瀬戸内海における海洋基礎生産に関する研究Ⅰ : 基礎生産および海況について

On primary production in the Seto Inland Sea I : Primary production and hydrographic condition

Endo Takuo

広島大学水畜産学部紀要

Journal of the Faculty of Fisheries and Animal Husbandry, Hiroshima University

　瀬戸内海において， 1963年6月に西部海域，同年9月lこ東部海域の基礎生産量を調査した.
　海況については，すでに報公されているように，豊後水道系の水は徐々に内湾的性格を強められながら備後灘を経て備讃瀬戸へ，また途中から分れて広島湾へと影響を及ぼしている.一方，紀伊水道系の水は，大阪湾においてかなり内湾的性格を強められるが，備讃瀬戸まで影響を及ぼしている.
　基礎生産lこ関連するクロロフィルa量，およびタンク法により測定した光合成量は，それぞれの場所で独特な値を示し，その変異の巾も大きい.6月の西部海域では，クロロフィルa量は0.21-1.38mg/m3で，光合成量は0.96-9. 63Cmg/m3/h，単位クロロフィルa量当りの光合成量は2.98-11.14C/h の範囲にある.9月の東部海域ではそれぞれ1.60-13.83mg/m3，6.09-102.29Cmg/m3/h，1.98-11.68C/hの範囲にある.
　これら基礎生産に関係する三種の値を，他の海域と比べると，黒潮・親潮流域と同程度の低い値もあるが，大部分の値はそれらより大きい.また同じ月の本邦沿岸水域(函館湾-長崎湾)とでは，ほぼ同程度の値で，赤潮の例(三つの値とも大きい)をのぞけば，変異の巾は内海の方がやや狭い.
　透明度とクロロフィルa量との間には，相関の有無の両例がみられ，内海におけるこの関係は複雑である.
　クロロフィルa量と単位クロロフィルa量当りの光合成量との聞では，約3分の2の測定値で，海域別に，相関がみられ，クロロフィルa量が多いと単位クロロフィルa量当りの光合成量は小さい.

As a part of a study on the primary production in the Seto Inland Sea, the photosynthesis (by 14C method) and the chlorophyll a content were measured at 21 stations in 1963. The measurement were carried out in the western half in June, and in the eastern half in September. (Text-fig. 1).

In the measurement of photosynthesis, the sample sea water was impregnated with Na214C03 (5μc/cc) and incubated in a tank at the temperature of surface water for 3 hours, being illuminated at about 12,000 lux with daylight-type fluorescent lamps. Chlorophyll a was measured by CREITZ and RICHARDS method with slight modification. In both measurements, filters of average pore size of 0.8p (Millipore AA) were used.

1) In the months when the measurements were carried out, the hydrographic conditions of the Seto Inland Sea exhibited a strong inshore character, especially in central rogion. (Text-figs. 2 and 4, Tables 1 and 2).

2) The photosynthesis (at a certain depth at a certain station) varied within the range of 0.96-9.63 C mg/m8 /h in the western half in June, and 1.60-13.83 C mg/m3 /h in the eastern half in September. Chlorophyll a content varied within the ranges of 0.21-1.38 mg/m3 and 1.60-13.83 mg/m3 respectively. And the photosynthesis per mg of chlorophyll a was within the range of 2.98-11.14 C mg/h and 1.98-11.68 C mg/h. These three variables varied from station to another over wide ranges. (Text- figs. 3 and 5, Tables 1 and 2).

3) These values are comparable in magnitude with the values obtained in 9 bays on the coasts of Japan in the corresponding months. When compared with the data reported from Kuroshio and Oyashio regions, however, they are mostly very much higher, although a few of them are of the same order. (Text-fig. 6).

4) A negative correlation is found between the chlorophyll a content and the photosynthesis per chlorophyll a in about two thirds of the measurement; namely, the ratio of photosynthesis to chlorophyll a tends to decrease as chlorophyll a content increases. (Text-fig. 8).

Fishing industry. Fisheries [ 660 ]

jpn

広島大学水畜産学部

[ISSN] 0440-8756

[NCID] AN00213563