A new peer-reviewed study published in Frontiers in Marine Science shows that Danish coastal waters have only partially recovered from the severe eutrophication of the 1980s — and that progress has stalled over the past two decades.

The study analysed long-term monitoring data from 109 Danish coastal water bodies between 1980 and 2023, tracking seven indicators of eutrophication. Using the integrated assessment tool HEAT 3.0, the team produced the first fine-scale eutrophication assessment of Danish coastal waters.

The results show that national nutrient reduction plans introduced from 1987 drove clear improvements until the early 2000s, after which recovery stagnated. Worryingly, chlorophyll a and water clarity have shown recent trend reversals. The authors conclude that current mitigation efforts are insufficient to bring Danish coastal waters to a state “not affected by eutrophication,” and that climate change is making recovery harder still.

The study began as an M.Sc. thesis by lead authors Marie Neel Jørgensen and Nanna Meilholm at the University of Copenhagen, carried out in cooperation with NIVA Denmark. The work was supervised by Lasse Riemann from University of Copenhagen and Ciarán Murray from NIVA Denmark.

Access the full article here: https://www.frontiersin.org/journals/marine-science/articles/10.3389/fmars.2026.1785011/full