Effects of the environmental factors on the propagation of epiphytic diatom Grammatophora marina (Lyngb.) Kuetz

The present study elucidated factors affecting the propagation of Grammatophora marina (Lyngb.) Kuetz. found on the nori thalli. The following results were obtained: 1) The mucilage pores of this species looked like the compound eyes were located on the valve side. 2) The range of the optimal temperature for good propagation was 15-25°C. 3) The optimal light intensity was above 5, 000 lx at 15°C and 2, 000 lx at 20°C. 4) The species grew optimally under the value of chlorinity from 14.1 to 15.8‰ at 15°C and 20°C. 5) The optimal pH was 8.0-9.0 at 15°C and 20°C. 6) Inorganic nitrogen, borate, silicate and thiamine HCl were necessary for the propaga-tion, and especially the first two compounds were essential. 7) When the inorganic nitrogen was rich in media, the propagation was accelerated by a few amino acids released from the nori thalli, while the lack of inorganic nitrogen caused to use several amino acids as the nitrogen source of the propagation. These results of the laboratory experiments were made to speculate about the propagation of this species in the nori cultivation ground.