Trace Element Deficiency, Especially Iron Deficiency, Causes the Discoloration of Sea Laver, Nori, in the Ariake Sea

Abstract

As a result of intensive chemical analyses of discolored sea laver (nori) samples, the direct cause of discoloration could be ascribed to the deficiency of trace metals, Fe, Cu, Mn and Zn, as well as to a deficiency of nitrogen and phosphorus. In this study, in order to clarify the effect of trace metals on the production of photosynthetic pigments, chlorophyll a and phycobilins, Porphylla yezoensis was cultured in the presence and absence of iron, and the production of the pigments was monitored. Also, the suspended mud specific to the Ariake Sea was found to be a good source of iron and other trace metals for the production of the pigments. The actual cause of discoloration of nori in the Ariake Sea was speculated in view of struggling for the trace metal nutrition between nori and phytoplanktons.