The river Our has its source in the Belgium Ardennes
and marks the boarder to Germany in the North of Luxembourg.
The river has a total length of 78 km,
and drains into the Sauer near Wallendorf.
Along the banks, many plants and animals can be discovered,
but deep under the water, between the gravel,
lives an animal that's not commonly known.
It is up to 10 cm long
and moves along the ground on one foot.
Hello, have you ever met a thick shelled river mussel ?
My name is Unio, and I'd like to invite you
to join me in my underwater world.
My great- great- great-, and many more great-grandparents
already lived here in the Our and in other rivers
and purified the water.
As a matter of fact, we exist since the age of the dinosaurs.
During spring I was released as a little larvae by my mother,
as a little larvae by my mother,
together with my brothers and sisters, into the water.
To develop, we river mussels
need a host fish.
That means we need a fish
onto who's gills we can attach.
By breathing in the water
the fish also inhales the tiny larvae,
and that's how I got hold onto the gills of a minnow.
That's where I developed from a larvae
to a small mussel.
After a few weeks,
when I've grown big enough
I let go of the fish, and let myself drop onto the stony riverbed.
Here, I use my foot to quickly burrow into the gravel,
where I can safely grow up to full size.
Only a few months later I'm ready
to pursue my favored pass time :
filtering the river water.
After 5 to 6 years
I'll release
my own larvae,
Do you want to know why I'm filtering water,
and how I do it?
Of course I do this to feed myself!
The mussel takes up water through its gills
and filters it for tiny particles.
These consist of single-celled organisms or small algae,
or tiny fragments of dead plants and animals.
The mussel rejects the filtered water back into the river.
Anything that it can't digest or use
is simply deposited into the gravel.
Many other animals profit
from this additional food source.
The mussel repeats this procedure 24/7
and can filter up to 50 liters a day.
Remarkably, during the procedure two things happen at the same time:
the mussel and many other creatures find enough food,
and additionally the river water remains clear.
This experiment shows my friends in action.
They work just as a modern filter
and this without any costs or materials,
since they don't need electric energy.
They grow in nature,
no need for factories.
Each mussel filters up to 2 liters of water every hour.
Thus, just a few mussels can filter
muddy water much faster
than a common aquarium pump.
But what about bigger quantities of water?
The water reservoir in Esch-Sauer
can hold up to 60 million m3 of water
and is important to provide the whole country with drinking water.
But first the water
needs to be filtered and treated
in order to be usable to humans.
A huge filtration plant is in charge of water purification.
It consumes a lot of time and energy,
since every one of us is using about 125 liters of water every day!
Theoretically the mussels could be very helpful in this process.
2 to 3 healthy mussels could
purify the water one person uses each day.
To supply the whole country,
at least 1.5 million mussels
would be needed.
How is it going? Fit?
Yes Unio, everything's running smoothly.
Nice of you to come and visit.
It's a hard job, no breaks…
There's always work to do!
Analyzing, filtering, pumping,
nonstop.
Why do I have to do all the work
when you and your family and friends are fit
and could help me filter the water?
We would love to give you a hand,
but unfortunately there are not many of us left
in the rivers and streams of Luxembourg.
Oh really, I didn't know that.
Why are there only so few mussels left?
Could you show me?
I never get out of here.
All sorts of hazards and dangers
have been giving us
a hard time to survive lately.
In pipelines that discharge into the river you'll find many things
that don't belong into the water.
Medication, chemicals, food left over's,
plastic, waste water, fertilizers,
and all sorts of rubbish
find their way into the water and are harmful for the whole ecosystem!
Just take a look at this mess!
Way too often untreated sewage still
discharges into the streams.
How are we supposed to live in this filth?
Our host fish no longer
have access to many sites
because of badly build pipes
instead of proper bridges.
Another problem is soil erosion.
When cattle drink from the stream,
they trample on the bank and mud enters the stream.
Spruce plantations contribute to muddy water as well.
Their roots can't get a good grip in the wet river banks,
so they can't hold back the soil.
Increased amounts of mud clog the riverbed.
When there is too much mud in between the gravel,
water can't run through it any more.
The small mussels that burrow into the gravel
can no longer get sufficient freshwater and oxygen.
So how can we help the thick shelled river mussel?
Huge amounts of gravel are deposited onto the river banks
every year, using heavy engines.
The river distributes the gravel
on hundreds of meters along the riverbed,
primarily during flooding events.
The river builds up a new layer
of clean gravel without mud.
The habitat of mussels and many other animals
is thus recreated.
The main host fish of the thick shelled river mussel,
the European minnow profits from this action as well.
The minnows deposit their eggs, similar to the trout
in high oxygenated spots in the riverbed.
In clean gravel,
the eggs, as well as the newly hatched larvae
have a good oxygen supply, and higher chances to survive.
The water quality is checked regularly.
On several springs and tributaries, the oxygen level,
conductivity and temperature
are checked weekly.
The same samples are taken to a chemical lab,
where further important parameters such as
the pH and nutrition level are checked.
A special rearing station has been installed
next to the river Our to breed young mussels.
Here the thick shelled river mussel
can grow up in a safe environment.
A regular control checks whether
the young mussels are healthy and grow well.
To help the mussels grow, they are fed twice daily,
using a special algae diet.
The algal mix is adapted to number and size of mussels
and thoroughly measured for each tank.
After 2 to 3 years on the rearing station
the small mussels are released into the river
to support their friends in the Our.
Mussels keep our rivers clean,
and play an important role in our ecosystem.
If we keep up protecting them, there is a chance
that more mussels will survive in our rivers in the future.
But to reach this goal, we have to take care
of the water and habitat quality, not only in Luxembourg,
but also across the borders.
That's why the collaboration and exchange
with foreign countries is so important !
All over Europe and the whole world
scientists are busy to improve this situation
Let me say Bye, Ciao and Salut,
don't hesitate to visit me again !
Many thanks that you stand up for
a pure nature and a clean Our!
Summing up we can say
healthy mussels lead to clean rivers,
and if the rivers are clean, many animals,
including us humans are healthy and happy !
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