Though it makes up between 95 to 99 percent of the total livable volume of the planet, the water column (which includes all of the water in the ocean between the surface and the seafloor) remains one of the most poorly explored environments on Earth.
While they may seem sparse, midwater animals have the full volume of the water column to move freely about in all three dimensions, making them sometimes difficult to find; however, the water column actually also holds a much greater biomass than the seafloor. From gelatinous animals such as jellies, siphonophores, and tunicates to fish and marine mammals, the organisms that live in the water column are an essential link in the marine ecosystem.
Algae near the surface incorporate carbon dioxide into organic matter through photosynthesis and are eaten by small zooplankton, which in turn are eaten by larger animals. Many zooplankton and small fish feed in the surface layer of the ocean at night and then swim to depth during the day. When these animals swim down in the morning, they move organic matter from the surface to greater depths, where eventually it sinks as marine snow to the seafloor, providing much-needed food. By moving massive quantities of energy from the surface to the deep ocean in what is known as the "carbon pump,” midwater animals provide an important food resource in what would otherwise be a food desert.
While the majority of our exploration focuses on surveying the seafloor to understand the habitat and life there, we are increasingly applying tools and technologies to learn about the abundant life that lives between the sea surface and the seafloor.
Mysteries of the Mesopelagic - NOAA Ocean Today
Exploring the Twilight Zone - Windows to the Deep 2019: Exploration of the Deep-sea Habitats of the Southeastern United States
Explorations Far Above the Musician Seamounts: A Crescendo for Midwater Explorers - Deep-Sea Symphony: Exploring the Musicians Seamounts
Why Do We Explore the Water Column? - Mountains in the Deep: Exploring the Central Pacific Basin
Exploring the Water Column - 2017 American Samoa Expedition: Suesuega o le Moana o Amerika Samoa