Data from: Nitrogen dynamics across a natural salinity gradient in Mediterranean streams

his dataset contains water and sediment chemistry data from a microcosm experiment designed to assess inorganic nitrogen dynamics (NH₄⁺-N and NO₃⁻-N) across a natural salinity gradient in Mediterranean streams.The dataset includes measurements of nutrient concentrations, dissolved organic carbon, conductivity, and calculated net rates of nitrogen transformation under ambient and nutrient-enriched conditions.Data were collected during controlled laboratory incubations (0, 4, 24, and 48 h).The dataset supports the analyses presented in the associated manuscript submitted to <i>Limnology and Oceanography</i>.