The deep waters off the coast of Alaska are a dark frontier that researchers are only just beginning to map.
Remotely operated vehicles are helping to do this. Marine scientists are analyzing recent 75-hour-long footage of underwater mountains and canyons to understand remote seafloor habitats.
The review uncovered 164 distinct types of corals and sponges, gathered in clusters of biological patchiness.
Which are the most notable and fascinating species living in the deepest Alaskan reefs?
What it takes to map deep subarctic waters in pitch darkness
Some of the most dramatic submerged topography and coldest ocean currents in North America are found in the Gulf of Alaska and the Aleutian region. The extreme depths and harsh weather meant direct sampling was limited over decades of attempts. Extensive stretches of the seabed were left uncharted.
Oceanographers motivated to gather baseline data took advantage of the advances in submersible technology, deploying specialized ROV units thousands of feet below the surface. They descended to record the cliffs, ridges, and valleys on the ocean floor, using strong lighting and high-resolution cameras to record the landscape.
The ROVs were not just focused on the topography. They also captured video of the marine life living on the exposed bedrock.
Later, researchers studied every frame of the 75-hour recording. They recorded structural organisms building complex habitats in the complete absence of light, providing the first detailed visual baseline of life in this subarctic zone.
Uneven distribution patterns and localized presence
While cataloging the organisms, scientists noticed spatial distribution that differed from what they expected. Around 63 percent of the 164 kinds of coral and sponges appeared at only one dive site.
This localized presence surprised biologists who assumed that deep currents would spread larvae across the neighboring seafloor. Conversely, some features hosted distinct biological communities. There was minimal overlap between sites just a few miles apart.
The unique microclimates along the different underwater slopes were the result of variations in current speeds, temperature, and surface type. Organisms thriving on one ledge were absent from a ridge nearby.
The high levels of isolation are an indication of how vulnerable these ecosystems are. If they are disturbed by bottom trawling or mining, communities that exist nowhere else could be destroyed.
Prominent coral discoveries in Alaskan depths
The video review revealed a varied collection of cold-water corals adapted to dark, high-pressure environments.
Among the most notable discoveries were bubblegum corals (Paragorgia), which have fan-like structures several feet tall that filter passing nutrients from the water for food. Researchers also documented dense stands of red tree coral (Primnoa pacifica) and jointed bamboo corals (Isididae). These species have calcified nodes that allow them to anchor and sway in the currents.
Other sightings were of golden spiral whip corals (Chrysogorgia), which wind upward in corkscrew patterns, and rare black corals (Antipathes) with branches like feathers.
Essential nursery habitats in the subarctic Pacific
These slow-growing corals serve as essential nursery habitats for deep-water rockfish and small invertebrates in subarctic Pacific waters, according to NOAA Ocean Exploration.
Video records are useful for visual documentation, but it is not possible to classify every organism down to the species level. They need tissue samples for this stage of the process, and these are difficult to get hold of. Even so, the observation that two-thirds of the species observed were gathered at just one spot gives insight into the Alaskan ocean’s fragmented biodiversity.
Conservation frameworks tailored around multiple distinct deep-sea mountains and canyons are needed to protect these fragile ecosystems.
Submersible robots have much to offer as scientists access regions of the Earth we have never seen before. What they offer to the field of conservation will take us far into the future.
The full study can be read here: Beckmann, L. M., Vad, J., & Waller, R. G. (2026). Diversity and environmental drivers of deep-sea sponge and coral communities in Alaska. Deep Sea Research Part I: Oceanographic Research Papers, 104683.
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