Seascape Alaska 3: Aleutians Remotely Operated Vehicle Exploration and Mapping

(EX2304)

Expedition Summary

From July 14 - July 25, NOAA Ocean Exploration and partners conducted the third in a series of Seascape Alaska expeditions on NOAA Ship Okeanos Explorer. Over the course of 12 days at sea, the team conducted 6 full remotely operated vehicle (ROV) dives, mapped nearly 16,000 square kilometers (6,180 square miles), and collected a variety of biological and geological samples. When combined with numerous biological and geological observations, data from the Seascape Alaska 3: Aleutians Remotely Operated Vehicle Exploration and Mapping expedition will help to establish a baseline assessment of the ocean environment, increase understanding of marine life and habitats to inform management decisions, and increase public awareness of ocean issues.

During the Seascape Alaska 3 expedition, the team completed a total of six full remotely operated vehicle (ROV) dives, exploring sites ranging from the water column to an extensive gas seep covered with tubeworms and an amazing coral garden. The data collected during mapping and ROV operations throughout the expedition will help to fill some of the gaps in our understanding of the deep waters around the Aleutian Islands. Video courtesy of NOAA Ocean Exploration, Seascape Alaska. Download largest version (mp4, 274.2 MB)

Operational Summary

  • Days at sea: 12
  • Full ROV dives: 6, ranging in depth from 780 to 2,800 meters (2,559 to 9,186 feet)
  • Biological samples collected: 22 primary samples, 31 associates
  • Geological samples collected: 6
  • Water samples collected for eDNA analysis: 28
  • Seafloor area mapped: nearly 16,000 square kilometers (6,180 square miles)
  • Science party participants: +40, from 5 countries
  • Live video views: Approximately 21,800
Map showing the location of dives conducted during the Seascape Alaska 3 expedition as well as preliminary bathymetry data collected during mapping operations.
Map showing the location of dives conducted during the Seascape Alaska 3 expedition as well as preliminary bathymetry data collected during mapping operations. Image courtesy of NOAA Ocean Exploration, Seascape Alaska. Download largest version (jpg, 3.3 MB).

 

 

New Species, New Records, New Observations

A major goal of the ROV dives conducted during the Seascape Alaska 3 expedition was to locate and characterize deep-sea coral, sponge, and chemosynthetic communities, and the dives did not disappoint!

Exciting biological discoveries made during the expedition included imaging a potential new (to science) species of Virgularia sea pen, a potential new species of Cladorhizid sponge, and an unusual "simple," non-branching gorgoncephalid basket star. Scientists also identified range extensions for brisingid sea stars in the genus Astrocles and Hemicorallium coral, neither of which had been previously observed in this region of Alaska.

 

 

 

 

On Dive 07 of the expedition, a high-biodiversity coral and sponge garden was discovered while exploring "Uliaga Mound," a feature north of Uliaga Island with several small, approximately 500-meter (1,640-foot) -high mounds on the seafloor. Based on initial observations, scientists identified at least 15 different species of coral (Octocorallia, Scleractinia and Stylasterida), at least the same number of species of sponges, and many more species of associates. However, due to the extremely high densities of organisms seen on the dive, these numbers are likely vastly underestimated and will only increase once image analysis can be performed on collected video footage.

Dive 07 of the Seascape Alaska 3 expedition was spectacular! We were treated to a colorful array of diverse marine life, notably corals and sponges that served as "ecosystem engineers," forming habitat for other organisms. The mound feature explored during the dive was indeed a hotspot for biodiversity. Video courtesy of NOAA Ocean Exploration, Seascape Alaska. Download largest version (mp4, 82.3 MB)

During the fourth dive of the expedition, the team discovered a large tubeworm and clam field on top of a hydrocarbon seep, located approximately 48 kilometers (30 miles) offshore Sanak Island, southwest of Anchorage. The seep was initially detected in mapping data collected during the Seascape Alaska 1 expedition. While the team was only able to survey a small fraction of the site during the ROV dive, they estimate that that field stretches nearly the length of two football fields, which would make it one of, if not the largest field of tubeworms and clams ever discovered.

Remotely operated vehicle shining lights on a field of tubeworms.
Remotely operated vehicle Deep Discoverer traverses over a dense field of chemosynthetic tubeworms that was discovered during Dive 04 of the Seascape Alaska 3 expedition. Image courtesy of NOAA Ocean Exploration, Seascape Alaska. Download largest version (jpg, 547 KB).
Chemosynthetic clams embed in seafloor sediment to extract sulfide. These clams were observed at a gas seep site discovered during Dive 04 of the Seascape Alaska 3 expedition.
Chemosynthetic clams embed in seafloor sediment to extract sulfide. These clams were observed at a gas seep site discovered during Dive 04 of the Seascape Alaska 3 expedition. Image courtesy of NOAA Ocean Exploration, Seascape Alaska. Download largest version (jpg, 1.8 MB).

In addition to the biological discoveries made during the expedition, unique observations of organisms captured in images and video reveal new insights into life in the deep ocean, increasing our ability to manage marine resources and our understanding of deep-sea ecosystem connectivity across the Pacific basin. Some of these observations are highlighted in the gallery below (click on a thumbnail to learn more about each observation!).

 

 

Geological Insights

During the Seascape Alaska 3 expedition, the team mapped nearly 16,000 square kilometers (6,180 square miles) of seafloor, laying the foundation for follow-up exploration during ROV dives and the opportunity for more exciting discoveries during the expedition itself and filling critical gaps in mapping data within deepwater areas around the Aleutian Islands.

“Big Bend Canyon,” a previously unmapped and unexplored submarine canyon that is cut into the current continental slope, was discovered during the Seascape Alaska 3 expedition. The canyon was revealed in new multibeam data collected during the expedition and, using that collected data, part of the canyon was visually surveyed via ROV during Dive 02. Scientists observed exposures of fractured bioturbated mudstone along the canyon walls and glacial dropstones from a previous glacial advance at or near the shelf edge along the canyon’s floor.

During the Seascape Alaska 3 expedition, the team mapped and thus discovered “Big Bend Canyon” and then explored part of the canyon during the second dive of the expedition. This image shows the dive track (white line) taken by remotely operated vehicles Deep Discoverer and Seirios during the dive overlain on collected multibeam bathymetry data with 100-meter (328-foot) contour intervals. Scale is water depth in meters.
During the Seascape Alaska 3 expedition, the team mapped and thus discovered “Big Bend Canyon” and then explored part of the canyon during the second dive of the expedition. This image shows the dive track (white line) taken by remotely operated vehicles Deep Discoverer and Seirios during the dive overlain on collected multibeam bathymetry data with 100-meter (328-foot) contour intervals. Scale is water depth in meters. Image courtesy of NOAA Ocean Exploration, Seascape Alaska. Download largest version (jpg, 827 KB).
The arm of remotely operated vehicle Deep Discoverer reaches out to collect a rock sample during Dive 02 of the Seascape Alaska 3 expedition. This well-cemented, fractured mudstone, collected at a depth of 2,165 meters (7,105 feet), was one of three geological samples collected during the dive.
The arm of remotely operated vehicle Deep Discoverer reaches out to collect a rock sample during Dive 02 of the Seascape Alaska 3 expedition. This well-cemented, fractured mudstone, collected at a depth of 2,165 meters (7,105 feet), was one of three geological samples collected during the dive. Image courtesy of NOAA Ocean Exploration, Seascape Alaska. Download largest version (jpg, 1.4 MB).
Numerous rounded cobbles and pebbles were present on the seafloor near the bend of Big Bend Canyon explored during Dive 02 of the Seascape Alaska 3 expedition. These rounded rock fragments, or clasts, suggest transport in turbulent conditions with grain-grain contact at some point in the past. Clast types observed during the dive ranged from hard, igneous clasts to softer mudstone like the one pictured here. It’s possible these were transported to the shelf-edge during the last glacial maximum and later delivered to the slope.
Numerous rounded cobbles and pebbles were present on the seafloor near the bend of Big Bend Canyon explored during Dive 02 of the Seascape Alaska 3 expedition. These rounded rock fragments, or clasts, suggest transport in turbulent conditions with grain-grain contact at some point in the past. Clast types observed during the dive ranged from hard, igneous clasts to softer mudstone like the one pictured here. It’s possible these were transported to the shelf-edge during the last glacial maximum and later delivered to the slope. Image courtesy of NOAA Ocean Exploration, Seascape Alaska. Download largest version (jpg, 1.3 MB).

Many of the dives that yielded the exciting biological discoveries mentioned earlier also held geological discoveries. Several morphologies of in situ methane hydrates were discovered with associated methane-derived authigenic carbonate at the seep site where the large field of tubeworms and clams were found during Dive 04. A sample of conglomerate cemented with authigenic carbonate was collected during the dive; the carbonate might provide insight into the age and genesis of the hydrate accumulations and associated seep.

During the fourth dive of the Seascape Alaska 3 expedition, the team was able to verify the presence of a gas seep first discovered in seafloor mapping data collected during the first Seascape Alaska expedition, finding bubbles from four active seeps, in situ methane hydrates, methane-derived authigenic carbonates, cemented worm tubes, dense clusters of very healthy chemosynthetic tubeworms that likely buried additional active seeps, Vesicomyidae clams, and a variety of additional marine life. Video courtesy of NOAA Ocean Exploration, Seascape Alaska. Download largest version (jpg, 79.3 MB).
During the fifth Seascape Alaska 3 expedition dive, we investigated a scarp feature that may be related to past landslide activity linked to a 1946 earthquake that caused a very large tsunami. Data collected during exploration of the headwall of the scarp could provide an important piece of this regional geologic puzzle and increase our understanding of geologic hazards overall. Video courtesy of NOAA Ocean Exploration, Seascape Alaska. Download largest version (jpg, 56.9 MB).

Lone Knoll Scarp, a very large landslide scarp, was explored during Dive 05 of the expedition. This scarp feature was previously interpreted as the landslide block partially responsible for the large and destructive 1946 tsunami that destroyed the Scotch Cap lighthouse on Uminak Island and crossed the Pacific and made it all the way to Antarctica.

All of these observations serve to increase our understanding of the geologic history of the region, which in turn can lend insights into potential causes and consequences of natural hazards such as submarine landslides and resulting tsunamis and the probability of future hazard occurrence.

 

 

Engaging the Scientific Community and the Public

On this expedition, over 40 scientists, resource managers, and students from around the world, including in the United States, Canada, Japan, Sweden, and New Zealand, participated in the dives from shore, thanks to telepresence technology on the ship. Additionally, that same technology allowed us to host ship-to-shore interactions and deliver live online streaming of ROV dives to the general public, opening a window of understanding into the deep waters off Alaska for audiences around the world.

On the ground, ship tours conducted in Kodiak prior to the start of the expedition provided local community members, including educators with the Kodiak Island Borough School District, interns with the Alutiiq Museum/Center for Alaskan Coastal Studies, and staff from the NOAA Fisheries Kodiak Laboratory and Alaska Sea Grant, a behind-the-scenes glimpse into exploration work on Okeanos Explorer. Several members of the media also were given a tour of the ship and opportunity to learn more about operations. And, on the other side of the globe, a team at the Tjärnö Aquarium created a new exhibit to allow aquarium visitors to dive deep into the expedition with expedition biology lead Rhian Waller, a researcher at the Tjärnö Marine Laboratory in Sweden.

NOAA Ocean Exploration expedition coordinator Thomas Morrow explains operations to a group during a tour of NOAA Ship Okeanos Explorer while the ship was in Kodiak.
NOAA Ocean Exploration expedition coordinator Thomas Morrow explains operations to a group during a tour of NOAA Ship Okeanos Explorer while the ship was in Kodiak. Image courtesy of NOAA Ocean Exploration, Seascape Alaska. Download largest version (jpg, 5.5 MB).
Shannon Hoy, expedition coordinator team lead with NOAA Ocean Exploration, briefs a group of interns from the Alutiiq Museum/Center for Alaskan Coastal Studies in the control room of NOAA Ship Okeanos Explorer.
Shannon Hoy, expedition coordinator team lead with NOAA Ocean Exploration, briefs a group of interns from the Alutiiq Museum/Center for Alaskan Coastal Studies in the control room of NOAA Ship Okeanos Explorer. Image courtesy of NOAA Ocean Exploration, Seascape Alaska. Download largest version (jpg, 4.9 MB).
Lova Eveborn, science communicator, giving a presentation about a Seascape Alaska 3 coral dive in the auditorium of the Tjärnö Aquarium.
Lova Eveborn, science communicator, giving a presentation about a Seascape Alaska 3 coral dive in the auditorium of the Tjärnö Aquarium. Image courtesy of Christian Nilsson. Download largest version (jpg, 5.5 MB).

Published September 29, 2023