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Long Term Study of Sedimentation and Biofouling at Cascadia Basin, the Site of the Pacific Ocean Neutrino Experiment

O. Aghaei, M. Agostini, S. Agreda, A. Alexander Wight, P. S. Barbeau, A. J. Baron, S. Bash, C. Bellenghi, B. Biffard, M. Boehmer, M. Brandenburg, D. Brussow, N. Cedarblade-Jones, M. Charlton, B. Crudele, M. Danninger, F. C. De Leo, T. DeYoung, F. Fuchs, A. Gärtner, J. Garriz, D. Ghuman, L. Ginzkey, V. Gousy-Leblanc, D. Grant, A. Grimes, C. Haack, R. Halliday, D. Hembroff, F. Henningsen, J. Hutchinson, R. Jenkyns, S. Karanth, T. Kerscher, S. Kershtein, K. Kopański, C. Kopper, P. Krause, C. B. Krauss, I. Kulin, N. Kurahashi, C. Lagunas Gualda, A. Lam, T. Lavallee, K. Leismüller, R. Li, S. Loipolder, A. Magaña Ponce, S. Magel, P. Malecki, G. G. Marshall, T. Martin, S. Mihaly, C. Miller, N. Molberg, R. Moore, B. Nührenbörger, B. Nichol, W. Noga, R. Ørsøe, L. Papp, V. Parrish, M. Paulson, P. Pfahler, B. Pirenne, E. Price, A. Rahlin, M. Rangen, E. Resconi, C. Ridsdale, S. Robertson, A. Round, D. Salazar-Gallegos, A. Scholz, L. Schumacher, S. Sharma, C. Spannfellner, J. Stacho, I. Taboada, A. R. Thurber, M. Tradewell, J. P. Twagirayezu, M. Un Nisa, B. Veenstra, S. Wagner, C. Weaver, N. Whitehorn, L. Winter, M. Wolf, R. Wroński, J. H. Wynne, J. P. Yañez, A. Zaalishvili

TL;DR

This study assesses long-term biofouling and sedimentation at the Cascadia Basin site to inform the P-ONE neutrino telescope design. Using STRAW pathfinders with both low- and high-precision optical measurements, combined with growth-model fits (Logistic and Gompertz) and microbiome analysis, it finds that upward-facing optical surfaces progressively lose transmission beginning around $2.5$ years, potentially reaching complete obscuration or as little as $35\%$ of the initial transparency in the long term. Downward-facing surfaces show far less fouling, supporting design choices that emphasize non-upward-facing sensing and robust calibration. The microbial community data guide mitigation strategies, including anti-fouling coatings, and the results motivate P-ONE-1 deployment plans to maintain light collection efficiency over a decade.

Abstract

STRings for Absorption Length in Water (STRAW)-a and b were pathfinder instruments deployed to characterize the anticipated site of the Pacific Ocean Neutrino Experiment (P-ONE), which is a future neutrino telescope that will be located in the North Pacific Ocean. Measurements of the evolution of the optical transmission efficiency from STRAW-a showed a decline over the detector's lifetime for the upward-facing modules. Video footage of the pathfinders strongly suggested this decline was caused by biofouling and sedimentation. We measure the effect of biofouling and sedimentation to be a decrease in the transparency of upward-facing optical surfaces over 5 years of operations. A majority of downward-facing optical surfaces, which will dominate P-ONE's sensitivity to astrophysical sources, showed no visible biofouling. Extrapolations motivated by biological growth models estimated that these losses started around 2.5 years after deployment, and suggest a reduction in transparency ranging from 35$\%$ of the original to complete obscuration for the upward-facing modules. Samples of biofouling were taken in order to identify the microbial diversity of these organisms and inform potential intervention strategies. Results of the microbial samples and a candidate anti-biofouling strategy that will be tested on upcoming P-ONE instruments are discussed.

Long Term Study of Sedimentation and Biofouling at Cascadia Basin, the Site of the Pacific Ocean Neutrino Experiment

TL;DR

This study assesses long-term biofouling and sedimentation at the Cascadia Basin site to inform the P-ONE neutrino telescope design. Using STRAW pathfinders with both low- and high-precision optical measurements, combined with growth-model fits (Logistic and Gompertz) and microbiome analysis, it finds that upward-facing optical surfaces progressively lose transmission beginning around years, potentially reaching complete obscuration or as little as of the initial transparency in the long term. Downward-facing surfaces show far less fouling, supporting design choices that emphasize non-upward-facing sensing and robust calibration. The microbial community data guide mitigation strategies, including anti-fouling coatings, and the results motivate P-ONE-1 deployment plans to maintain light collection efficiency over a decade.

Abstract

STRings for Absorption Length in Water (STRAW)-a and b were pathfinder instruments deployed to characterize the anticipated site of the Pacific Ocean Neutrino Experiment (P-ONE), which is a future neutrino telescope that will be located in the North Pacific Ocean. Measurements of the evolution of the optical transmission efficiency from STRAW-a showed a decline over the detector's lifetime for the upward-facing modules. Video footage of the pathfinders strongly suggested this decline was caused by biofouling and sedimentation. We measure the effect of biofouling and sedimentation to be a decrease in the transparency of upward-facing optical surfaces over 5 years of operations. A majority of downward-facing optical surfaces, which will dominate P-ONE's sensitivity to astrophysical sources, showed no visible biofouling. Extrapolations motivated by biological growth models estimated that these losses started around 2.5 years after deployment, and suggest a reduction in transparency ranging from 35 of the original to complete obscuration for the upward-facing modules. Samples of biofouling were taken in order to identify the microbial diversity of these organisms and inform potential intervention strategies. Results of the microbial samples and a candidate anti-biofouling strategy that will be tested on upcoming P-ONE instruments are discussed.

Paper Structure

This paper contains 10 sections, 9 equations, 8 figures, 2 tables.

Table of Contents

  1. Introduction
  2. Measuring the Transparency of STRAW Optical Modules
  3. The *straw Detector
  4. Method Using Low-Precision STRAW Data
  5. High-Precision Method and Results
  6. Time Dependence of Fouling Effects
  7. Sampling of Biofouling and Sedimentation
  8. Discussion
  9. Results of This Study
  10. Impact on P-ONE

Figures (8)

  • Figure 1: The *straw instrument Boehmer2019Bailly2021. *poc modules consisted of different wavelength diodes that could be pulsed at known intensities and acted as flasher beacons Henningsen2021. The *sdoms acted as light collecting modules and consisted of an upward- and downward-facing *pmt. Figure reproduced from Ref. Bailly2021 with kind permission of the European Physical Journal (EPJ).
  • Figure 2: *rov footage of *sdom1 on *straw. The module is shown clean shortly after deployment in 2018 (a.). An amount of buildup is visible in the 2020 survey (b.). The final 2023 survey shows a developed macro-fouling population, composed primarily of hydroids (c.).
  • Figure 3: Relative *pmt trigger rates seen by both upward-facing and downward-facing optical surfaces in *straw due to ambient light sources, such as bioluminescence. The total light was averaged monthly across all upward- and downward-facing *pmts, and then normalized to March 2019. On large time scales, fluctuations in the light measured are observed in correlation between orientations.
  • Figure 4: *straw *sdom1 during the *rov survey (a.) and on deck after recovery (b.), showing an unobstructed downward-facing optical surface.
  • Figure 5: Evolution of the light transmission efficiency of selected upward-facing module surfaces. The shaded region shows the one sigma confidence interval for the ratio obtained using ambient bioluminescence light. Individual points show the results of direct measurements using the flasher. All data is normalized to March 2019, and a scaling factor is used between the two data sets to account for different systematic uncertainties between the two methods.
  • ...and 3 more figures