During the recent years, SOFC research has mainly been aimed at reducing the capital cost to effectively compete with other power generation technologies. CMR Prototech, Norway is a provider of technical solutions, product designs and tools for various application areas. Currently, CMR Prototech is planning to develop 2 MW modular fuel cell systems for subsea operation. Each module consists of 200 stacks, each stack producing 10kW. In order to address the technical challenges faced during this development and to make SOFC technology feasible for offshore applications more research on fuel cells in marine environment is necessary. This research was aimed at determining the effects of a) reducing partial pressure of oxygen and b) NaCl contamination on the performance of the SOFC cathode of a single SOFC cell. This present paper focuses on the effect of oxygen partial pressure. Single cell tests were performed in a versatile test station, fully automated and controlled using LabVIEW programming. The fluid handling system with mass flow controllers and four-points measurement probes along with field-point connections were installed in the test station. A set of experiments were conducted, reducing the partial pressure of oxygen supplied to the cathode stopwise (at thre relevant temperatures, namely 800, 850 and 900oC). All the cells were characterized and analyzed by I-V curves. The grain structures of the cells were characterized by scanning electron microscopy (SEM) before and after the experiments.