample recovery and depressurization.

The modular design provides a flexible platform for future studies of microbial metabolism across different water depths and pressure regimes, including investigations in the deep ocean, oxygen minimum zones, and other low-oxygen environments. The approach can also be adapted to a wide range of biogeochemical and microbial incubation experiments.