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Marine macroalgae are widely used indicator species for monitoring environmental radioactivity. Empirical studies have demonstrated a range in radionuclide transfer coefficients, or concentration ratios (CRs), between taxonomic groups, however the CR values used for dose estimation assume that macroalgae are a homogenous group, represented by a single CR. This study demonstrates the presence of a taxonomic signal in macroalgae CRs for multiple anthropogenic and naturally occurring radionuclides (137Cs, 241Am, 239+240Pu, 210Po) based on a collation of available data. A Residual Maximum Likelihood (REML) mixed model was applied, producing relative estimate CRs specific to each species within the datasets. The collated data was also analysed for a phylogenetic signal, but only a weak signal was found for one radionuclide in one group (239+240Pu in Phaeophyceae). A theoretical case study using the estimated CRs and the ERICA tool was carried out to demonstrate the implications of these findings in a real-world scenario. • Activity Concentrations for 200+ macroalgae species from existing sources were collated. • Analysis revealed significant taxonomic signals but weak phylogenetic signals. • IAEA CR values are generally reasonable but may underestimate doses for some taxa. • A trait-based approach may further explain the drivers behind variation in CRs. [ABSTRACT FROM AUTHOR]

With the rapidly expanding global nuclear industry, more efficient and direct radiological monitoring approaches are needed to ensure the associated environmental health impacts and risk remain fully assessed and undertaken as robustly as possible. Conventionally, radiological monitoring in the environment consists of measuring a wide range of anthropogenically enhanced radionuclides present in selected environmental matrices and using generic transfer values for modelling and prediction that are not necessarily suitable in some situations. Previous studies have found links between taxonomy and radionuclide uptake in terrestrial plants and freshwater fish, but the marine context remains relatively unexplored. This preliminary study was aimed at investigating a similar relationship between brown seaweed, an important indicator in radiological monitoring programmes in the marine environment, and Caesium-137, an important radionuclide discharged to the marine environment. A linear mixed model was fitted using REsidual Maximum Likelihood (REML) to activity concentration data collected from literature published worldwide and other databases. The output from REML modelling was adjusted to the International Atomic Energy Agency (IAEA) quoted transfer value for all seaweed taxa in order to produce mean estimate transfer value for each species, which were then analysed by hierarchical ANalysis Of VAriance (ANOVA) based on the taxonomy of brown seaweeds. Transfer value was found to vary between taxa with increasing significance up the taxonomic hierarchy, suggesting a link to evolutionary history. This novel approach enables contextualisation of activity concentration measurements of important marine indicator species in relation to the wider community, allows prediction of unknown transfer values without the need to sample specific species and could, therefore, enhance radiological monitoring by providing accurate, taxon specific transfer values for use in dose assessments and models of radionuclide transfer in the environment. • Pre-existing data collated for Cs137 activity in brown seaweeds. • REML generated TFs are more representative of the brown seaweed community. • Taxonomic patterns provide useful tool for prediction and dose assessment. [ABSTRACT FROM AUTHOR]