Inorganic nitrogen and phosphorus uptake kinetics in Palmaria palmata (Rhodophyta)

摘要

The N and P uptake responses were studied in a northern Spanish population of the edible red seaweed Palmaria palmata (Linnaeus) Kuntze. The fronds were incubated at different concentrations, and the nutrient depletion in the medium was measured at successive times to calculate uptake rates. Palmaria palmata uptake response was biphasic and nonsaturable for inorganic P. This would allow the species to exploit transient pulses of high P concentration in natural and fertilized conditions. Such a response is a common feature of algae avoiding nutrient deficiency. At average concentrations measured in the ocean, the response was nonsaturable for inorganic N sources, except for ammonium in autumn and winter when it is not the major N source. In contrast to the general rule of ammonium being taken at a higher rate than nitrate, we found similar affinity for both nutrients corresponding to the minor role of ammonium as N source for field populations over the year.