The Unknown and the Unexplored: Insights Into the Pacific Deep-sea Following NOAA CAPSTONE Expeditions

August 28, 2019

Remotely operated vehicle dives conducted during the 2017 CAPSTONE Mountains in the Deep expedition offered the first-ever glimpses at the deepwater habitats around Jarvis Island within the Pacific Remote Islands Marine National Monument and were described by members of the science party as being 'amazing.' Video courtesy of the NOAA Office of Ocean Exploration and Research, Mountains in the Deep: Exploring the Central Pacific Basin. Download (mp4, 38.8 MB)

In one of the largest U.S. exploration efforts ever conducted, NOAA and partners organized and implemented a three-year, Pacific-wide field campaign entitled CAPSTONE: Campaign to Address Pacific monument Science, Technology, and Ocean NEeds. Under the auspices of CAPSTONE, NOAA mapped 597,230 square kilometers (230,590 square miles) of the Pacific seafloor (with approximately 61 percent of mapped area located within U.S. waters), including 323 seamounts; conducted 187 remotely operated vehicle (ROV) dives totaling 891 hours of ROV benthic imaging time; and documented more than 347,000 individual organisms.

This comprehensive effort was detailed and analyzed for the first time in a new paper  published in Frontiers of Marine Science, led by Brian Kennedy (Boston University), Kasey Cantwell (NOAA Office of Ocean Exploration and Research), Mashkoor Malik (NOAA Office of Ocean Exploration and Research) and Randi Rotjan (Boston University). Lead author Kennedy notes: “CAPSTONE is one of the largest dedicated ocean exploration efforts ever undertaken by the United States and provides an unrivaled dataset covering all of the U.S. Pacific.”

While exploring "Ridge" Seamount during the CAPSTONE 2017 Laulima O Ka Moana: Exploring Deep Monument Waters Around Johnston Atoll expedition, Deep Discoverer encountered an alien-like community composed almost exclusively of glass sponges with their concave sides directed towards the current. Video courtesy of the NOAA Office of Ocean Exploration and Research, 2017 Laulima O Ka Moana. Download larger version (mp4, 40.3 MB).

CAPSTONE yielded dramatic insight into differences in biodiversity across depths, regions, and features at multiple taxonomic scales and, for the first time, is helping to quantify what we don’t know about deep-sea biodiversity. For all deep-sea taxonomic groups large enough to be visualized with the ROV, the study found that fewer than 20 percent of the species were able to be identified. Cantwell notes: “so much of the deep sea is unknown – with every day of seafloor mapping and every ROV dive, we learned new things, revealed new details about the geomorphology of the features we explored, and discovered new species.”

The most abundant and highest diversity taxa across the dataset were from three phyla (Cnidaria, Porifera, and Echinodermata). The study further examined these phyla for taxonomic assemblage patterns by depth, geographic region, and geologic feature. Within each taxa, there were multiple genera with specific distribution and abundance by depth, region, and feature. Rotjan notes that “there were definitely surprises – I would never have guessed that some taxa prefer to dwell on the vertical sides of atolls versus islands, for example. Does the shallow-water lagoon really influence the distribution of organisms in the deep sea? More investigation is needed, but this study tantalizingly suggests that surface factors impact deep-sea organisms more than we’ve previously realized.”


The areas explored in the Musicians Seamounts during the 2017 Video courtesy of the NOAA Office of Ocean Exploration and Research, Deep-Sea Symphony: Exploring the Musicians Seamounts. Deep-Sea SymphonyDownload (mp4, 121.4 MB)

On August 3, 2016, during the Deep DiscovererVideo courtesy of the NOAA Office of Ocean Exploration and Research, Deepwater Wonders of Wake. Deepwater Wonders of WakeDownload larger version (mp4, 133.4 MB)


To date, only 13.8 percent of the Pacific has been mapped using modern methods. Kennedy remarked, “I am always amazed at how little of U.S. waters are mapped in high resolution. While this project made a major impact in our deep-sea mapping, there is still so much left to do.”

Despite the incredible amount of new known and unknown information about the Pacific deep sea, CAPSTONE is far from the culminating experience the name suggests. Rather, it marks the beginning of a new era for exploration that will offer extensive opportunities via mapping, technology, analysis, and insights.

The full open access paper can be viewed here: 

This sponge was documented during the CAPSTONE 2015 Hohonu Moana: Exploring Deepwaters off Hawaiʻi expedition, while exploring deepwater habitats in Papahānaumokuākea Marine National Monument. At the time, it was the largest sponge known in the world. Video courtesy of NOAA Office of Ocean Exploration and Research, 2015 Hohonu Moana: Exploring Deep Waters off Hawaii. Download (mp4, 30.8 MB).