Iron requirement of the brown macroalgae Laminaria japonica, Undaria pinnatifida (Phaeophyta) and the crustose coralline alga Lithophyllum yessoense (Rhodophyta), and their competition in the northern Japan Sea

Abstract

The iron uptake rates of the brown macroalga Laminaria japonica Areschoug and the coralline alga Lithophyllum yessoense Foslie were determined using 59Fe as a tracer. The uptake rates of Laminaria were saturated at a higher level of iron than Lithophyllum. Furthermore, the saturated uptake rate of Laminaria was approximately 50 times higher than that of Lithophyllum. The growth of Laminaria, the brown macroalga Undaria pinnatifidaHarvey (Suringar) and Lithophyllum was compared in iron-rich and iron-limited media. A medium enriched with iron promotes the growth of Laminaria and Undaria. In contrast, Lithophyllum grew even in an iron-limited medium <1 nM Fe). The iron concentration in coastal seawater collected from the Japan Sea, where rocks or rock beds are covered with coralline algae, is extremely low <2 nM Fe). This may explain why coralline algae (Lithophyllum) dominate, whereas growth of brown macroalgae is severely limited.