Geology, environment, and life in the deepest part of the world’s oceans

Abstract

The hadal zone, mostly comprising of deep trenches and constituting of the deepest part of the world's oceans, represents the least explored habitat but one of the last frontiers on our planet. The present scientific understanding of the hadal environment is still relatively rudimentary, particularly in comparison with that of shallower marine environments. In the last 30 years, continuous efforts have been launched in deepening our knowledge regarding the ecology of the hadal trench. However, the geological and environmental processes that potentially affect the sedimentary, geochemical and biological processes in hadal trenches have received less attention. Here, we review recent advances in the geology, biology, and environment of hadal trenches and offer a perspective of the hadal science involved therein. For the first time, we release highdefinition images taken by a new full-ocean-depth manned submersible Fendouzhe that reveal novel species with an unexpectedly high density, outcrops of mantle and basaltic rocks, and anthropogenic pollutants at the deepest point of the world's ocean. We advocate that the hydration of the hadal lithosphere is a driving force that influences a variety of sedimentary, geochemical, and biological processes in the hadal trench. Hadal lithosphere might host the Earth's deepest subsurface microbial ecosystem. Future research, combined with technological advances and international cooperation, should focus on establishing the intrinsic linkage of the geology, biology, and environment of the hadal trenches.

Dawn of complex animal food webs: A new predatory anthozoan (Cnidaria) from Cambrian

“…In summary, early Cambrian epibenthic lingulids and primitive anthozoans, such as Nailiana , inhabited the same shallow-sea-bottom environment (although some modern anthozoan descendants have migrated to the deep seafloor 34 ); their record of mutual interaction provides a unique snapshot of the early evolution and subsequent retention of efficient predation using flexible tentacles in epibenthic anthozoan cnidarians. Given that the Chengjiang medusozoan Yunnanoascus possessed nematocyst batteries, 31 and given also that stem cnidarian Xianguangia bore feather-like tentacles, 18 it follows that both the ancient (suspension) and the derived (predatory) feeding modes co-existed, and that both basic body forms (polypoid and medusoid) of modern cnidarians originated at least as far back as the early Cambrian.…”

Macrofauna and Nematode Abundance in the Abyssal and Hadal Zones of Interconnected Deep-Sea Ecosystems in the Kuril Basin (Sea of Okhotsk) and the Kuril-Kamchatka Trench (Pacific Ocean)

“…However, it was markedly lower than in the abyssal plain adjacent to the Kuril-Kamchatka Trench (Fischer and Brandt, 2015;Schmidt and Martínez Arbizu, 2015). The northwestern Pacific Ocean region adjacent to the Kuril Islands, with its high level of primary production and a large terrigenous runoff of organic matter from the continent and the islands, is one of the most productive regions of the world's oceans, characterized by a high organic matter content of bottom sediments (Sokolova, 1976(Sokolova, , 1981Itoh et al, 2011;Kitahashi et al, 2012Kitahashi et al, , 2013Stewart and Jamieson, 2018;Du et al, 2021). The abundance of food material provides favorable habitat conditions for a diverse and abundant bottom fauna (Filatova, 1960;Belyaev, 1989;Brandt et al, 2015;Fischer and Brandt, 2015;Schmidt and Martínez Arbizu, 2015), especially on the abyssal plain, where more organic matter is accumulated in bottom sediments than on the oceanic slopes of the Kuril Islands (Sattarova and Aksentov, 2018).…”

Role of deep-sea equipment in promoting the forefront of studies on life in extreme environments

“…It brings marine technology to an unprecedented new level, opening a powerful gate that can explore any place in the ocean. The Chinese full-ocean-depth manned submersible ‘Fendouzhe’ was applied to research on the Mariana Trench, and reveal novel species with an unexpectedly high density at a depth of 10,909 m in 2020 as well ( Du et al., 2021 ).…”