12/31/2023 0 Comments Challenger deep vs mariana trenchPrevious studies demonstrated that bottom-axis sediments (10,817 m depth), have higher organic carbon content 7, and more intense organic matter diagenesis than adjacent slope sites 7, 8. The average particulate organic carbon accumulation rates in southern CD seafloor are estimated roughly at ~1.5 × 10 −5 g cm −2 yr −1 6. The V-shaped topography of the trench enables the collection of significant amounts of particulate organic matter (POM) from the upper water column and abyssal seafloor to CD. CD experiences frequent shallow earthquakes 3 that are likely to trigger gravity flows of sedimentary and volcanic material from the adjacent margin into the hadal zone 4, 5. The Challenger Deep (CD) is the deepest part of the world’s oceans located in a tectonically active area at the southern end of the Mariana Trench in the Western Pacific. Technological challenges constrain sampling and bathymetric observations in hadal trenches, placing them among the least-explored marine environments. Hadal trenches are geological formations isolated in deep-sea environments (6000–11,000 m depth) that account for the deepest 45% of the oceanic depth range 1, 2. Our results expand knowledge of microbially-mediated elemental cycling in hadal sediments, and reveal differences in distribution of processes involved in nitrogen loss across the trench. Complete pathways for anaerobic ammonia oxidation are predominantly identified in genomes recovered from bottom-axis sediments compared to slope sites. Metagenome and metatranscriptome data support reduction and biotransformation of arsenate for energy gain in sediments that present a two-fold greater accumulation of arsenic compared to non-hadal sites. These predominantly heterotrophic microbes can recycle macromolecules and utilize simple and complex hydrocarbons as carbon sources. 26% of prokaryotic 16S rDNA reads in metagenomes were novel, with novelty increasing with water and sediment depths. Analyses of 586 metagenome-assembled genomes retrieved from 37 metagenomes show distinct diversity and metabolic capacities between bottom-axis and slope sites. Here, we collected sediments across the slope and bottom-axis of the Challenger Deep that enable insights into its in situ microbial communities. It receives organic matter and heavy metals from the overlying water column that accumulate differently across its V-shaped topography. The 11-kilometer deep Challenger Deep is the least explored due to the technical challenges of sampling hadal depths. The hydrophone also picked up sound from ship propellers, as Challenger Deep is close to Guam, a regional hub for container shipping with China and the Philippines.Hadal trenches are the deepest and most remote regions of the ocean. The ambient sound field is dominated by the sound of earthquakes, both near and far, as well as distinct moans of baleen whales and the clamor of a category 4 typhoon passing overhead. Instead of being one of the quietest places on Earth, scientists found that at the deepest part of the ocean, there is almost constant noise. Coast Guard were surprised by how much they heard. Once they had a listen, researchers from NOAA, Oregon State University, and the U.S. However, scientists had to wait until November to retrieve the hydrophone due to ship schedules and persistent typhoons. The device remained anchored to the seafloor until scientists returned. ![]() The device recorded deep-ocean ambient sound levels in the 10–32,000 Hz range continuously over 23 days. Researchers deployed the hydrophone from the Guam-based U.S. Coast Guard Petty Officer 3rd Class Dylan Hall. ![]() Coast Guard Cutter Sequoia, homeported in Apra Harbor, Guam, prepares to throw a grappling hook to retrieve a NOAA hydrophone from Challenger Deep near the Federated States of Micronesia, November 3, 2015. ![]() Petty Officer 3rd Class Jonathan Gonzales, a boatswain's mate aboard the U.S.
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