Plain Language Hadal trenches (depth >6,000 m) are the remotest and the least‐explored places on our planet, with characteristics of low temperatures, high pressure, limited food and frequent geological activity. Knowing the source of organic matter for hadal life is key in understanding the ocean carbon cycle and the biological adaptation in trenches. We report the first 14C results of hadal amphipods from three trenches in the West Pacific, including the deepest ocean trench, Mariana, which indicates that the organic matter for amphipods is mostly from the surface water. This tight linkage between the organic matter within the hadal fauna and in surface water points out that the anthropogenic pollution can reach the deepest ocean trench rapidly via the food chain. Moreover, the bomb 14C dating method can be applied to hadal amphipods, thereby suggesting a low tissue turnover rate and an unexpectedly long lifetime, which might be a result of an adaptation to the impoverished and harsh environment.