RECLESS: Baltic 2026
How does oxygen depletion affect the ocean’s nitrogen cycle, microbial activity and, ultimately, the ocean’s role in the climate system? In summer 2026, researchers from the RECLESS project will board R/V Skagerak to investigate areas with extremely low oxygen levels in the Gotland Deep in the Baltic Sea.
In large parts of the world’s oceans, nitrogen is one of the key elements controlling how much plankton and other organisms can grow. Nitrogen therefore also influences how much carbon dioxide the ocean can take up from the atmosphere. However, in oxygen-depleted marine areas, the nitrogen cycle changes. Microorganisms can convert biologically available nitrogen into nitrogen gas and nitrous oxide — a powerful greenhouse gas.
Oxygen minimum zones expected to become more common in the oceans
Oxygen-depleted areas, known as oxygen minimum zones, occur in several parts of the world’s oceans and are expected to become more common as the climate changes. The Baltic Sea is a particularly important area to study, as parts of it regularly experience very low oxygen levels. The Gotland Deep is one of the best-known deep basins in the Baltic Sea and provides a natural setting for investigating how microorganisms control the movement of nitrogen through the ecosystem.
During the expedition to the Gotland Deep in summer 2026, the research team will collect water samples and carry out advanced measurements of oxygen, nitrogen and microbial processes. Using new technology, including highly sensitive oxygen sensors and analyses of microorganisms at single-cell level, the researchers aim to understand what is actually happening in these oxygen-depleted water masses.
Seeking new knowledge about the vital role of nitrogen
The results from the Baltic Sea will be compared with data from other oxygen-depleted marine areas around the world. The aim is to improve understanding of how nitrogen is transformed in the ocean, how much nitrogen is lost, and how these processes may affect ocean productivity, ecosystems and climate in the future.
