Table of Contents

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

Samples for the Bermuda Atlantic Time-series Study (BATS) were collected during monthly cruises in July 2021 (AE2112), November 2021 (AE2124), March 2022 (AE2204), July 2022 (AE2214), November 2022 (AE2224), and March 2023 (AE2306) for seasonal comparison. Particle Interceptor Traps (PITs) were deployed at depths of 150 m, 200 m, and 300 m.

Sinking particles were collected using triplicate polycarbonate gel cups per depth, each containing 100 mL of 12% Tissue Tek polyacrylamide gel to preserve particle structure (Durkin et al., 2015; Ebersbach & Trull, 2008). Gel cups were housed in 70 mm diameter PIT tubes overlaid with dense seawater collected below the halocline (~1000 m), which was filtered (0.2 µm capsule filter, Pall Corp.) and fixed with 2% formalin (final concentration).

Triplicate PIT tubes fitted with acid-cleaned polycarbonate membrane filters (0.8 µm pore size) and filled with poisoned seawater brine (50 g NaCl L⁻¹, 0.7% formalin) were deployed alongside gel cups to measure bulk particulate organic carbon (POC) flux. Membrane filters were processed using standard BATS protocols for C/N analysis (Knap et al., 1997). See the related dataset for more information on the BATS Sediment Trap Particle Flux dataset. 

After recovery, seawater above the dense brine layer was siphoned off, and the remaining seawater was drained. Excess seawater on gel cup surfaces was removed before storage at -80°C. Gel cups were transported on dry ice from Bermuda Institute of Ocean Sciences (BIOS) to Arizona State University for image analysis.

Gel cup surfaces were imaged with a Zeiss Discovery.V12 Stereo Microscope equipped with a 3.2 MP color camera. A Python-based image analysis pipeline was used to segment particles and quantify sinking particle types and size distributions. For most gel cups, 20 non-overlapping images were collected per cup, divided evenly between two focal planes: one at a higher Z-plane to capture smaller particles near the gel surface and one at a lower Z-plane to capture larger particles near the bottom of the gel. Two scale images were captured for each change in Z. The only exception was the July 2021 sampling, where each of the nine gel cups was imaged with 10 pictures and one scale image per cup.

Particles were categorized as fecal aggregates (dense, dark), phytodetrital aggregates (fluffy, amorphous), crustacean fecal pellets (ovular, dense), euphausiid fecal pellets (cylindrical, dense), or debris (fragments <60 µm, amorphous). Sinking particles like animal tissue, molts, and swimmers were excluded.

Particle areas (µm²) were measured using the Particle Image Analysis tool, then converted to biovolumes (µm³) using shape-specific formulas: spherical for fecal and phytodetrital aggregates, combined spherical/cylindrical for crustacean fecal pellets, and cylindrical for euphausiid pellets. Debris particles were treated as spherical. Biovolumes were converted to carbon content (mg C per particle) using published conversion factors from multiple ocean regions (Alldredge & Gotschalk, 1990; Silver & Bruland, 1981; Durkin et al., 2021).

Raw images of sinking particles collected in polyacrylamide gel cups were processed using a Python-based image analysis pipeline. The pipeline utilizes the Particle Image Analysis tool (version 1.0; Rao & Blanco-Bercial, 2023) to perform image segmentation and masking, allowing for precise delineation of individual particle boundaries and measurement of particle area (µm²).

Particle areas were converted to biovolumes (µm³) using shape-specific formulas applied to different particle categories (e.g., spherical for fecal and phytodetrital aggregates, cylindrical for euphausiid pellets). Biovolumes were then converted to carbon content (mg C) using empirically derived conversion factors from multiple oceanographic studies (Alldredge & Gotschalk, 1990; Silver & Bruland, 1981; Durkin et al., 2021).

All image processing and data extraction steps were automated within the Python pipeline to ensure reproducibility and consistency across samples. Additional information can be found on the Zooplankton Vertical Migration website referenced below (Zooplankton Vertical Migration).

- Imported "BCO_DMO_Particle_Sizes.csv" into the BCO-DMO system
- Added deployment and recovery times from BATS dataset, working with submitter
- Converted deployment and retrieval dates to ISO 8601 UTC datetime format, YYYY-MM-DDTHH:MM:SSZ
- Converted longitudes to the preferred BCO-DMO format, adding negative to values that are West
- Renamed fields to comply with BCO-DMO naming conventions, removing units, special characters, and spaces
- Replaced 2205 with 2204 in the "Cruise_num" parameter, based on deployment information
- Added "Particle_ID" values provided by the submitter
- Exported file as "982170_v1_pits_particle_sizes.csv"

NSF Award Abstract:
The purpose of this collaborative project is to advance understanding of the role of marine planktonic animals (or zooplankton) in the biological pump, or transport of carbon from surface to deeper ocean waters. This movement of carbon from surface to deep ocean water can ultimately affect carbon dioxide in the atmosphere, with implications for global climate. Many marine zooplankton, including species of copepods and krill, play a direct role in the biological pump both because they are abundant and because they can migrate from surface waters at night, where they feed, to depths of more than 500 m at night. At the same time, some organisms called flux feeders will remain at depth and do not migrate. Instead, they rely on particles produced by other zooplankton feeding in surface waters. In this project, the investigators are focusing on populations of flux feeders in the deeper ocean waters of the Sargasso Sea. They are leveraging an ongoing long-term research program, conducting field collections using specialized nets and particle traps, as well lab experiments, as a way to understand how these organisms modify the particles around them. This project is supporting a postdoctoral scientist and providing research experiences for undergraduates at two institutions. An education specialist is creating lesson plans for an award-winning Ask-A-Biologist website, designed for public and K-12 audiences. Images of zooplankton will be disseminated to the public and scientific community via EcoTaxa (a web platform devoted to plankton biodiversity, with images and taxonomic annotation) and physical samples will be archived as part of a teaching library.

The oceanic biological carbon pump refers to the export of dissolved and particulate organic carbon to the deep ocean, and it is a significant driver of atmospheric carbon uptake by the oceans. Evidence from long-term research carried out at the Bermuda Atlantic Time-series Study (BATS) site suggests that the spectrum of particles collected by gel-traps below the euphotic zone changes drastically below 150 m, which is attributed to resident populations of zooplankton that feed on vertically migrating zooplankton as well as sinking particles. The goals of this study are to investigate the role of different zooplankton taxa on both particle aggregate formation and in particle transformation, and to compare and characterize the particles generated by the zooplankton communities with those collected by particle traps. The investigators are combining field collections with experiments onboard ship and in environmental chambers. They are collecting samples over two years, with three cruises a year to capture distinct seasons. They are assessing high-resolution vertical distribution of zooplankton in the upper 600 m using Multiple Opening-Closing Net and Environmental Sensing System (MOCNESS) tows during day- and night-time, to distinguish diel vertical migrators from resident populations and to quantify contributions to particulate organic carbon flux via fecal pellet production. On each cruise, sinking particles are being collected using gel trap tubes attached to the particle traps deployed monthly at BATS. In addition, roller tank experiments are determining how individual zooplankton mediate aggregate formation. Particle types and fecal pellets are being characterized using image analysis and DNA-based analysis of microbial communities. Finally, ongoing data collection from the long-term BATS program is providing invaluable environmental context and will ensure results from this study contribute to ongoing community efforts to observe and predict the fate of carbon in our global system.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.