Dumping of silt into a nearby lake to ensure the passage of the Norwegian Encore cruise ship by Meyer Werft through the Ems River to the North Sea at the beginning of October has killed 1.5 tonnes of fish.
The dumped silt deprived the fish of oxygen, and the water of the Ems that was part of the dumped mixture increased the salinity levels of the lake. While these factors would have not normally been a problem, the combination of low oxygen and high salinity has led to the fish deaths, Wasser- und Schifffahrtsamt (WSA) Emden said.
Prior to the dredging of the Ems, there was a flood event, which naturally leads to an increase in salinity levels. In addition, the oxygen levels of the lake were at 1.9 mg/l of water three days before the silt was pumped into the lake, which is low as biologists label 4 mg/l as critical for organisms to survive.
The WSA argues that the fish are acclimatised to these conditions because every time a new ship is launched at Meyer Werft, the channel has to be dredged, which amounts to about three times a year, and the lakes serve as dedicated dumping grounds for the sediment.
However, the authority has announced it will ensure levels are monitored to avoid further fish deaths.