From August 25–28, 2026, IOW oceanographer Michael Naumann, together with Taavi Liblik, physical oceanographer and head of the Division of Marine Physics at Tallinn University of Technology (TalTech, Estonia), conducted a measurement campaign to test autonomous measuring devices in shallow waters off the coast of Mecklenburg-Western Pomerania near Warnemünde. The campaign is part of the IOW’s “Shore to Basin” (S2B) research cluster on shallow water processes, which focuses on investigating the shallow coastal zones of the Baltic Sea—an area that has received little research attention to date.

Shallow coastal zones are regularly affected by oxygen depletion and water warming, which can lead to phenomena such as fish kills and toxic algal blooms. Therefore, the study and long-term monitoring of these shallow coastal areas are of great importance in order to better understand these phenomena and evaluate their consequences.

The researchers conducted the shallow water measurements from aboard the IOW workboat Klaashahn off the coast of Elmenhorst and Nienhagen all the way to Heiligendamm. They were accompanied by the University of Rostock’s research vessel Limanda, led by IOW marine physicist Peter Holtermann. For the shallow-water measurements, an autonomous underwater vehicle (AUV; SEABER, France) from TalTech was used to collect data on the temperature, salinity, and oxygen concentration of the seawater along 3-km-long transects running perpendicular to the coastline from Elmenhorst to the cargo ships' anchorage. The underwater vehicle is an unmanned, torpedo-shaped diving robot with a low weight (9.5 kg in air) and compact dimensions (123 cm long, 12 cm in diameter), which can be used to take measurements in the water column while on board the boat. It can reach speeds of 1.5 to 3 meters per second and operate at depths of up to 300 meters. During the measurements, it repeatedly descended to the seafloor and then swam back to the sea surface and, thus, moved in a wave-like motion throughout the entire water column. In parallel with the AUV measurements, water parameters such as temperature, salinity, and oxygen concentration were measured manually using a handheld CTD probe. This allows the data collected by the AUV to be compared with that from the CTD probe. Based on these measurements, the researchers now aim to determine to what extent AUVs can be used in the future for the IOW’s regular shallow water measurements and what spatial and temporal resolution they offer. Measurements are often particularly challenging in shallow coastal waters because this area is only accessible to smaller boats for the use of measuring devices and for diving operations when the weather is good. A compact AUV like the one from TalTech could therefore be of great benefit to the IOW in the future for studying shallow water processes.

During the campaign, the researchers were able to use the AUV to detect an upwelling of saltier bottom water near the coast—a phenomenon known as an upwelling event. On Tuesday, August 25, 2026, an easterly wind began blowing during the measurement campaign, which by August 27, 2026, had caused oxygen-poor deep water to flow to the surface, leading to a lack of oxygen there. However, the oxygen concentration did not drop to levels harmful to marine life, so-called oxygen depletion (<2 milliliters per liter), but remained at a minimum of 3–4 milliliters per liter. The AUV, together with data measured by researchers aboard the research vessel Limanda as well as by moored stations, enables this upwelling event to be studied in a level of detail that was previously impossible. It is now possible to investigate how meteorological conditions—in this case, wind conditions—affect the water body.

There are plans to further strengthen the collaboration between IOW and TalTech in the future. The current campaign provides an important foundation for this. This measurement campaign marks the first collaboration between the IOW and TalTech on this oceanographic topic in the western Baltic Sea.