Deep‐sea hydrothermal vents host exceptional ecosystems with lush animal communities primarily relying on organic matter (OM) produced by chemoautotrophic microbes. Though energy sources and food webs at vents have been extensively studied, the exact carbon sources of chemosynthetic primary production, such as methane (CH4) and carbon dioxide (CO2) in the vent fluid or bottom water, have not been elucidated quantitatively across spatial scales. Here, we investigate carbon and nitrogen sources of 12 vent animal species at the Iheya North field, Okinawa Trough inhabiting different distances from the central venting area and with various feeding ecologies using natural‐abundance radiocarbon (Δ14C) in combination with conventional stable carbon and nitrogen isotope ratios (δ13C and δ15N). Our results show that generally, animals living closer to vent orifices were more depleted in 14C, indicating they assimilate more carbon from vent fluid CO2. Those relying on methanotrophs, however, exhibited low Δ14C values regardless of distance due to the lack of methane in the non‐vent‐influenced bottom water. Organisms with low Δ14C values also tend to exhibit low δ15N values, implying NH4+ assimilation into biomass in environments with high NH4+ concentrations. Our results demonstrate that 14C can clearly distinguish between chemoautotrophically fixed carbon originating from the vent fluid and detrital OM derived from surface primary production, and also discriminate between CO2‐ and CH4‐based chemoautotrophy. Although vent animals rely on vent fluid energetically, our results highlight that the dependency on vent fluids as carbon source varies greatly depending on habitat, as well as carbon fixation pathways of microbial primary producers.

中文翻译：

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利用自然 14C 丰度和栖息地水温阐明热液喷口动物的碳源

深海热液喷口拥有特殊的生态系统，其中有茂密的动物群落，主要依赖化能自养微生物产生的有机物（OM）。尽管能源和喷口的食物网已被广泛研究，但化学合成初级生产的确切碳源，例如甲烷（CH4）和二氧化碳（CO2）在喷口流体或底层水中，尚未在空间尺度上进行定量阐明。在这里，我们利用自然丰度放射性碳（Δ14C) 与常规稳定碳氮同位素比值 (δ13C 和 δ15N）。我们的结果表明，一般来说，生活在靠近排气口的动物体内的水分消耗更多。14C，表明它们从排出液 CO 中吸收了更多的碳2。然而，那些依赖甲烷氧化菌的细菌表现出较低的 Δ14由于不受喷口影响的底层水中缺乏甲烷，C 值与距离无关。低 Δ 的生物体14C 值也往往表现出较低的 δ15N值，表示NH4+在高 NH 环境中同化为生物量4+浓度。我们的结果表明14C 可以清楚地区分源自喷口流体的化能自养固定碳和源自地表初级生产的碎屑 OM，并且还可以区分 CO2‐ 和 CH4基于化能自养。尽管喷口动物大力依赖喷口流体，但我们的研究结果强调，对喷口流体作为碳源的依赖程度因栖息地以及微生物初级生产者的碳固定途径而异。