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Abstract The coastal region of the Western Antarctic Peninsula is considered a biological hotspot with high levels of phytoplankton productivity and krill biomass. Recent in situ observations and particle modeling studies of Palmer Canyon, a deep bathymetric feature in the region, demonstrated the presence of a recirculating eddy that traps particles, retaining a distinct particle layer over the summer season. We applied metagenomic sequencing and Imaging Flow Cytobot (IFCB) analysis to characterize the microbial community in the particle layer. We sampled across the upper water column (< 200 m) along a transect to identify the locations of increased particle density, categorizing particles into either living cells or cellular detritus via IFCB. An indicator species analysis of community composition demonstrated the diatomCorethronand the bacteriaSulfitobacterwere significantly highly abundant in samples with high levels of living cells, while the mixotrophic dinoflagellateProrocentrum texanumand prokaryotes Methanomassiliicoccales andFluviicola taffensiswere significantly more abundant in samples with high detritus within the particle layer. From our metagenomic analysis, the significantly differentially abundant metabolic pathway genes in the particle layer of Palmer Canyon included pathways for anaerobic metabolism, such as methanogenesis and sulfate reduction. Overall, our results indicate that distinct microbial species and metabolic pathway genes are present in the retained particle layer of Palmer Canyon.
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This content will become publicly available on July 16, 2026
Optimizing an image analysis protocol for ocean particles in focused shadowgraph imaging systems
A variety of imaging systems are in use in oceanographic surveys, and the opto-mechanical configurations have become highly sophisticated. However, much less consideration has been given to the accurate reconstruction of imaging data. To improve reconstruction of particles captured by Focused Shadowgraph Imaging (FoSI)—a system that excels at visualizing low-optical-density objects, we developed a novel object detection algorithm to process images with a resolution of ~ 12 μm per pixel. Suggested improvements to conventional edge-detection methods are relatively simple and time-efficient, and more accurately render the sizes and shapes of small particles ranging from 24 to 500 μm. In addition, we introduce a gradient of neutral density filters as a part of the protocol serving to calibrate recorded gray levels and thus determine the absolute values of detection thresholds. Set to intermediate detection threshold levels, particle numbers were highly correlated with beam attenuation (cp) measured independently. The utility of our method was underscored by its ability to remove imperfections (dirt, scratches and uneven illumination), and by capturing the transparent particle features such as found in gelatinous plankton, marine snow and a portion of the oceanic gel phase.
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- Award ID(s):
- 2128438
- PAR ID:
- 10657090
- Publisher / Repository:
- BCO-DMO
- Date Published:
- Journal Name:
- Frontiers in Marine Science
- Volume:
- 12
- ISSN:
- 2296-7745
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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