It has been guessed from literatures and the author's unpublished study that the absorption curves derived from natural sea water will change according to the differences of species composition of planktonic fauna and flora; of physiological activities of phytoplankton and, also of present quantity of the colored organic detritus suspending in original sea water. Then, in the present paper, when sea water was preserved in the dark, the changes of phytoplankton's features such as cell number, species composition and disappearance of chromatophores, etc. and the change of absorption spectra related to depression of phytoplankton's activity by the dark condition were observed by means of microscope and spectrophotometer, respectively, and the results were obtained as follows. (1) The difference of phytoplankton's composition at the start of the observations influenced effectively on the subsequent change of phytoplankton's feature. Chaetoceros was tolerant against the dark condition, Skeletonema being not so. (2) In the first seven days of observations, optical reaction of chromatophores against the dark condition was not yet so conspicuous but, in the next seven days, normal chromatophores disappeared and changed wholly to abnormal ones and the empty cell occurred in part, and after that it was gradually increased. (3) The absorption spectra derived from the preserved sea water, changed gradually from normal form to abnormal one, and especially, the changes occurred continuously in the duration from five days to fourteen days, and were conspicuous on about the seventh day in most of the observations. After that the form of the spectra collapsed wholly. (4) The absorbencies at each wave length decreased steadily according to the progress of days for the preservation, but the rate of decrease was conspicuous at shorter wave length as compared with longer one in each wave length, showing a regularity as following. Decrease rate of the absorbency at 400mμ in wave length>Decrease rate at 430mμ≒Decrease rate at 480mμ>Decrease rate at 600mμ>Decrease rate at 665mμ (5) As a matter of course, the ratio of absorbency at blue maximum to that at red maximum increased steadily according to the progress of days spent for preservation. (6) Recoveries of concentrated and disappeared chromatophores in a cell, resulting in the dark preservation, were seen when the sea water was replaced in the light. Replacement of samples in the light after preservation for one month in the dark restored chromatophores to normal condition with the rate of 16% of the cells investigated. From results described above, it became obvious that phytoplankton's reaction in the dark coincided well both in microscopic and spectrophotometeric observations, and also that depression of phytoplankton's activities was well shown as changes of absorption spectra.

海水の吸光曲線は原海水に含まれるプランクトン組成・活力及び有機デトリタスの存在により特徴ある型を呈することが推論されるので,植物プランクトンの生理のおとろえが吸光曲線におよぼす影響を顕微鏡的及び分光光度計的手段により観察した.植物プランクトンの生理のおとろえは海水を暗室に保存することにより,含まれる植物プランクトンを完全に光から遮断して生ぜしめた. 各節の結論のうち主たるものは次の如くなる. (1)暗所保存海水中の植物プランクトンは当初の種組成が,その後の組成変化,細胞数の減少率に影響し,Chaetocerosは暗所条件に強い方向,又Skeletonemaは弱い方向で組成の変北と細胞数の減少に作用する. (2)処理当初から7日目までは色素体の収縮現象はほとんどないが,7～14日の間で暗所条件が色素体に与える影響は大となり,この間に正常色素体は消失,収縮粒状化すると共に空白細胞数も増加する.その後空白細胞のしめる割合が増大する. (3)1ヶ月の暗所保存後に行った明所復帰処理は16%の細胞群に正常色素体えの回復の可能性を証明した. (4)各波長別吸光度の減衰率は長波長部ほど大で D400の減衰率>D430の減衰率≒D480の減衰率>D600の減衰率>D665の減衰率である.この規則性が吸光曲線のクズレ現象を規則あるものとす.吸光曲線は暗所保存後5日目～14日目の間に正常型からクズレの型え移行する.特に7日目前後は保存効果が顕著にあらわれる. (5)第一主吸収帯・第二主吸収帯の吸光度比Dλ1/Dλ2の値は保存後の経日的に増加する. 以上の諸結果から結論として,暗所保存が植物プラントに与える効果は顕微鏡的及び分光光度計的手段によっても処理1週間から2週間の間に顕著にあらわれることで一致した.又植物プランクトンの生理の衰えは吸光曲線の変型であらわれることも明かになった.

長崎大学水産学部研究報告, v.15, pp.100-115; 1963