| Project/Area Number |
09660202
|
|---|
| Research Category |
Grant-in-Aid for Scientific Research (C)
|
| Allocation Type | Single-year Grants |
|---|
| Section | 一般 |
|---|
| Research Field |
General fisheries
|
|---|
| Research Institution | Kochi University |
|---|
Principal Investigator |
NISHIJIMA Toshitaka Kochi University, Fac.of Agriculture, Professor, 農学部, 教授 (60036738)
|
|---|
| Co-Investigator(Kenkyū-buntansha) |
FUKAMI Kimio Kochi University, Fac.of Agriculture, Professor, 農学部, 教授 (30181241)
|
|---|
| Project Period (FY) |
1997 – 1999
|
| Project Status |
Completed (Fiscal Year 1999)
|
| Budget Amount *help |
¥3,100,000 (Direct Cost: ¥3,100,000)
Fiscal Year 1999: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1998: ¥600,000 (Direct Cost: ¥600,000)
Fiscal Year 1997: ¥2,000,000 (Direct Cost: ¥2,000,000)
|
|---|
| Keywords | Skeletonema / Heterosigma / Gymnodinium / Red tide / Organic nitrogen / Organic phosphorous / Alkaline Phosphatase / Selection of species / 有機汚濁水域 / 赤潮鞭毛藻 / 選択的増殖 / skeletonema / 最小細胞内窒素含量 / 最小細胞内リン含量 |
|---|
| Research Abstract |
Serious fish damages by red tides have persisted in coastal seawater in Japan. Preservating red tide outbreak is an important and urgent issue for fisheries in Japan. Present paper describes the utilization of organic nitrogen and phosphorous by red tide phytoplankters, and their effects of organic nitrogen and phosphorous on the growth and the domination of the phytoplankton species in polluted coastal seawaters.
Red tide phytoplankters, Gymnodinium mikimotoi, Heterosigma akashiwo and Skeletonema costatum were found to use organic nitrogen and phosphorous compounds for their growth. But these species differed in potential utilization of the different organic compounds. For that matter, all of these species could use tryptophan and glutamic acid, while only G.mikimotoi could use urea as a nitrogen source. Similarly, G.mikimotoi and S.costatum, but not H.akashiwo, were found to use mono-phosphoric esters as a phosphorous source and to produce alkaline phosphatase. The enzyme activity was markedly high and enhanced under the phosphate-depleted conditions.
The concentration of organic nitrogen and phosphorous in the polluted coastal waters was fairly high. In these waters, contrib utions of organic nitrogen and phosphorous to the growth of red tide phytoplankters were comparable to those of inorganic nitrogen and phosphorous. The alkaline phosphatase hydrolyzable phosphorous constituted more than 30% of dissolved organic phosphorous contents in a polluted seawater. In nonwinter seasons when the alkaline phosphatase activities derived from algal cells increased, phytoplankters which could use organic phosphorous compounds dominated in the polluted coastal seawater.
From the present study, it is revealed that potential utilization of organic nitrogen and phosphorous differs among red tide phytoplankton species, and that these differences could be reflected on the domination and/or succession of phytoplankton species in polluted seawaters.
|
