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.

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” .

Toulon site ~ 2400 m deep

Capo Passero site ~3300 m deep

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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.

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

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

About the sources...

D

B

C

A

Blue LEDs

Reference PINs

Experimental set – up (3)

The “biofouling” process

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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:

Transparency..and its variations…

North

Latitude on the OMs

time

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Transparency time evolution and variations

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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

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

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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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

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Latitude on Oms

2% transparency loss per year

@ the Equator has been taken from

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.

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°…

Underwater currents [cm/s]

Capo Passero site Toulon site

Time Time

Current

Compass Angle

Roll Angle

Pitch Angle

Time

Focusing our attention...

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Latitude on Oms

Downward - looking surfacesDownward - looking surfaces

Dividing the time slice in 7 equal parts and doing the same analysis...

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Upward - looking surfacesUpward - looking surfaces

Focusing our attention... (2)

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Latitude on Oms

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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)

…the end ……the end …

Luminescent bacteria quantity

ANTARES site

NEMO site

ANTARES transparency evolution

Transparency evolution for

downward-looking PINs

Transparency evolution for upward-

looking PINs

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

Angular resolution + biofouling (only for NEMO)

Angular resolution + biofouling (only for NEMO)

No effect for energies >

10TeV