Uptake kinetics and storage capacity of dissolved inorganic phosphorus and corresponding dissolved inorganic nitrate uptake in Saccharina latissima and Laminaria digitata (Phaeophyceae)

Uptake rates of dissolved inorganic phosphorus and dissolved inorganic nitrogen under unsaturated and saturated conditions were studied in young sporophytes of the seaweeds Saccharina latissima and Laminaria digitata (Phaeophyceae) using a "pulse-and-chase" assay under fully controlled laboratory conditions. In a subsequent second "pulse-and-chase" assay, internal storage capacity (ISC) was calculated based on V-M and the parameter for photosynthetic efficiency F-v/F-m. Sporophytes of S. latissima showed a V-S of 0.80 +/- 0.03 mu mol center dot cm(-2) center dot d(-1) and a V-M of 0.30 +/- 0.09 mu mol center dot cm(-2) center dot d(-1) for dissolved inorganic phosphate (DIP), whereas V-S for DIN was 11.26 +/- 0.56 mu mol center dot cm(-2) center dot d(-1) and V-M was 3.94 +/- 0.67 mu mol center dot cm(-2) center dot d(-1). In L. digitata, uptake kinetics for DIP and DIN were substantially lower: V-S for DIP did not exceed 0.38 +/- 0.03 mu mol center dot cm(-2) center dot d(-1) while V-M for DIP was 0.22 +/- 0.01 mu mol center dot cm(-2) center dot d(-1). V-S for DIN was 3.92 +/- 0.08 mu mol center dot cm(-2) center dot d(-1) and the V-M for DIN was 1.81 +/- 0.38 mu mol center dot cm(-2) center dot d(-1). Accordingly, S. latissima exhibited a larger ISC for DIP (27 mu mol center dot cm(-2)) than L. digitata (10 mu mol center dot cm(-2)), and was able to maintain high growth rates for a longer period under limiting DIP conditions. Our standardized data add to the physiological understanding of S. latissima and L. digitata, thus helping to identify potential locations for their cultivation. This could further contribute to the development and modification of applications in a bio-based economy, for example, in evaluating the potential for bioremediation in integrated multitrophic aquacultures that produce biomass simultaneously for use in the food, feed, and energy industries.