Transfer of 14C from peat and plant litter to different ecological groups of earthworms and associated biological responses under controlled conditions

Radiocarbon ( 14 C) transfer in terrestrial ecosystems remains poorly understood, particularly for soil fauna under conditions where soil organic matter- and litter-derived carbon pools may contribute differently to animal assimilation. This study quantified the relative contributions of peat- and litter-derived carbon to earthworms representing contrasting ecological strategies, using peat as a naturally 14 C-depleted proxy for older soil organic carbon in a controlled peat–litter microcosm experiment. Two earthworm species, an epigeic species ( Eisenia fetida ) and an anecic species ( Lumbricus terrestris ), were exposed for 10 days under six treatments differing in litter availability. Short-term biological endpoints (survival, weight change, and avoidance behavior) were included to assess habitat suitability and to aid mechanistic interpretation of carbon uptake patterns, rather than to evaluate radiotoxic effects per se . Epigeic earthworms showed high survival (65–78%), weight gain, and measurable incorporation of peat-derived carbon (up to 12%), whereas anecic earthworms showed low survival (18–75%), weight loss, and negligible peat-derived carbon contribution across treatments. Both species showed a preference for soft litter, although this did not translate into increased peat-derived carbon incorporation. Radiocarbon signatures in both species remained close to modern values, indicating preferential assimilation of rapidly cycling carbon pools, while incorporation of older peat carbon was limited under the constrained experimental conditions. These findings demonstrate that earthworm carbon sourcing is strongly influenced by ecological strategy and habitat suitability, and they provide new empirical data relevant for improving representations of 14 C transfer in terrestrial food webs and soil fauna compartments of radioecological and biosphere models.