1998 Fiscal Year Final Research Report Summary
Studies on evaluation of carrying capacity of Sanriku coastal waters
| Project/Area Number |
09660191
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
General fisheries
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| Research Institution | The University of Tokyo |
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Principal Investigator |
FURUTA Ken The Univ.Tokyo, Grad.School Agri.Life Sci., Associate Professor, 大学院・農学生命科学研究科, 助教授 (30143548)
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| Co-Investigator(Kenkyū-buntansha) |
OTOBE Hirotaka The Univ.Tokyo, Ocean Research Institute, Associate Professor, 海洋研究所, 助手 (10169328)
KOMATSU Teruhisa The Univ.Tokyo, Ocean Research Institute, Associate Professor, 海洋研究所, 助教授 (60215390)
KISHI Michiko Hokkaido Univ., Faculty of Fisheries, Professor, 水産学部, 教授 (90214767)
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| Project Period (FY) |
1997 – 1998
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| Keywords | phytoplankton / carrying capacity / wakame culture / Sanriku ria / primary productivity / physical-ecological model / natural fluorescence |
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| Research Abstract |
Primary productivity and nutrient consumption of both phytoplankton and commercially-cultured wakame, Undaria pinnatifida were investigated to evaluate carrying capacity of the Sanriku ria coast from January to April of 1998. Field experiments were conducted in Otsuchi Bay, Iwate prefecture. Water exchange frequently occurred between the bay and outside due to the wind-induced circulation. During the periods of the weak water exchange, phytoplankton bloom composed of centric diatoms developed. The bloom disappeared with strong water exchange that transported phytoplankton outward and brought nutrients inward.
Chlorophyll a and primary productivity was monitored using natural fluorescence photometer moored at the central part of the bay. Bio-optical measurements were intensively conducted and, specific light absorption coefficient and quantum yield of phytoplankton photosynthesis were applied to conversion of natural fluorescence to chlorophyll a and primary productivity. Both calculated
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chlorophyll a and primary productivity showed high correlation with directly measured values. These time series data of primary productivity were used with the integrated water column production derived from bio-optical spectral model to estimate primary production of the entire bay that was oberved to be 1.7*10^3 tC during the investigation period of investigation.
U.pinnatifida showed steady growth and primary production until March, while growth was much reduced in April and most part of the primary production was lost by removal of aged part of the thallus. Total primary production of cultured wakame during the period of investigation was estimated to be 45 tC in the bay and only 81% of the total was harvested to land. The rest was a loss.
Phytoplankton primary production consistently exceeded that of wakame by more than 20 times and was 38 times higher. Therefore, herbivorous consumption of phytoplankton by zooplankton and cultured shell fish is important for evaluation of the carrying capacity of this bay. Less
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