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Characterization of biofouling process on glass
spheres in Toulon and Capo Passero
sites.
Characterization of biofouling process on glass
spheres in Toulon and Capo Passero
sites.
Manuela Vecchi KM3NeT CM Pylos April 16th 2007
Antonio Capone, Jean Pierre Schuller, M.V.
Manuela Vecchi KM3NeT CM Pylos April 16th 2007
Antonio Capone, Jean Pierre Schuller, M.V.
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OutlineOutline
The “biofouling” process …what does it mean?
Experimental set - up. Biofouling : what kind of effects? Parametrisation of transparency variation
as a function of “latitude” on the OMs. Time evolution of the fouling “speed” .
The “biofouling” process …what does it mean?
Experimental set - up. Biofouling : what kind of effects? Parametrisation of transparency variation
as a function of “latitude” on the OMs. Time evolution of the fouling “speed” .
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Toulon site ~ 2400 m deep
Capo Passero site ~3300 m deep
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TimeTra
nspa
renc
y
The “biofouling effect”Cause: the growing - up of bacteria colonies
and sedimentation processes.
Effect: it can led to OMs transparency losses.
The “biofouling effect”Cause: the growing - up of bacteria colonies
and sedimentation processes.
Effect: it can led to OMs transparency losses.
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Sphere A
Sphere D Sphere C
Sphere B
Experimental Set -upBuoy
Modem
Buoy
Releases
Ballast
Current meter
Metal frame 2m × 2m
equipped with 4 Benthos spheres
Sphere A contains: CPU, 14 detectors, 1 source (blue LED);Sphere B contains: 2 sources (blue LEDs);Sphere C contains: 1 source (blue LED), 14 detectors;Sphere D was empty and used to balance the structure.
Antares sea campaign:June 2000 – October 2001
NEMO sea campaign:March 2003 – October 2004
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Photodiodes
14 photodiodes (PINs) have been placed on the
internal surface of Benthos Sphere A and
C.
B
C
A
C
PINs on sphere A as seen from sphereB
PINs on sphere C as seen from sphere B
Experimental set – up (2)
TOULON DATA:
For technical reasons we
cannot use the sources on sphere B
TOULON DATA:
For technical reasons we
cannot use the sources on sphere B
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About the sources...
D
B
C
A
Blue LEDs
Reference PINs
Experimental set – up (3)
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The “biofouling” process
Tra
nspa
renc
y
Time
PINs onphere A as seen from B
PINs on sphere C as seen from B
Latitude on the OM North
Transparency has been estimated using:
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Transparency..and its variations…
North
Latitude on the OMs
time
Tra
nspa
renc
y va
riat
ion
Tra
nspa
renc
y va
riat
ion
Time
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Transparency time evolution and variations
Tra
nspa
renc
y
The most regular contributions are likely to
come from the biofilm growing - up.
Tails contain events with bigger fluctuations.
Transparency variation per sample interval
Time
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Double gaussian fit
Experimentally observed: ΔTransp/Δt distributions fit the sum of 2 gaussian
functions.
Transparency variation per sample interval
Biofilm
Sediments
€
χ 2
ndf≅ 3
€
χ 2
ndf≅1
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Sphere A
Sphere D Sphere C
Sphere B
Is there a relation between ∆Transp/∆t and the latitude on the
OMs?
Nor
th
Latitude on Oms
... we can calculate the transparency
loss for several latitudes…
... we can calculate the transparency
loss for several latitudes…
Considering that …
Considering that …
PINs onphere A as seen from B
PINs on sphere C as seen from B
Photodiodes disposition on OMs
For each PIN we can calculate
the transparency
variation
For each PIN we can calculate
the transparency
variation
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Tra
nspa
renc
y va
riat
ion
[% p
er y
ear]
Tra
nspa
renc
y va
riat
ion
[% p
er y
ear]
Transparency variation vs latitude
Latitude
Latitude
Transparency variation as a function of latitude on OMs.
Toulon site
Capo Passero site
Astropart. Phys. 19 (2003) 253-267ANTARES Collaboration
Nor
th
Latitude on Oms
2% transparency loss per year
@ the Equator has been taken from
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Systematic error evaluation
for ANTARES data
The evaluation comes from the value (-2% per year at
the Equator) previously obtained by the ANTARES Collaboration and slightly
changing it.
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Short summary…
● Biofouling does matter!● Transparency variation is slight for
downward-looking surfaces ~ -2% per year (or less in CP site);
● Transparency variation is important for upward-looking surfaces, both in CP and Toulon especially for latitudes bigger than 50°…
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Underwater currents [cm/s]
Capo Passero site Toulon site
Time Time
Current
Compass Angle
Roll Angle
Pitch Angle
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Time
Focusing our attention...
Tra
nspa
renc
y va
riat
ion
[% p
er y
ear]
Nor
th
Latitude on Oms
Downward - looking surfacesDownward - looking surfaces
Dividing the time slice in 7 equal parts and doing the same analysis...
Tra
nspa
renc
y va
riat
ion
[% p
er y
ear]
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Tra
nspa
renc
y va
riat
ion
[%pe
r ye
ar]
Upward - looking surfacesUpward - looking surfaces
Focusing our attention... (2)
Nor
th
Latitude on Oms
TimeTime
Tra
nspa
renc
y va
riat
ion
[%pe
r ye
ar]
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…close to the end ……close to the end …
● Biofouling process can reduce OMs transparency;
● Transparency losses depend on latitude!! especially for upward-looking
surfaces;● The speed of this process depends
on underwater current behaviour (“saturation-like” trend for transparency losses at CapoPassero / fouling speed rise at Toulon
site)
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…the end ……the end …
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Luminescent bacteria quantity
ANTARES site
NEMO site
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ANTARES transparency evolution
Transparency evolution for
downward-looking PINs
Transparency evolution for upward-
looking PINs
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Effective area reduction because of the biofouling process (only for
NEMO)
€
Aeff (t)
Aeff (t = 0)
€
Aeff (t)
Aeff (t = 0)
20% reduction after 10 years @ E < 1TeV
Less than 5% reduction after 10yrs @ > 10 TeV
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Angular resolution + biofouling (only for NEMO)
Angular resolution + biofouling (only for NEMO)
No effect for energies >
10TeV