ABSTRACT Tropical volcanic islands contribute significantly to coastal nutrient budgets, particularly through river inputs, driven by steep topography, intense rainfall and rapid chemical weathering. In the oligotrophic oceanic waters surrounding the Lesser Antilles, these inputs can strongly influence nearshore phytoplankton productivity. However, the magnitude of riverine nutrient inputs can vary from daily to interannual scales, reflecting the interplay between rainfall, land use and hydrology. To assess this temporal variability, we analysed a 12‐year monitoring of hydrology and solute concentrations (major ions, macronutrients, metals, dissolved organic carbon) in the Capesterre River, a major river in southern Basse‐Terre, Guadeloupe (French West Indies), offering a temporal resolution from days to decades. Solute‐discharge relationships revealed distinct behaviours depending on element type: a main dilution pattern for Ca, Mg, SiO 2 , Sr, NO 3 − ; chemostatic for PO 4 3− ; and enrichment up to a saturation threshold for Fe, Al and DOC due to interactions with colloids and organic matter. Monthly flux estimates over 12 years showed increased inputs in July, August and November, December, associated with higher discharge, while interannual flux variability remained limited. A spatial comparison with other rivers in southern Basse‐Terre Island revealed significant differences in solute fluxes, driven by contrasting sources such as hydrothermal inputs, weathering and agriculture. This study focused on riverine hydrology and solute fluxes, providing a terrestrial baseline for interpreting nutrient dynamics in adjacent coastal waters. This long‐term dataset provided critical insight into element delivery from tropical volcanic catchments and underscored the complexity of solute transport in small volcanic basins. Given the dynamic nature of these inputs, extending monitoring beyond river mouths to coastal waters is essential. Such integrated observations are key to understanding how nutrient inputs impact marine ecosystems over time.
Moreau et al. (Sun,) studied this question.