Table of Contents

• Coverage
• Dataset Description
  • Methods & Sampling
  • Data Processing Description
• Data Files
• Supplemental Files
• Related Publications
• Related Datasets
• Parameters
• Instruments
• Deployments
• Project Information
• Funding

The Underwater Vision Profiler (UVP5) is an underwater camera system that was designed to record the vertical distributions of large aggregates and zooplankton (> 102 µm) down to 6000 m. Two units that consist of red-light emitting diodes (LEDs) illuminate (in 100 µsecond flashes) an area of 4 X 20 cm which provides a volume sampling of ~1L per frame. The UVP5 was mounted on the bottom of each CTD rosette and collected data on each CTD cast (data are collected during the down cast). The methodology generally follows Picheral et al., 2010.

The Underwater Vision Profiler 5 (UVP5) was utilized to collect in situ images of particles and plankton across the 2015 P16N repeat hydrography transect from French Polynesia (17°S) to the northern Gulf of Alaska shelf (56.3°N), primarily along the 151°W and 152°W meridians. The UVP5 was integrated within the conductivity temperature depth (CTD) rosette, and several images per second were acquired during the downcasts, resulting in a total of 171 vertical profiles from both legs of the cruise, most spanning from the surface down to near the bottom. The UVP captured in situ images of particles and plankton in a mixed processing mode in which particles were sized, counted, and tabulated in real time during the profile. Subsequent processing bins these particle counts into discrete, pre-defined size bins ranging from 102 µm to >26 mm in equivalent spherical diameter. Particle biovolume was also computed for each size bin. All data contained here is inclusive of both living and non-living particles and plankton.

Supplemental file "file_header_uvp5_sn009_2015_p16n_BCO-DMO_PAR.txt" contains additional metadata from the original file header.

Known Problems:
Some profiles did not extend to the full depth of the CTD cast because of problems with the rechargeable lithium ion battery onboard the UVP.

The UVP5 software acquires and processes images in real time. The gain, shutter and LED pulses are controlled and the background image is removed. Images are acquired and processed to get size and grey level for each image. Size information on all detected particles is stored and images of individual particles and plankton larger than 500 µm in equivalent spherical diameter are segmented and saved for later identification. Image post processing and metadata creation is accomplished with the Zooprocess software. Tabulated particle data are used to sum the number and volume of particles within predefined size and depth bins, allowing for the computation of the Datasets. Data and images have been uploaded to the Ecotaxa website (http://ecotaxa.obs-vlfr.fr/) which serves as a tool for particle and zooplankton identification with machine learning and human verification, as well as a repository for all globally collected UVP data. Data files for particle and zooplankton abundances are exported from the Ecotaxa particle module in detailed Ocean Data View (ODV) format, and reformatted for submission to BCO-DMO. The size distribution data is reported in non-differential forms (simply the concentration of particles in each size bin) as well as on a numeric and particle volume basis assuming all particles are spherical. The size bin limits are defined in equivalent spherical diameter (ESD), where ESD = (4 Sm π-1)-0.5 where Sm is the projected area of each particle in mm² and the particle concentrations are reported for each size bin defined by the log-transformed center of each size bin in µm. The biovolume is computed as the sum of the individual spherical volumes of each particle issued from the calibrated ESD.

This dataset was prepared using the scripts archived in this Github repository: https://github.com/britairving/UVP_submission_formatting. This repo has been forked by BCO-DMO to ensure a copy of the code is available. This can be accessed at https://github.com/BCODMO/UVP_submission_formatting. A .zip file of the code is also attached to this dataset as a Supplemental File.

BCO-DMO Processing Notes:
-added conventional header with dataset name, PI name, version date;
- added ISO_DateTime_UTC field with times formatted following ISO8601 conventions;
- renamed fields to comply with BCO-DMO naming conventions;
- replaced "-9999.000000" with "nd" to indicate "no data".

NSF abstract:
The sinking of particles from the sunlit zone of the ocean into the ocean interior constitutes a dominant component of the sequestering of carbon into the deep ocean, otherwise known as the ocean's biological carbon pump. The quantities of particulate matter being exported out of the sunlit zone, as well as the tapering-off of these fluxes with respect to depth, have a substantial impact on the distribution of carbon and other important elements throughout the oceans and control the concentration of carbon dioxide in the atmosphere. For these reasons, it is critical that we gain a comprehensive understanding of the magnitude of these elemental fluxes, their variability in space and time, and the processes that control them. The focus of the of this project is to make new, broadly informative discoveries with regard to the function of the ocean's biological carbon pump and the ability to quantify and monitor its strength and efficiency at high spatial and temporal resolutions. In addition, this project will provide the first quantitative and mechanistic study of sinking particle fluxes in the northern Gulf of Alaska by working in conjunction with the ongoing Seward Line Long-term Observational Program. The project will be carried out under the direction of an early career faculty member and provide a training opportunity for a postdoctoral researcher. Results from the study will be shared with the broader public through a variety of print and digital platforms.

The fluxes of carbon out of the euphotic zone and through subsurface waters are poorly quantified and understood, especially relative to other dominant oceanic carbon flows such as the air-sea gas exchange of carbon dioxide or rates of primary production in surface waters. The inability to differentiate between variability in particle concentration and sinking velocities as the drivers of flux variability is a critical gap in our understanding of the biological carbon pump. The Gulf of Alaska is an optimal site for investigating these processes as the cycling of carbon and other elements in waters above continental shelves, such as the Gulf of Alaska, is highly complex due to the dynamic interplay of chemical, physical, biological, and anthropogenic processes. Using a creative application of short-term sediment trap deployments combined with the use of a unique pair of in situ optical instruments, the researchers will aim to accomplish two specific goals: 1) Quantify the average sinking velocities of small particles and their contribution to the total carbon flux from particles of all sizes; and 2) Determine the relative variability in particle abundances and sinking velocities and assess how it translates into variable patterns of particle flux in the northern Gulf of Alaska.

Affiliated Programs:
Seward Line LTOP, NGA-LTER, US GO-SHIP