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Investigating Mesopelagic Organism Occurrence Along the Southeastern United States
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  • Quinn Girasek,
  • Adrienne Copeland,
  • Katharine Egan,
  • Allen Collins
Quinn Girasek
Juniata College

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Adrienne Copeland
NOAA Ocean Exploration
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Katharine Egan
NOAA Ocean Exploration
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Allen Collins
Smithsonian National Museum of Natural History
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More than half of Earth is covered by ocean, yet little is known about the deep sea (> 200 meters), particularly the water column. From 200 to 1,000 meters below the ocean surface is the mesopelagic zone, where a variety of organisms thrive. Within this zone, there is a portion of the water column where mesopelagic organisms are highly abundant due to light differences and predator avoidance, causing the region to be acoustically dense; this is known as the deep scattering layer (DSL). We hypothesized that there are more organism sightings per minute in the DSL than other regions of the water column and more organism sightings per minute in the Gulf Stream than outside the Gulf Stream. NOAA Ocean Exploration conducted video transects in the mesopelagic zone during expeditions in the deep waters off the Southeastern United States and Puerto Rico using NOAA Ship Okeanos Explorer and remotely operated vehicles (ROVs), Deep Discoverer and Seirios. During three expeditions from 2018 and 2019, imagery, environmental, and acoustic data were collected. Satellite-derived current data were also incorporated for Gulf Stream comparisons. The number of sightings per minute above, within, and below the DSL differed significantly. There were significantly more sightings per minute inside than outside the Gulf Stream. This furthers our understanding of the organisms present in these regions, which is important because of the movement of nutrients in the Gulf Stream and DSL organisms’ role in the food web.