Effect on Metal Elements on Fading Laver in the Ariake Sea

A fading phenomenon of laver arose in the Ariake Sea, Japan from the end of 2000 to the beginning of 2001. It was said that consumption of the major nutrient (N, P. etc.) of sea water by the large phytoplankton caused this phenomenon. In the present study, the relationship between the fading phenomenon of laver and metal elements in sea water was examined. It was found that the amount of essential trace metal elements (especially Fe, Mn and Zn) of the faded laver was less than those of normal laver. In addition, the concentration of these metals in sea water collected near the area around the color-faded laver decreased extremely compared with previous data. From these results, it was deduced that not only the major elements (N and P), but also trace essential elements (Fe, Mn and Zn), could be consumed by phytoplankton. Therefore, the deficiency of these elements could be the major reasons for the fading phenomenon of laver in the Ariake Sea.