donderdag 14 februari 2013

2013-02-12 Turbidity test Vinkeveen versus Toolenburgplas


Weather : Clear / S wind 4 bft / Rain 0 mm / 1009.8 hpa
Divers : Rick, Jan,Jack,Arthur, Axel,
Goal : Get sediment sample and do a visibility reading with Secchi 10 cm
Max depth : 9.6 mtr
Duration : 48 minutes
Air temp : 0.0 celsius
Water temp : 2.4 celsius minimum
Fish: > few Perch, Ruff
Dutchi visibility: 6.5 mtr
Secchi visibility: 9.0 mtr
Plants:bronmos
Comment: Just out of curiousity I took a sample of the bottom next to the bus at 9,6 mtr depth.
Since I also have the bottom sample of Toolenburgplas from 26 mtr I decided to do a little turbidity test.
Now ofcourse comparing them is not really good.. because I should have taken a sample from Vinkeveen from the same depth as Toolenburg.
Left sample tube represents the Toolenburgplas sample which consists of clay 
Right sample tube represents the Vinkeveen sample which mainy consists of sand and peat.
I gave both tubes a good shake and to photo's to see what happens.

Offcourse it is no surprise that clay takes way longer to settle than sand. Even after two hours the Toolenburg sample remains a little turbid (just look at the bottom end where the sediment is). 
Under the microscope Toolenburg sample holds tiny clay plates and some diatoms. There's is life in that tube with active copepods swimming around. The Vinkeveen sample is without life though and I have found 1 diatom.

It is clear that Toolenburg is very prone to bad visibility with wind blowing over the surface. That wind creates a natural current in the water which keeps clay particals airborn. Especially when fish and or divers agitate the sediment.

 










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