1997 Fiscal Year Final Research Report Summary
Roles of the inflowed coastal Oyashio Water to Funka Bay on the spring bloom as a trigger of its occurrence.
| Project/Area Number |
08458139
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Environmental dynamic analysis
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| Research Institution | HOKKAIDO UNIVERSITY |
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Principal Investigator |
MIYAKE Hideo Hokkaido Univ., Fac.of Fish.Ass.Prof., 水産学部, 助教授 (60002127)
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| Co-Investigator(Kenkyū-buntansha) |
NAKATANI Toshikuni Hokkaido Univ., Fac.of Fish.Ass.Prof., 水産学部, 助教授 (80188979)
SHIGA Naonobu Hokkaido Univ., Fac.of Fish.Lec., 水産学部, 講師 (30091466)
SAITOH Seiiti Hokkaido Univ., Fac.of Fish.Ass.Prof., 水産学部, 助教授 (70250503)
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| Project Period (FY) |
1996 – 1997
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| Keywords | Coastal Oyashio / spring bloom / chlorophyll-a concentration / sediment trap / wind-driven currents / copepod nauplii |
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| Research Abstract |
Hydrographic conditions and low trophic productivities were investigated with using mooring systems, satellite image analysis and ship observations during the spring bloom in 1997. Results are summarized as follows ;
1) Chlorophyll-a concentrations and fluxes of settling organic particles in the sediment trap were poor in middle March. It is concluded that the phytoplankton bloom was weak in spring of 1997. Coastal Oyashio Water flowed weakly into the bay. This is a reason why the spring bloom was weak in 1997.
2) Ocean color satellite and ship observations showed high chlorophyll-a areas off Muroran to the center of the bay mouth. Waters of the high chlorophyll-a areas moved into the bay. This suggests that the wind-driven currents are important for the distributions and movements of the plankton.
3) Resuspention perticles from the bottom sediments were trapped under the southeasterly winds. This is explained as follows ; high wind waves and resuspentions of the shallow sediments inside the bay cause by the southeasterly winds which have a long fetch. These particles move with the southeastward flows drived from the vortex pair and fall into the trap at the center of the bay.
4) Copepod nauplii are main organisms in early life stage of walleye pollock. After the inflow of the coastal Oyashio Water, large copepod nauplii become to be abundant near the bay. When spawning areas shifted the northeast ward, Oyashio Water was favor food conditions for the larvae, and it transported efficiently eggs and larvae into the bay. This is one of reasons for the long term variabilities of the year class strength of walleye pollock.
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