1993 Fiscal Year Final Research Report Summary
Studies on biological production on lower trophic levels in the vicinity of seamount and adjacent waters
| Project/Area Number |
04660204
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
General fisheries
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| Research Institution | Mie University |
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Principal Investigator |
FURUYA Ken Fac. Bioresources, Mie Univ., Assoc. Prof., 生物資源学部, 助教授 (30143548)
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| Co-Investigator(Kenkyū-buntansha) |
TAGUCHI Kazunori Fac. Bioresources, Mie Univ., Res. Assist., 生物資源学部, 助手 (30226972)
ODATE Tsuneo Fac. Bioresources, Mie Univ., Res. Assist., 生物資源学部, 助手 (60224250)
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| Project Period (FY) |
1992 – 1993
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| Keywords | Seamount / Western North Pacific Ocean / Plankton / Biological production in lower trophic levels / Upwelling / Primary production / Nutrients / Chlorophyll a |
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| Research Abstract |
Observations were conducted in the vicinity of the Komahashi No.2 Seamount during June of 1993, using the T/S Seisui Maru, Mie University. Nutrient ynamics, phytoplankton distributions, and grazes' consumption were investigated. In addition methods to determine DNA amount were established using cultured microalgae to evaluate growth retes of natural phytoplankters.
The field observations revealed upward shifted isothermal line in the vicinity of the seamount. Being paralleled with the line, high concentration of nitrate (1 muM) reaced the euphtic layr. Integrated nitrate within 0-200 m water column was 1.6 times higher above the seamount than in the adjacent water. The N/P retio increased with depth, suggesting that uptake was faster for nitrate than phosphate. Simulation based on the sequential observations showed that it should take more than two weeks when eddy diffusion could elevate concentration of nitrate at 100 m to 1 muM.Since water column structure and current system changed within a few days, non-equilibrium of the current system is morr essential than the eddy difusion for supply of nutrients.
Diurnal variations of phyto- and zooplankton were investigated traching a buoy. Wet weight of zooplankton varied between 80 and 140 mg m^<-3> (mean(〕SY.+-.〔)1SD, 100(〕SY.+-.〔)15 mg m^<-3>). Chlorophll a concentration in the water colum (0.12-0.22 mug L^<-1> : 0.16(〕SY.+-.〔)0.03 mug L^<1->) was high in day and low in night. Zooplankton gut pigments were high in night. Chlorophyll a / (chlorophyll a^+phaeopigments) ratio of the gut pigments became the maximum at 1500 and the minimum at 2100, showing an inverse correlation with the variation of chlorophyll a in the water column, suggesting grazing controls of phytoplankton abundance. Data are further analyzing for understanding of dynamics in lower trophic levels around the seamount area.
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