Investigating Mesopelagic Organism Occurrence Along the Southeastern
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.