Feeding Style Controls on Rare Earth Element Fractionation Patterns in Macrofauna Inhabiting Hydrothermal Vents

Rare earth elements (REEs) serve as an important proxy for tracing life processes, elemental sources, and the feeding styles of organisms. Feeding styles, such as filter‐feeding, parasitic, and symbiotic dependent are key factors influencing REE characteristics within these organisms. Hydrothermal vents provide an ideal natural laboratory for isolating this feeding imprint, as they host at least three distinct styles within close proximity: (a) obligate endosymbiont‐bearing tubeworms and mussels, (b) heterotrophic filter‐feeding or grazing‐filter gastropods, and (c) parasitic polychete. However, most studies of hydrothermal fauna have treated REE signatures as passive recorders of vent fluid chemistry, leaving the influence of feeding strategy largely unaddressed. By integrating REEs and structure analysis of sediments and representative macro‐fauna collected from PACManus and Iheya North Knoll hydrothermal fields, we demonstrated that REE patterns could reflect their feeding styles and environmental information. Filter‐feeding, parasitic, and obligate endosymbiont hosts (i.e., mussels) closely reproduce the hydrothermal fluid pattern with heavy‐REE enrichment and positive europium (Eu) anomalies, Eu sn /Eu sn * value in mussel gill up to 17.27. Obligate endosymbiont hosts (i.e., tubeworm) show positive Eu anomalies in the plume and anterior vestimentum, where hydrothermal particles are trapped, and negative anomalies in the posterior vestimentum and trophosome. Therefore, Eu anomalies cannot be regarded as passive thermometers; rather, their signals are first modulated by feeding style, making them ecological palimpsests. As a result, future reconstructions of ancient vent activity or modern biogeochemical budgets must explicitly account for nutritional guild, and future research should enhance the comprehensive analysis with biogeochemistry and biological structure.