vrijdag 22 februari 2013

Meervalmanie in DuikeninBeeld.tv

Het is een erg leuk artikel in duikeninbeeld.tv van Annet van Aarsen over de meerval met prachtige beelden van Cor Kuyvenhoven en Ted Huikeshoven.
Het volledige artikel kun je lezen door op de foto te klikken.

woensdag 20 februari 2013

2013-02-16 10:24 hrs hbos mist coming up again?

Weather : Some clouds / WNW wind 2 bft / Rain 1.1 mm / 1023.7 hpa
Divers : John, Koos, Iva, Jan, Axel,
Goal : sediment sample and secchi visibility check
Max depth : 19.3 mtr
Duration : 38 minutes
Air temp : 5.0 celsius
Water temp : 3.4 celsius minimum
Fish: > 1 Perch
Big Secchi Visibility vertical         9,5 mtr
Big Secchi Visbility horizontal      9,5 mtr
small Secchi Visibility horizontal  9,5 mtr
Dutchi horizontal                       7,0 mtr
Plants: none
Comment: First time diving with GNT wetgloves. There really warmer than drygloves underwater.
First we went via surface to measurepile and did a vertical visibility reading with the big secchi.
I guess my eyes are better than Jan's. I still could see a glimps of the disk at 10 mtr, but Jan saw it at 9 mtr. Average of those measurements is 9,5 mtr. On the horizontal still the big and smaller secchi give the same readings. Dutchi gives 2,5 mtr less as expected. That may turnout completely different when visibility becomes less then 3 meters.
From there I did a quick check on SETL H106. On it a common fishleach had settled on a corner of the plate. Both plates still are home to many shrimp. From there we descended and head 150 degrees out.
John had the courtesy to take a sediment sample from 20 mtr depth which he did ofcourse. After that we headed back to the entrypoint.  At 19 mtr mist is starting to come up although we do not know if this is caused by diver activity or a result of nutreants being released from the sediment
Length of daylight is 9:59 hrs might have something to do with the growth of algea. Temperatures are still low.
This sediment sample is full of life in the form of copepods. Comparing this sample with the one from Toolenburg from 26 mtr depth is that this sample has an uncountable quantity of copepods.

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
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.


zondag 10 februari 2013

2013-02-10 09:53 Toolenburgplas How deep can we get

Weather : Sunny / S wind 4 bft / Rain 0 mm / 1009.8 hpa
Divers : John, Kacper, Robin, Axel,
Goal : How deep can we get, sediment sample.
Max depth : 26.9 mtr
Duration : 32 minutes
Air temp : 0.0 celsius
Water temp : 3.0 celsius minimum
Fish: > 3 Perch, 2 Pike at 26 mtr depth
Estimated visibility: 2-3 mtr
Plants: none
Comment: As we went down the slope we hit 26 mtr in 10 minutes. Robin signalled us and two large Perch swam away. In a very small valley at 26.9 mtr I took my sediment sample.  We noticed a lot of plastic and cans. Pretty tough to do with my Neorpene gloves under my drygloves. Then we saw a pike lying there. Then John gave a turnaround signal so we turned a quarter to the left. With that move Robin and I lost Kacper and John. It is very hard to search with a 2 meter visibility to Robin and I proceded our way back. Along the way Robin spotted another pike. The slopes are gradually going up. Robin found a piece of rope with a weight on it and a stainles steel shackle. It looked as a perpendicular. Eight minutes later than us John and Kacper surfaced. Now I'm going to check out the sediment sample.

zondag 3 februari 2013

2013-02-03 09:54 hbos Viz test big Secchi

Weather : Clouded / SW wind 5 bft / Rain 0 mm / 1014.7 hpa
Divers : John, Patrick, Koos, Kacper, Axel,
Goal : Visibility test Secchi 20 cm horizontal and vertical verus 10 Secchi and Dutchi /  SETL check
Max depth : 16.1 mtr
Duration : 41 minutes
Air temp : 5.0 celsius
Water temp : 4,6 celsius minimum
Fish: > 2 Perch
Dutchi visibility: 3 mtr depth -> 8 meters.
Secchi visibility:  3 meter depth -> 11,5 mtr
Plants: Elodea only found in scattered small bushes at 10 mtr and deeper.
Comment: Mussels at 3 meters and 6 meter now dislodged from measurement pile.
A lot of copepods are swimming in the watercolumn from surface to 16 mtr depth.
Visibility is amazing you can see the slopes at the bottom. 

SETL H136 Start 27-09-12 (grows very small mussels on it which are now bigger than the ones I had found on H135.
SETL H106 Start 15-12-12 has some brown patches (diatoms) on it.
AT both plates many shrimp use it as a savehaven.

Secchi disk 20 cm  
Vertical from surface using divemask. = 11,5 mtr
Horizontal at 3 mtr depth                   = 11,5 mtr
Horizontal at 6 mtr depth                   = 11,5 mtr
Secchi plate test 10 cm
Vertical from surface not possible       = n/a
Horizontal at 3 mtr depth                   = 11,5 mtr
Horizontal at 6 mtr depth                   = 11,5 mtr

Dutchi plate test
Vertical from surface not possible
Horizontal at 3 mtr depth                   = 8 mtr
Horizontal at 6 mtr depth                   = 8 mtr

Conclusion  from this one-off test is that regardless the size both Secchi disk and plate give the same readings.
There is no difference between horizontal and vertical reading when using divemask at surface. There will be a significant difference when you do not have a waterscope or divemask. Reflections / glare and waves at the watersurface have a negative affect on the reading.