donderdag 26 juli 2012

2012-07-25 20:15 hbos Dense milky layer up to 7-8 mtr

Weather : Clear / N wind 2 bft / Rain  0.0 mm / 1016 hpa
Divers : Ted, Axel
Goal : Visibility, Watersample, check TC
Max depth : 16.7 mtrs 
Duration : 72 minutes
Air temp :  27.7 celsius
Water temp : 17.2 celsius minimum
Fish: > young fish (perch) more scattered also at 14 mtr depth- no waterfleas nore copepods (eenoogskreeftjes)
2 Eal, > 20 Ruffe, 1 Zander at 14 mtr. And as far as I can see quite a lot of Melt (Esmerus Eperlanus) (Spiering)
Plants : Pondweed (ELodea) Gutweed still in same state being shrunk in small quantities
Potamogeton species still there.
Visibility  : 2 mtr at 3 mtr depth, 2.5 mtr at 6 mtr depth
Yellow viz: 2 mtr at 3 mtr depth, 2,5 mtr at 6 mtr depth
Remarks: The milky white layer more like a dense mist and light scatters. You cannot even see 100% sharp anymore. Layer is from 7-8 mtr depth upto the surface. Underneath that layer the temperature graph on my computer shows a sawtooth model. Going up and down 0,7 celcius. You can actually see the dustlayers in the water.
At 14-15 mtrs another layer and at 16 mtr the temp drops from 18.3 to 17.2. Not a major difference though.
This time we experimented visibility with a Secchidisk like plate with yellow/black and with white/black squares. No difference between white and yellow. This time Baseline viz with lightsource and yellow viz without lightsource gave same readings. 
In nighttime you often see small elongated fish desperately trying to escape from your lightbeam. Occaisionally they swim right into the lightbeam hitting your lamp. It guess it is a Melt (Spiering).


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