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Carbon-14 (C-14) has been a major contributor to the human radioactive exposure dose, as it is released into the environment from the nuclear industry in larger quantities compared to other radionuclides. This most abundant nuclide enters the biosphere as organically bound C-14 (OBC-14), posing a potential threat to public health. Yet, it remains unknown how this relatively low radiotoxic nuclide induces health risks via chemical effects, such as isotope effect. By establishing a trophic transfer model involving algae (Scenedesmus obliquus), daphnia (Daphnia magna) and zebrafish (Danio rerio), we demonstrate that rapid incorporation and transformation of inorganic C-14 by algae into OBC-14 facilitates the blending of C-14 into the biomolecules of zebrafish. We find that internalized C-14 is persistently retained in the brain of zebrafish, affecting DNA methylation and causing alterations in neuropathology. Global isotope tracing metabolomics with C-14 exposure further reveals the involvement of C-14 in various critical metabolic pathways, including one-carbon metabolism and nucleotide metabolism. We thus characterize the kinetic isotope effects for 12C/14C in the key reactions of these metabolic pathways through kinetic experiments and density functional theory computations, showing that the isotopic substitution of carbon in biochemicals regulates metabolism by disrupting reaction ratios via isotope effects. Our results suggest that inorganic C-14 discharged by the nuclear industry can be biotransformed into OBC-14 to impact metabolism via isotope effects, providing new insights into understanding the health risk of C-14, which is traditionally considered as a low radiotoxic nuclide. [ABSTRACT FROM AUTHOR]

To understand energy and material cycles on surface Earth, it is important yet challenging to estimate trophic transfer through ecosystems. To address this issue, the integrated trophic position (iTP), defined as a biomass-weighted average TP of a given food web, is useful because the iTP can be a proxy for the configuration of ecological pyramid. Here we conducted the compound-specific nitrogen isotope analysis of amino acids for macroinvertebrate communities collected from the Ado and Yasu Rivers in the Lake Biwa watershed, Japan, to estimate their iTP values. Unlike previous studies, no clear relationships between iTP and biodiversity (Shannon index H') were found. However, by comparing the irrigated period and the non-irrigated period within the Yasu River, the decrease in iTP values was fairly characterized by the increase in H'. A significant difference in the observed iTP values compared to those reported in the previous study suggests that the configuration of ecological pyramid in stream ecosystems is dynamic rather than static. We also found that the iTP values of stream macroinvertebrate communities (2.37 ± 0.24) (n = 43), marine mesozooplankton communities (2.33 ± 0.34) (n = 14), and animal communities with various taxonomic groups (2.42 ± 0.21) (n = 158) are all comparable with each other, suggesting that partial communities involving macroinvertebrates well represent the configuration of total ecological pyramid. This finding clearly delineates the promising performance of the iTP index for the trophic transfer of energy, which should be further explored in a variety of ecosystems. [ABSTRACT FROM AUTHOR]

Abstract To understand energy and material cycles on surface Earth, it is important yet challenging to estimate trophic transfer through ecosystems. To address this issue, the integrated trophic position (iTP), defined as a biomass-weighted average TP of a given food web, is useful because the iTP can be a proxy for the configuration of ecological pyramid. Here we conducted the compound-specific nitrogen isotope analysis of amino acids for macroinvertebrate communities collected from the Ado and Yasu Rivers in the Lake Biwa watershed, Japan, to estimate their iTP values. Unlike previous studies, no clear relationships between iTP and biodiversity (Shannon index H’) were found. However, by comparing the irrigated period and the non-irrigated period within the Yasu River, the decrease in iTP values was fairly characterized by the increase in H’. A significant difference in the observed iTP values compared to those reported in the previous study suggests that the configuration of ecological pyramid in stream ecosystems is dynamic rather than static. We also found that the iTP values of stream macroinvertebrate communities (2.37 ± 0.24) (n = 43), marine mesozooplankton communities (2.33 ± 0.34) (n = 14), and animal communities with various taxonomic groups (2.42 ± 0.21) (n = 158) are all comparable with each other, suggesting that partial communities involving macroinvertebrates well represent the configuration of total ecological pyramid. This finding clearly delineates the promising performance of the iTP index for the trophic transfer of energy, which should be further explored in a variety of ecosystems.

Silver nanoparticles (AgNPs) are increasingly used in various consumer products and industrial applications, raising concerns about their environmental impact on aquatic ecosystems. This study investigated the physicochemical stability, trophic transfer, and toxic effects of citrate-coated AgNPs in a freshwater food chain including the diatom Cyclotella meneghiniana and the gastropod Lymnaea stagnalis. AgNPs remained stable in the exposure medium, with a minimal dissolution (<0.06%) after 24 h, indicating that particulate forms dominated during exposure. AgNPs inhibited the growth of C. meneghiniana without significantly affecting chlorophyll-a content or reactive oxygen species (ROS) production. Scanning electron microscopy revealed extracellular polymeric substance (EPS) secretion, which likely formed eco-coronas, reducing AgNPs bioavailability and oxidative damage. However, trace element analysis showed significant depletion of iron, manganese, and nickel, indicating early metabolic stress and redistribution of essential metals to support antioxidant defenses. In L. stagnalis, toxicokinetic analysis showed distinct patterns of Ag uptake and depuration across exposure routes. Waterborne and foodborne exposure resulted in similar and higher Ag accumulation compared to the combined group. Waterborne exposure showed the highest non-eliminable fraction and a bioconcentration factor (BCF) > 1, indicating efficient uptake and retention. Foodborne exposure exhibited a biomagnification factor (BMF) > 1, despite efficient elimination. Combined exposure had the highest depuration rate, with BCF > 1 and BMF < 1, reflecting reduced trophic transfer potential. Oxidative stress in L. stagnalis was highest during combined exposure, with increased ROS in hemolymph during uptake. Foodborne exposure caused prolonged immune stress, evidenced by elevated total antioxidant capacity (TAC) and protein levels. In the hepatopancreas, foodborne exposure during depuration led to increased lipid peroxidation and TAC, indicating oxidative and metabolic challenges specific to dietary exposure. These results highlighted the complex interactions of AgNPs with primary producers and consumers in freshwater ecosystems, emphasizing the need for multi-route assessments in nanoparticle risk evaluations., Competing Interests: Declaration of Competing Interest ☒ The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2025. Published by Elsevier Ltd.)