ElbeXtreme: Ad hoc field investigations in the tidal Elbe

To specifically investigate our research focus on extreme events, scientists from the ElbeXtreme project, together with associated partners from the Hamburg Port Authority (HPA), carried out ad-hoc field investigations in July 2025 in response to a persistent oxygen deficit in the tidal Elbe.

A pronounced lack of oxygen causes considerable ecological stress in the estuary: the critical range of oxygen concentration for fish begins at values below 4 mg/L. In July 2025, however, the daily average temporarily dropped to below 2 mg/L — including at the Bunthaus monitoring station.

Colleagues from AWI, GEOMAR, HEREON, and BSH examined the impacts of this extreme event on various parameters. In-situ water samples were collected between July 18 and July 24, 2025. On July 22, 2025, sampling was conducted in cooperation with the HPA, which provided the vessel Reinhard Woltman for this purpose. Further information on the ad-hoc campaign as well as on the definition and impacts of oxygen deficiency can be found here on our website.

Water sample collection (Photo: GEOMAR).

Such episodes of low dissolved oxygen concentrations are predictable: as part of preparations for early warning systems, ElbeXtreme scientists at Hereon are working on a statistical model to forecast hypoxic events. More information about this model will follow in the coming weeks.

Within ElbeXtreme, we maintain continuous exchange with regional stakeholders: in December 2025, we built on the success of the first ElbeXtreme stakeholder workshop and conducted a second round of engagement. Together with a diverse group of local stakeholders, the focus was on addressing key risks for local ecosystems as well as the valuable services they provide to different sectors.