17 Denmark

17.1 Nitrogen pollution

This reporting covers the period 22 September – 26 October, i.e. in continuation of the extensive oxygen depletion in mid-September, which was the second largest rec- orded so far. In the following two weeks, the poor oxygen conditions were maintained and in some areas worsened even further. The strong wind during October improved the oxygen conditions significantly. At the beginning of October, the most severely affected areas of oxygen depletion were Mariager Fjord, Aarhus Bay and many of the east Jutland fjords south of here, the southern Little Belt, the Southern Funen Archi- pelago and Marstal Bay. In several of these areas, the bottom water was devoid of oxygen, and toxic sulphide was released from the bottom. Dying fish and benthic an- imals were observed at the inner part of Horsens and Vejle Fjord at the end of Sep- tember and at the beginning of October. At the end of October, there was only wide- spread oxygen depletion in the inner Danish waters in the southern Little Belt be- tween Als and Ærø

DCE (2023) Iltsvind i danske farvande 22. september – 26. oktober 2023 (pdf)

Figure: Oxygen loss in Danish Waters

Stormfloden i oktober 2023 havde ødelæggende konsekvenser på landjorden, men under vandoverfladen var der måske grund til positive miner.

Det havde nemlig potentielt haft en positiv effekt på iltningen af havbunden,

Videnskap.dk (2023) Iltsvindet er stadig højt på trods af stormflod