Eutrophication and occurrences of harmful algal blooms in the Seto Inland Sea, Japan
スポンサーリンク
概要
- 論文の詳細を見る
The Seto Inland Sea is the largest enclosed coastal sea in Japan and is also a major fishing ground including aquacultures of fish, bivalves and seaweeds. The incidents of red tides dramatically increased in frequency and scale in the Seto Inland Sea along with serious eutrophication in the 1960s and 1970s. The maximum incident of 299 was recorded in 1976, but the incident has since shown a clear decreasing trend, reaching about 100 per year in the late 1980s by virtue of regulation by law, and this level has been maintained thereafter with the level of nutrients supporting red tide occurrences. The “Law Concerning Special Measures for Conservation of the Environment of the Seto Inland Sea” was legislated in 1973 and industrial loading was decreased to half the level of 1972. The important red tide organisms causing huge fishery damages by fish-kill are Chattonella antiqua, C. marina, C. ovata and Heterosigma akashiwo (Raphidophyceae), and Karenia mikimotoi and Cochlodinium polykrikoides (Dinophyceae). The maximum fishery damage (death of 14.2 million yellowtails) was 7.1 billion yen (about US $60 million) caused by C. antiqua in Harima-Nada in 1972. In 1988, a novel red-tide dinoflagellate species Heterocapsa circularisquama appeared for the first time, and has repeatedly killed both natural and aquacultured bivalves, with the highest damage of 3.9 billion yen to cultured oysters in Hiroshima Bay in 1998. Among the important red-tide organisms, C. antiqua, H. circularisquama and C. polykrikoides are rated as extremely harmful species that can easily reach the warning level of fishery damage by consuming only small amounts of nutrients. In toxic blooms, the dinoflagellate Alexandrium tamarense has become dominant in the Seto Inland Sea in the spring season, causing toxicity in short-necked clams and cultured oysters almost every year. Many countermeasures have been applied for harmful algal blooms in Japan. Laws for the regulation of water quality have been most effective in decreasing red-tide occurrences. No physical and chemical controls have been successful except for clay treatments. Clay spraying has been investigated and implemented in Kyushu and Korea for the removal of C. polykrikoides red tides. As environment-friendly mitigation strategies for red tides, biological controls using algicidal bacteria and viruses are proposed. A new finding of the abundant existence of algicidal bacteria on the surface of seaweeds suggests that co-culturing fish and seaweed is a prevention strategy for harmful algal blooms by virtue of the continuous release of many algicidal bacteria to the surrounding seawater. The artificial development of seaweed beds would also be effective as a prevention strategy for red tides.
- 2006-05-01
著者
-
Imai Ichiro
Laboratory Of Marine Environmental Microbiology Division Of Applied Biosciences Graduate School Of A
-
Imai Ichiro
Laboratory Of Conservation Of Coastal Ecosystems Graduate School Of Global Environmental Studies
-
Hori Yutaka
Fisheries Technology Institute Hyogo Prefectural Technology Center For Agriculture Forestry And Fish
-
Yamaguchi Mineo
Red Tide Research Division National Research Institute Of Fisheries And Environment Of Inland Sea Fi
-
Yamaguchi Mineo
Red Tide Research Division National Research Institute Of Fisheries And Environments Of Inland Sea
-
Yamaguchi Mineo
Red Tide Research Division Nansei National Fisheries Research Institute
関連論文
- Identification of overwintering vegetative cells of the bivalve-killing dinoflagellate Heterocapsa circularisquama in Uranouchi Inlet, Kochi Prefecture, Japan
- Seasonal distribution of the shellfish-killing dinoflagellate Heterocapsa circularisquama in Ago Bay monitored by an indirect fluorescent antibody technique using monoclonal antibodies
- Effects of the substances secreted from Closterium aciculare (Charophyceae, Chlorophyta) on the growth of freshwater phytoplankton under iron-deficient conditions
- Selenium Requirement for Growth of a Novel Red Tide Flagellate Chattonella verruculosa (Raphidophyceae) in Culture
- Relationships between intracellular bacteria and the bivalve killer dinoflagellate Heterocapsa circularisquama (Dinophyceae)
- Effects of Harmful Dinoflagellate Heterocapsa circularisquama Cells on the Growth of Intracellular Bacteria
- Eutrophication and occurrences of harmful algal blooms in the Seto Inland Sea, Japan
- Complexation of iron by microbial siderophores and effects of iron chelates on the growth of marine microalgae causing red tides
- Evaluation of major nutrients regulating the growth of diatoms in Harima-Nada, the Seto Inland Sea, Japan
- Cryopreservation of a Virus (HaV) Infecting a Harmful Bloom Causing Microalga, Heterosigma akashiwo (Raphidophyceae)
- Factors inducing resting - cell formation of Coscinodiscus wailesii Gran (Bacillariophyceae) in culture
- The effect of irradiance and irradiation time on the size of initial cells in vegetative cell enlargement of Coscinodiscus wailesii (Centrales, Bacillariphyceae) in culture
- Horizontal distribution of calanoid copepods in the western Arctic Ocean during the summer of 2008
- Newly identified resting stage cells of diatoms from sediments collected in Ago Bay, central part of Japan
- Interannual and latitudinal changes in zooplankton abundance, biomass and size composition along a central North Pacific transect during summer : analyses with an Optical Plankton Counter