Denderleeuw (Brussel Morning Newspaper) – A severe fish die-off hit the Dender near Denderleeuw due to oxygen depletion caused by drought and heavy thunderstorms, prompting emergency cleanup efforts.
Due to a shortage of oxygen in the water brought on by the recent thunderstorm and the ongoing drought, the fish perished.
“In the meantime, the oxygen level is back to normal, but we will definitely continue cleaning up until tonight,”
says Wouter Michiels of the fire station in Denderleeuw.
Yesterday at the Sas van Denderleeuw, a group of dead fish in the Dender were spotted by onlookers. The Flemish Environment Agency (VMM) collected water samples and the fire department came on the scene. These demonstrated that the water’s oxygen content is low.
“The cause is the persistent drought and the thunderstorms of a few days ago,”
the fire department said.
“As a result, the streams and waterways that connect to the Dender were churned up and that water ended up in the Dender en masse. That created an oxygen shortage in a short time.”
The fire brigade has therefore placed aerators in the water around the Sas van Denderleeuw, in order to bring oxygen back into the water.
“In the meantime, the oxygen level is back to normal, but only now are all the dead fish floating to the surface,”
it sounds.
The fire department has been busy all day to remove the dead fish from the water.
“The pleasure boating around the Sas van Denderleeuw has been temporarily stopped and we are on the water with 3 boats to collect the dead fish and remove them from the water,”
says officer Wouter Michiels of the fire station in Denderleeuw, Belgium.
The fire department was able to fill eight barrels of about 150 liters with dead fish.
“We expect to have everything cleared up around 6 pm this evening,”
says Michiels.
How did the thunderstorm contribute to the fish die-off in Denderleeuw?
The ground stores nutrients and organic matter following a drought. Heavy rain from a thunderstorm causes a lot of organic material to be carried into the river or pond by runoff. Increased microbial activity brought on by the abrupt inflow of these materials quickly depletes the water’s oxygen supply.
Thunderstorms can cool the water’s warm surface layer, making it denser. This causes the warm layer to sink and mix with the colder, oxygen-poor bottom layer. This is especially true when wind and heavy rain are present.
Because of this mixing, the oxygen in the water column is diluted, which frequently leads to a general decrease in dissolved oxygen levels that is too low to sustain fish existence.
