1. 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.

2. Outline 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”.

3. Toulon site ~ 2400 m deep Capo Passero site ~3300 m deep

4. Time Transparency 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.

5. Sphere A Sphere D Sphere C Sphere B Experimental Set -up Buoy 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

6. 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 

7. About the sources... D B C A Blue LEDs Reference PINs Experimental set – up (3)

8. The “biofouling” process Transparency 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:

9. Transparency..and its variations… North Latitude on the OMs time Transparency variation Time

10. Transparency time evolution and variations Transparency 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

11. Double gaussian fit Experimentally observed: ΔTransp/Δt distributions fit the sum of 2 gaussian functions. Transparency variation per sample interval Biofilm Sediments

12. Sphere A Sphere D Sphere C Sphere B Is there a relation between ∆Transp/∆t and the latitude on the OMs? North 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

13. Transparency variation [% per year] Transparency variation vs latitude Latitude Transparency variation as a function of latitude on OMs. Toulon site Capo Passero site Astropart. Phys. 19 (2003) 253-267 ANTARES Collaboration North Latitude on Oms 2% transparency loss per year @ the Equator has been taken from 

14. 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.

15. 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°…

16. Underwater currents [cm/s] Capo Passero site Toulon site Time Current Compass Angle Roll Angle Pitch Angle

17. Time Focusing our attention... Transparency variation [% per year] North Latitude on Oms Downward - looking surfaces Dividing the time slice in 7 equal parts and doing the same analysis... Transparency variation [% per year]

18. Upward - looking surfaces Focusing our attention... (2) North Latitude on Oms Time Transparency variation [%per year]

19. …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)

20. …the end …

21. Luminescent bacteria quantity ANTARES site NEMO site

22. ANTARES transparency evolution Transparency evolution for downward-looking PINs Transparency evolution for upward-looking PINs

23. Effective area reduction because of the biofouling process (only for NEMO) 20% reduction after 10 years @ E < 1TeV Less than 5% reduction after 10yrs @ > 10 TeV

24. Angular resolution + biofouling (only for NEMO) No effect for energies > 10TeV