Surge uptake of ammonium and nitrate by four intertidal seaweed species was examined under standard conditions (16.5 or 20°C, 72 μE m-2 s-1), at both subsaturating and saturating initial nutrient concentrations. Uptake rates were positively correlated with the surface area: volume (SA:V) ratio of the thallus: Ulva curvata (Ku ̈tzing) DeToni > Fucus evanescens C. Agardh ≈ Gracilaria tikvahiae McLachlan > Codium decorticatum (Woodward) Howe. A positive correlation was also found for the relationship between SA:V and the initial slope of the curves of uptake rate vs. external concentration. These results support the predictions of an earlier funtional-form model, and suggest the usefulness of the SA:V ratio as a comparative index of nutrient uptake capability in co-occurring seaweeds. © 1984.