Editing Oceanic trench (section)

== Hydrothermal activity and associated biomes ==

As sediments are subducted at the bottom of trenches, much of their fluid content is expelled and moves back along the subduction décollement to emerge on the inner slope as [[mud volcanoes]] and [[cold seeps]]. [[Methane clathrates]] and [[gas hydrates]] also accumulate in the inner slope, and there is concern that their breakdown could contribute to [[global warming]].{{sfn|Stern|2005}}

The fluids released at mud volcanoes and cold seeps are rich in [[methane]] and [[hydrogen sulfide]], providing chemical energy for [[Chemotroph|chemotrophic microorganisms]] that form the base of a unique trench [[biome]]. Cold seep communities have been identified in the inner trench slopes of the western Pacific (especially Japan{{sfn|Fujikura | Lindsay |  Kitazato |  Nishida |  2010 }}), South America, Barbados, the Mediterranean, Makran, and the Sunda trench. These are found at depths as great as {{convert|6000|m|sigfig=1|sp=us}}.{{sfn|Stern|2005}} The genome of the [[extremophile]] ''[[Deinococcus]]'' from Challenger Deep has sequenced for its ecological insights and potential industrial uses.{{sfn|Zhang |Huang |Qin |Quan |2021}}

Because trenches are the lowest points in the ocean floor, there is concern that [[plastic debris]] may accumulate in trenches and endanger the fragile trench biomes.{{sfn|Peng |Bellerby |Zhang |Sun |2020}}