Caladan Oceanic-Affiliated Scientific Publications

“Revised Depth of the Challenger Deep from Submersible Transects; Including a General Method for Precise, Pressure-derived Depths in the Ocean” (NOAA Science Staff Members) (2021)

A revised estimate (12/2021) of the maximum depth of the Challenger Deep, generally considered the deepest area of the world’s oceans, based on a series of submersible dives conducted in June 2020. These depth estimates are derived from acoustic altimeter profiles referenced to in-situ pressure and corrected for observed oceanographic properties of the water-column, atmospheric pressure, gravity and gravity-gradient anomalies, and water-level effects. We also present comprehensive methods to determine depth from observed pressure using modern standards and estimate the associated uncertainty. For the Challenger Deep, the deepest observed seafloor depth was 10,935 m (±6 m at 95% C.I.) below mean sea level.

“Maximum depth extensions for Hydrozoa, Tunicata and Ctenophora” (2023)

The observation of rare species in the deep sea is extremely valuable for gaining a census of biodiversity. At hadal depths (> 6000 m), these records provide a more complete picture of the vertical distribution of fauna. In this study, we present new maximum records for Trachymedusae (Hydrozoa), Ascidiacea (Tunicata), and Tentaculata (Ctenophora) taken by submersible and supporting landers in the western Pacific Ocean.

“Depth distribution of the bigeye hound shark Iago omanensis and other deep-sea species observed by baited-camera in the Red Sea” (2023)

The Red Sea is a largely homogeneous water column beyond the top 300 m, unique in exhibiting warm bottom water (∼21.5 °C) at depths down to ∼2900 m. This study presents a rare investigation of the deep Red Sea bigeye hound shark Iago omanensis and provides a full depth distribution for the species in these unusual conditions.

“Worldwide Distribution and Depth Limits of Decapod Crustaceans (Penaeoidea, Oplophoroidea) Across the Abyssal-hadal Transition Zone of Eleven Subduction Trenches and Five Additional Deep-sea Features” (2021)

Decapod crustaceans are conspicuous members of marine benthic communities to at least 7,700 m deep. To assess the bathymetric extent of this taxonomic group, baited landers were deployed to across the abyssal-hadal transition zone of 11 subduction trenches spanning the Pacific, Atlantic, Southern, and Indian oceans and additional sites…

“Barriers to gene flow in the deepest ocean ecosystems: Evidence from global population genomics of a cosmopolitan amphipod.” (2022)

The deepest marine ecosystem, the hadal zone, hosts endemic biodiversity resulting from geographic isolation and environmental selection pressures. However, the pan-ocean distribution of some fauna challenges the concept that the hadal zone is a series of isolated island-like habitats. Whether this remains true at the population genomic level is untested. We investigated phylogeographic patterns of the amphipod, Bathycallisoma schellenbergi, from 12 hadal features across the Pacific, Atlantic, Indian, and Southern oceans and analyzed genome-wide single-nucleotide polymorphism markers and two mitochondrial regions. Despite a cosmopolitan distribution, populations were highly restricted to individual features with only limited gene flow between topographically connected features. This lack of connectivity suggests that populations are on separate evolutionary trajectories, with evidence of potential cryptic speciation at the Atacama Trench. Together, this global study demonstrates that the shallower ocean floor separating hadal features poses strong barriers to dispersal, driving genetic isolation and creating pockets of diversity to conserve.

Safety and Conservation at the Deepest Place on Earth: A Call for Prohibiting the Deliberate Discarding of Nondegradable Umbilicals from Deep-Sea Exploration Vehicles” (2021)

Exploration vehicles can introduce vast quantities of single-use, plastic-coated tether that have been deliberately discarded as observed at the deepest site of all Earth’s oceans. Manned submersible dives to Challenger Deep (10,925 m deep) in the Mariana Trench in 2019 and 2020 revealed hundreds of meters of yellow and white tether strewn across the seafloor. Due to its composition, these fiber-optic tethers will not only persist environmentally, but form a significant risk to equipment and life…

“Hadal Biodiversity, Habitats and Potential Chemosynthesis in the Java Trench, Eastern Indian Ocean” (2022)

The Java Trench is the only subduction trench in the Indian Ocean that extends to the hadal zone (> 6,000 m water depth), and except for seven benthic trawls acquired around the 1950s, there has been little to no sampling at hadal depths undertaken since. In 2019, we undertook a 5-day expedition comprising a scientific dive using a full ocean depth-rated submersible, the DSV Limiting Factor, seven hadal-lander deployments, and high-resolution bathymetric survey…

“Hydrozoans, Scyphozoans, Larvaceans and Ctenophores Observed
in Situ at Hadal Depths” (2021)

Hydrozoa, Scyphozoa, Larvacea (Appendicularia) and Ctenophora are not typically associated with hadal communities. Here, we report observations of these groups based on 136 benthic camera lander deployments that spanned all five oceans, encompassing 14 deep sites, culminating in >1000 h of video in the near-bottom waters between 5000 and 10 925 m.

“No Recovery of a Large-Scale Anthropogenic Sediment Disturbance on the Pacific Seafloor After 77 years at 6460 m Depth” (2022)

Habitat restoration and recolonization of benthic communities after physical perturbation in the deep sea has long been thought to be extremely slow. This study reports on a serendipitous opportunity to survey the current state of a large mechanical disturbance of sediments at 6460 m in the Pacific Ocean. The impact was caused 77 years ago by the sinking of the USS Johnston. The surrounding debris field had little impact on the sedimentary habitat, other than in the provision of artificial hard substrates, while the troughs that formed as the ship impacted the seafloor and slid down the slope of the Philippine Trench were still completely void of animal tracks and burrows, or any observable epifauna, and in some areas subsurface stratification was still exposed at the surface. This suggests that mechanical perturbations of sediments in the deep Pacific may remain ecologically significant for, at the very least, 100 years..

“The Quest for Seafloor Macrolitter: A Critical Review of Background Knowledge, Current Methods and Future Prospects” (2021)

This paper reviews current knowledge and methods, identifies existing needs, and points to future developments that are required to address the estimation of seafloor macrolitter.

The Multi-oceanic Distribution of the Hadal Amphipod, Hirondellea Dubia Dahl, 1959 (Crustacea, Amphipoda) (2022)

The research team discovered hadal amphipod Hirondellea Dubia to be a single species even though it’s geographic range was found to extend from the Southwest Pacific to the Mariana Trench (Northwest Pacific), the South Sandwich Trench (Southern), and the Puerto Rico Trench (North Atlantic). Most samples were collected on the Five Deeps Expedition.

Hadal cephalopods: First Squid Observation (Oegopsida, Magnapinnidae, Magnapinna sp.) and New Records of Finned Octopods (Cirrata) at Depths Greater Than 6000 m in the Philippine Trench (2022)

During the Ring of Fire Expedition to the Philippine Trench in 2021 the tea, discovered the second ever records of cirrate octopods at hadal depths and first ever finding of a hadal squid: the big fin squid Magnapinna.

Hadal Fauna of the South Sandwich Trench, Southern Ocean: Baited Camera Survey From the Five Deeps Expedition (2021)

This paper described the results of the Five deeps expedition to the South Sandwich Trench in Antarctica. We document the mobile fauna from 6000 to 8300 m, including habitat classifications from a trench never before explored.

A Global Assessment of Fishes at Lower Abyssal and Upper Hadal Depths (5000 to 8000 meters (2021)

Over a decade of hadal lander deployments were complied from 14 subductions to produce a global assessment of lower abyssal and hadal fish. A significant portion of data was obtained during the Five Deeps and Ring of Fire Expeditions.

High-resolution Multibeam Sonar Bathymetry of the Deepest Place in Each Ocean (2021)

Prior to the Five Deeps expedition, we did not know where all five deeps were. This paper documents exactly where the deepest point in every ocean really is and the true depths. All derived from EM124 multibeam echosounder data from the Five Deep Expedition.

Hadal Zones of the Northwest Pacific Ocean (2021)

During the Five Deeps Expedition, our team was inspired to re-evaluate the refine the true extent of hadal zone in region particularly complex when it comes to hadal environments.

Fear and Loathing of the Deep Ocean: Why Don’t People Care About the Deep Sea? (2020)

To provide food for thought, scientists and guests on the Five Deeps Expedition joined up to share their perspectives on how we, as a society, communicate and perceive the deep-sea as a whole.

Revisiting the 1964 Archimède Bathyscaphe Dive to 7300 m in the Puerto Rico Trench, Abundance of an Elasipodid Holothurian Peniagone sp. and a Resolution to the Identity of the ‘Puerto Rican Snailfish’ (2020)

During the Five Deeps Expedition we had the opportunity to revisits in exact location in the Puerto Rico Trench that the Archimède explored in 1964. We found that the original observations of hadal snailfish were in fact holothurians.

Exploration of the Puerto Rico Trench in the mid-20th Century: Significance and Relevance Today (2020)

Inspired by the ‘deepest point in the Atlantic Ocean’ campaign on the Five Deeps Expedition, we reflect on the legacy of the Puerto Rico Trench in ultra-deep scientific diving.

First in Situ Observation of Cephalopoda at Hadal Depths (Octopoda: Opisthoteuthidae: Grimpoteuthis sp.) (2020)

During the Five Deeps Expedition we found, for the first time, that there are indeed inhabited by the Octopods. Here was document the presence of the Dumbo octopus in the Java Trench at depths of nearly 7000m.

The Five Deeps Expedition and an Update of Full Ocean Depth Exploration and Explorers (2020)

Post Five Deeps Expedition we summarize the current state of full ocean depth human occupied vehicles and take a look at those who dared to journey really deep.

The Hadal Manned Submersible “Limiting Factor” (2019)

In this paper our scientist and engineers describe the new full ocean depth rated human occupied submersible, the DSV Limiting Factor. As of 2022, the submersible has made more descents to Full Ocean Depth than any other vehicle in history.


The Five Deeps: the Location and Depth of the Deepest Place in Each of the World’s Oceans (2019)

Before we embarked on the Five Deeps Expedition we first analyzed all best available public bathymetric data sets to establish likely candidates for where the deepest point in every ocean actually is.