The reason of the nutrient decrease of the Seto Inland Sea and its management

2013 Fiscal Year Final Research Report

• Project/Area Number: 23310007
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Environmental dynamic analysis
• Research Institution: Kagawa University
• Principal Investigator: TADA Kuninao 香川大学, 農学部, 教授 (80207042)
• Co-Investigator(Kenkyū-buntansha): ICHIMI Kazuhiko 香川大学, 瀬戸内圏研究センター, 准教授 (70363182) ; YAMAGUCHI Hitomi 香川大学, 農学部, 准教授 (50464368) ; ISHIZUKA Masahide 香川大学, 工学部, 准教授 (50324992) ; HONJO Tsuneo 香川大学, 瀬戸内圏研究センター, 特任教授 (80284553) ; TARUTANI Kenji 独立行政法人水産総合研究センター, 西海区水産研究所, グループ長 (20371966)
• Project Period (FY): 2011-04-01 – 2014-03-31
• Keywords: 生物海洋学

Research Abstract

The nutrient decrease in the Seto Inland Sea. During high economic growth since the 1960s, the Seto Inland Sea became heavily eutrophicated. However, the total nitrogen (TN) and phosphorous (TP) loads decreased from 1990s following the enactment of the Law for Conservation of Environment of Seto Inland Sea in 1973. Nutrient concentrations also gradually decreased. Recently, Nori culture has often heavily damaged due to the lack of nutrient. One explanation for the gradual decrease of DIN concentrations from 1970 to present is fundamentally due to the law enacted by the Environmental Agency. But the reason for the recent decrease of DIN concentrations is still unknown. It was thought that the decrease of the upward nutrient flux across the overlying water-sediment interface greatly affected the water column nutrient concentrations. From the relationship between nutrient and red tide occurrence, appropriate nutrient concentration was also discussed.

Research Products

• [Journal Article] Long-term (36-year) observations on the dynamics of the fish-killing raphidophyte Chattonella in Harima-Nada, eastern Seto Inland Sea, Japan (2014)
  • Author(s): Nishikawa, T., Hori, Y., Nagai, S., Miyahara, K., Nakamura, Y., Harada, K., Tada, K., Imai, I.
  • Journal Title: Journal of Oceanography Volume: 70 Pages: 153 - 164
• [Journal Article] 新川・春日川河口干潟(瀬戸内海備讃瀬戸)における懸濁粒子中のリンの挙動 (2014)
  • Author(s): 朝日俊雅・竹本沙紀・一見和彦・山口一岩・多田邦尚
  • Journal Title: 海の研究 Volume: 23 Pages: 29-44
• [Journal Article] PIP/PP ratio as an indicator of phytoplankton activities and origin of particulate matter in Harima-Nada, the Seto Inland Sea, Japan (2014)
  • Author(s): Asahi, T., Yamaguchi, H., Ichimi, K. and Tada, K.
  • Journal Title: La mer Volume: 52 Pages: 1-11
• [Journal Article] Horizontal distribution of particulate matter and its characterization using phosphorous as an indicator in surface coastal water, Harima-Nada, the Seto Inland Sea, Japan (2014)
  • Author(s): Asahi, T., Ichimi, K., Yamaguchi, H. and Tada, K.
  • Journal Title: Journal of Oceanography Volume: 70 Pages: 277-287
• [Journal Article] 瀬戸内海東部海域の栄養塩減少とその低次生産過程への影響 (2014)
  • Author(s): 多田邦尚・西川哲也・樽谷賢治・山本圭吾・一見和彦・山口一岩・本城凡夫
  • Journal Title: 沿岸海洋研究 Volume: 52(印刷中)
• [Journal Article] 香川県における河川水の栄養塩形態と備讃瀬戸・播磨灘への影響 (2013)
  • Author(s): 石塚正秀・石川真菜・宮川昌志・赤井紀子・多田邦尚
  • Journal Title: 土木学会論文集(水工学)B1 Volume: 69 Pages: I_1423 - I_1428
• [Journal Article] Optically active components and light attenuation in an offshore station of Harima Sound, eastern Seto Inland Sea, Japan (2013)
  • Author(s): Yamaguchi, H., Katahira, R., Ichimi, K. and Tada, K.
  • Journal Title: Hydrobiologia Volume: 714 Pages: 49 - 59
• [Journal Article] Total organic carbon and nitrogen contents in surface sediments of Harima Nada, eastern Seto Inland Sea, Japan : A comparison under two different trophic states
  • Author(s): Yamaguchi, H., Hirade, N.,Kayama, M., Ichimi, K. and Tada, K.
  • Journal Title: Journal of Oceanography Volume: (in press)